Unrepentant Geek (matthew) wrote,
Unrepentant Geek

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Makerbot madness

I finally took some time to poke at my makerbot again. gordonmessmer and I tried to get it working again in a fairly standard config only to be reminded of how much the mk4 extruder sucks. Many moons ago when I was spending more time with this machine I had printed and intended to make a Wade's Extruder work on my makerbot but ran into some unspecified issue with the extruder firmware or hardware. Folks in #reprap pointed me to this article on how to get a makerbot to use a stepper driven extruder. Since I happen to have an extra stepper board I set about combining all these things. Lo and behold, it actually worked... mostly. So, if you have a makerbot and want better extrusion without spending the cash on a Mk5 extruder (which I still have my doubts about) follow these exciting instructions:

Build your own Wade's extruder and assemble it. I used this tool to make hobbing the easier. After breaking my one good M3 tap I picked up a 6-32 tap and used that to hob the bolt. This works better as a #6 calls for a clearance hole of about 3.5mm which should provide better grip on the 3mm filament.

Cut one of these out of 6mm plywood or similar. I also highly recommend the use of adjustable endstops. I even went so far as to design some adjustable endstop flag mounts for my Makerbot. They work ok, but are probably due a redesign. Assemble everything and mount it all up in your makerbot.

Follow these directions to hook up your stepper controller. I used an external stepper driver rather than using the extruder's H-Bridges as I had an extra gen3 stepper driver and I have some doubts as to how well my H-bridges are working right now. I followed the directions to grab the source code and reflashed my extruder to use an external stepper. I mounted my extruder and extra stepper controller above the mainboard on the side of my makerbot. Very tidy!

Download the latest ReplicatorG (0023 as of this writing.) I've been manually modifying the generated gcode by doing a global search and replace of "M108 S255" with "M108 R6". 6 RPM seems to work well. I tried a decimal number but that caused a java exception while estimating build time. 8 RPM was too fast, and 5 too slow. 6 appears to work well as all of the objects I have printed since come out quite strong.

The only change that I have so far made to skeinforge is in Multiple. The default is set to 'on' with the center at 0,0 which puts the printed object in the lower left of the build platform. The problem is that any overhangs into the -X and -Y direction cause the bot to trigger the endstops, which makes the prints all wonky. Instead, set the center in Multiple to 50,50 and the bot will move there when it starts to print and avoid all that.

Do all of the above and printing is as simple as:

  1. Start up ReplicatorG, connect to the bot, open the control panel and set the build platform temp to 120.

  2. Open your design, center, scale, etc and generate the gCode. Pick the appropriate profile and edit it for Multiple as above.

  3. Once the gcode is generated, use Find to do a search and replace of "M108 S255" with "M108 R6"

  4. Once the build platform is at temp, use the Home menu to home all 3 axes.

  5. Hit the Build button

The Makerbot will do it's little startup ritual. Once you clear the test extrusion and hit Yes it will move to somewhere in the middle of the build platform and start a raft. After that it's just a matter of waiting for the print to finish.
Tags: makerbot

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