Thing-O-Matic Hackage
Ed Nisley
the mechanical bits of Thing-O-Matic 286 seem to be flying nicely in
formation. I made several changes to the stepper motor controller
boards, the extruder controller board, and the mechanics that should
improve overall reliability and eliminate many of the weird glitches and
random behavior that seem to plague the thing.
I'll be dumping the notes & photos to my blog over the next week or two,
with the first post up today:
I'm doing this in bite-sized chunks and will appreciate any comments /
suggestions / critiques / improvements on each part. After my TOM
accumulates more power-on hours and you've kicked my notes around, I'll
write up a summary of whatever seems to be the consensus.
Still to do: Thermal Core measurement and tweakage...
Andrew Plumb
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"The future is already here. It's just not very evenly distributed" -- William Gibson
Me: http://clothbot.com/wiki/
Ed Nisley
> fixes that can be done to existing boards
That's the ticket: they're all modifications I applied to the existing
boards. Indeed, I applied them *before* firing the thing up for the
first time. Most are fairly easily removed if you decide they're not for
you, albeit the boards will be scarred for life.
I've given the good folks at Makerbot a heads-up on most of these and
(assuming what I'm doing makes any / enough sense) they can do a far
better job than I of blending any changes into the next board revision.
> thermal paste-type material
I just stuck half a dozen thermocouples onto the instrumented Thermal
Core and started running the first measurement this morning. It'll take
a while to work through all that...
> tinning the underside of the housings with lead-free solder
That probably won't work well, simply because the resistors have an
anodized aluminum shell: tough to get solder stuck on that. I like the
idea, though. Perhaps carve a pocket on the bottom of the resistors and
cast some solder in place?
Good old JB Industro-Weld epoxy is rated to 500 F = 260 C, which should
barely suffice. The MSDS sheet says it's 10-20% iron filled, so it's
probably thermally conductive enough for the job; a thin layer of nearly
anything is a pretty good thermal conductor.
Numbers! We need numbers!
Andrew Plumb
On Thu, 2011-01-06 at 10:18 -0500, Andrew Plumb wrote:fixes that can be done to existing boards
That's the ticket: they're all modifications I applied to the existing
boards. Indeed, I applied them *before* firing the thing up for the
first time. Most are fairly easily removed if you decide they're not for
you, albeit the boards will be scarred for life.
thermal paste-type material
I just stuck half a dozen thermocouples onto the instrumented Thermal
Core and started running the first measurement this morning. It'll take
a while to work through all that...tinning the underside of the housings with lead-free solder
That probably won't work well, simply because the resistors have an
anodized aluminum shell: tough to get solder stuck on that. I like the
idea, though. Perhaps carve a pocket on the bottom of the resistors and
cast some solder in place?
Good old JB Industro-Weld epoxy is rated to 500 F = 260 C, which should
barely suffice. The MSDS sheet says it's 10-20% iron filled, so it's
probably thermally conductive enough for the job; a thin layer of nearly
anything is a pretty good thermal conductor.
Numbers! We need numbers!
Makerbot Number Nine... #9... 0x09... 0o11... 0b1001...
http://clothbot.com/wiki/MakerBotNumberNine
Andrew Plumb
Ed Nisley
> tempted to drill a couple of thru-holes
The reason for not doing that is that the MOSFET Source pins (all three
of 'em!) are on the top surface. The Drain has all those heatsink vias
to the bottom surface, but they're all on islands isolated from the
ground plane.
The only current you want in those additional ground pins comes from the
Source pins a few millimeters away, so the biggest fattest widest
connection to the ground plane is the way to go.
The next time I have the hood up, I'll probably lay a fatter wire across
the Source pin connections, too, but they're probably Good Enough as-is.
> the DC driver was at the long end of the 12V trace
That ought not be a problem after getting 11+ amps of heater current off
the board, although measuring the actual voltage drop to the motor
driver would be a Good Idea.
Let me know how it works out...
hybot
I also like Andrew's idea of drilling thru-holes for the ground, if only because it's less likely I'd screw that up.
hybot
Ed Nisley
> connection in the screw terminal block I'm oblivious to?
Nope, cutting the trace isolates the +12 V terminal from the rest of the
board, so you could poke two wires in the same hole with no problem.
The only reason I used those pins was that they allowed a semi-permanent
power connection to the board that's independent of the heater wires.
Having to not only get the heater wires in the proper terminals, but
*also* doubling up the +12 V lines, seemed like I'd be able to get it
right almost all the time...
hybot
Ed Nisley
> Even though I botch about 50% of my electronics projects
Well, I'll be writing about a few mistakes of my own... as soon as I
work through the humiliation. [grin]