McWire Successor

Great work Arvin, your video helped me understand significantly what you are trying to accomplish with the cable-auger. I think this really has the potential to serve as a good alternative to the other linear travel solutions. I'm considering adding it to my wolfstrap design when I finally get to building. Please keep us appraised on it's functionality.

On the Wolfstrap front, I just came across another similar drawer-slide design, the BrandRap

Wonder why he calls it BandRap? Wish he had a movie of it printing. Is there a link to a blog?

BrandRap (I assume) is named after it's creator, whose first name appears to be Brando (maybe Brandon, it's not quite clear from the flickr account)

I am continuing to find a number of RepStraps based on drawer-slide linear supports, which leads me to think that they're pretty reliable. Here's a few:

RepRap += 1;
Mothra CNC
PingIsTheCoolest RepStrap

On the otherhand, I wonder why, if so many people have built with drawer-slides, has there not been more mention of this. I see a lot of evidence online about them, but very little discussion on the forums here about Repstraps that are not McWires (save for Hydraraptor, Tommelise, etc.)

Anyone care to chime in about this? I'm gonna guess it's not drawer-slid related as much as it is something else like loss-of-interest, unavailability of materials, lack of support in the community, and so on and so forth? Do I have that all wrong? Where did these people go?

Anyone care to chime in about this? I'm gonna guess it's not drawer-slid related as much as it is something else like loss-of-interest, unavailability of materials, lack of support in the community, and so on and so forth? Do I have that all wrong? Where did these people go?

Maybe Thingiverse? It tends to eat most of our users-with-working-repraps.

On the otherhand, I wonder why, if so many people have built with drawer-slides, has there not been more mention of this.

Simple. They got it to work, they're happy, they don't make noise about it. With McWire, most people don't get it to work, so there's lots of noise.

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

The problem with drawer slides is that they have lots of play in the sideways direction (when mounted like drawer).

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> The problem with drawer slides is that they have
> lots of play in the sideways direction (when
> mounted like drawer).

I wonder if that could be practically handled with a tensioning spring, to hold the slides a certain direction. I don't know what the cutoff point is in terms of slides - you can certainly buy exceptionally well machined slides. They cost a fortune of course.

I tried drawer slides and wasn't happy with the stability. Was originally trying to make a cnc that could also be a reprap.

I'm trying to make something that is cheap and easy that just works.

This cable drive might be the ticket. It's cheap and easy (if you have three hands). The makeup wire won't be strong enough to take the constant flexing but fishing line might be. Won't need to be very strong, so will have a very small diameter. That will also make the pulley much shorter. I have a new spool of Firewire. Somewhere.

I can't find my fishing rod!

I kind of feel like I'm butting in here, but here it goes:

I'm just beginning to build my repstrap. I have stepper motors and access to a near-unlimited supply of things like aluminum rail (my dad does demolition and we have basically a junkyard in our backyard) plus there is a junk electronics shop (they buy things that don't sell well in bulk and sell the components) near my house. I also have tons of time and will document/take pictures.

I was thinking about building a McWire but I'm not too excited about building something that will take ~80 hours to print Mendel, but I do really like the aluminum rail/ball bearing design (Also, the store by my house sells skate bearings for 35 cents..). Before I start, though, what kind of designs should I experiment with?

I am just about to start building my McWire offshoot. If you have read the rest of this thread, I think most of the recent talk is about using cable or cogged belt drive instead of threaded rod drive to improve the speed. Or you can build the wooden dowel with much coarser thread pitch to get fast speed.


If you have lots of aluminum and time, you can increase the accuracy of the stages by using round rod or using several bearing on three sides of the box channel, similar to what bjsquared is doing more accurate linear bearings. There are also several people using drawer slides, but I fear the accuracy drops off as you travel away from center.

I am also planning to build one with welded 3/4" or 1" steel box tubing. It should actually be cheaper than the water pipe (although your demolition resources may make the framework free) and also be stronger. But a welder is needed.

Hope this helps.

Mike

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

The wood dowel has been canned. It's TOO FAST.

The opposite of the problem with the threaded rod.

Now I'm looking at a 5/16"/ 8mm smooth rod. That will slow it almost in half and actually fit the skate bearing.

Also eliminate the slight eccentricity I was getting with the dowel.

Congratulations on successful experimentation! Not all experiments confirm the original hypothesis, but all well done experiments result in learning more about the topic. Thanks you for sharing your results with us.

Mike

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

I was wondering about that, reduce the angle so you have more steps per movement?
Arvin Wrote:
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> The wood dowel has been canned. It's TOO FAST.
>
> The opposite of the problem with the threaded rod.
>
>
> Now I'm looking at a 5/16"/ 8mm smooth rod. That
> will slow it almost in half and actually fit the
> skate bearing.
>
> Also eliminate the slight eccentricity I was
> getting with the dowel.

freds Wrote:
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> I was wondering about that, reduce the angle so
> you have more steps per movement?

Reduce the angle as from 1.8 degree/step to .9? I could also use half step or even 1/16 step but since the wood dowel was a little wobbly I'll try a smaller shaft first. I did change the timing delay per step and could get it to go slow but it became horribly noisy and almost no power.

Maybe freds meant that you could try putting a tighter pitch on your dowel?

jbayless Wrote:
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> Maybe freds meant that you could try putting a
> tighter pitch on your dowel?


Pitch?

I once heard a quote. Something like: "The only thing separating the English and the Americans is a common language."

Arvin Wrote:
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> I once heard a quote. Something like: "The only
> thing separating the English and the Americans is
> a common language."

Actually, if I remember correctly the quote was:

Quote
George Bernard Shaw
Two peoples separated by a common language.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Yes rather then taking a 15 degree cut, take a five degree cut. I have read the problem with high fractional micro stepping is sometimes its an average in that the motor is not guarteed to move.

So rather then taking a 15 degree cut, take a five degree cut. I have read the problem with micro stepping is sometimes it’s an average in that the motor is not guaranteed to move on any particular micro step.

Try to come up with a ratio that has the same number of half or full steps per millimeter as the belt solution. Another target is a good medimum step rate for the motor when printing at 16mm per second, with possibly 32mm per second as the top end speed.

The basic problem with using a bolt in the McWire is that it's 16-20 turns per inch, where as most movement stages have ball screws that are 5 turns per inch range. At the higher TPI your stepper motors have to be really "stepping along" to get any decent movement speed.

jbayless Wrote:
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> Maybe freds meant that you could try putting a
> tighter pitch on your dowel?

Quote
George Bernard Shaw
Two peoples separated by a common language.


@Bob Morrison ... Ah yes...I stand corrected.

@freds...The dowel that's being replaced by a bolt is in the drive mechanism but it wraps a cable around it to pull the stage. It's turned by the stepper to wind the cable not to move the stage directly.

the movie is on youtube at [www.youtube.com]
here I'll stick it in.

Oh! You're using it as a capstan. That's very smart. Sorry, I misunderstood... I thought you were using the dowel as a leadscrew.

In that case, perhaps try using a thinner dowel?

@Arvin looks like you've had great progress while I was away!

Somethings you might consider trying:

Instead of wire or cable consider using Dacron fishing line. It is woven very strong, has minimal stretch and has excellent grip when wrapped around things. I bet you would only need 2 or 3 wraps around the dowel.

How about notching the dowel or inserting a smaller section of dowel in the middle to gear it down and prevent the travel up and back?

How about an aluminum rod with sandpaper or some texturing?

Auger now has some NEMA17s but still need to couple it to the drive screws. Life has been getting in the way but perhaps this weekend I will be driving the XY tables with RepG.

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B^2 : [replibot.blogspot.com]

~~ We Are The Factory ~~

Question for the group:

Is the McWire bot the "official" bot because it's the best choice/most reasonable/made by Zach, or simply because it was the most well-documented at the time... It seems like the old page that listed RepStraps listed the McWire along with Hydraraptor, Tommelise one or two others, so I'm trying to determine the official-ness of the McWire.

Because Mcwire is the easiest completely self sourced way to build a printer.

It's not really supported anymore because it doesn't do a very good job printing Mendel parts, that's the reason for the push for a successor.

All RepRap is really looking for is a cheap printer that is completely off the shelf, that can produce the RP parts for the RepRap flagship printer of the time.


I think the long term goal is to make it possible, with no access to RP parts for you to go from

Design->Hardware store->Mcwire->Mendel->Next generation

The next generation printer will not necessarily be printable by a Maker bot or Mcwire.

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repraplogphase.blogspot.com

I've been fiddling with that idea for three years. Never came up with a replacement for the expensive timing gear/belt drive that was fast enough to be acceptable.

I think the cable drive is going to be the one. Have spent the last week going through several versions of a machine that can be built with a jig saw and a drill.

Here's a look at the latest. Several iterations and I'm back to almost what I had to start. Lots of megs lighter on the hard drive though.

Thoughts?

From reprap

The sketchup file is: [dl.dropbox.com]

I am also working on a set of instructions on how to make the extruder without a lathe. I was able to drill the copper mig welder tip to 5/32" and within an 1/8" of the end without popping out somewhere. I was not as good on drilling the 3+ mm hole in the PTFE. Pictures and blog hopefully coming soon.


Arvin, once I build a fairly standard McWIre but with cable drive, I will try plywood variants. I think for quick and easy the draw slides are a possibility. But the old fashioned direct drive to threaded rod will be cheaper and easier to make than the cable drive with pulleys and guides.


Mike

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

Hmmm. I had all the parts to make a standard McWire. Maybe I should just dig them all up and start over but use the cable drive.

I bought some 50lb test braded fishing line. No luck. It started out great but seemed to flatten and then rolled up on the other layers. Still worked but the steps would not be the same length for those versus the lower layer.

My next thought is kite string. I'm worried it will do the same thing. Mayb I just need to find a source for really thin steel cable. Did some searching earlier with no luck. I'll try again.
Arvin

Alvin,
I may be thinking of larger diameter pulleys than you are. For my drive pulleys, I am planning on using the 1 11/16" plastic sliding glass door wheels plastic pullies. I plan to put a plate on the other side of the pulley with a set screw for the stepper motor shaft, then bolt the plate to the pulley to drive it. I think that the 1/16" steel cable should work around that. If not, then I will have to re-think that. I should have this going in the next few days.

Mike

Yeah. The pulleys I used are only 1" diameter.

Post a picture of what you're doing. I found some 1/32" steel cable at McMaster-Carr that might work. Minimum length to buy is 50 feet at $0.07/foot and 185lb strength. I will buy some when I can remember what the other thing was I needed!

I've been building a McWire over the last couple months from purely what I've found in the forums and various blogs. I just started documenting all of my findings in a blog of my own. In the next couple of days I'll be adding my experience in converting McWire to a belt drive.

http://shayfir.blogspot.com/

PS, I just want to say...great job everyone. The Reprap community is the greatest I've ever seen.

Nice work, Safyr. I also cut my lexan with a table saw. To get the rounded corners I used a small, wood cutting bandsaw. With a narrow blade, it actually worked quite well. I just started my blog as well.

Blog Team Open Air

Mike

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Team Open Air
Blog Team Open Air
rocket scientists think LIGHTYEARS outside the box!

How big of a hurdle is inverse kinematics for a delta bot? This McWire successor costs $70 and can be made with several servo's, several hours, and virtually zero tooling:
[letsmakerobots.com]

or the Festo iFab if you are looking for a bigger work envolope and prefer steppers:
[www.youtube.com]