Monday, September 08, 2008

 

PIC24 printing from SD card


A few pictures to show where we are, this output has been made without any stops and starts of the extruder.

The twin drive extrusion head that produced these parts is not quite the same as the standard Bitz from Bytes item.
The head features Opto speed control feeding back to a PWM output to the two motors.
Extrusion speed held +/-1rpm.
The temperature control is just an "on if under, off if over" control via a FET.
Temperature is held +/- 1 DegC
Round other side of the controller is an LCD readout of the setting and achieved values for temp and speed. Both temp and speed have adjustable POT's for local setting and quick testing, it saves so much time if you can make these changes on the fly.
The next step is to hook up the serial link and make changes via the G-Code.
I still have a fair way to go but first indications are looking good.

Build of the bracket, left and below, is without any fill







It aint perfect but when I get the cooling sorted out!
The rather nice rim on this "glass" is due to a failure in the Z-Drive part way through.
All parts are saved onto the SD-Card, ond only take a fraction of the space available.
Each of the parts above had well over 5000 lines of G-Code. I dont think we would have any problem putting a whole machine on a single card.

Comments:
Twin drive? im all excited - tell me more?

It looks like the extruder mount you show is just edge and no infill ?
 
Notes added
 
are you using the 24f demo board or are you using a custom board?

Also what are you using for output to the controller boards the parallel port?

post some more info I have been looking into this myself but with using the Arduino the PIC24 or 24F looks to be a lot easier and cleaner. I think working with out a computer would be a huge feature we need to get this to move into every body's home!!

Great Job!! And I would love to help out..
 
This is great work! Please post more info and pics. Those are some really nice looking prints even without things being all nice and fixed.

Demented
 
Brilliant! Great stuff! :-D
 
Yeah, love this stuff! Maybe this twin drive is also an option for me. Many of your design choices are inspiring. I hope I'll be milling PCBs soon as well. I've made the dremel toolhead you described:
http://forums.reprap.org/read.php?1,13435,16750#msg-16750

Making the PCBs and parts from SD card would be an extremely cool way of producing subsequent RepRaps. You just ship someone parts and one SD card and he can do the same... The contents of the card would have to be adjustable, so you can make various choices.
 
Thanks for the comments Erik, the PCB milling worked better than I expected, only thing to watch was keeping the tool vibration to a minimum plus keep it all in tight to the axis to control the torque reaction of the tool.
The router attachment has all been removed now to run the extruder head.
Twin motors were used to reduce the duty and improve reliabiltiy. I tried single and twin drive back to back and the twin motors seem to hold the speed more stable than one alone plus they will have twice the pull out torque to cope with tight spots.

Ian at Bitz from Bytes produced the special top plate for me so if you want to try one then drop him a line.
 
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