Sunday, March 28, 2010

Minor... Setbacks

In an overnight "let's get this thing done all in one go" event, my project parter and I spent six hours cursing over the Arduino software, my ineptitude at understanding instructions, and the cheapo $3 serial cable's complete and utter failure to do anything at all besides act as a loopback.

Burning the sketch with my USBtinyISP never worked, and the Arduino software spouted unfixable errors. This may be due to it being the mac port of version 18. I'll boot ubuntu and install everything there and see if I can make it work.

In exasperation, I thought that maybe, just maybe, plugging everything in and powering it on would make things work. Actually, powering the motherboard might have been good by itself, but we had a far more interesting experience from everything at once.
As the PSU spun up, the Y stepper driver began to fiz from the linear regulator, sparking like a... sparkler. Needless to say, something was wrong.

Now, I know for a fact that the regulators we used are not the ones the schematics called for, but those were on backorder and these were extremely similar. Maybe not enough.
I should really go and dig up the data sheets for them so anyone reading this can learn what to avoid improvising with.

I really hope the $5 stepper chip on the board is not dead.

Friday, March 26, 2010

Productive Day

Whoo hoo!
Some days are just so much better work working in.

Today I finished the X and Y pulleys (by fusing the layers) and made modifications to the Cupcake's X platform so that it would take an M8 bolt rather than M6 or whatever it was.
I also removed the slightly bent Z threaded rod and replaced it with a much nicer piece, and used the not so great one as material for making idler axles from.
Then I re-assembled the stages, and they look usable! I just need to get the electronics working now, and I can begin to test out the machine's movement.

As for extruders, well, that's for later.
I have one extruder that we think will work, borrowed from the club.

No pictures today, as the camera was borrowed for something else.

Tuesday, March 23, 2010

Week's Worth of Update

I think I said I was going to update "tomorrow" two weeks ago.
Time sure passes fast when you're having fun!
Anyway, a LOT of stuff has happened, which I'll have to recount concisely.

First off, I decided that the mild warping on the plywood Z platform was not going to work. That was a really easy fix, as I just had to go find a sheet of acrylic of the right general shape, saw it squared, and lazzor away.

The same day, I got tired of the Z-stage coming off of the washers that are used to move it around.
At the risk of cracking it, I designed and installed some extra layers to hold it in place. I'm quite happy with how they turned out, actually. The result is that the platform cannot come off of the washers, they are totally locked in place. This has added some resistance, and it seems to stem from a moderately bent Z rod. I have some more M8 left over, so I think I'll replace it.

The other thing from last week wa
s producing the X and Y motor pulleys... yet again based on random belts I pulled from printers. Th
ese were a bit larger than I expected, but Griffin was able to produce the correctly toothed pulleys for them with only one re-try. He would model the pulley and send me the file, and I'd run to the laser and cut it out, then bike over to his house to see if it worked. I think the plan worked great. They pulleys are pretty much perfect, and base
d on a comment on my last post I've opted to reverse my layer order so that the edges of the pulley are convex. This means the belt will be held tighter in the middle and due to variations in radius resulting in different RPM at the edges, it ought to stay on better too.

I've been reminded by two people now to talk about one of my improvisations on the machine.
Because I could not find a source for linear bearings that were both low friction AND cheap, I decided to scrap the designs that need "precision steel rod" and substitute my own low-cost alternative. In this case, I went to a local and small hardware store and poked things together. I found a meter of aluminum rod for less than $5 and a
foot of good copper tube for about $4. I was in luck, not only d
o these two things have a low coefficient of friction, they were cheap! I bought them and then sawed the rod in half and the tube into short sections the same length as the X and Y stages are wide. Now, the tube's outer diameter is not the same as the inside diameter that the makerbot was made to take... so I lazzored out an entirely new XY stage. The rod is M8, so it fit correctly. However, I made a silly error and made my cut exactly 1cm off from center, so one rod was too long and the other too short. As a result I had one rod that simply needed trimming to fit, and one that could never be augmented.
Quite the dilemma, or so I thought. Then I remembered that I have a laser cutter at hand. I simply made some hole-extenders from the endcap design and bolted them onto the inside. Turns out there is a lot of wasted space in the Makerbot Cupcake. Another triumph of frugality and improvised parts!

Next up, I finally discovered why my package from Digikey was taking so long... I had supplied the wrong address! The keys 9 and 6 are hard to accidentally interchange, but what can I say? I re-ordered and the package arrived last monday (yesterday as of writing). I gathered up everything I thought we would need and carried it all over to Griffin's to solder the last parts onto the boards. Great success! They're looking nice, and the only thing that has an issue is the big resistor on the motherboard. It's there to put a load on the PSU to get it to turn on (talk about an odd safety system). Sadly, we got a 5W .30ohm resistor... the machine needs a 5W 30ohm one. Whoops. We also have a 5W 3.0ohm resistor, so thi
s is comical. If only we could test it.

That brings me to the next item I want to talk about! I read this walkthrough on converting a nokia phone cable to a USB->TTL serial cable, and decided that that was the most cost effective way of getting the needed programming cable. I was able to get one of these cables for $3, shipped. That's a terrific deal. Or it would be, if I could make it work.
The cable declares itself to my computer, and USB probing makes me think that it is indeed working. However, in the step where I must probe the voltage on the Tx and Rx lines, I get a minute amount of power out of it. Not sure how to continue, so I just soldered the lines to a makeshift port anyway, though I am afraid to try to use it. Would rather not have to buy one.
If anyone knows what my issue there might be, let me know or I just might fry something.

Tomorrow I'll be building an extruder based on the PAXtruder, but with a NEMA-23 stepper as a drive. Ought to work, but I have not done any math to prove it. I'll also be making four more conventional gearmotor extruders, for the TEClub to use with our always-advancing Prolight Mill headcrab. It may be able to print up to six copies of something at the same time!
Lots to do, lots to do!

Sheesh, this is a very long post.
Thanks for reading!

Tuesday, March 9, 2010

Makeshift Motor Pulley

So, I had time to work out another solution to my lack of a motor pulley.
I decided to build it around a rubber wheel-thing from a paper roller out of a printer that gave up its belts for the machine anyway. This means I no longer have to worry about much in the way of play on the attachment between pulley and motor.
It works pretty well, but I made an error when fusing the layers, and the two layers that constitute the toothed section are not aligned correctly, and the belt skips every 20 turns or so. I've managed to run the motor with an older reprap stepper driver (powered from a SCSI enclosure) and it works great, minus the skipping. The driver produced so much heat that I was afraid to burn it out by running for too long. The enclosure PSU is probably made for more demanding devices - its normal function is as a soldering station power supply with a few PC fans attached in series around the edge to suck away fumes.

I'll make another one tomorrow, and clamp it to dry with the belt attached.

Monday, March 8, 2010

Custom Laser Cut Pulleys

As I mentioned before, my project partner and I decided to re-use the belts from an assortment of printers and scanners, which meant we needed to design pulleys to go with them.
Yet again, the laser cutter proved invaluable, allowing us to try design after design until we no had perfect meshing. Griffin did the measuring and modeling with calipers and Inkscape, I worked the laser and assembled the four layers needed to create a pulley from a flat sheet. We used an acrylic solvent glue, and they're now single solid objects. They fit the M8 rod perfectly, and are then clamped down with nuts and washers.

The motor-fitted pulley still has some issues however, as neither of the versions we have tried are quite right. Luckily, we have tons of plastic to work with, so the limiting factor is (as usual) time. I hope to report back with success tomorrow.

If I ever figure out what model printer the belts came out of, I'll upload the designs to thingiverse.


Well, I was immediately reminded that I should post some visual media about these projects.
Here goes.
Firstly, here is the initial photo I took of the Cupcake, after I laser cut the plywood body. Note the acrylic side; I initially wanted a machine that was entirely clear, but I forgot to compensate in the designs for a 1mm greater thinkness, and thus all the tabs failed. This was taken in October, only weeks into the project.

Next up is the laser-cut X and Y stages, they're looking nice and clean, and are the correct thicknesses. This was completed less than three weeks later, possibly faster even. I plan to illuminate the build platform sometime in the future, I'm sure it will look terrific.

After that I lazed off and took no more pictures until just recently, when I worked out the improvised X-Y sliders. The final picture is the most close to current version, you can see the rods and tube in place, as well as the mostly-done electronics clingning to the side half heartedly. None of them are testably complete, though I have burned the bootloader for the extruder controller (ironic, as I do not even have one yet!).

Sunday, March 7, 2010

Real Content!

Ok, might as well use a blog I already started to talk about stuff!

As a re-introduction, my name is Ben and I'm a student at Roosevelt High School. Here, like many places, seniors are tasked with completing a self-guided project (a "Senior Project," so creative a name).
My project was, originally, running my bike on an electric motor. I got bored with that idea, and decided to build an air engine, the sort of which you might have once seen on a powered airplane model. I acquired plans for a five-piston engine, and began to build it, but got distracted and bored yet again. Finally, I settled on something, and that's what this blog is now about.

A friend of mine from middle school became obsessed (to put it lightly) with replicating machines. He introduced me to the RepRap project some time in sophomore year, or something like that. Possibly earlier. In junior year, and he brought up the subject again.
I realized that Roosevelt High School was already positioned perfectly for launching into reprap production, and even had a laser engraver capable of cutting sheets of acrylic (sourced as FREE scraps from ever-awesome local businesses). Researching the topic is relatively easy, and there's a big community already in place (and growing) to look for news from.

Boom, RHS' TEClub* was born. We're a collection of students with varied interests in technology. At the moment we're working with a local rep-strapper to convert our ProLight CNC mill into a three-six headed FDM beast. That was a bit more than a year ago now, and we've made serious progress (hindered by student laziness). We've got our machine "nearly working," which means... we need to build extruders, fix the firmware, and probably some other things that should have happened a year ago. We're also making a laser-based 3D scanner (someday we'll have software), and some other things.

Whoops, this post was about me, more on TEC later.

Anyway, after a half-year of TEC and one scrapped laser-cut Darwin, I realized I was now a senior. Time to kick it up a notch perhaps. As I stated earlier, my senior project ideas were pretty crazy. With help from best friend Griffin (original introducer), I decided to aim even higher and build my own 3D Printer. The darwin parts were done, but the price on the non-lasercut parts was too high. That's when I found the Makerbot Cupcake CNC. A simple printer, less print area than the Darwin or later Mendel, and a huge price tag. However, I realized that I could probably get all the parts locally, and a large part for free.

The plywood was mooched out of TEC's supplies, and laser cut for free. That and the free acrylic provided me with 50% of the parts (by volume). As for the electronics, well, I knew how to solder, and so I simply ordered the PCBs alone and over time ordered the components from Mouser and Digikey (a note about this later!). As for the other parts, well, I have Tacoma Screw nearby to go to for cheapish nuts n' bolts, and Harwicks' for other parts.
After thinking about it, I decided to improvise wherever a component would cost too much(more than $50, I'm cheap), and so I have a custom $10 X-Y stage from aluminum rod and brass tubing, and I've been designing a laser cutting pulleys for belts taken from printers. Actually, it was Griffin that did the designing for the first pulleys on Z. They work great.

That note about the electronics? Yeah, never, ever order $40 in crucial parts via usps just because they are the cheapest! It's been three weeks, and they're still in the mail!

March 7th, and the electronics are nearly done (grr), the frame is complete, and the X, Y, and Z stages need little more than their pulleys to be cut out. The extruder is non-existant, and I need to build the entire thing - luckily, I have a laser cutter.

That's all I can write for today, but I'm going to go submit this to the aggregated reprap and makerbot blogs. G'night all.

* Depending on who you ask, this is either "Tacgnol" or "Torchwood" Engineering Club... Club.