Wednesday, 27 May 2009

Finding parts

The key to finding RepRap or RepStrap parts: keep your eyes open, and don't be afraid to ask: experiment, try things out, and tweak your design to what you can find. I've found a few useful bits over the last couple of months.

I wanted to add an encoder to my GM3 drive motor, but I've previously blown my three spare opto-switches.
Asking around at work, I found an old ball mouse with a broken USB plug, and got permission to take it home from sysadmin.
Logic dictated that running off USB (5v) it might contain some opto-switches that I could recycle. Taking it apart, a quick inspection revealed two components either side of a slotted wheel that looked right:
From RepRap_bits

I desoldered them, ripped out the broken IR sensor from the x-max endstop board, and just soldered them in.

From RepRap_bits

Hooking it up to the arduino, it works perfectly!

Other extruder bits:

I found some thin-walled alumininum an brass tube in a Model shop in Westbury. It's imperial (5/32) but the internal diameter is exactly right for my 3.1mm filament.
From RepRap_bits

I think it might work well to make vik's no-lathe/ariel extruder, or to make a Nophead-style thin-walled extruder. I've got a large heatsink from a core2 CPU to go with it.

I've been looking for a block of metal to make nophead's resistor heater for a little while - it's not something you can buy in B&Q, and I don't happen to have aluminium bar stock in my garage. :-)

In the middle of Bath, down by Sainsburys, I walked past a little tool shop that was selling scrap metal outside. I went in and asked, and...
From RepRap_bits

Hey presto, the chap disappeared out the back and came back with a 10mmx30mm bar - and cut me off a couple of 30mm lengths from it. The best bit : cost 25p. So, a shout-out to the guys at Avery Knight and Bowlers, Bath - thanks guys. They've been consistently helpful and the shop is full of tools and other useful bits. I also grabbed some m6 coupling nuts - might be useful to attach nozzles - and a 7.5mm drill, which is the right size for my resistors.

I've thrown a few quid away on some tattoo tips from a dodgy overseas company (like these ones). I wanted to have a look to see if they would be useful to turn into nozzles. When (if) they arrive, I'll post some measurements and photos.

Edit: half-hour after posting this, I noticed a big split in the mains cord insulation for my wife's hairdryer. 'It's not safe, we'll have to you get a new one' - of course, nothing to do with the fact it's full of nichrome wire....


Erik de Bruijn said...

I like the idea of using the mouse's quadrature encoders. You should even be able to determine the direction. But that's if you use a slotted disc (like the one the mouse has) with the right spacing.
In this case, it's also a cheap source for opto's. Thanks for finding this out. This is really builders wiki material, it contains various alternatives to the mainstream electronics. Would be great for people living remotely or off a tight budget to have these kinds of alternatives.

Erik de Bruijn said...

B.t.w. Did you know toasters have the same failure prone power cords... :)

Renoir said...

Thanks for the nice comments.

For the moment, I'm just controlling the speed with a single simple encoder.
I haven't bothered with the quadrature - I'm relying on the fact that it's going in the direction I told it to.

Erik de Bruijn said...

I've been wanting to get it closed loop or otherwise switch to stepper based driving of the filament.

Which firmware have you been using for it? I've tried setting up interrupt based speed measurements but I've got a lot to learn programming AVRs. I have some more experience with PIC electronics.

Pat Galea said...

This is exactly the kind of stuff that goes down well at ETech!

Great post, Mr Renoir! :-)