Thursday, February 26, 2009

RepStrap: pen to paper...

I finished soldering my other two stepper motor controller boards last night. I have yet to start making the extruder. The addition of these two boards completes all but the extruder assembly. I decided to follow Nophead's lead and rig a pen to the X bracket mount with a bit of capa. The first thing I did was write up some firmware to draw squares. I wanted to test out the precision of my pulleys, stepper motors, and rig.

I continued this work tonight and was very excited with the result. I started off tonight by drawing a 1000 step by 1000 step square and measuring it. It turned out to be 81mm wide / tall. This means that I am getting a higher resolution than expected! I should be able to print parts to a 0.081mm resolution! Wow!

Next I decided to show off and write a short script to scribe with my repstrap. Here is a picture of "onshoulders" being written at 13mm and 25mm. I am using a BIC pen I got at a Marriott... so a better pen would obviously give a better result.

And here is a video of my repstrap in scribe action. I brought up the size to 100mm so that the motions would show up better on camera.

onshoulders, written by a repstrap from gavilan on Vimeo.

Now I need to draw my attention to the Z axis and see if I can rig up some tests for it. Then it's build time for an extruder, and I still need to pick up some HDPE.

Tuesday, February 24, 2009

RepStrap: SMT without a hot plate...

I have had the electronic components and connectors needed to build three stepper motor driver boards for two weeks now and have been waiting on the printed circuit boards from RRRF. Again, patience is a virtue, and in this case it is deserved. Zack has been abroad as of late spreading RepRap. His contributions do not go unnoticed. Anyways, the boards came last night and I had my soldering iron out momentarily. The boards are surface mount or SMT and with me never working with SMT I did not know to purchase a hot plate and some flux. I decided to make what I had work.

As you can see the joints are solid but do not look pretty. Also, this job took me an hour or more and I missed the directional pin, requiring troubleshooting and resoldering. I would not suggest others working with SMT boards without a hot plate. Still, I plan on soldering up the other two boards the same way.

Thanks, Zack, for a solid design and a working tutorial, even if I did not follow it. I am thankful that I get to bypass the PIC phase of the RepRap design.

Update: December 29, 2009

I recently soldered up the same board with a hot plate and got much better results. Observe:

Sunday, February 15, 2009

RepStrap: bigger tooth pulleys...

The instructions for building a Darwin say to have the pulley molds made by a rapid prototype shop. If you can't tell by now I am too cheap for that. My solution, and I think that it is unique, is to cut PVC end caps to the width of the tooth ribbon and sandwich it between two pieces of MDF.

One thing I have noticed, however, is that the hole is not in the center of the pulley with the way that I do this. I hope this doesn't cause problems as the holes are only off by two millimeters, tops.

I will be fitting these to the machine later today. I hope to be building the stepper motor controller boards later this week.

Saturday, February 14, 2009

RepStrap: just too small...

Things were really starting to shape UP (literally) this morning.

However, as hypothesized, the toothed pulleys are just too small, causing too much friction for the Z axis stepper motor. I can barely turn the shaft by hand.

And to think I spent most of today on this... Oh well. I will have to redo all of the work. I need bigger pulleys. On the plus side, I can use those smaller pulleys on the Y axis, saving me +/- 20 minutes. :)

RepStrap: capa rocks!

I got my order of ShapeLock / capa in today. I thought it arrived this morning but it turned out that I was just another rookie who fell for the "at unit" USPS naming convention. It did come in the afternoon, however.

The ShapeLock instructions describe it as "modeling clay on steroids" and I have to admit that I agree with them. This stuff rocks! Boil some kernels in some water and mold away.

It took me 45 minutes to mold these four tooth pulleys per the RepRap instructions.

I didn't expect the results to be so good! My only concern is that I made these pulleys too small for the Z axis. We will have to see.

Saturday, February 7, 2009

RepStrap: some mdf and 5 / 16 rods...

I got my rods right after the nuts and bolts came in. I ordered the rods from Cutting them to length was a quick job with a 12 inch metal saw. One more $8 tool to add to the overall cost. I am keeping a running cost of materials and tools to keep me honest and smart about this. It is too easy to throw money at something in order to get it working faster. After cutting my rods to length I began making complicated parts like the X bracket shown below. I grabbed a piece of pine to make this part out of before admitting that thin MDF was the only way to go. Once again, Bruce steered me in the right direction.

Here is a picture of one of the more complicated motor brackets. This was made out of MDF and pine.

And then a picture of the whole rig as it is shaping up currently.

Wednesday, February 4, 2009

RepStrap: nuts...

My nuts and bolts came in the mail today. I am very satisfied with the price model and quality of the supplier Bolt Depot. It is amazing how much time I spend waiting for parts! However, I think patience and a good work ethic are essential with this kind of hobby. I always want everything TODAY and sometimes find myself sacrificing quality to get it. I'll blame it on my age. :) Seriously though, waiting for parts is the perfect excuse to accurately plan and research your next move.