Monday, April 12, 2010

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!

Sunday, April 4, 2010

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.