Quick Change Build Platform for TOM
by tomlombardi, published
I really love my heated build platform with an aluminum top covered with Kapton tape! It's an awesome way to go, but I REALLY miss the automated build platform for repetitive, decorative and small parts. I miss the fun of watching a part dropping on my desk. The sadness of your trusty ABP sitting on a shelf... it's just not right.
This thing makes it right again, no tools, just unplug and press the release and in 20 seconds you've swapped out the HBP with an ABP! Another benefit is that you can pop out a platform to service it, i.e. put new tape or fix a belt.
I've designed this upgrade to be completely non destructive, a bolt in replacement. You won't loose any build area, it replaces the undercarriage of both platforms.
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All parts were printed on a TOM with a MK6+ on a heated build platform. My settings were: Object infill% 35, Layer height(mm) .32, Number of shells 0, feedrate (mm/s) 32.
Instructions: Print all of the parts on a HBP for accuracy. Take the time to clean up all of the flash in the slots, I use an xacto and an emery board. Make sure you clean up the ridge along the side of the carriage, you want that to mate nicely.
Remove the bearings (or buy extras) from your ABP and press them into the carriage, don't glue them they will stay in just fine. You'll need twenty 3X10mm screws and two 3X20mm screws. Install the new sides, front and back to your ABP and test fit your carriage, it should snap in nice and snug. I put a little pressure on the release to keep the wear down on the latch.
If everything looks good it's time to remove your HBP from your TOM. Before taking apart your HBP slide the carriage on the X axis rods and test fit it in the machine. This is where I had problems, because we are printing this carriage in plastic and plastic tends to shrink I had to tweak the carriage dimensions to get it to slide freely. Mine was just slightly too wide (< 0.05mm) so I got it out of the TOM slipped the two rods through and gave it a slight squeeze, when I placed it back in the machine it slid freely. Get this right before you proceed, you can still put the HBP back in, tweak and reprint a new carriage if you need to.
Once you are sure the carriage fits install the belt to the bottom of the carriage. Use the belt block and two 3X20mm screws and nuts, the notched edge of the belt block points toward the front. Snug the block down but NOT TOO tight, you'll notice a SLIGHT bow in the wall behind it. Give it a tug, it's not going anywhere!
Install the carriage in your TOM, nose forward, the belt will be looser because I've fixed the geometry, the belt is inline with the carriage and doesn't tighten up towards the end of travel. Reassemble the Y stage and adjust the belt.
Install the new front back and sides to your HBP. This is where I ran into another problem, the slots on the HBP and ABP were the same in the MBI drawings so I thought I'd only need to design one set of interchangeable sides, I found my HBP slots to be slightly narrower. I have build 3491 and there was an update so I designed some that work with my build. I've included both sets of files, if you are not sure what you need you might want to print both before you rip the thing apart!
So now that you've got it all together, grab a platform and hook the back of it around the back of the carriage, and snap the front down until it clicks. I put a little pressure on the release to keep the wear down. Next plug the cable back in and fire up your TOM.
You'll need to recalibrate for both platforms. The motherboard onboard preferences will need to be changed each time you change out the platform so I've included two handy scripts, "USE ABP" and "USE HBP". Once you get the new calibration numbers for each platform just enter them into these scripts then when you change platforms select the appropriate script and it will write the values in your motherboard onboard preferences. Place these scripts where the File->Scripts->Calibration live so they are handy. These scripts will remind you to change the machine type i.e. "Thingomatic w/ ABP...". Don't forget to select the correct platform when generating new gcode.
Notes: I almost didn't post this thing because of my concern of whether the carriage will fit correctly in other TOMs. I'm use to much higher precision while working with metal, even if I get it right others with slightly different setups could get different results.
Also note: I shut down my TOM before I unplug my platform just to be safe. An ESD could kill your board and it's better to be safe than sorry.
Well that's it. Sorry for being long winded, I've spent days on this project and piled up a small mound of rejected parts, I hope it works out for others. Owning my TOM has been a wild ride, what an amazing little device, my thanks to all of the people at MBI and all of you in Thingiverse.
PieterBos made me aware of thing 8158 a Thing-O-Matic X-Axis Follower, which has origins back to Ed Nisley and has been improve / modified by Cariac, Tbuser, Joakim and others which would solve my biggest concern with my thing. I had to print many variations to get the carriage to slide freely and included the one that worked. If I modify my thing to include this follower idea it would solve this problem, however I don't have any 693 bearings laying around. I spent a few hours today modeling an experimental carriage that includes this follower feature. If someone out there would like to play with this I would appreciate it. I've incorporated a .1mm preload suggested by Ed Nisley. I've left a .8 mm space behind the bearing for a spacer / washer. I have these bearings on order and I'm going to try this asap.
For the experimental carriage you'll need two 693 (8mm X 4mm X 3mm) bearings, two 20mm X 3mm screws, nuts and washers.
I received my 693 bearings in the mail from VXB and printed the new experimental carriage. The experimental carriage is no longer experimental, it works! I'm very impressed by this X axis follower idea, it is ultra smooth with no slop! So go with the carriage with follower if you can get the bearings, this makes this upgrade fool proof.
UPDATE 12/27/2011 I unintentionally left out the T-slots on the center part of the ABP sides, I've fixed this problem and uploaded the new files.