Cost and quality for either Darwin or Seedling
Posted by Joshua Merchant
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Re: Cost and quality for either Darwin or Seedling July 18, 2008 07:22PM |
This is still a research project. Many of your questions cannot be easily answered because no one actually knows. If you're looking for a kit-type project that will work out of the box, pick up a Fab@home or wait another 6 months 
That being said, I'll do my best to sort out your concerns.
First, I don't think anyone has actually gotten a seedling working well, so you'll be taking your chances with that. The Darwin hardware is generally better documented and more established. Just my opinion though - others may disagree. A seedling is significantly cheaper though, especially for those of us in the States, what with the weak dollar and shipping.
As far as quality goes, you can take a look at the "What can it make?" page at This is still a research project. Many of your questions cannot be easily answered because no one actually knows. If you're looking for a kit-type project that will work out of the box, pick up a Fab@home or wait another 6 months
That being said, I'll do my best to sort out your concerns.
First, I don't think anyone has actually gotten a seedling working well, so you'll be taking your chances with that. The Darwin hardware is generally better documented and more established. Just my opinion though - others may disagree. A seedling is significantly cheaper though, especially for those of us in the States, what with the weak dollar and shipping.
As far as quality goes, you can take a look at the "what can it make?" page at [reprap.org] to get an idea of build quality (and how far it has come since the first objects!) The highest quality that has been achieved so far is by Nophead's machine, but everything from his hardware to his build strategy are custom, so it may be difficult to replicate that success. See his work at [hydraraptor.blogspot.com].
Hope that answers your questions. I have faith that Things Will Get Better, but quite frankly, we aren't to the point where you can order a box, download instructions off the 'net and have a reliable printer. That's been 6-8 months away for a year or so now.
That being said, I'll do my best to sort out your concerns.
First, I don't think anyone has actually gotten a seedling working well, so you'll be taking your chances with that. The Darwin hardware is generally better documented and more established. Just my opinion though - others may disagree. A seedling is significantly cheaper though, especially for those of us in the States, what with the weak dollar and shipping.
As far as quality goes, you can take a look at the "What can it make?" page at This is still a research project. Many of your questions cannot be easily answered because no one actually knows. If you're looking for a kit-type project that will work out of the box, pick up a Fab@home or wait another 6 months
That being said, I'll do my best to sort out your concerns.
First, I don't think anyone has actually gotten a seedling working well, so you'll be taking your chances with that. The Darwin hardware is generally better documented and more established. Just my opinion though - others may disagree. A seedling is significantly cheaper though, especially for those of us in the States, what with the weak dollar and shipping.
As far as quality goes, you can take a look at the "what can it make?" page at [reprap.org] to get an idea of build quality (and how far it has come since the first objects!) The highest quality that has been achieved so far is by Nophead's machine, but everything from his hardware to his build strategy are custom, so it may be difficult to replicate that success. See his work at [hydraraptor.blogspot.com].
Hope that answers your questions. I have faith that Things Will Get Better, but quite frankly, we aren't to the point where you can order a box, download instructions off the 'net and have a reliable printer. That's been 6-8 months away for a year or so now.
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Re: Cost and quality for either Darwin or Seedling July 19, 2008 02:40AM |
reece.arnott Wrote:
-------------------------------------------------------
> The difference between the Silver and Gold kits
> seems to be that the Gold includes:
> "All rods and fittings will be supplied bright zinc
> plated.
> End caps and nut covers will be supplied for all
> protruding bars and fittings.
> Acrylic bed will be supplied."
Heh. Pimp my RepRap?
> The other main limit is that overhangs need to be
> less than 45 degrees or you need support material
> to hold it up which is planned for the 1.1 version.
Won't a second toolhead be required for that? If so, then you could just use a second extruder head loaded with a thermoplastic with a lower melting point. Fill in the holes with it, and at the end melt it away. Might be a problem if the two materials mix instead of staying separate though. Anyway, there are a lot of options for the support materials, so I'm not too worried about that.
> The roughness of the parts so far is a combination
> of factors but mainly its because we're still
> figuring out the exact details eg. how to turn off
> the extruder so it doesn't drag 'spiderwebs' over
> what are supposed to be voids, what the best speed
> and temperature is to minimise any shrinkage or
> warping as the layer cools etc.
Interesting. Most of that can be easily (well...) adjusted by running a series of experiments on a simple, quickly generated object (that takes less than 10 minutes or so to finish). After generating a few hundred of the object with varied settings, I think there would be enough data to properly calculate these things (perhaps storing preferred methods based on attributes of the object, extruder, and thermoplastic material, etc. in a set of tables that can be used to adjust settings automatically).
As to turning off the extruder... that seems rather trivial, as well. I suppose it would have to be played around with, but basicallyyou can try: [I had to revise this section because it was really big and full of fluff.]
1) simply turning off the motor.
2) putting a brake/clamp etc. on the motor to halt its motion.
3) reversing the current flowing to the motor.
4) using some sort of camera shutter in front of or inside the nozzle... While it is really cool to imagine one of those diaphragm shutters with 3 or more blades opening and closing in front of/inside your nozzle... this would probably be too high tech (and thus too expensive)... I think a simple one-leaf shutter or focal plane shutter attached to a motor would work fine. It would have to either be positioned just inside or right in front of the nozzle. In front of the nozzle would probably be simpler in design, but it might be messier in practice (if, for example, it is not flush with the nozzle and the stuff leaks out around the shutter and jams the output, as well as the movement of the shutter).
So basically, turn off and/or reverse the motor and block the nozzle, and you've stopped extrusion. Fine tuning would be required to get the timing right, but the changes seem fairly simple to make. If it works, go to 0. If the shutter explodes your extruder... well... *runs away*
[Note - most camera shutters I know of are plastic. It would probably be necessary to use a metal/PTFE/etc. shutter, but the design is the same.]
As to the rest of the information in your post, thanks! I think that basically answers all the questions I had...
Now for more!
JohnWasser Wrote:
-------------------------------------------------------
> Yes, but to build a RepStrap you need a
> Thermoplastic Extruder. That leaves you with a
> similar chicken and egg problem because the
> current Thermoplastic Extruder design uses RP'd
> parts. A thermoplastic extruder design that can be
> built from commonly available materials using
> commonly available tools would be a great boon to
> us all.
It shouldn't be impossibly difficult to create an extruder without an extruder. The chicken came from an egg, and the egg came from the species that the first chicken evolved from. The chicken species started in an egg. You didn't need a chicken to make the first egg, you just needed the creature that was similar to the chicken (the reproductive cells of which genetically mutated to create the chicken's DNA). It's the same idea with having a RepStrap. For me, I'm betting it's going to go like this:
RepStrap with
-Gen2 Electronics (Arduino-based)
-McWire Cartbot
-Bootstrap Extruder (Name: Seedling Extruder v0.1? Thermoplast Extruder v0.1?)
Once I get it semi-stable, I make the RP parts for the Thermoplast Extruder v1.1, and construct it. I then use the new extruder to make the same RP parts (which are better, assuming that my bootstrap extruder will be imperfect in its extrusion), and then dissassemble the extruder and reassemble it with the better parts.
I then have:
RepStrap with
-Gen2 Electronics (Arduino-based)
-McWire Cartbot
-Thermoplast Extruder v1.1
Which is called "Seedling" on this site... personally I think it would be more of a seedling if it used its own separate, simpler extruder. In any case, I then use this improved RepStrap to produce the RP parts for the Darwin. I assemble it and I then have:
RepRap with
-Gen2 Electronics (Arduino-based)
-Cartbot v1.0
-Thermoplast Extruder v1.1
Yay. That's all nice in text, but someone actually paying attention might notice that I don't give any details as to the building/acquisition of this bootstrap extruder... [as I type what I'm typing now, I still have no idea as to what these details are...]
The first thing I notice about the Mk II extruder and the v1.1 extruder is that they use screws to drive the plastic rod. This causes a problem of rotation which is solved by external holding apparatus. Personally, I wouldn't have thought of the screw driven method immediately. I would think more along the lines of a gear or other such circular object whose circumference rotates and makes contact with the rod, pushing it down. That is, if it is a gear, the teeth would contact the side of the rod and move it along (just as the thread on the screw does the same job). I suppose the screw allows for more points of contact, but personally I think the gear thing is simpler in design. Unfortunately, the gears may be harder to acquire/produce than the screws [ironically, the gear idea would work better using an existing RepRap in that it is RepRappable, whereas the current design requires the long metal screw which is obviously not RepRappable at this time...]
One cool thing about the gear idea is that you can have two gear trains on opposite sides of the rod (or I suppose you could have 4 gear trains, one pair perpendicular to the other), and the gear trains could be spring loaded. That is, springs could push on each of the trains, squishing the gears against the thermoplastic material. Why is this cool? Because it allows for multiple diameters of material, that's why. Not as cool as an extruder that can use granules, but that is hardly the kind of thing that should be included on a Seedling design. Oh, right, back to the Seedling...
Anyway, I'm tired so I'm going to wrap this up quick:
The basic parts that make the extruder hard to make without already having a RepRap are the plastic parts that form a sort of frame, not the actual operational parts (which are mostly metal etc). The actual fact that makes these parts hard to produce cheaply with simple tools is that they are complex shapes. Simplify the shapes (e.g. make the entire thing more linear, what's with the angle between the motor and the polymer guide? It necessitates the steel wire on the drive screw, which is an unnecessary complication as far as I can tell) and the parts become trivial to create out of existing objects with cheap tools. For example, while the motor drive assembly looks shnazzy, unless I misunderstand the functionality, it's just a 2-gear geartrain connecting a motor to a screw... I bet it could be redesigned to be held by one or two flat plates (plastic, wood, metal, whatever) with holes and notches drillable with a cheap bit and a couple axles for the gears made out of screws (like hex bolts going through holes in the plates, held together with nuts, with the gears resting between spacers on the flat part of the bolt inside the two plates). The difference? Take a look at the gear assembly on the v1.1 extruder. Then think about a couple of gears on a couple of bolts between two cheap pieces of flat plastic. Then compare. Sure, you can probably make it more schnazzy and compact with the complex RP'd geartrain... but we're talking about a Seedling here. In any case, tomorrow I'm going to start designing concepts on my simplified extruder. Wish me luck (maybe I'll get some inspiring dreams in a few minutes... or maybe just some good honk-shus...).
By the way, this kind of simplification of parts is not limited to that gear assembly... for example, the poly holder and screw holder (green and blue in the exploded view on the extruder v1.1 page) can be simplified by, say, just using a simple tube/rectangular prism with properly drilled holes in it.
Of course, some specific aspects of what I describe are incorrect (because I don't have a full understanding of the workings of the systems, mainly due to the fact that the information on the site is more designed at showing how to build the parts, rather than showing how they work; I think it's more assumed that you can see it for yourself/imagine it yourself; I will, of course, be able to imagine the entire specific workings, but not without further research (or rather, mostly just a matter of time and concentration), which is not possible because I am now falling asleep [I think I'm one of the few people who writes such long posts over such a long time period that I start to fall asleep... sorry about that.]
Anyway. It's REALLY the end of the post this time.
PP: (Post-post, like post-script)
Sorry about the long post, I get carried away and it takes twice as long to edit it and I usually cannot bring myself to remove more than 1/10 of the post [actually this time I made an effort to condense it, but I still couldn't remove much]... also, if I come off as a big idiot/jerk etc, blame it on my psychiatric medications, they're always a convenient (and possibly accurate) excuse
-------------------------------------------------------
> The difference between the Silver and Gold kits
> seems to be that the Gold includes:
> "All rods and fittings will be supplied bright zinc
> plated.
> End caps and nut covers will be supplied for all
> protruding bars and fittings.
> Acrylic bed will be supplied."
Heh. Pimp my RepRap?
> The other main limit is that overhangs need to be
> less than 45 degrees or you need support material
> to hold it up which is planned for the 1.1 version.
Won't a second toolhead be required for that? If so, then you could just use a second extruder head loaded with a thermoplastic with a lower melting point. Fill in the holes with it, and at the end melt it away. Might be a problem if the two materials mix instead of staying separate though. Anyway, there are a lot of options for the support materials, so I'm not too worried about that.
> The roughness of the parts so far is a combination
> of factors but mainly its because we're still
> figuring out the exact details eg. how to turn off
> the extruder so it doesn't drag 'spiderwebs' over
> what are supposed to be voids, what the best speed
> and temperature is to minimise any shrinkage or
> warping as the layer cools etc.
Interesting. Most of that can be easily (well...) adjusted by running a series of experiments on a simple, quickly generated object (that takes less than 10 minutes or so to finish). After generating a few hundred of the object with varied settings, I think there would be enough data to properly calculate these things (perhaps storing preferred methods based on attributes of the object, extruder, and thermoplastic material, etc. in a set of tables that can be used to adjust settings automatically).
As to turning off the extruder... that seems rather trivial, as well. I suppose it would have to be played around with, but basicallyyou can try: [I had to revise this section because it was really big and full of fluff.]
1) simply turning off the motor.
2) putting a brake/clamp etc. on the motor to halt its motion.
3) reversing the current flowing to the motor.
4) using some sort of camera shutter in front of or inside the nozzle... While it is really cool to imagine one of those diaphragm shutters with 3 or more blades opening and closing in front of/inside your nozzle... this would probably be too high tech (and thus too expensive)... I think a simple one-leaf shutter or focal plane shutter attached to a motor would work fine. It would have to either be positioned just inside or right in front of the nozzle. In front of the nozzle would probably be simpler in design, but it might be messier in practice (if, for example, it is not flush with the nozzle and the stuff leaks out around the shutter and jams the output, as well as the movement of the shutter).
So basically, turn off and/or reverse the motor and block the nozzle, and you've stopped extrusion. Fine tuning would be required to get the timing right, but the changes seem fairly simple to make. If it works, go to 0. If the shutter explodes your extruder... well... *runs away*
[Note - most camera shutters I know of are plastic. It would probably be necessary to use a metal/PTFE/etc. shutter, but the design is the same.]
As to the rest of the information in your post, thanks! I think that basically answers all the questions I had...
Now for more!
JohnWasser Wrote:
-------------------------------------------------------
> Yes, but to build a RepStrap you need a
> Thermoplastic Extruder. That leaves you with a
> similar chicken and egg problem because the
> current Thermoplastic Extruder design uses RP'd
> parts. A thermoplastic extruder design that can be
> built from commonly available materials using
> commonly available tools would be a great boon to
> us all.
It shouldn't be impossibly difficult to create an extruder without an extruder. The chicken came from an egg, and the egg came from the species that the first chicken evolved from. The chicken species started in an egg. You didn't need a chicken to make the first egg, you just needed the creature that was similar to the chicken (the reproductive cells of which genetically mutated to create the chicken's DNA). It's the same idea with having a RepStrap. For me, I'm betting it's going to go like this:
RepStrap with
-Gen2 Electronics (Arduino-based)
-McWire Cartbot
-Bootstrap Extruder (Name: Seedling Extruder v0.1? Thermoplast Extruder v0.1?)
Once I get it semi-stable, I make the RP parts for the Thermoplast Extruder v1.1, and construct it. I then use the new extruder to make the same RP parts (which are better, assuming that my bootstrap extruder will be imperfect in its extrusion), and then dissassemble the extruder and reassemble it with the better parts.
I then have:
RepStrap with
-Gen2 Electronics (Arduino-based)
-McWire Cartbot
-Thermoplast Extruder v1.1
Which is called "Seedling" on this site... personally I think it would be more of a seedling if it used its own separate, simpler extruder. In any case, I then use this improved RepStrap to produce the RP parts for the Darwin. I assemble it and I then have:
RepRap with
-Gen2 Electronics (Arduino-based)
-Cartbot v1.0
-Thermoplast Extruder v1.1
Yay. That's all nice in text, but someone actually paying attention might notice that I don't give any details as to the building/acquisition of this bootstrap extruder... [as I type what I'm typing now, I still have no idea as to what these details are...]
The first thing I notice about the Mk II extruder and the v1.1 extruder is that they use screws to drive the plastic rod. This causes a problem of rotation which is solved by external holding apparatus. Personally, I wouldn't have thought of the screw driven method immediately. I would think more along the lines of a gear or other such circular object whose circumference rotates and makes contact with the rod, pushing it down. That is, if it is a gear, the teeth would contact the side of the rod and move it along (just as the thread on the screw does the same job). I suppose the screw allows for more points of contact, but personally I think the gear thing is simpler in design. Unfortunately, the gears may be harder to acquire/produce than the screws [ironically, the gear idea would work better using an existing RepRap in that it is RepRappable, whereas the current design requires the long metal screw which is obviously not RepRappable at this time...]
One cool thing about the gear idea is that you can have two gear trains on opposite sides of the rod (or I suppose you could have 4 gear trains, one pair perpendicular to the other), and the gear trains could be spring loaded. That is, springs could push on each of the trains, squishing the gears against the thermoplastic material. Why is this cool? Because it allows for multiple diameters of material, that's why. Not as cool as an extruder that can use granules, but that is hardly the kind of thing that should be included on a Seedling design. Oh, right, back to the Seedling...
Anyway, I'm tired so I'm going to wrap this up quick:
The basic parts that make the extruder hard to make without already having a RepRap are the plastic parts that form a sort of frame, not the actual operational parts (which are mostly metal etc). The actual fact that makes these parts hard to produce cheaply with simple tools is that they are complex shapes. Simplify the shapes (e.g. make the entire thing more linear, what's with the angle between the motor and the polymer guide? It necessitates the steel wire on the drive screw, which is an unnecessary complication as far as I can tell) and the parts become trivial to create out of existing objects with cheap tools. For example, while the motor drive assembly looks shnazzy, unless I misunderstand the functionality, it's just a 2-gear geartrain connecting a motor to a screw... I bet it could be redesigned to be held by one or two flat plates (plastic, wood, metal, whatever) with holes and notches drillable with a cheap bit and a couple axles for the gears made out of screws (like hex bolts going through holes in the plates, held together with nuts, with the gears resting between spacers on the flat part of the bolt inside the two plates). The difference? Take a look at the gear assembly on the v1.1 extruder. Then think about a couple of gears on a couple of bolts between two cheap pieces of flat plastic. Then compare. Sure, you can probably make it more schnazzy and compact with the complex RP'd geartrain... but we're talking about a Seedling here. In any case, tomorrow I'm going to start designing concepts on my simplified extruder. Wish me luck (maybe I'll get some inspiring dreams in a few minutes... or maybe just some good honk-shus...).
By the way, this kind of simplification of parts is not limited to that gear assembly... for example, the poly holder and screw holder (green and blue in the exploded view on the extruder v1.1 page) can be simplified by, say, just using a simple tube/rectangular prism with properly drilled holes in it.
Of course, some specific aspects of what I describe are incorrect (because I don't have a full understanding of the workings of the systems, mainly due to the fact that the information on the site is more designed at showing how to build the parts, rather than showing how they work; I think it's more assumed that you can see it for yourself/imagine it yourself; I will, of course, be able to imagine the entire specific workings, but not without further research (or rather, mostly just a matter of time and concentration), which is not possible because I am now falling asleep [I think I'm one of the few people who writes such long posts over such a long time period that I start to fall asleep... sorry about that.]
Anyway. It's REALLY the end of the post this time.
PP: (Post-post, like post-script)
Sorry about the long post, I get carried away and it takes twice as long to edit it and I usually cannot bring myself to remove more than 1/10 of the post [actually this time I made an effort to condense it, but I still couldn't remove much]... also, if I come off as a big idiot/jerk etc, blame it on my psychiatric medications, they're always a convenient (and possibly accurate) excuse
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Re: Cost and quality for either Darwin or Seedling July 19, 2008 05:24PM |
NOES! The back button ate my really long post... 
And it was so perfect...
Gah!
I'm typing this one in Notepad.... and I'm saving constantly just in case the power goes out or something like that...
[Right then. Brace yourself for much ado about... what were we talking about, again?]
So anyway, I have some basic designs for the bootstrap extruder.
Main Construction Material
The main construction material is variable, and is meant to be able to be replaced by RP... but it is MUCH simpler than something that would require RP (that is, it's much simpler than the v1.1 extruder, even if it is a bit less sophisticated). The basic idea was that I could take an acrylic glass plate 1/2 inch thick and manually cut out all of the pieces. It could also be cut out of wood, PTFE, steel, etc etc. I would think the three materials best suited for use as the main material would be a RepRappable plastic, handcut/lasercut acrylic glass, or wood. As I said before, I'm liking the idea of the handcut acrylic glass, but the use of wood would make this a really cool bootstrap available with even less advanced technology (it's easier to cut a tree down and make wooden logs than to create acrylic glass plates, or so I assume).
Anyway.
Heated Barrel
The heated barrel is the same as that used in the v1.1 extruder. The relevant attributes of the barrel are: it ends in a 16mm diameter PTFE tube with a 3mm hole in the center.
Barrel Clamp/Attachment
The clamp is a two piece shape that can be thought of as a 4cm x 4cm x 1cm block with a 16mm hole (drilled) in the center, and then cut in half, forming two 4cm x 2cm x 1cm blocks with half-cylinder holes in them (and probably even created in such a way).
Something like this (I'm looking at it in Lucida Console font in notepad; you could just copy the text-images and paste them into the reply box to get an idea of what they should look like [looks like you'll actually have to go into the raw source to get the correct number of spaces... anyone know how to maintain spacing in this forum?][Edit- fixed with code tags, thanks Ru.]):
as a cross section. The diamond looking thing should actually be a circle. I tried using () but it made it look like a 4x5 rectangle instead of a 4x4 square.
Anyway, that's the shape. On the 4x1 side of the blocks, two 3mm holes should be drilled for screws. The centers of the holes should be 5mm from the 4cm-long sides and 9 mm from the 1cm-long sides. That essentially means that each screw will be 3mm above the edge of the PTFE tube; the tube extends to 16/2=8mm above the center of the blocks. Adding 3mm spacing between the tube and the screw hole, we get 8+3=11mm from the center. 20-11=9mm away from the side. [Note that I'm not entirely clear on the dimensions yet, I think they would depend on material strengths etc. and may require some expert input and/or testing on my end.]
The cross section would look like this if you had an x-ray to see the holes:
Not that you needed a visual representation... it's just fun to make them.
Anyway, so you drill the 3mm holes, insert the screws (which should be around 5cm long), and then loosely attach a nut on each of them, such that the nut stays on the screw and stops the two blocks from coming apart, but still allows the blocks to move a bit along the screws (note that the holes should be large enough such that the screws can rotate in the holes, or more importantly move laterally along the holes).
Insert the PTFE tube into the big 16mm hole, tighten the nuts, and voila, you have a working clamp.
[I think I overcomplicated the explanation on that one, sorry.]
[Edit - I just realized the official clamp design doesn't clamp like this... it isn't really a clamp (or rather the clamp isn't used in the long run), more of a fastening device that has screws that actually go straight through the PTFE, holding it in place with nuts and bolts... well, that's depressing, because I was kinda proud of my design... anyway, it can be fixed by simply moving the screws from being just outside of the PTFE tube area, to being just inside of the PTFE tube area... essentially moving the two screws closer to each other (each moves about 6mm, so they are 12mm closer)... some simple changes in construction would be necessary.]
Filament/Screw Holder
Now on to the filament/screw holder. I think they can be created as one piece. It is a bit harder to make, but it is simpler in design and thus smaller and cheaper. The "harder" part means that you'll have to spend more time on it though (and perhaps you might break a piece or two while trying to make it; I still think it would be cheaper, even considering that).
The basic design is a 1cm x 1cm x ?cm rectangular prism. The ?cm means I'm not entirely sure on the length dimension (as stated before, dimensions are up in the air). Anyway, a 3.5mm filament hole and a 3mm screw hole are drilled such that they ever so slightly overlap. The positioning of these holes is up in the air as well; I can't decide on the best locations. Here are a few that I've considered:
1) The two holes placed horizontally in the square cross section, sorta like this:
2) Next I tried putting them in the diagonal, which is 14.14mm in length instead of the 10mm length I placed them in above (pythag theorem/distance formula). It's a bit harder to show in fixed width text, unfortunately. But basically, the distance between the hole edges and the corners would be: (14.14-(3.5+3))/2=3.82mm. Of course, the distance between the hole edges and the square sides is a bit less than this, but it is still better than the 1.25mm in 1). I could calculate it, but it would take a while and frankly it's not worth it (at least right now).
3) Aesthetically (and when building) it might be better to have the filament in the center of the holder:
The filament hole center would be 7.07mm away from the corner. The edge of the hole would be 7.07mm-(3.5/2)=5.32mm from the corner. The screw hole would be 5.32-3=2.32mm from the edge. I'm guessing this would be structurally unstable, like 1), but I'm not sure. In any case, the screw can be changed to a 2mm screw, changing the distance to 5.32-2=3.32mm.
4) I like symmetry. How about two screws on opposite sides of the filament?
5) If 4) could work, maybe this would work too:
4) and 5) might require some synchronization of the screws (I really don't know), and might be totally impractical. In any case, the general idea should work (perhaps with some variations).
6) Oh, one more idea: the problem with 1) was that the wall-hole distance was small and might be structurally unstable. We can increase the distance by increasing the holder's dimensions. I'd like to only do this along one dimension, because this will keep the other one at 10mm, which is easily an acrylic glass thickness.
[There are quite a few more variations, such as a cylinder being used instead of a rectangular prism, but for various reasons I prefer the ones on this shortlist.]
The v1.1 extruder has some half-bearing lands in the screw holder... it shouldn't be too hard to implement these similarly. I'm thinking put them at the ends of the holder, where the hole for the screw is slightly widened on one side (the side opposite the filament hole), allowing for placement of some lubricated thingy. (High-tech lab jargon.)
Now that I am reviewing the v1.1 extruder, it seems that the reason for separating the two pieces was to allow for the use of springs to press the screw against the filament. Well, my design can probably do this too. I think maybe if I make the lubricated thingies long enough, they can contact enough of the screw on both sides. I can drill a hole in the side, that meets the screw's hole where the lubricated thingy would be. Inserting the lubricated thingy into the screw hole, and then a spring into this new hole, the spring can press against the lubricated thingy, which can then shove the screw against the filament. (This would be necessary on both sides.) There are quite a few possible variations.
Filament-/Screw-Holder Holder-Block
Now, to attach it to the "clamp" and thus make it flush to the PTFE tube:
More blocks! A block, say 4cm x 4cm x 0.5cm, with a "square hole" cut out of its center, 1cm x 1cm (the size and shape of the screw & filament holder) is used. This can be made in a few ways - directly cutting the square out of the 4x4x0.5 block is the preferred method, but this may be a bit difficult with common tools. Alternately, 4 or 2 pieces can be used:
For the 4 piece method (probably the easiest method):
1) Cut the 4x4x0.5 into a 4x1.5x0.5 and a 4x2.5x0.5.
2) Cut the 4x2.5x0.5 into a 4x1.5x0.5 and a 4x1x0.5. You should now have two 4x1.5x0.5 blocks and a 4x1x0.5 block.
3) Cut the 4x1x0.5 block into a 1.5x1x0.5 and a 2.5x1x0.5.
4) Cut the 2.5x1x0.5 into a 1.5x1x0.5 and a 1x1x0.5. Discard/store the 1x1x0.5. You should now have two 4x1.5x0.5 blocks and two 1.5x1x0.5 blocks.
5) Positioning the blocks in their original positions and then screwing them together (without passing a screw through the center square "hole") yields the proper shape.
[Note that this is for a 10mm x 10mm filament/screw holder with the filament in the center.]
This block is not intended as a clamp, but rather as a positioning guide.
The clamp for the PTFE tube has 4 holes drilled near each corner for screws. The screws need to be really long (as long as the clamp and the filament/screw holder combined, and then some more). 4 holes are drilled in the new block that coincide with the holes in the clamp. 4 screws are pushed through the holes in the clamp, with the heads on the PTFE tube's side. The new block is slid onto these screws, and made flush with the clamp. Nuts are tightened (a loooong way down) to hold the two together, with a LOT of screw left sticking out. The filament/screw holder should be able to be slid into the square hole in the new block, with the filament hole lining up with that of the PTFE tube.
Biplate Geartrain, Motor mounting, and Filament-Screw Divergence
Now for that two-plate geartrain contraption I mentioned in my last post.
The basic idea is that you take two parallel plates with some space between them (of the material - plastic/wood/whatever), place them perpendicular to the screw, and put a motor and geartrain between the plates, attaching to the screw and rotating it.
The first problem with this design is that if you allow the screw and the filament to maintain their relative positioning by keeping them straight, then when you try to attach a gear or something to the screw, you find that it smacks against the filament. This could either cause jamming or prevent placement of the filament/gear (or some other problem). I think this is why the motor drive/gear assembly in the v1.1 extruder is tilted, and uses a bendable steel wire to transfer the motion.
There are three options for solving this that I see. First, use a gear smaller than the screw diameter. This is rather difficult, and might present problems when the screw moves around due to the springs in the holder (the ones used to allow for slight variations in filament size). The second option is to have the filament bend away from the screw. Basically, one hole is drilled on the lower plate, which coincides with the hole in the holder and which is touching the hole for the screw, and then one hole is drilled on the upper plate, which is slightly apart from the hole for the screw. Essentially, the hole is displaced horizontally forcing the filament to go through the two-plate contraption at an angle. The third option is to have the screw bend away from the filament. This is what is done by the v1.1 extruder. The way the v1.1 does it is not, however, the only way to bend a rotating screw and transfer motion! Personally, I thought it would be simpler to use a universal joint or something similar (http://en.wikipedia.org/wiki/Universal_joint), but then I remembered that you still have screw movement due to the springs... so I figure I'll probably stick with the steel wire idea for now (unless anyone has some better suggestions; I don't really like the idea of having to solder a steel wire to the screw; it's not very low-tech).
Then again, if it isn't a problem to bend the filament as described above, then I'd like to do that (I'm not sure if it breaks the filament/messes it up somehow or if some of the harder plastics can't even be bent like that).
The Mk II extruder seems to bend the filament, so I'm hoping it's feasible.
If it is, then the design will basically be like this:
Filament gets bent as described by the section option. Screw goes straight up through the top plate, and is held in the top plate by a bearing and some nuts and washers (I think if you layer it nut-washer-bearing in plate-washer-nut it should work and still rotate, right?). A gear is attached on the screw, right below the top plate (so that the gear doesn't touch the filament). This gear meets a gear next to it, which is the end of the gear train. The gear train is essentially a bunch of gears on rods (possibly just bolts allowed to rotate between the plates) which decreases rotational speed and increases torque (a series of small gear to big gear meetings, from the motor). The motor is placed vertically between the plates, with a small gear on its rod, which contacts the first big gear in the train (might need to drill tiny holes for the leads, depending on the motor).
Four holes are drilled (this is probably one of the first things to be done) in each plate, coinciding with the 4 long screws from the clamp, and nuts are placed on each side of each plate, holding them in place. It may be necessary (depending on plate size) to put additional bolts through the plate to stabilize the structure.
Cartbot Attachment
I'm not entirely clear on the connection of the extruder to the cartbots, but it should be a trivial matter to make an attachment.
Silly Ending Section Title
So that's about it, unless I'm forgetting something. Electronics etc. can be placed between the plates, if necessary (or perhaps above/below, I think this consideration is more aesthetics though).
Seems simple enough to me. Comments?
Oh, and please don't flame me for being silly/naive. It's only my third day of RepRap knowledge.
Edited 1 time(s). Last edit at 07/20/2008 12:38PM by Joshua Merchant.
And it was so perfect...
Gah!
I'm typing this one in Notepad.... and I'm saving constantly just in case the power goes out or something like that...
[Right then. Brace yourself for much ado about... what were we talking about, again?]
So anyway, I have some basic designs for the bootstrap extruder.
Main Construction Material
The main construction material is variable, and is meant to be able to be replaced by RP... but it is MUCH simpler than something that would require RP (that is, it's much simpler than the v1.1 extruder, even if it is a bit less sophisticated). The basic idea was that I could take an acrylic glass plate 1/2 inch thick and manually cut out all of the pieces. It could also be cut out of wood, PTFE, steel, etc etc. I would think the three materials best suited for use as the main material would be a RepRappable plastic, handcut/lasercut acrylic glass, or wood. As I said before, I'm liking the idea of the handcut acrylic glass, but the use of wood would make this a really cool bootstrap available with even less advanced technology (it's easier to cut a tree down and make wooden logs than to create acrylic glass plates, or so I assume).
Anyway.
Heated Barrel
The heated barrel is the same as that used in the v1.1 extruder. The relevant attributes of the barrel are: it ends in a 16mm diameter PTFE tube with a 3mm hole in the center.
Barrel Clamp/Attachment
The clamp is a two piece shape that can be thought of as a 4cm x 4cm x 1cm block with a 16mm hole (drilled) in the center, and then cut in half, forming two 4cm x 2cm x 1cm blocks with half-cylinder holes in them (and probably even created in such a way).
Something like this (I'm looking at it in Lucida Console font in notepad; you could just copy the text-images and paste them into the reply box to get an idea of what they should look like [looks like you'll actually have to go into the raw source to get the correct number of spaces... anyone know how to maintain spacing in this forum?][Edit- fixed with code tags, thanks Ru.]):
. __ __ . | || | . | /\ | . | \/ | . |__||__|
as a cross section. The diamond looking thing should actually be a circle. I tried using () but it made it look like a 4x5 rectangle instead of a 4x4 square.
Anyway, that's the shape. On the 4x1 side of the blocks, two 3mm holes should be drilled for screws. The centers of the holes should be 5mm from the 4cm-long sides and 9 mm from the 1cm-long sides. That essentially means that each screw will be 3mm above the edge of the PTFE tube; the tube extends to 16/2=8mm above the center of the blocks. Adding 3mm spacing between the tube and the screw hole, we get 8+3=11mm from the center. 20-11=9mm away from the side. [Note that I'm not entirely clear on the dimensions yet, I think they would depend on material strengths etc. and may require some expert input and/or testing on my end.]
The cross section would look like this if you had an x-ray to see the holes:
. __ __ _ . |__||__| |.| . | /\ | .. or like this from the 4x1 side | | . |__\/__| |.| . |__||__| |_|
Not that you needed a visual representation... it's just fun to make them.
Anyway, so you drill the 3mm holes, insert the screws (which should be around 5cm long), and then loosely attach a nut on each of them, such that the nut stays on the screw and stops the two blocks from coming apart, but still allows the blocks to move a bit along the screws (note that the holes should be large enough such that the screws can rotate in the holes, or more importantly move laterally along the holes).
Insert the PTFE tube into the big 16mm hole, tighten the nuts, and voila, you have a working clamp.
[I think I overcomplicated the explanation on that one, sorry.]
[Edit - I just realized the official clamp design doesn't clamp like this... it isn't really a clamp (or rather the clamp isn't used in the long run), more of a fastening device that has screws that actually go straight through the PTFE, holding it in place with nuts and bolts... well, that's depressing, because I was kinda proud of my design... anyway, it can be fixed by simply moving the screws from being just outside of the PTFE tube area, to being just inside of the PTFE tube area... essentially moving the two screws closer to each other (each moves about 6mm, so they are 12mm closer)... some simple changes in construction would be necessary.]
Filament/Screw Holder
Now on to the filament/screw holder. I think they can be created as one piece. It is a bit harder to make, but it is simpler in design and thus smaller and cheaper. The "harder" part means that you'll have to spend more time on it though (and perhaps you might break a piece or two while trying to make it; I still think it would be cheaper, even considering that).
The basic design is a 1cm x 1cm x ?cm rectangular prism. The ?cm means I'm not entirely sure on the length dimension (as stated before, dimensions are up in the air). Anyway, a 3.5mm filament hole and a 3mm screw hole are drilled such that they ever so slightly overlap. The positioning of these holes is up in the air as well; I can't decide on the best locations. Here are a few that I've considered:
1) The two holes placed horizontally in the square cross section, sorta like this:
. ____ . | | . | OO | . |____|The problem with this design is that the piece may break when drilling the holes or at some other time, because the distance between the hole sides and the sides of the 1cm x 1cm square is small: 10-(3.5+3)=3.5/2=1.25mm on each side. Scary.
2) Next I tried putting them in the diagonal, which is 14.14mm in length instead of the 10mm length I placed them in above (pythag theorem/distance formula). It's a bit harder to show in fixed width text, unfortunately. But basically, the distance between the hole edges and the corners would be: (14.14-(3.5+3))/2=3.82mm. Of course, the distance between the hole edges and the square sides is a bit less than this, but it is still better than the 1.25mm in 1). I could calculate it, but it would take a while and frankly it's not worth it (at least right now).
3) Aesthetically (and when building) it might be better to have the filament in the center of the holder:
. ____ . | o| . | () | . |____|
The filament hole center would be 7.07mm away from the corner. The edge of the hole would be 7.07mm-(3.5/2)=5.32mm from the corner. The screw hole would be 5.32-3=2.32mm from the edge. I'm guessing this would be structurally unstable, like 1), but I'm not sure. In any case, the screw can be changed to a 2mm screw, changing the distance to 5.32-2=3.32mm.
4) I like symmetry. How about two screws on opposite sides of the filament?
. ____ . | o| . | () | . |o___|I'm not sure if it would work. But if it would, it would give twice the surface area, spreading the pressure across the filament.
5) If 4) could work, maybe this would work too:
. ____ . |o o| . | () | . |o__o|Four screws, each positioned between a corner and the filament.
4) and 5) might require some synchronization of the screws (I really don't know), and might be totally impractical. In any case, the general idea should work (perhaps with some variations).
6) Oh, one more idea: the problem with 1) was that the wall-hole distance was small and might be structurally unstable. We can increase the distance by increasing the holder's dimensions. I'd like to only do this along one dimension, because this will keep the other one at 10mm, which is easily an acrylic glass thickness.
. _______ . | | . | oO | . |_______|This can also be applied to get the filament hole in the center of the holder.
[There are quite a few more variations, such as a cylinder being used instead of a rectangular prism, but for various reasons I prefer the ones on this shortlist.]
The v1.1 extruder has some half-bearing lands in the screw holder... it shouldn't be too hard to implement these similarly. I'm thinking put them at the ends of the holder, where the hole for the screw is slightly widened on one side (the side opposite the filament hole), allowing for placement of some lubricated thingy. (High-tech lab jargon.)
Now that I am reviewing the v1.1 extruder, it seems that the reason for separating the two pieces was to allow for the use of springs to press the screw against the filament. Well, my design can probably do this too. I think maybe if I make the lubricated thingies long enough, they can contact enough of the screw on both sides. I can drill a hole in the side, that meets the screw's hole where the lubricated thingy would be. Inserting the lubricated thingy into the screw hole, and then a spring into this new hole, the spring can press against the lubricated thingy, which can then shove the screw against the filament. (This would be necessary on both sides.) There are quite a few possible variations.
Filament-/Screw-Holder Holder-Block
Now, to attach it to the "clamp" and thus make it flush to the PTFE tube:
More blocks! A block, say 4cm x 4cm x 0.5cm, with a "square hole" cut out of its center, 1cm x 1cm (the size and shape of the screw & filament holder) is used. This can be made in a few ways - directly cutting the square out of the 4x4x0.5 block is the preferred method, but this may be a bit difficult with common tools. Alternately, 4 or 2 pieces can be used:
For the 4 piece method (probably the easiest method):
1) Cut the 4x4x0.5 into a 4x1.5x0.5 and a 4x2.5x0.5.
2) Cut the 4x2.5x0.5 into a 4x1.5x0.5 and a 4x1x0.5. You should now have two 4x1.5x0.5 blocks and a 4x1x0.5 block.
3) Cut the 4x1x0.5 block into a 1.5x1x0.5 and a 2.5x1x0.5.
4) Cut the 2.5x1x0.5 into a 1.5x1x0.5 and a 1x1x0.5. Discard/store the 1x1x0.5. You should now have two 4x1.5x0.5 blocks and two 1.5x1x0.5 blocks.
5) Positioning the blocks in their original positions and then screwing them together (without passing a screw through the center square "hole") yields the proper shape.
[Note that this is for a 10mm x 10mm filament/screw holder with the filament in the center.]
This block is not intended as a clamp, but rather as a positioning guide.
The clamp for the PTFE tube has 4 holes drilled near each corner for screws. The screws need to be really long (as long as the clamp and the filament/screw holder combined, and then some more). 4 holes are drilled in the new block that coincide with the holes in the clamp. 4 screws are pushed through the holes in the clamp, with the heads on the PTFE tube's side. The new block is slid onto these screws, and made flush with the clamp. Nuts are tightened (a loooong way down) to hold the two together, with a LOT of screw left sticking out. The filament/screw holder should be able to be slid into the square hole in the new block, with the filament hole lining up with that of the PTFE tube.
Biplate Geartrain, Motor mounting, and Filament-Screw Divergence
Now for that two-plate geartrain contraption I mentioned in my last post.
The basic idea is that you take two parallel plates with some space between them (of the material - plastic/wood/whatever), place them perpendicular to the screw, and put a motor and geartrain between the plates, attaching to the screw and rotating it.
The first problem with this design is that if you allow the screw and the filament to maintain their relative positioning by keeping them straight, then when you try to attach a gear or something to the screw, you find that it smacks against the filament. This could either cause jamming or prevent placement of the filament/gear (or some other problem). I think this is why the motor drive/gear assembly in the v1.1 extruder is tilted, and uses a bendable steel wire to transfer the motion.
There are three options for solving this that I see. First, use a gear smaller than the screw diameter. This is rather difficult, and might present problems when the screw moves around due to the springs in the holder (the ones used to allow for slight variations in filament size). The second option is to have the filament bend away from the screw. Basically, one hole is drilled on the lower plate, which coincides with the hole in the holder and which is touching the hole for the screw, and then one hole is drilled on the upper plate, which is slightly apart from the hole for the screw. Essentially, the hole is displaced horizontally forcing the filament to go through the two-plate contraption at an angle. The third option is to have the screw bend away from the filament. This is what is done by the v1.1 extruder. The way the v1.1 does it is not, however, the only way to bend a rotating screw and transfer motion! Personally, I thought it would be simpler to use a universal joint or something similar (http://en.wikipedia.org/wiki/Universal_joint), but then I remembered that you still have screw movement due to the springs... so I figure I'll probably stick with the steel wire idea for now (unless anyone has some better suggestions; I don't really like the idea of having to solder a steel wire to the screw; it's not very low-tech).
Then again, if it isn't a problem to bend the filament as described above, then I'd like to do that (I'm not sure if it breaks the filament/messes it up somehow or if some of the harder plastics can't even be bent like that).
The Mk II extruder seems to bend the filament, so I'm hoping it's feasible.
If it is, then the design will basically be like this:
Filament gets bent as described by the section option. Screw goes straight up through the top plate, and is held in the top plate by a bearing and some nuts and washers (I think if you layer it nut-washer-bearing in plate-washer-nut it should work and still rotate, right?). A gear is attached on the screw, right below the top plate (so that the gear doesn't touch the filament). This gear meets a gear next to it, which is the end of the gear train. The gear train is essentially a bunch of gears on rods (possibly just bolts allowed to rotate between the plates) which decreases rotational speed and increases torque (a series of small gear to big gear meetings, from the motor). The motor is placed vertically between the plates, with a small gear on its rod, which contacts the first big gear in the train (might need to drill tiny holes for the leads, depending on the motor).
Four holes are drilled (this is probably one of the first things to be done) in each plate, coinciding with the 4 long screws from the clamp, and nuts are placed on each side of each plate, holding them in place. It may be necessary (depending on plate size) to put additional bolts through the plate to stabilize the structure.
Cartbot Attachment
I'm not entirely clear on the connection of the extruder to the cartbots, but it should be a trivial matter to make an attachment.
Silly Ending Section Title
So that's about it, unless I'm forgetting something. Electronics etc. can be placed between the plates, if necessary (or perhaps above/below, I think this consideration is more aesthetics though).
Seems simple enough to me. Comments?
Oh, and please don't flame me for being silly/naive. It's only my third day of RepRap knowledge.
Edited 1 time(s). Last edit at 07/20/2008 12:38PM by Joshua Merchant.
|
Bootstrap Extruder [Under Development] July 20, 2008 02:39AM |
Kyle Corbitt Wrote:
-------------------------------------------------------
> That's a lot of text! Sounds like you have some
> interesting ideas - maybe you should try building
> a prototype and reporting back to all of us how it
> works? I'm interested, but you've got quite an
> elaborate plan and it would be easier to visualize
> with a working model.
>
> Good luck - innovation is like currency around
> here!
Heh, thanks. I'm working on the specific designs (getting those actual numbers and stuffs) and I should be done by the end of the weekend (which happens to be in 22.5 hours for me
). I'll probably order any parts that need to be ordered Sunday night or Monday morning, then take a break through Wednesday (I have to take a test then and up until then I'm guessing I'll be "studying"). I'll resume Thursday and by the end of next weekend I should have pictures and cool stuffs to show. If the extruder is working by then, I'll need to start building the cartbot [and the rest of the circuitry]. I might actually similarly make my own cartbot based on the McWire (simplifying shapes for ease of construction, etc.), but I don't know yet. In any case, I feel confident that my designs will work (so far I've got specifics ready on everything but the biplate geartrain, and it's looking nice on paper).
I'd say to wish me luck, but you already did that
-------------------------------------------------------
> That's a lot of text! Sounds like you have some
> interesting ideas - maybe you should try building
> a prototype and reporting back to all of us how it
> works? I'm interested, but you've got quite an
> elaborate plan and it would be easier to visualize
> with a working model.
>
> Good luck - innovation is like currency around
> here!
Heh, thanks. I'm working on the specific designs (getting those actual numbers and stuffs) and I should be done by the end of the weekend (which happens to be in 22.5 hours for me
). I'll probably order any parts that need to be ordered Sunday night or Monday morning, then take a break through Wednesday (I have to take a test then and up until then I'm guessing I'll be "studying"). I'll resume Thursday and by the end of next weekend I should have pictures and cool stuffs to show. If the extruder is working by then, I'll need to start building the cartbot [and the rest of the circuitry]. I might actually similarly make my own cartbot based on the McWire (simplifying shapes for ease of construction, etc.), but I don't know yet. In any case, I feel confident that my designs will work (so far I've got specifics ready on everything but the biplate geartrain, and it's looking nice on paper).I'd say to wish me luck, but you already did that
|
Re: Bootstrap Extruder [Under Development] July 20, 2008 04:49AM |
Quote
| o|
| () |
|o___|
You'll probably find your diagarms work significantly better if you wrap them in code tags. It isn't perfect (leading spaces still get stripped) but internal spacing gets preserved.
ie,
.____. | o| | () | |o___|
Now I'll actually sit down and read it
|
Re: Cost and quality for either Darwin or Seedling July 21, 2008 02:59AM |
GregM Wrote:
-------------------------------------------------------
> Hey Joshua, I like your enthusiasm!
>
> I am also a beginer as of yesterday, and plan on
> getting started on my rep rap as soon as possible.
As soon as possible? "Right now" is the only proper time for anything
> I have thought much about my lineage/evolution of
> my machine and have come up with a very similar
> plan to yours,(start with a repstrap, use the
> mcwire bot, build my own extruder from raw
> materials, then print a reprap).
Cool. We should be able to give each other tips as we progess, especially on the bootstrap extruder (which is not documented at the moment); this will speed up the process for both of us (and for anyone who wants to do the same and takes a look at our forum posts). Eventually, I hope we can get a perfected bootstrap extruder design officially used in the Seedling design, making it much easier for newcomers to get into RepRapping.
> Man i swear you and I are the same mind, you
> basically took my first few quesions right out of
> my mouth, and then our plans about repstrap to
> reprap are exactly the same, its freakin me out a
> little.
Well, the whole point of the RepStrap project was precisely that - the creation of a simpler RepRap that could be used to make the RP parts for the official RepRap (Darwin, currently). If bootstrapping wasn't the purpose of the RepStrap, it wouldn't be called RepStrap (unless someone had a weird sense of humor or an excess of spontaineity).
> I have not thought much about how I will build my
> extruder yet, though I have noticed you have. I
> look foreward to comparing things with you, maybe
> getting some fresh ideas as I have not seen many
> bootstrap extruders yet in my research.
Aye, collaboration (even the indirect collaboration we are currently participating in) will help.
> I encourage you to start a blog on the site, as I
> plan to do soon to loosely chronicle my build.
I probably won't blog or anything like that; I'm betting the majority of my research will be posted here in the forums, for a few reasons (don't ask why - I just typed out the reasons and it would take the average reader quite a while to read it, so I deleted them).
-------------------------------------------------------
> Hey Joshua, I like your enthusiasm!
>
> I am also a beginer as of yesterday, and plan on
> getting started on my rep rap as soon as possible.
As soon as possible? "Right now" is the only proper time for anything
> I have thought much about my lineage/evolution of
> my machine and have come up with a very similar
> plan to yours,(start with a repstrap, use the
> mcwire bot, build my own extruder from raw
> materials, then print a reprap).
Cool. We should be able to give each other tips as we progess, especially on the bootstrap extruder (which is not documented at the moment); this will speed up the process for both of us (and for anyone who wants to do the same and takes a look at our forum posts). Eventually, I hope we can get a perfected bootstrap extruder design officially used in the Seedling design, making it much easier for newcomers to get into RepRapping.
> Man i swear you and I are the same mind, you
> basically took my first few quesions right out of
> my mouth, and then our plans about repstrap to
> reprap are exactly the same, its freakin me out a
> little.
Well, the whole point of the RepStrap project was precisely that - the creation of a simpler RepRap that could be used to make the RP parts for the official RepRap (Darwin, currently). If bootstrapping wasn't the purpose of the RepStrap, it wouldn't be called RepStrap (unless someone had a weird sense of humor or an excess of spontaineity).
> I have not thought much about how I will build my
> extruder yet, though I have noticed you have. I
> look foreward to comparing things with you, maybe
> getting some fresh ideas as I have not seen many
> bootstrap extruders yet in my research.
Aye, collaboration (even the indirect collaboration we are currently participating in) will help.
> I encourage you to start a blog on the site, as I
> plan to do soon to loosely chronicle my build.
I probably won't blog or anything like that; I'm betting the majority of my research will be posted here in the forums, for a few reasons (don't ask why - I just typed out the reasons and it would take the average reader quite a while to read it, so I deleted them).
|
Bootstrap Extruder [Under Development] July 21, 2008 02:54PM |
nophead Wrote:
-------------------------------------------------------
> The original design for the extruder used direct
> drive and that is the version I am using
> succesfully at the moment with just a few tweaks.
> I have made all the parts for a Darwin bot with it
> and Vik Olliver also made his child machine with
> the direct drive version. So no need to make
> gears.
Cool! I had heard about using "direct drive" before, but I didn't think to look up the definition until now.
> I recommend if you are trying to bootstrap it, the
> simpler design is a better starting point.
Aye, I've been trying to get it as simple (and cheap) as possible without extending the construction time to some silly amount. Now that I don't have to make gears (and the gearmaking device itself), it should take considerably less time.
> I bootstrappped it with a milling machine, so if
> the McWire is stiff enough to mill plastic you can
> make all the extruder parts (the older version)
> with that.
Interesting, I didn't think of that. I suppose I could build the cartbot and Arduino electronics first and attach some milling head (I'm guessing some simple drill styled device) to create the custom extruder parts, instead of having to do it by hand. (Unfortunately, this will delay the construction of my extruder, as I will be making the cartbot and electronics before I make the extruder, obviously.)
Thanks.
I have one question though. How exactly can I connect my motor to my drive screw? The shaft coming from the motor is a bit less than 2mm in diameter, and about 7mm long. I'm hoping I can just drill a 2mm (or maybe 1.75mm) hole in the drive screw and shove the motor's shaft into the hole, but I'm not sure if there would be enough friction between the hole walls and the motor's shaft to spin the screw without slipping. I'm considering applying a bit of glue to the motor's shaft and then shoving it in, or perhaps shoving the shaft into the hole and then applying some solder (the kind I use for circuitry). Not sure how strong any of these connections would be.
Any suggestions? What's the traditional method for this kind of thing?
-------------------------------------------------------
> The original design for the extruder used direct
> drive and that is the version I am using
> succesfully at the moment with just a few tweaks.
> I have made all the parts for a Darwin bot with it
> and Vik Olliver also made his child machine with
> the direct drive version. So no need to make
> gears.
Cool! I had heard about using "direct drive" before, but I didn't think to look up the definition until now.
> I recommend if you are trying to bootstrap it, the
> simpler design is a better starting point.
Aye, I've been trying to get it as simple (and cheap) as possible without extending the construction time to some silly amount. Now that I don't have to make gears (and the gearmaking device itself), it should take considerably less time.
> I bootstrappped it with a milling machine, so if
> the McWire is stiff enough to mill plastic you can
> make all the extruder parts (the older version)
> with that.
Interesting, I didn't think of that. I suppose I could build the cartbot and Arduino electronics first and attach some milling head (I'm guessing some simple drill styled device) to create the custom extruder parts, instead of having to do it by hand. (Unfortunately, this will delay the construction of my extruder, as I will be making the cartbot and electronics before I make the extruder, obviously.)
Thanks.
I have one question though. How exactly can I connect my motor to my drive screw? The shaft coming from the motor is a bit less than 2mm in diameter, and about 7mm long. I'm hoping I can just drill a 2mm (or maybe 1.75mm) hole in the drive screw and shove the motor's shaft into the hole, but I'm not sure if there would be enough friction between the hole walls and the motor's shaft to spin the screw without slipping. I'm considering applying a bit of glue to the motor's shaft and then shoving it in, or perhaps shoving the shaft into the hole and then applying some solder (the kind I use for circuitry). Not sure how strong any of these connections would be.
Any suggestions? What's the traditional method for this kind of thing?
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