Monday, April 19, 2010

Slowly moving forward

Well, I haven't posted recently because I haven't spent much time actually building this thing, but here's a post to sum up what's been going on as of late. It's a bit long, but a lot is talked about here! MakerBots, Extruders, Thermocouples and firmware!

  • Got onto FamiLAB's MakerBot, and with the help of it's owner, began working on building Mendel pieces. We tuned it up a bit to get somewhat decent results out of it and started spitting out some decent builds. I built about 25 pieces over the course of a couple weeks worth of work (taking a bit of time every day after my normal day job).
  • Got the extruder mostly assembled, just need to cut/bore out the heater block and get the solid state relay for the heater part. Hopefully the cartridge heater will work well!
  • Brought most of my parts over to FamiLAB and started assembling a few pieces.. Looks like I'll be going with Nophead's pulleys for the belts, as they only require one small flat on the shaft of the stepper. Since one of my steppers has no flats, that'll be a lot less filing for me to do.

But, oh no! Tragedy strikes! The MakerBot begins having issues extruding! For some reason the heater does not seem to be getting hot enough and the motor is unable to push the filament through! I cleaned out the inside of the nozzle twice. We installed a new MakerGear HeatCore and got the new heated bed, but we're still having issues with temps. Now, the extruder controller board seems to reset when we begin extruding. This is an issue.
I tested my TechZone extruder controller, and it had the same issue. Seems the motor is getting up to 900mA at certain points when hooked directly to a 12v supply, so it may be pulling too much current, causing the current limiting on the power supply to drop the voltage far enough where the controller resets.

I've decided to try and speed up things a little here by switching out the entire extruder. My Wade's geared extruder seems to be ready for primetime, and looking at it, I should be able to make up a small bracket to mount the extruder on the MakerBot's Z platform. (Someone made a laser-cut bracket here) However, I'm having issues trying to figure out how to set up the firmware for using a stepper, and also how to set it up for a thermocouple, as we'd noticed somewhat widely fluctuating temps while using the thermistor. (Would slowly climb to 189, then jump to 195, then 203, then  221, etc). I have two K-type thermocouples with those nice amplifiers I had shown previously, so I want to hook one in and use that as we may get slightly better readings. (I had the two hooked up side-by-side, and while the thermistor temps wavered around, the thermocouple was rock solid)

So, my main issue currently is trying to edit and get the new 2.0R1 MakerBot firmware to actually compile. I've loaded Arduino 0018, and when I get the Sanguino extensions, it seems they no longer come with the libraries their website lists in the install directions on their main page. I downloaded the sources for the MakerBot firmware from G3 Firmware @ Github, and modified the Configuration.h.dist file to support the motor, but I can't find how to set it up for the thermocouple. I searched for an hour or so and found a place where it seems to sample a thermocouple (Heater::sample_thermocouple()), however, it seems to be written for the up-and-coming extruder controller, which has what looks to be a Maxim chip of some sort, which provides a digital (serial) output of temps, rather than just reading an analog input.
The older firmwares seem to be able to do this, but I'm not sure if i should just comment out the code inside there and replace it with a routine to measure and return the temp using the analog input, or what format it's wanting the temp to be returned in, or how to even properly activate thermocouple use.
I'm trying to get ahold of some of the people writing the firmware such as Phooky to see if they might know what I should do. Rest assured, I will be creating a page on the MakerBot Wiki to document how it is done from start to finish, as I'm sure I'm not the only one wanting to use a thermocouple analog-style.

In other news, from a very helpful comment on the MakerBot Operators group on Google Groups, I've been provided with an interesting insight into some difficulties we've been having with the MakerBot while building parts.
Basically, there's been a number of issues with communication with the extruder, showing up as random pauses in the X/Y axis while the extruder keeps extruding. These last upwards of 10 seconds at a time, causing a huge blob of plastic to form around the head, ruining the piece for all intents and purposes. Since recovery is rarely possible due to resetting the extruder being the only way to fix it, you will at best, lose one part, and at worse, lose a whole tray of parts. This is very frustrating. I tried every bit of info I could find on it, to no avail; we continued to have problems. However, this fix is interesting. Since in our situation we have all the opto endstops unplugged due to issues with light getting in, and the fact that there is no terminating resistor in the spot near the top of the extruder, it may be as something as simple as the RS485 bus not having a terminating resistor on it. This could very well cause the problem, and I will be adding a link into the MakerBot Wiki troubleshooting page as something that should be checked when there are print pausing issues. Here is a link to the RepRap Wiki showing the component, it's value and location, as well as purpose. I'll be doing this first thing when I get back to FamiLAB.

Here's hoping it goes well! I'll keep updating with the status of my progress with this MakerBot geared extruder thing...

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