Kyle Corbitt Wrote: ------------------------------------------------------- >... > - A longer extruder head, leading to decreased > build area unless the extruder mount is > redesigned. >... > Thoughts? Well, the current clamp which holds the extruder and connects it to the carriage could be modified from a flat shape like . ___ to something like . __ . | . _| with the exby Joshua Merchant - Mechanics
nophead Wrote: ------------------------------------------------------- > Another problem with this idea is that the > filament moves very slowly, so unless you have a > very high resolution encoder you only get feedback > relatively infrequently. That makes it harder to > get a stable feedback loop as there is a big lag > between changing the motor PWM and seeing its > effectby Joshua Merchant - General
Well, this is rather good news I think. It gives me a convenient excuse to not use glue (for some reason, I seem to hate glue) - the fact that it wouldn't work anyway . The countersink and 0-80 flat head screws (#91781A071) should work fine though, provided I'm careful when countersinking.by Joshua Merchant - Mechanics
Okay, regardless of whether or not this is what Demented had in mind, this is what I plan to do: Instead of the 96" of channels (4 13" lengths, 2 21" lengths ): 1/2" plywood (yes, some of the scrap from the 1/2" backplate) is cut into 3/4" wide strips. 1/8" thick 1/2" wide PTFE bar (#8735K11, the same as used for the bearings) is cut into 1/8" wide strips (4 1/8"-wide strips out of a 1/2"-wide bby Joshua Merchant - Mechanics
nophead Wrote: ------------------------------------------------------- > The spring tension required varies with the type > of plastic and is quite critical with the current > extruder design. Too little and the screw thread > fails to bite into the plastic and propel it. Too > strong and the the friction is too high for the > motor. > > The values in the wiki are for PCLby Joshua Merchant - General
Demented Chihuahua Wrote: ------------------------------------------------------- > Oh, don't bite the bullet on this one. I have the > afore mentioned expensive channel and angle set up > on my repstrap. Works okay but there is still a > bit of friction there that I don't like and that > we could reduce and save ourselves some angle > doing it. Alright. Thanks for the info in yby Joshua Merchant - Mechanics
.] Does anyone know what I can use as a suitable replacement of the 1/8" thick aluminum angle and channels in the McWire ? The angle (#88805K57) is $25.95 and 96" long (I only need 43"), and the channel (#9001K34) is $22.63. The total is $48.58, which is significant compared to the total price of the project. Anyone have any ideas for alternatives? The angle seems to just be a structural suppby Joshua Merchant - Mechanics
peteredworthy Wrote: ------------------------------------------------------- > For the heater barrel a brass bolt, or cap screw > may be cheaper and more available. Hacksawing the > head off is very easy with brass and the softer > metal should make drilling the centre hole easier > as well. > > My guess as to a problem with any poor heat > conductor is it becomes hard toby Joshua Merchant - General
Forrest Higgs Wrote: ------------------------------------------------------- > Good luck. ROFLby Joshua Merchant - Controllers
nophead Wrote: ------------------------------------------------------- > They don't need to be precise because you adjust > the tension with the nuts, but they do need to be > very strong, e.g. 1.5mm x 9mm x 25mm.. I only use > two at the bottom and space the pump halves at the > top with two or three washers. I got them from the > lid hinges of an A3 scanner. In that case I mayby Joshua Merchant - General
I'm trying to finalize my shopping list for my Seedling, and I'm going to be replacing the steppers with encoded DC motors. I'm planning on starting with the 101-5433-EV Mountain Switch encoders (or perhaps one of the slight variations), but I don't know exactly how I'm going to interface them with the rest of the system, and thus I don't know what parts I need to order to make them work. The oby Joshua Merchant - Controllers
Okay now that I've got a clear idea of my components lists for the cartbot and electronics (I hope I'm not forgetting anything in those), I think it's time to make a rough list for the extruder. Basically, it will use the standard heated barrel, connected to a plywood frame, using the same GM3 as the standard extruder. It will be direct drive, with a bend in the filament. Anyway. The drive scrby Joshua Merchant - General
Kyle Corbitt Wrote: ------------------------------------------------------- > I hope you're talking about the extruder here, and > that you realize that you will absolutely without > question NEED to put encoders or some kind of > feedback on all three axes if you hope to use them > with DC motors... Yeah, I figured I would need the encoders on the axes, but I also want to experimeby Joshua Merchant - Controllers
Some great news! SparkFun's claim that the SN754410 is a suitable pin-for-pin replacement of the L293D seems to be supported by other sources. says "L293D from Texas Instruments is rated at 600ma and includes the diodes" and "SN754410 from Texas Instruments is rated at 1A and does have the clamping diodes." "Duncan" says "...incidentally, this chip has a higher current handling (1A vs. 600mA)by Joshua Merchant - Controllers
Ru Wrote: ------------------------------------------------------- > Using cheaper motors and gears really impacts you > when moving the head short arcs... you need to run > the whole thing so slowly that it becomes > extremely tedious to use as a tool. Well, you get what you pay for. Having to move exponentially more slowly for a lower price is just expected. > Forrest has a lotby Joshua Merchant - Controllers
Kyle Corbitt Wrote: ------------------------------------------------------- > To me, the goal is to start with something that > *works* and try to reduce cost and complexity from > there. People keep saying that! I wonder why... > It will be no fun trying to determine > whether your persistent encoder error is coming > from a flaw in the extruder design or a loose bolt > inby Joshua Merchant - Controllers
> It's not *that* much more expensive, and much less of a hassle. The 10-bit (1024ppr) encoders are $12 each (or more). A 12ppr encoder costs $0.54. If you buy 4 (one for each axis, and one for the extruder), that's $12*4=$48, compared to $0.54*4=$2.16. That's $45.84 more. It is good to know that it's possible though. As to the inaccuracies from backlash... you get what you pay for, I guess.by Joshua Merchant - Controllers
Kyle Corbitt Wrote: ------------------------------------------------------- > Perhaps not the GM3 (I get the feeling that it's > too slow and weak) but there are many other DC > motors you can get for cheap that would work the > same way. This is a valid strategy, and one that > Forrest has pursued before. Check out his blog > archives for more info. Be warned though that inby Joshua Merchant - General
Hm... based on the limitations you just listed, I think I'll put the idea on the shelf for now. I'll probably come back to it after I get a few things working on my own setups, but for now it's too theoretical, too challenging, and not necessary enough. Oh well.by Joshua Merchant - RepLab Working Group
This idea just popped in my head while thinking about rotor position encoders (and reading that post about the mouse encoder). Why can't you just attach a gear train to the shaft to be measured, using a mechanical advantage to achieve more accurate measurements? That is, you put a big gear on the shaft, and have it contact and spin a small gear. Say the small gear completes a revolution every,by Joshua Merchant - Controllers
peteredworthy Wrote: ------------------------------------------------------- > Clamp diodes on the inputs aren't the same as on > the output, each protects different parts of the > chip. > The good news is that clamping diodes are very > simple to add as they can be added to the wiring > leading to the stepper. Each of the four stepper > wires needs two diodes connecting toby Joshua Merchant - Controllers
Hm. Isn't traditional waterjet cutting equipment designed for cutting metals? If we were only going to cut thermoplastics, then couldn't we scale down the equipment? Wouldn't they require much lower pressures? Oh, and remove abrasive materials and just use water (to not make such a mess as described by R.B.)? As to the depth control... there is a max depth at which a waterjet can cut. What doesby Joshua Merchant - RepLab Working Group
I searched for the L293D on SparkFun and came up with the SN754410 . They say it "is a pin to pin compatible replacement for the L293D". It's also sold by Mouser ($0.10 cheaper than SparkFun at $2.25/unit). So can I just use this instead of the L293DNE? I don't see why I couldn't. Am I missing something? The thing that doesn't make sense is that they (Texas Instruments) would make essentially thby Joshua Merchant - Controllers
It just occurred to me that the stepper motors are more expensive than I thought. I don't mean that I miscalculated somewhere, but rather that I failed to mention the fact that these are a prime source for the high cost. The stepper motors themselves are $25 each, and each one needs a stepper motor driver, which are about $27 each. And you need 3. The total cost of using stepper motors will be $1by Joshua Merchant - General
greenarrow Wrote: ------------------------------------------------------- > There's always the option of interlocking slots, > and a little glue to hold it. Not quite as elegant > but simple and easy Or, similar to this idea, you could design a standard connection with an opening for a heating element (like a soldering iron or something) such that when you insert the heating element, thby Joshua Merchant - Mechanics
The posts about Big Blue Saw's free parts day (http://forums.reprap.org/read.php?1,14888 and ) led me to Big Blue Saw's site, which has information on their laser cutting and waterjet cutting methods. Laser cutting seems to be getting some attention here already, but the waterjet cutting looked really cool. I'm thinking that it may be cheaper to implement some simple water jet toolheads than toby Joshua Merchant - RepLab Working Group
Hm. I'm not entirely sure I understand your post, Mr. Attwood, but it sounds like you're saying that if I melted granules in the primary chamber and transferred them directly to the secondary chamber as I described, then the fluid will be a suspension of air bubbles in the liquid thermoplastic, which, when pumped through the nozzle, will extrude inconsistently and allow bubbles to distort the buiby Joshua Merchant - Mechanics
Andromodon Wrote: ------------------------------------------------------- > I would just like to add my two cents. > > There has been a lot of talk about putting > heatsinks on the heater barrel in this and in > other threads. Won't such designs require more > power and heat the room significantly? Trying to > heat one end of a metal pipe (even if it's > stainless steelby Joshua Merchant - Mechanics
I'm back, yay. nophead Wrote: ------------------------------------------------------- > The main reason for warping is that hot layers are > extruded onto cold layers that have already > frozen. They in turn freeze but they are still hot > so they contract afterwards. This puts the layer > below under stress leading to it curling upwards. Is heating the object feasible? That is, hby Joshua Merchant - Plastic Extruder Working Group