Much, much better week

First Off:

The machine runs!

This last week we ordered replacement parts for the driver boards and ordered new driver boards for redundancy. We built up a plastic extruder based on the Plastruder mk-4, with modifications to the "dino" support structure. We borrowed a heater system from the supplies built for TEClub, as it is not yet being used, and began to test it out. I made some more

modifications to various plastic components, and tuned the hardware until I could rely on good movement and solidity. We saved the burned up board -- on the same day new drivers arrived. I ran some tests and confirmed it working, but because we could not have three of the same driver I have retired them for now, but they will be back in service on the next 'bot.

We had some interesting setbacks!

First and foremost, we found that the 200W PSU is not able to drive both the heater and the steppers, and would power down when both

were used. This was "solved" with the addition of a second PSU to power the motors. The two PSUs share a ground, but are otherwise not attached in any way. This is a sub-optimal solution, because as we found out the stepper motors would continue if for some reason the heater and its PSU went down (probably a short or something). We may invest in a really good PSU later. For now, it works.

Another issue we discovered was that despite acting as a loopback, the hacked-together serial cable really just seems to have stopped working. I bit the bullet and bought one that was tested from the Metrix Create Space, best place ever for people working on interesting hardware to hang out. With the new, working cable, we programmed all the boards (on the first try, too!).

From there, with working heater, boards, and motors

, it was only a few hours of debugging and reprogramming (extruder board inexplicably decided not to drive motor one on its own pins) for the machine to actually begin to extrude hot plastic. Today, we made the first few prints in just an hour of tuning skeinforge. We first tried a teacup, but the Y-stage went bonkers and every layer was off by many millimeters. We fixed that, and went with an open rectangle, and this showed us that we needed to adjust the feed rate -- we get something higher than expected, about 35mm/second. When the rectangle worked well enough, we moved on to the terrific dodecahedron. After a few false starts and some strange power-downs, this shape printed out very cleanly.

I think it looks great. We made another one so that each of us user/developers could have one. I also took a video of the build, and intend to use it for my presentation. That's in one day, so I'll be working on that for a few hours.

Visit our reprap wiki page for more info!

Two Steps Forward...

Some large number of steps back.

This week we got the mobo programmed!

The Tx and Rx lines on the serial cable I hacked together were reversed, whoops. With the motherboard programmed (extruder still playing hard-to-get) we actually got the machine sorta running.

Now, we also found a solution (or, as I explain later, not a solution) to the

regulator problem.

The problem is the lack of regulators. The solution was jumping the 5v ATX line to the 5v output on the regulator pad, thereby supplying the board with 5v from the PSU. In practice, this was 6.4v.

This solution worked fine, though we were not able to make the board that sparked work (probably dead now). With two SMD 2.3 boards and one SMD1.2, We got it to connect to Replicator G with about 12 hours worth of resetting, plugging in, resetting, etc. After an 11 minute "print" (no extruder), there was a smell like ozone in the room. I ignored it. On the next startup, the smell returned, stronger. Ten seconds into operation, there was some serious sparking, smoke, and fire from one of the stepper boards. Capacitor c-6 had blown up.

Ouch. The capacitor has rotated perpendicular to its original orientation, and there is a hole burned into the board blow it. I am not yet sure if the chip itself is dead. if it is, that leaves us with only one SMD 2.3 board that still works... not much of a machine. The SMD 1.2 is on loan, and not meant to be a permanent addition to our machine.

With one week before presentation, classes starting tomorrow, and very little money left with which to order parts, this development is pretty bad. I have ordered more capacitors, some real linear regulators, and some resistors that were near the blast that might need replacement. The chips themselves may need replacement too, but I want to diagnose what we have and not spend money we don't.

Here's a shot of the board with the capacitor removed.

On a non-reprap note, I also dropped my laptop on the serial cable's USB end, and tore out a USB port. No way do I have the money to replace that ><;. I've simple amputated it for now. That leaves me with only one USB port. This is not, as may be intuited, a good week of work.

Oh, and my dog died. No, seriously.

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.

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.

Week's Worth of Update

I think I said I was going to update "tomorrow" two weeks ago.
Whoops.
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!

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.

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.