Sunday, 31 May 2009

Tips, Tips and more tips

I've recently ended up with a whole bunch of welding tips and some tattoo tips.
I thought it might be interesting to compare them.
From RepRap_bits
  • Halfords SIP Welding tips, 0.6mm or 0.8mm hole, M5 thread - 5 for £4.99

  • B&Q, MIG Contact tips, 0.6mm or 0.8mm hole, M6 thread - 5 for £4.99

  • Ebay, Tattoo tips, various sizes, no thread - 18 mixed for approx £10. can be bought singly.
From RepRap_bits
Halfords are the smallest : an M5 thread, and a short body (18mm). B&Q have a larger M6 thread and are nearly 24mm long. Both welding tips are copper, and the tattoo tips are stainless steel. The tattoo tips have a long barrel, but a huge hole for a rubber band in the side. (white line is 3mm standard ABS filament)
From RepRap_bits
The nozzle holes are all similar sizes. the first two are 0.6mm Halfords. The next two are 0.8mm from B&Q. The tattoo tips come in various sizes. These are the two smallest round holes: I think they're designated R1 and R2, and look to be a similar size to 0.6/0.8mm. Some of the tattoo nozzles are much larger.
From RepRap_bits
The shapes are very different: the Halfords tip has the 'best' shape, a 45degree taper. The B&Q has a flat tip - it might cause the extrudate to stick, although it would be easy to reshape with a drill and file.
Both the welding tips need to be carefully drilled out - typically 3mm - to within a whisker of the exit hole - so that the thin section is as short as possible.

The tattoo tips seem to be made by drilling a 6.8 or 7mm hole, then a 2mm? hole right through - then a tube of the required dimension is (brazed?) attached to bring the diameter down to the exit hole, and the tip shaped(guessing). From visual inspection, it looks like the 2/2.5mm hole extends almost all the way to the tip.
From RepRap_bits

I think that if the excess tube is 'trimmed' it will form a good nozzle shape internally.
The tattoo tips need to be attached and/or the big hole in the side sealed. a few initial thoughts are:
  • tap the internal diameter and screw in a standard reprap drilled bolt
  • cut an 8mm thread in the outside and screw into a coupling nut or threaded block
  • drill a 'heater block' like nopheads to 8mm and press-fit/solder/braze the tube to form a good seal.
I'll have a play with them (I've got 18, so plenty of spares) and see if anything works.

Of course, if 0.6 or 0.8mm is too big for you, you can always use the nichrome wire/high temp solder trick to get a smaller exit hole.
Since solder is a generally softer, has anyone tried blocking the hole and drilling the solder with a small drill bit to get a 0.4 hole?

Saturday, 30 May 2009

Hacked Firmware for simple encoder

I've started hacking the firmware to add support for my simple speed controller.

Current version is here:

Warning: this is straight off my development version. Read (and modify) before using.

speed 1 = fast
speed 255 = slowest

It *should* run encoder at a constant rate.

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....

Tuesday, 26 May 2009

Radio Renoir back on the air!

Sorry it's been a bit quiet recently, I've been off work with depression. There's been a lot going on in my life, and it all got a bit too much. However, the doc gave me some stronger tablets and I'm back to full form! Everyone's been really supportive, work have been great about it, really understanding (thanks D and J).
While I was low, I wrote a really rambling, bizarre post that make no sense at all, trying to explain. Glad I didn't post that one!

Very little progress made on the RepRap in the last month. However, I'm putting together a talk for my work colleagues on 9th june, so I'll post a copy of the presentation when I'm done. I'll also write up the couple of tweaks I have made, and some new bits I bought today.