So I’ve posted here about this before but here we go again. So I’m having an issue where the cut paths don’t line up with the file. I have a relatively simple Hexagon file that consists of one pocket tool path to hog out some material and leave some standoffs and then a contour file to cut the piece out. The stock material is a 6x6x0.50" piece. My shapeoko starts cutting about 0.25" closer to 0 on the Y axis than it should.
as you can see the files believe the piece should be centered. Carbide motion thinks the piece should be centered. To address what will be asked:
No there was no crash, nothing held the bit from moving, the spindle didn’t run into anything.
Yes my 0 is set, yes it matches the origin in the file. I even verified the 0 was correct again after this error as you can see from the bit floating over the 0 point on my fences here
as you can see from the above image the machine cuts the hexagon about a quarter inch too low. Anyone else running into this sort of an issue? I would love a fix this is getting really old, I do a lot of two sided machining and if things aren’t indexed perfectly it’s a huge issue.
From this thread it seems calibrating the machine for belt stretch would be something you would do to optimally dial in the machine past the base settings. I’m a woodworker and only run wood and acrylic on here, and honestly I only need like 0.001 tolerances. Do you feel that doing this optimization is going to fix this problem or were you more of wondering if maybe I screwed something up while doing said optimization?
Sorry you’re 100% correct on this particular one, I actually ran the 6x5.4375 file on a 6x6 piece of material so that’s definitely where that huge deviation is coming from. HOWEVER, I was going to post about this before running that piece as I have been having issues with other pieces aligning between the file and real world. I re ran the file on a 6x6 and this was the result. Still not matching what carbide motion thinks it’s sending out.
Top
The left and right distances should be 0.266 evenly top and bottom should be 0.565
So here’s the two pieces next to each other 1st run with the wrong sized file on the left new one on the right, so you can see it’s closer but it’s still not right.
How did you set your work zero? If you want something centered on your stock, use the center of your stock as your work zero.
Can you measure the width of your cut slot?
Work Zero is referenced off a fence. I regularly recalibrate the 0 to the fence with a bitzero as well as using it to set my Z 0 when I switch material thicknesses. Width of cut varies from 0.250 to 0.256 depending on where in the slot so within tolerances I would expect from machining MDF.
There are many ways to get something centered in your stock, in this case the vectors are aligned to center stock in Carbide Create before the toolpaths are created. I assure you it’s centered in the stock as you can see from the images I’ve attached of both the Carbide Create file as well as the preview out of Carbide Motion. You can check out the file I’ve uploaded to this thread if you don’t believe me
Are you using bitzero v1? if so, I believe tool diameter used to zero will make a difference in x, y. I could be wrong because I do not have a bitzero but using a Triqueta with cncjs, I had to write custom macros to account for tool diameter to zero with bits of different diameter. I do not use a touch probe anymore, favoring Neil’s suggestion of zeroing x,y to stock center.
I believe you that the design is centered in your files, but it is not centered on the stock (the reason we’re here). If you set zero at the stock center, the result will be centered regardless of dimensional accuracy issues due to belt stretch or deflection or calibration settings or effective cutter diameter or errors in your XY zero.
In the c2d file you posted your design is in the center of your stock. I would think that if the hex is dimensionally accurate, the .5" squares are the correct size and in the right position, the machine is in good working order. The only other variable is how and where you set X/Y zero. I’d try diagonal lines corner to corner and a vee bit at the intersection to set X/Y zero.
So you’re suggesting that if I drew a line from each corner of the stock across the face and set the zero at their intersection that the file would somehow behave differently than with the zero set at the bottom left like I have it?
What in the world is the point of having a bit zero and a fence setup if I’m going to have to manually set the zero to the middle of a work piece every time and more to the point since my values all line up on the model and on my real world stock pieces why am I experiencing such errors? I understand you’re saying that doing a center zero is likely going to help with this due to the nature of the zero being in the center keeping things better centered regardless of the stock size but why is this necessary if all the data is correct in my file with the zero set bottom left? Seems like the machine isn’t working like it should be at that point. Also my hexagons are coming out at 4.350 instead of the 4.370 which means the tolerances are 0.020 which is higher than I can work with for woodworking and definitely higher than anyone doing any real machining would need, It’s not like there’s just runout in one direction, the whole hex is smaller than it should be.
Sorry if my tone is coming off as frustrated, I am, and I really appreciate the help. I spent all weekend making test pieces that were all wrong on an expensive piece of equipment I’ve spent years learning that I thought I had a real solid handle on that’s suddenly decided to not cooperate with me.
This wasn’t an issue until the last few months and so I’m just really struggling to understand why it’s suddenly such a big issue.
Cutting aligned to the center of a piece of stock by registering at the lower-left (or any) corner will only work if:
the stock is accurately measured and secured square relative to the motion of the machine
the machine is calibrated so that its motion matches that of the measurement used for the stock
The usual way that I ensure things are square/centered is to use an over-size stock area in Carbide Create and first machine a pocket to put the stock into — then secure the stock centered in that pocket, then cut w/o changing the origin.
Sure, but would this affect the hexagon being smaller than it’s supposed to be by 0.02"? My complaint isn’t that the cut paths aren’t square to the edges of the stock, it’s that their real world values have shifted to not be what Carbide Motion shows me it thinks it’s outputting.
How would one do this calibration? Is this the belt calibration that you linked further up in the thread?
So anchor an oversized piece of waste material to the spoilboard, machine a pocket in said material, then anchor the stock to be milled into that pocket?
Again I really appreciate all the help here y’all invaluable.
You need to calibrate the machine for belt stretch in order for it to move at the specified dimensions.
Then, once machine movement is as expected you will need to adjust for how material reacts to being cut — usually the best way to dial in a cut is to cut slightly oversize, then adjust the file/tool specification and take a finishing pass. Iterate on this until you get the desired level of precision/accuracy.
