Sunday, May 1, 2011

Prusa Mendel Almost Assembled

Man, this is fun! Sure, it takes time, but you are also building a cool machine from scratch! I take it easy, and think through every step as much as I can in my head, before actually doing it. You can come up with a few tweaks here and there, and really, you don't have to do exactly what documentation says. I mean, as long as you know what you are doing, you can do things differently.
These differences may even be for the better... For now though, I will just build this to make it work printing. Then I will probably optimize some. Like rerouting wires in the base and just basically clean it up so it looks nice too. And maybe also add a fan and end-stops for Max values (currently you use for Min values, which means motors will stop at basically point 0,0,0 (Home position). You may also want this "Max value" so you for instance can let the Z motor go all the way to the top when a print is done for example). I just love the flexibility you have with this open source/hardware 3D printer!

There have been a few bumps, and redoing during this time, but it's really stimulating to have eureka moments every now and then when you reach certain milestones. I had one when the motors worked, and the first time you move the platform back and forth, you do it for like 10 minutes because it's exhilarating that it works. And just now I used repsnapper to turn the heat on in the nozzle (extruder, hot-end), and checking the temperature. And I was happy to see it worked! It's important to test these things, especially the nozzle because if it gets too hot, that ain't good. I was afraid the thermistor (the component that reads temperature) wasn't properly installed with the crimps. But thankfully it works as it should! Would have been a lot of extra work to expose that part again, as it's in there, in that black thing you see in the picture...

There is a function in repsnapper to set the heat to a certain value, and I was amazed how well it worked. I read the thermistor value periodically, and could see the temperature increase to the set value (in this case 100 degrees Celsius). Then, it went little over (to 110C), and then went down to the set value (100C) and stayed around there. Turning the heat off, and I could also see the temperature drop... I also tested just unplugging the USB to the Arduino, and was glad to see that it means power off to the nozzle as well. That is good news as that means the heat won't continue to increase if you just unplugged.

I was also glad to see end-stops are working. These are important so the motors will stop and also, so it can "go home" and the printer knows where it is, and can use that as a reference for printing.

You communicate over serial with the Arduino 2560, and here are some useful starter commands for reference:

M998 - Turn on pull-up resistors. (Needed for M999)
M999 - Get X and Y endstop values. (1 means not triggered, 0 means triggered)

M105 - Read thermistor temperatures

And here is a list of many more:

More images and updates to come.... I basically only have to connect the heatbed (the big red thing you see in the picture), and then I'm off to actually try to print something...

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