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Minor Project Setback

So far with the screw-based drive for the X table, I've been able to get a speed of 15 inches per minute with the NEMA-17 stepper motor. I was thinking that this wasn't too bad, as my experience with the CNC TAIG mill was that I could get 45 inches per minute out of the larger NEMA-23 motors.

But then I saw a page talking about the feed rates used with the newer plastic extruder head, where they were talking 45 mm/SECOND feed rates, which translates to about 106 inches per minute.


Okay, the screw drive just isn't going to manage that. The plastic wants much faster than I could hope to get with the 20:1 gear reduction the lead-screw provides. It might be fine in metalworking, but not for plastruding. So back to the drawing board CAD.

ACE hardware seems to be rather lacking in the supply of belts and pulleys. I'm going to take a look at possibilities of using chains and sprockets from a bike or auto store, but things are looking bleak for using easily found off-the-shelf parts. I may have to settle for merely making a super-sized CupcakeCNC type design, with just mostly off the shelf parts. Well, I can live with that. McMaster-Carr has plentiful options of pulleys and belts, at the least.

So, the project description is now throttled back to:
How to make a 3D printer like the CupcakeCNC, but that can print larger items, using the same plastruder and electronics, and parts from any ACE hardware affiliate store, and a couple parts from McMaster-Carr.

Doesn't exactly roll off the tongue.

On a lighter note, I've decided that I'm going to call my design the CheesecakeCNC. It's bigger than a cupcake, and definitely cheesy in design.


( 10 comments — Leave a comment )
Oct. 9th, 2009 01:42 pm (UTC)
Take a look at kevlar timing belts from autopart stores. They are even toothed. Alternatively, if the mass is low, look at junked inkjet printers - they have a belt to move the printhead back and forth with considerable precision.
Oct. 9th, 2009 01:43 pm (UTC)
I think the shelves-o-stuff you want might be found in a hobby store that specializes in boat, plane, an car RC models. There's one in my area in NC and it has a whose range or gears, sprockets, and chains as replacement parts for the drive trains and control linkages in RC models.
Oct. 9th, 2009 02:43 pm (UTC)
Oh, hey, thats a damned fine idea!
Oct. 9th, 2009 01:45 pm (UTC)
And I've often wondered about using photoenamels in 3d printing. They use it in the manufacture of ICs. Spray a layer of the liquid plastic, expose it to light via projector for 30 seconds, spray a layer, expose, spray, expose... you could build a model out of hardened plastic limited only by the resolution of your projector in no time flat.
Oct. 9th, 2009 02:53 pm (UTC)
There's a few variations on that theme that get used in various styles of 3d printing. One common one is using ink-jet tech to spray down a fixative polymer onto successive layers of powder. Another uses a laser to point harden a layer of liquid polymer in a pool. They do get good resolution, but have drawbacks as well... The powder-and-fixative varieties tend to make parts that are fragile, but you have effective built-in support for overhangs. The liquid polymer method has very expensive consumables. Both methods are very messy. :)

The plastic extrusion method I'm going for has the benefit of making durable parts, and it's not nearly so messy, but it'd kinda slow, and it doesn't handle overhangs as well.

Edited at 2009-10-09 02:55 pm (UTC)
Oct. 9th, 2009 06:51 pm (UTC)
Angus and I were working numbers for laser-sintering systems a few weeks back. He'd looked at the CandyFab widget, which uses a hot air jet to fuse sugar. Powdered sugar is readily available, and a laser would fuse it much more precisely. Downside is that this is slow if using non-blinding lasers, and still pretty slow if using lasers in the 100 mW range. Upside is that you can get 100-micron resolution without any trouble at all.

Angus also proposed using copier toner as the fused material. It should be possible to produce sturdy parts with it, with the main difficulty being temperature control (burning it would not be good).
Oct. 9th, 2009 06:57 pm (UTC)
I think there's actually a (relatively) cheaper and fast commercial 3D printer that basically lays down successive layers of toner-like material using principles from laser printer design. ie: toner sticking to the photo exposed portions of a drum using static charge.
Oct. 9th, 2009 06:47 pm (UTC)
I'm pretty sure that plastic extrusion would work at 1/10th the feed rate. Have you tried testing it with the feed rate dialed down to check this?

Oct. 9th, 2009 06:55 pm (UTC)
I only got the parts for the plastruder yesterday, and haven't built it yet, so I'm relying on the numbers from the folks who designed it.
Oct. 9th, 2009 11:16 pm (UTC)
Is a rack and pinion approach out of the question? It might be overkill, though - and possibly hard to fit to the existing mechanism.
( 10 comments — Leave a comment )