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Discuss any sort of mechanical stuff here: positioning systems, gears, extruding methods, etc.
Re: RRRF HDPE spools - 18 years ago
This site says 3mm HDPE is 220ft/lb (147.833175m/kg). The 5lb reel, then, is about 1100ft (335m).by degroof - Plastic Extruder Working Group
Re: Changes that need to be made to the extruder - 18 years ago
I suppose a single set of parts could be designed to do either, depending on how it's put together. Assemble it this way and it uses a curved drive; assemble it that way and it uses a straight drive. I expect that, once we have a few people with working machines, we'll start to see variants on the extruder popping up here and there.by degroof - Plastic Extruder Working Group
Re: Why Java3D - 18 years ago
I've noticed that the graphics, the build simulation in particular, tend to bog down the app. It's better than it was but still a bit sluggish. As far as I can tell, the renderer is spending a lot of cycles sorting the Z-order of all those filament segments. Anything that could be done to speed that up would help a lot.by degroof - RepRap Host
Re: Digg found us again - 18 years ago
I wonder how many new members we got from that. I'm guessing Ian and Zach will be seeing an increase in orders.by degroof - General
Re: Reusing The Plastic - 18 years ago
There's some info on a possible granule extruder here: Might work with shredded plastic as well. Feeding plastic bags into it might be interesting.by degroof - General
Re: Thermister (Why are we cutting into the barrel?) - 18 years ago
> I think I would like to just buy a nut that fits > over the barrel. I could then drill a hole > through the side of that nut and JB weld the > thermister so it is in that hole sitting against > the barrel. Similar idea using a penny: My current configuration is a thermistor wrapped in PTFE tape and strapped onto the barrel using a piece of twisted wire.by degroof - Plastic Extruder Working Group
Re: Reusing The Plastic - 18 years ago
I managed to do a small quantity in the oven at 350F. Probably not practical for larger volumes, though.by degroof - General
Re: Bulding the extruder HELP!! - 18 years ago
Yeah, the way the extruder fits together isn't very intuitive, with the Ts going in opposite directions and all. There are probably enough photos from various blogs that could be incorporated into the main build instructions. That might help a bit. I just did a Google image search on the words "reprap" and "extruder" and got 150 hits. Quite a few good shots. Also a picture of Mickey Mouse, for soby degroof - General
Re: Reverse Engineering - 18 years ago
As far as I know, the teardrop is supposed to be 90 degrees. This is based on the RepRap being able to handle an overhang of up to 45 degrees without support material. Not sure why it's coming out off a couple degrees.by degroof - Mechanics
Re: How fast can an $18,000 commercial system extrude.... - 18 years ago
Sounds like those empty spools could be a good source of filament. Is it 3mm?by degroof - Plastic Extruder Working Group
Re: Reusing The Plastic - 18 years ago
One of the plastics we've been working with, HDPE, is the same stuff that milk jugs and grocery bags are made of. I worked out that I accumulate 1.5lb (700g) of grocery bags each year. That's nearly enough to build another RepRap. I can just imagine what'd happen if someone came up with an easy way to use grocery bags as feedstock. The local grocery store has a big bin at the front door where pby degroof - General
Re: Unreprapable RepRap Parts - 18 years ago
I agree that a proper FDM machine needs a way to produce support material. I think there's a practical advantage to having a minimal, one-head system that can produce its own replacement parts, though. Or, at the very least, it'd be handy if a minimal, one-head system can produce its own paste extruder. That would give new owners a practical first project.by degroof - General
Re: Review of alternate Thermistor part options? - 18 years ago
When I was playing with the temperature equations I found that, for high temperatures, there just wasn't enough resolution. As far as I can tell, using a 100k thermistor with a 1nF C3 should give a decent range for most temperatures. DigiKey has a 100k one with a beta around 3800. I might have to order one just to see. The 1% ones are $10 but the 5% ones are only $.80. I'm not sure if the toleby degroof - Plastic Extruder Working Group
Unreprapable RepRap Parts - 18 years ago
The other day I was looking at the quick-fit clamp in AOI. I wanted to see how I could modify it to grip the PTFE barrel better. I wanted to make sure whatever I came up with didn't violate the >45 overhang rule. That's when I realized it already has overhangs. There are 3 horizontal holes without the 45-degree peaks, a beveled edge that creates a 60-degree overhang and dome-shaped indentationby degroof - General
Re: RepRap Host: Extruder Exerciser target temp / auto heat control - 18 years ago
I took the equations from GenericExtruder.java and dumped them into a spreadsheet. From there I just played with the numbers until I got a decent set of values that would cover the desired temperature spread. One thing I've learned from all this is that the current setup doesn't seem to work well for high temperatures. The relationship between temperature and the picTemp value (the R/C timer outby degroof - Plastic Extruder Working Group
Re: RepRap Host: Extruder Exerciser target temp / auto heat control - 18 years ago
Alright, I picked apart the code and I think I see what it's doing. Assuming vRefFactor=7 and tempScaler=4 (those are the defaults), it looks like a good set of values is: cap=0.000003 Rz=4837 beta=550 I *think* I've got that right. There aren't any real thermistors like that but, since you're emulating, it shouldn't matter.by degroof - Plastic Extruder Working Group
Re: RepRap Host: Extruder Exerciser target temp / auto heat control - 18 years ago
We're working with a 0-255 range, right? With 0 being maximum temperature and 255 being minimum? I'm guessing that we'd want a temperature range of 20C-300C to translate to a timer value range of, say, 250-100. I think that'd work out to a worst-case resolution of about 4 degrees over the working range. Something like that. If you could send me info on the emulation formula you're using, I thinkby degroof - Plastic Extruder Working Group
Re: RepRap Host: Extruder Exerciser target temp / auto heat control - 18 years ago
I think a lot of this has to do with the RC value of the thermistor circuit. As the temperature increases, the resistance of the thermistor decreases. This translates to a shorter pulse width on the RC circuit. The shorter the pulse width, the lower the "raw" value will be. The problem comes in when you start getting into the single digits. The difference between 50 and 49 is 2% but the differeby degroof - Plastic Extruder Working Group
Re: Parts website recommends PIC-PG3 - 18 years ago
Yeah, I ran into the no-parallel-port problem a while ago. My current PC (Dell) has no built-in parallel port. I do have an older PC with one but it's inside and arcade cabinet. I bought the PG3, realized my mistake, ordered a PG2 and used the PG3 attached to my arcade machine until the PG2 showed up. I'm currently using COM1 on the Dell for both the PG2 and the RepRap. It's easy enough to conby degroof - Controllers
Re: UNOFFICIAL: Top 10 needs of the RepRap community (a bit USA centric) - 18 years ago
These places might carry UHMWPE welding rod. Kinda hard to tell. It looks like the first site carries 1/8" rod at $150 for a 2000ft roll. Their order form implies they can do 3mm.by degroof - Reprappers
Re: UNOFFICIAL: Top 10 needs of the RepRap community (a bit USA centric) - 18 years ago
One thing I noticed recently -- and I'm not sure if it fits here -- is that some of the RP part models are not RepRap-able. As far as I can tell, a number of the pieces in the extruder have > 45 degree overhang, no matter which way you orient them. It's a relatively easy fix but it still needs doing. I've also noticed that the RepRap host software throws a wobbler if the area it's filling isby degroof - Reprappers
Clock STL - 18 years ago
There's a zip file here: that contains an STL of a clock mechanism. Here's what happened when I tried to use it: - Opened file in RepRap app. Very small. - Used the inch-to-mm scaler. RepRap app locked up. Killed app. - Opened file in AOI. Scaled up to about 100mm long. Exported to STL. - Opened new file in RepRap. - Started build simulation. This is where the fun started. My PC became complby degroof - RepRap Host
Re: Plastic for filling FDM objects - 18 years ago
I've used Alumilite before. It's a two-part urethane that's low-viscosity and fast-setting. Might be interesting to create a two-chamber toolhead that mixes them as it dispenses. Something like this:by degroof - Plastic Extruder Working Group
Re: Practical Darwin 1.0 Extruder materials - HDPE - 18 years ago
The hose clamp seems to work well but I had to re-tighten it once the barrel heated up. I was playing with AOI yesterday and added a ridge to the quick-connect extruder. Interesting thing: There's no orientation of that part that has no overhangs > 45 degrees. It'd have to be modded to make it RepRap-able without support material.by degroof - Plastic Extruder Working Group
Re: RepRap Calculator - 18 years ago
All the calcs are done in a single html file, so you could just save the page to your local drive.by degroof - Reprappers
Re: RepRap Calculator - 18 years ago
Just noticed that it didn't work with IE. Fixed now.by degroof - Reprappers
Re: How fast can an $18,000 commercial system extrude.... - 18 years ago
I found one reference that said a Stratasys prints at 1 cu in/hr (not sure which model). That's 16 cc/hr or 4.6 cubic mm/s. Assuming .01" extrusion (.25mm), the head would be moving at 3.5 in/s (88mm/s). If that's right, then it'd take 2.6 days to make the Darwin RP parts. Granted, it's at 4 times the resolution of what you're doing but it seems to be only slightly faster volume-wise. I wonderby degroof - Plastic Extruder Working Group
Re: Practical Darwin 1.0 Extruder materials - HDPE - 18 years ago
I just got my extruder running reliably. 1. I *think* I'm running HDPE at 180C but my thermistors keep dying. 2. I can get a reasonable amount of extrusion at a setting of 50. Full speed is possible but seems to strain the extruder. 3. I'm getting a 1.2mm extrusion using a .55mm tip 4. At a extruder motor setting of 50, I was getting about 2mm/s. At full speed, about 7mm/s. --- 1. I agree. Iby degroof - Plastic Extruder Working Group
RepRap Calculator - 18 years ago
This weekend, I was doing a lot of measurements and calculations. Things like, if I run this length of 3mm filament in and get that length out, what's the extrusion diameter. I got tired of scribbling stuff down or using a spreadsheet, so I wrote a calculator in JavaScript. I've put a cleaned up version here: It's split into three sections but the common information carries downward. Example 1by degroof - Reprappers