Wednesday, 30 March 2011

repstrapping the cartesian bot

The next stage was to add the parts required to turn the Cartesian bot into a repstrap.

For this I needed an extruder, this basically feeds the plastic into the hot end.
There are a few options for extruders, I went for a Wades geared extruder as there where readily available on e-bay.


This also requires a hobbed bolt, I also got this on ebay





Add one stepper motor and assemble and you end up with something like this.

Now my gear is actually on upside down, this is due to two reasons, one the hobbed bold seems to have the hobbing in the wrong place, and secondly the gear would catch on the stepper motor bolts. It works fine this way.



Next I needed a way to melt the plastic, this consists of two parts, the heat core and the hot end.
Due to time constraints, I wanted this before x-mas, I got a local engineering firm to make me the equivalent of a mendel parts v5 hot end  The peek and the PTFE came from DOTMAR, the brass the engineer has in his scrap bin.


For the heatcore I ordered one from makergear The instructions where very complete, even a near sighted monkey could make these.


I tested the heat core and hot end just by pushing plastic into the back of it, and got a nice 0.5 stream of plastic.

I joined the Extruder to the hotend with wood screws to a block of wood. The block of wood has a hole threw it for the 3mm plastic


Next I needed real reprap electronics so the software would be able to control things.

Once again I went to ebay.com and found that Gen3 electronics where readily available


These came pre flashed with the reprap firmware and boot loaders.

I wired everything together for testing and found I had an issue, the stepper motors I have wouldn't work on the extruder controller.


these are Lin Engineering steppers from alltronics 

Attaching the stepper to the extruder is a bit of a hack, they use standard motor controllers to drive the stepper motors. It apparently works really well, unless, you guessed it, you have Lin Engineering steppers.

But all was not lost, I just needed a real stepper controller, I found that a local supplier robokits.co.nz is New Zealands distributor of Pololu products including their very nice stepper controller so I orded one.

I made a simple break out board for the Pololu

 
The connectors are now compatible with a standard reprap stepper board.

After more testing I was happy that all the electronics works as it should, I attached it to the Cartesian bot




And a repstrap was born.

In the next installment software...
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