Tuesday, 30 June 2009


Today I wrapped teflon tape around the sliding blocks on the X stage. I doubt that it'll be as durable as using teflon blocks as such, but it's what I could find. If it becomes a problem, I'll look online for real blocks. It may be a good idea to round the edges on the blocks, I'll see if they tear.

Also marked where the hole in the other end should go. I have cut the threaded rod long enough to go through the other end, which means the rod will not be hanging from the drive nut. I considered adding a drive nut in the other end, but I imagine it could cause problems if they are not perfectly aligned.

There are already some problems with the omega-shaped holder for the drive nut, as it has a groove that the nut can slide back and forth along. Not sure what to do about that. Glue might work, but that should be only on the holder, I want to be able to swap things out.

I'll need to grind down or cover the part of the rod that goes through the hole in the other end, and the fastening method to the motor is uncertain, probable duct tape for a proof of concept.

Saturday, 27 June 2009

Good news for Europeans

There is now a European source for RepRap pieces: http://reprapsource.com/en/shop has kits, PCBs, screws and various other useful things. Finally, we don't have to worry about whether we'll end up paying $30 worth of fees on $20 worth of parts. Yay!

Progress: Stepper driver, X stage, endstops

With some help from a Norwegian friend, I have made significant progress.

I have the rails for the X frame bolted onto the end pieces.
I have the X stage acrylics mounted with nut and sliders (though I need to wrap some teflon around the sliders).
I have tested and fixed a soldering issue on one of the stepper drivers, it now works for all I can tell.
I have gotten an Ethernet cable that can actually communicate with the opto endstops.
I have tested the opto endstops, and found that they work... on and off. And not in the manner I expected.

I still need some way to connect the threaded rod to the motor, I figure duct tape will do for testing purposes. I am also out of solder.

Tuesday, 23 June 2009

Useful heads

Collecting in this post various types of head that might be useful once the 2D part is actually running:

  • Fabric painter (might be able to get one from the US)
  • Wood engraving burning tool (seen at local crafts store for DKK ~500)

Some things to make

While I'm trying to get things done, here's some things I'd like to do once the RepStrap is actually working:

Electronics organizing cabinet thingy.
Resistor lead shaping tool.

My work yesterday was trying to put the frame together. It was foiled by 1) The narrowness of the rails made it really hard to turn the bolts, instead I should enlarge the holes slightly to allow the bolt to be thrust through, and 2) the holder for the moving rod was a different size than the layout used, I'll have to redrill.

Sunday, 21 June 2009

Further work

Todays work:

Epoxied together the X and Y stage acrylics. It's been a lot of unnecessary extra work to grab too thin sheets. Can't recommend it, but I think it'll work.

Drilled the X and Y stage attachments' holes for fixin' to the ends. Using a dull drill bit to drill aluminium is interesting: Rather than cutting, I had to run it at full speed so that it eventually melted the aluminium. Apart from being extra work, it also meant that there was a rim of molten metal around the hole afterwards, which took a fair amount of dremeling to remove. And my dremel is now stuck with a half-used grinding ball on it, as it has shown its crappiness (it's off-brand) and worn itself to where I cannot remove the bit. Bugger.

Tested the one stepper motor driver that seems to work. The Arduino could talk with it, and the exercise program showed that only one side of the motor connectors works.

Sunday, 14 June 2009


So I swapped out the power supply I hadn't been able to get to work for one my brother had lying around, and voilá -- success! My car bulb lit up, as did one of my stepper motor driver boards. The other board has a short, it lit up briefly and then went out, after which the 12V line was dead until I unplugged the power supply and plugged it back in. However, the 5V and 3.3V lines were fine and under load from the 10 ohm 7W resistors put in -- which got quite hot in the process, as my fingers can attest to after trying to remove one:)

Pictures of the board with the short:


On the down side, I found that the acrylics should be about 1/4" thick (which is 6mm, mine are 3mm). To not waste the drilling I just did, I'll try to glue two pieces together.

Saturday, 13 June 2009

Tip for drilling pipes

I don't have a drill press yet. I want one, but can't afford to get one that I trust to be of OK quality. So drilling into pipes is tricky, the drill moves off the spot even worse than when drilling on flat surfaces. At the last hole (of course:) I hit on the trick of taking the metal saw and making a little X centered on where the holes should be. Voila, no more drill movement.

Imperial vs. metric

It's kinda annoying that the McWire bot is designed partly in imperial units, partly in metric, and always described in metric. Some parts are in really odd imperial lengths that turn out to be very nice metric sizes, while others are nice in imperial units. And the printouts for cutting the acrylic pieces for the stages? Made for 8.5" x 11" paper, which means it doesn't quite fit on A4. Grumpf. Everybody know that metric has won.

Bits and pieces assembled

I now have most of the bits and pieces assembled for making my RepStrap (Seedling). I have:

Two finished but untested stepper motor drivers
Three stepper motors
An Arduino
1m 10mm threaded rod (just enough for all three stages!)
Piping galore
Rails and angle pieces, cut and with holes drilled as appropriate
Nuts, bolts and other misc hardware
A 1m x 30cm acrylic sheet (perhaps not thick enough, but it was cheap:)
A PC power supply that refuses to stay on for more than a second:(
Teflon tape (couldn't find teflon pieces, so I'll cover some bits of acrylic with teflon:)

Forwards build!