Is there a simple extruder I can build for a repstrap?

I'm looking at converting my McWire Pipe CNC to a repstrap to start building a real reprap. I'm a bit confused as to what I do for an extruder. My funding is limited, as in whatever change I can find in the couch, so I need to build the entire thing from scratch rather than just ordering either a kit or the completed head. I do have a small lathe and milling machine so I'm pretty sure I can build one but I'm at a loss as to what I'm looking for in the design. Is there one out there that details building from scratch? I seem to recall from earlier lurking on the web site a version that used a screw as the feed but I'm not sure I remember that correctly.

Can someone point me in the right direction?

One other thing, which material is recommended for a beginner to, well, begin with and where do I go about getting some in the USA. Also, yes I know I'm a pain, how much should I be looking at getting in an initial purchase, pounds, feet or ???

Ok, final question, for now, I was thinking that I might start out by printing a RepRapPro Huxley so to have a smaller unit to work with at first then build a bigger one but I'm still not sure so is there any consensus on what machine a beginner is better off starting with, other than the repstrap itself that is.



Thanks.

With a lathe and a milling machine, you can make a replica of a wade's geared extruder. You can get the designs from thingiverse. The hardest part is making the gears. One option is to find 2 gears at a hobby or surplus store and modify the size of the wade's to compensate. 3mm designs are more common and end up being cheaper.

The motor mount / body can be made of hardwood, it's cheap and easy to machine. Aluminum could be nice but it's harder to work with.

If you use wood, Forstner bits are excellent for making the holes for the hot-end and bearings. The holes are the perfect size and have flat bottoms.

There also may be a DXF version of wade's geared extruder that you can mill if your McWire is working.

The hot-end itself only requires a lathe to make. I made my own PEEK / PTFE hybrid with a resistor as a heater. Unfortunately these materials are essential to the design of the hot-end. I've tried many different designs that i thought would work on the cheap but they all failed. Not to say that you may not have success but in my mind you would save yourself alot of trouble and many weeks of your free time.

When it comes to material, Go with ABS, I started with PLA and it's very difficult to get it working consistently. PLA is also unsuitable for making extruders and x-carriages as it has a lower melting temp. 3mm is cheaper to buy but harder to extrude. Your extruder and hot-end must be built for the correct size filament you'll be using. I bought a 5lb roll and had enough filament left over after working out all the bugs to print a new machine.

My first machine was a prusa mendel, it's very simple and easy to disassemble/reassemble.

Hope this helps!

Thanks, that is the info I was looking for. I had seen a web page where the person used stainless steel bolts, nuts and large washers for the hot end to dissipate the heat with a fan and I was looking to use that style since I have the hardware and I don't have any heat resistant plastic and now that I've seen a couple plans for the extruder driver on Thingverse I have a better idea of where to start. I have the nichrome wire from an old toaster that I thought I might be able to use for the actual heat tip just have to dig up a thermister and a build up something to monitor the temp.

Is there a list somewhere of places that sell 3mm PLA in the states?

Do you know of anywhere that compares the different versions of reprap side by side? The table on the wiki page is so so and I'd love to see a side by side comparison for size, work envelope, parts count and difficulty in construction along with the good and bad points listed. Right now I still want to do further research into the diferences of the Prusa Mendel vs the RepRapPro Huxley to see what exactly is the size and envelope difference. The idea of a relatively small printer for smaller parts appeals to me as long as I can build a bigger one for the large size stuff I might want to print later. Besides 2 printers beats one printer anyday

The upper end of the extruder is pretty straight forward. Since you mentioned CNC, I built my first set of gears on my cnc router with a 1/8" dia bit. You just have to manually cut into the roots of the teeth with a small saw. I used a band saw, you might be able to use a coping saw. The goal is for the stepper to drive a 11 to 39 reduced shaft where the filiment is pinched against the shaft and driven down via a bunch of teeth. Folks are using 1.75dia filiment that can be driven directly from the output of the stepper resulting in a smaller upper end.

The hot end of the extruder is very tricky with a lot of good and bad ideas floating around. Stay away from any hot end design that involves winding resistor wire for your extruder. Use 5 watt resistors that are attached to a block where the nozzle screws in. Many posts on this site are about issues with the lower end of their extruder. I'd do a lot of reading before you commit to an approach.

On material you can use either PLA or ABS. PLA is cheaper, had no oder when extruding, holds its shape well, but not very heat resistant. You leave this material out in the sun and it will deform. check out Makerbot for ABS or Ultimachine for PLA. These days many vendors sell both.

sounds good to me
will come back and leave further comments

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