Does anyone have a strategy for milling the mounting holes for replacing the Hybrid Table mdf boards? I’ve been scratching my head about how to handle this. Because of the travel limitations of the SO4 XXL you can only bore 3 of the 4 holes required for a replacement. As far as I can tell Carbide hasn’t given up the Cad files for these boards so all my measurements are off the existing layout and a few posts people have done. I know I’m going to have to flip the board to mill the 4 hole, but I haven’t come up with a really strong strategy for relocating the board so that the 4th hole is positioned correctly after the flip. I know this is going to be similar to a tiling operation but I won’t have dowel locating pins to do the locating. I’ve been experimenting but have wasted a good bit of MDF trying to get that last hole in the right spot. Anyone successfully done this yet? As a side note I’m finding that the SO4 ability to return to a previous home position between ops on my machine seems to drift and its unclear why, some time as much as .020" ± on x,y and I’m not rehoming.
If you rotate the board, it will fit — I just put a thin sheet of MDF down a bit larger, mill a pocket w/ dogbones, drop the board in that and machine away.
I’m thinking this through what you did. So you milled out something to retain the blank, so that when you flipped the board the positioning stayed the same. I guess in that case I’m going to have to make sure the length of the board is absolutely symmetrical. My thought was that the center of the work piece should be the origin to help remove some of the board to board variation but I suppose as long as the boards are the exact same length what you’re describing should work.
I cut from larger sheets, so rough-cut over-size, secure in the center of the even more over-sized pocket, and machine the holes first, then screw into matching hardware in the MDF filler strips (it was too fussy trying to line up w/ the T-tracks), then remove clamps and machine the perimeter.
Yeah I see how you did it. I have all of my strips cut. They are about 1/8 longer than 40" it might be possible to work a jig like this.
Given that Carbide3D intends for customers to mill their own replacement boards, could the company provide some templates or other resources to simplify this process. Otherwise, every customer will need to reinvent the wheel or rely on a third-party.
Please see:
Wow. I actually think that confused me more but I’m assuming that is working from a whole sheet of MDF and not in the case if you have already cut the strips down to dimension and are working board by board. I’m hoping to have time to tackle this again tonight and see if I can get a workflow that is repeatable.
I don’t have a Pro, but I have a machine that uses a typical aluminum extrusion bed. It’s setup for vacuum, but I typically keep strips on it. It’ll cut a full sheet of material; however, I find it more efficient to cut the strips and drill the holes off the machine. You could make a jig for the holes, I did, but never use it.
I might be wrong on this, but perhaps it may be easier and simpler to just drill the holes by hand and just have enough clearance to account for the tolerance you can realistically get? Otherwise it kind of seems like a huge pain to create new slats for the hybrid table based on what I’m reading here. Could be wrong though as I haven’t had to do this yet.
Getting the first 3 holes is easy. Its relocating the last hole precisely after a flip which is more complicated. I could do it by hand but its certainly faster to have a cnc workflow that will do the counterbore and hole and flip. Honestly if there was some way possible to add probing to a Shapeoko the world would be a much easier place. I have the bitzero v2 and I don’t find it to be all that accurate for locating unless you are just roughly finding the corner of the piece and roughly trying to find Z. The Z offset values I get out of mine are usually off by .010-.020" so its a game of compromises with this flip operation.
I can’t imagine why a waste board slat would require any degree of precision. I make mine out of Phenolic or HDPE, so at least $425++ per sheet material cost. I run the slats off on a table saw, but you could use anything, track saw, circular saw ect. Then I scribe some hole locations, drill through and then counter bore. I don’t try very hard.
The problem here is many folks only have the CNC, and no other power tools — an XXL slat is a long cut to do by hand — I think you could get a largish flat sheet sufficiently on the wasteboard to hold it in place and drill holes, secure in place, and then cut out, but it would require an outfeed table or something else at the same height as the machine baseplate.
To be fair I’m making my boards out of Mic-6 to add more mass to the unit. I like the T-slots vs a single plate of aluminum so that leaves less margin of screwing these up.
Well any additional words of wisdom. I know my cad model is right, cam is simple with boring operations. I calibrated over and over in this machine but I can solve positional inconsistency issues to get 3 stupid holes bored out . Im not losing steps but over the course of the most of the Y axis my 3rd hole is always a few mm off such that I can’t get a bolt in. Ive had the worst time ever with this xxl pro with getting reliable accuracy which is odd because I didn’t chase this stuff like this in the SO3. Ive only had this thing for a few months and while the rails may be more rigid this kind of stuff makes working with larger projects worthless because I can’t reliably place features without cutting 20 scraps first
I was very overwhelmed when I got my cnc and needed to make new slats. I ended up just custom ordering them from Carbide 3d. Can’t remember the cost, but it was super reasonable.
Have you calibrated for belt stretch?
Yes but I’m learning that the tolerance for calibration is less than 12” or so and then the calibration shifts. My guess is the reason this was easier is on my SO3 xl it was easier to Calibrate and hold tolerance because the belts were shorter. On the so4 xxl the belt stretch pattern is basically uneven so the calibration is shifting based on where I’m cutting these positional holes . That’s the best I can come up with
Please measure what you can and send that in to support@carbide3d.com and we’ll do our best to work through this with you.
Things I think are worth trying:
- flip belts end-for-end — does this change where things are?
- a new set of belts — let us know at support@carbide3d.com and we’ll send them
The fall-back position for this is the sort of work @RichCournoyer has done where parts and feature are made over/undersized, things are measured, and the file adjusted based on the placement/size of things from the roughing pass — that shouldn’t be necessary for MDF though.