Why low thermal inetria? I thought the flow was started and stopped by reversing the motor. In which case don't you want the barrel at a constant temperature which is aided by high thermal mass?by nophead - Reprappers
In the meantime it is very easy to download them. You don't need SVN you can just browse and right click download.by nophead - General
The extruder is in the SVN repository here: STLs and AOIsby nophead - General
I have no experiance of this but I think Paraffin is the recommended lubricant for aluminium.by nophead - Reprappers
Zach, No it was lying around on my desk in a room with a north facing window so it never got any direct sunlight. I doubt that it ever saw anything above 25C. One possibility I have thought of is that perhaps I bolted it on before it had finished shrinking, leaving it under tension against the metal. When I removed it it was allowed to relax and so no longer fits.by nophead - General
As promised I made a new pen holder in the microwave. Conclusions: Well I wouldn't recommend microwaving as a way of melting PolyMorph because it is not even enough. The outer edge, where it is in contact with the glass dish, is a lot cooler. Also it does not absorb microwaves anything like as well as water does. I think most of the shrinking and curling occurs when it first cools down but I caby nophead - General
I will be doing something very similar soon. I need to change the RepRap software to send Ethernet UDP messages to my machine. I am not a Java programmer but I am a professional programmer in C, C++ and Python. I should be able to hack Java well enough for my purposes. I will post my observations / code when I do it so it might be some help to cncreprap if you are prepared to wait a few weeks.by nophead - Reprappers
Forrest, Vic, The best "before" image I have is here but it is taken from the wrong angle to show the flat surfaces and it was already a couple of weeks old by then I think. The bottom and back faces were flat and at right angles when I last used it though because the pen was locked solidly. Now it spins around the single bolt because the back face is no longer in contact with the metal. I cby nophead - General
Hot water is used to melt it. The instructions say to put the granules into hot water at 62C. When it fuses and turns transparent remove it with tongs and sqeeze the water out. I found it hard to melt with water at 62C so I used water straight out of the kettle. I assumed the water was only mechanically combined, not chemically but then I know nothing about chemistry. I might try microwaving itby nophead - General
Here is the after picture I think I first used it the day after making it so it should have cooled by then and I think it was still flat at that point. It was definitly stressed when cast because I pushed it into the corner of the metal and held it there while it set. I was a bit worried at the time that I had squeezed all the water out. I suppose I should make another one and monitor it.by nophead - General
No but I think it has. I just removed it and had a close look. The bottom edge, which should be perfectly flat as it was cast against the sheet metal, is now quite curved. I don't think it has seen any heat. The room window is north facing.by nophead - General
I made a pen holder a few weeks ago out of PolyMorph, you can see it here . I made it by pressing it into the corner of a folded sheet of metal while it was warm. When it had cooled I drilled a hole through it and the metal and bolted in on. As I remember it was a perfect fit. I removed it and left it on my bench for a few weeks. Now I have refitted it and it seems to be lose. I'd say it has shrby nophead - General
Hmm, I think that is illegal in the UK, it's called defacing coins of the realm. Not sure what the sentence is.by nophead - General
Hi Joost, As an alternative to trapped nuts in wood you could try the method I used here: . I just drill a hole at right angle to the path of the bolt and fill it with molten polymorph. When it sets I drill it and let the bolt tap a thread for itself. It spreads the load into the wood quite well. Similar to a system with captive metal cylinders used on Ikea furniture. Chrisby nophead - Darwin
ZachHoeken Wrote: ------------------------------------------------------- it *may* be possible to treat them as bipolar motors, but YMMV. You can use bipolar motors with unipolar drives but not the other way round. Also, I think this motor is too small. Seems to be a floppy drive motor, only 1.65 in square. I doubt that it has enough torque and the shaft is smaller and it has 100 steps ratherby nophead - Reprappers
Forrest Higgs Wrote: ------------------------------------------------------- > Given how fragile the nichrome wire is it's > probably more sensible to just have > interchangeable Mk II's. Yes that bit has always looked fiddly and fragile to me. That is why I intend to have a go at making an induction heater. That way you use very thick wire and it does not need to be thermally coupled tby nophead - Reprappers
But if your next batch of filament is bigger then you are in trouble. The filament needs to come with a stated tolerance and the hole needs to be a bit bigger. Does anybody know how much gap we can tolerate? We might need to have several interchangeable barrels.by nophead - Reprappers
I found a source of 3.1, 3.2 and 3.3mm drill bits here They also have long 1/8th bits which would be good if your filament is not oversized like mine.by nophead - Reprappers
Mike, Would these composites be suitable for making something very rigid, like a lathe bed for example? Chrisby nophead - General
I do have an old 1/8th drill, it would need sharpening, but 3.2mm is bigger than 1/8th. Maybe I have managed to find a poor supplier of filament, but I think the wiki instructions should be updated as 3mm hole for 3mm filament does not seem sound engineering.by nophead - Reprappers
The instructions on the Wiki say to drill the extruder barrel with a 3mm drill. The spec for the filament is 3mm so that does not leave any clearance. I have purchased some 3mm HDPE welding filament but it measures about 3.1 - 3.2mm. The next size drill I have is 3.5mm. Will that work or will the clearance be too much? I suppose if it is too much the melted plastic may flow back up the barrel ratby nophead - Reprappers
A link I picked up from the Fab@Home forum:by nophead - Polymer Working Group
I have two plans: one is to do conventional SMT with a milled PCB, solder paste deposited by robotic syringe instead of using a paste mask, pick and place done semi-manualy using a suction head controlled by a joystick and magnifying camera (my eyesight is not up to placing modern parts these days). Soldering by hot air, or possibly a robotic soldering head. My second plan is to extrude a plastiby nophead - General
In the distant past I used an aquarium pump to make a 400 CD jukebox. I converted it into a vacuum pump by sealing the case with glue and connecting a pipe to the air inlet hole. I had a robotic arm with a suction cup on the end to lift the CDs and place them in the player. I plan to scale this concept down to make a tiny pick and place head for my machine to place surface mount components.by nophead - General
A friend just sent me this: At that price I think I will get one and give it a play.by nophead - General
Thanks Forrest, I can get HDPE filament easy enough so I will go with that. I will probably do some home rolled PolyMorph tests first as I can re use it after it has been extruded, something I can not do with HDPE yet. Ultimately I would like to recycle the free supply of HDPE milk bottles that are coming my way since I mentioned the project to my family. One thing that worries me a bit is tby nophead - Reprappers
Ok thanks Zach I will wait for the DB. I have already got bare nichrome so I will give it a go first. My plan is this: 1) Lay down a thin layer of JB weld and let it set. Possibly turn it down on the lathe if it too uneven. 2) Wind the nichrome under tension with another wire side by side so that the turns all touch each other. 3) Remove the spacer wire keeping the nichrome taught. 4) Applby nophead - Reprappers
I have ordered a bunch of the extruder parts listed in the wiki (studding, rods, nuts and bolts, etc) from Farnell. A lot of the part numbers have rotted, due to ROHS I think, so I made substitutions. When I get the parts and have checked them I will post the new numbers. Or, if you give me permission I can update the wiki, or should these go straight into Zach's DB? The PTFE rod was out of stocby nophead - Reprappers
Having a Cartesian system doesn't mean you can only draw straight lines. Its just a matter of the firmware controlling the motors. You should be able to draw a circle with all the points on its circumference accurate to within half the step size, i.e. 0.05mm. Since the filament is going to be at least 0.5mm I don't think you are really going to notice the X,Y quantisation. If you did it is probabby nophead - General
Is the amount the filament expands after it has left the nozel related to the length of the hole or is it just a property of the plastic?by nophead - General