The Darwin specified a dual shaft for the Z axis because it needed the shaft on the opposite side of the motor from the mount; you could get around it with long bolts though. No need for dual shafts on Mendel; I do like to use 5 kg*cm Nema 17's for my extruders, but 3 kg*cm should be OK. Eventually someone will gear the extruder down even more, reducing the torque required even further. Wadeby Wade - Stepper Motors, Servo Motors, DC Motors
I use 5 kg*cm steppers on mine, but you can make do with less if you don't want to extrude quickly. Adrian has a nema 14 extruder design in subversion, but I haven't heard of anyone using it yet. How much torque do your steppers have? Wadeby Wade - Reprappers
Correct; try to measure the temperature with a known temperature. The best way is to insert a thermocouple down the barrel and measure the temperature there.by Wade - Plastic Extruder Working Group
Bruce, that's a great idea - the trapezoid (the two horizontal bars are still parallel, right?) uses the smooth Z rods for cross bracing; a very elegant solution. Will try it myself. Wadeby Wade - Reprappers
That does sound nice - and it's pretty quick too. Nice to see ever more copies of my extruder out there! Wish I'd included a "send me beer" clause in the license. But then I'd have to send half of each beer to Adrian, then Nophead, etc down the line... As for the wobbling of the Mendel, I don't think switching steels will get you much. Stronger steels are stronger - they can take higher loby Wade - Reprappers
Still required as of the last official release. Can't say what the current version in svn does though.by Wade - Firmware - mainstream and related support
A quick fix would be to insulate the heater barrel and most of the nozzle (just leave the tip clear) with some fibreglass insulation - that should keep the tip from cooling too much. If you put 5 mm or so of insulation on, you can wrap it with some electrical tape. It wouldn't hurt to calibrate your thermistor either - those things are notorious for being the wrong value or having the wrong tabby Wade - Plastic Extruder Working Group
There are mesh modellers like Blender and Rhino (in beta at least) that work well on a Mac, and I believe OpenScad will run, but it's more of a scripting language than traditional CAD. Autocad has a version out now for about $4k, but I have had good luck running Alibre ($100) in either a VM or with bootcamp and windows 7. It was pretty slow with an XP VM though, but it worked fine when bootcampby Wade - Reprappers
Check for ground loops, especially if you're using a laptop to run the RepRap. Make sure everything is plugged into the same AC circuit, and then look for AC signals with your multimeter between the various grounds. Grounding the chassis on my laptop helped a lot with an older version of the circuit boards.by Wade - Reprappers
Nophead is correct; although mine usually turn out to have a diameter of 6.2 mm or so, but I don't cut them very deep. Additionally, varying nozzle sizes will result in different E steps/mm values - I use 2.02 as a starting point, and then vary the E parameters in Skeinforge to get the flow rates right. There's an overly complicated spreadsheet at the end of my wiki page that may or may not helby Wade - General Mendel Topics
I'm interested, but I have a few questions - First off, are these open source? I was looking for schematics, couldn't find anything on the webpage. They look pretty similar to the standard reprap electronics. Also, is the mosfet one of the protected ones? Doesn't matter, as I have protected ones I can replace it with, but it would be nice to know. Thanks. Wadeby Wade - For Sale
I bought cheap M8 shoulder bolts, fairly soft, and used equally cheap taps on it. I didn't even use a real jig; just two skate bearings held firmly (but not firmly enough to lock the bearings), and spun the tap in a hand drill. Details are on the wiki page; I've made several now without too much trouble. The one thing I would be careful about is hobbing the threaded part of the bolt or rod - oby Wade - General
240 deg C might help too, come to think of it.by Wade - General
Reduce your first layer height, turn off the fan, switch to PLA, or try a heated bed.by Wade - General
K type thermocouples have a sensitivity of 41 µV/°C, so that's about 0.01 V change over a 300 deg C range - you need an amplifier to detect that with the Arduino analog inputs. Lots of cheaper alternatives though: I just picked up some Max 6675 breakout boards from Adafruit - $17.50, plus the cost of the thermocouple ($10). Haven't tried them yet, but Adrian already has code to read the digitby Wade - Reprappers
#1 - set your motor current more carefully next time. I've been running nothing but PLA extruders for years and have not melted one yet. A warm motor is fine, but if it feels hot, turn down the current. As for hot ends, I'm looking for a better one as well, although both my PTFE hot ends are still working fine. One did fail two years ago when I had a thermocouple come loose, causing the hot eby Wade - General
Ah, yuck, notepad. Notepad isn't showing the end of line characters. Probably what happened there is there is a configuration.h.dist, which is the generic file. You have to rename it to configuration.h; the .dist is to keep it from over-writing your personal configuration when you upgrade to a newer version of the firmware.by Wade - General
Interesting - I haven't used ABS in years, so can't really say how well it works. Any chance you could hook up a scale of some sort and do some pull tests? Wadeby Wade - Reprappers
As an aside, the bicycle pedals are an interesting case - the left pedal turns clockwise relative to the crank, which would tend to loosen a left hand thread in a friction only situation, but due to precession from the rotating moment load, it actually tightens a left hand thread. I've used that same precession trick to assembly tiny nuts inside of watches where I could only touch the top of theby Wade - Mechanics
I don't think mirroring will work very well, as you don't want too much tension on the hobbed bolt - you only want to keep it lined up with the filament slot and the gears. If you tighten it up, the skate bearings are probably going to bind, and you might even collapse the main block over time. Plus, if it tightens up over time, the alignment will shift. Better to leave it a little loose, andby Wade - Mechanics
Your extruder flow rate looks too low, and perhaps the flow rate is not constant. Try building some simple cubes, make sure you get good smooth extrusion. Building solid parts will tell you right away if your density calculations are off - make sure you watch it carefully, as a solid part printed at too high a density will cause the head to start ploughing plastic, possibly breaking something.by Wade - Reprappers
Hey, if it's only the opto's you need, you could just use microswitches instead; they work better in some situations, and can be wired up with a resistor or two, no pcb required.by Wade - For Sale
Send me your parts list, and I'll send you a price. Figure about $60 plus shipping, unless they're all big parts. Wade wbortz at gmail dotcomby Wade - Wanted
Sounds like your Z min endstop is not working right.by Wade - Reprappers
You'll have to ask the Techzone guys to be sure, as I haven't used those, but that's probably it. You also need to set the current in the gcode, assuming you're using Adrian's firmware. Wadeby Wade - General Mendel Topics
That's a new one - I've never seen anything quite like that! It looks like it's extruding in stops and starts - is the extruder running smoothly? Maybe you've got some extra large gear teeth that are causing it to skip regularly? Or your stepper current is set too low, causing the stepper to skip, or too high, causing the driver chip to periodically overheat? Got any photos of the extruder itby Wade - General Mendel Topics
Kurtis, just to chime in here, I think having good temperature measurements is key. It sounds like you're having problems with your thermistor; see if you have any loose connections anywhere. I can't speak for thermistor circuits, but I usually get less than 1 deg C of noise with a thermocouple; any more and it's usually an indication of a bad connection somewhere, or a short between the heaterby Wade - General
Hey Justice, send me your address and I'll mail you that extruder. Freshly printed one sitting in my desk. Wadeby Wade - Canada, Vancouver RepRap User Group
Some of the older RepRap firmwares will run with a DC extruder (I used several a few years ago), but it's not a great idea unless you've got an encoder on your dc motor - you have to spend a lot of time calibrating and recalibrating, and you never really know how much plastic your extruder is putting out. Plus there's the ooze problem... Have a look at the older firmwares in the sourceforge dirby Wade - Firmware - mainstream and related support
Very nice work! Glass seems like an ideal material for extruders - it's slippery at the transition point, and the thermal conductivity is fairly low - only 4 times higher than PTFE. And it should be far stronger and more stable than hot PTFE. Nophead's experiments indicated that the friction from the transition point is much higher than the friction from the nozzle, at least for ~0.5 mm nozzleby Wade - General