Help: Test aluminium part is oversized

So I was doing a test on the onefinity to cut a 0.5" aluminium block out 6061-T6. I got it cut out and the block measures 0.5110" on one side and .5110" on the other side. I have a 123 block that I measured to check the caliper (mitutoyo) accuracy and it measured 1.0005. Any suggestions on why the block is coming out 0.01" bigger on both sides (x & y)

Did you mean to write the accuracy as to within .01" ?

Yes I did. Thanks I corrected with a edit.

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could it be the diameter of the end mill off by a frog hair?

What were you feeds & speeds and bit size? If you push the bit to hard I find a bit of deflection happens which could account for your increased even sizing. Bit is turning clockwise so the extra would always be on the outside of the piece.

& DOC as well


Is this an unusual result for your set up? I have a different controller, and needed to use the axis calibration feature to dial in the accuracy during my testing of the 1F. I do not have a precision scale, but using various measuring devices found it was off about 1mm over 800mm initially. After three attempts I had a needle probe repeatedly show the correct measure, landing in the exact spot after moving home and various saved work coordinates. Perhaps you could do these tests if not done already.

Is it standard practice to calibrate steps per mm for cnc machines?

I am new to CNC work, but when setting up my 1F using my Masso G3 controller i was happy to have great repeatability of motion and position. It made me wonder however if when I tell it to move 750mm along the x axis, for example, it was actually moving that distance. That is when I calibrated it having found it to be off a small amount. It was only after calibrating the x and y axes that I checked these axes for square using the 3-4-5 triangle method.
Here is a video of the process but for someone using a different CNC and mach 3 software:

Follow these steps - I had to make some minor adjustments to get my machine spot-on.

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Thanks for the response. I was out of town for the weekend. I did mesure the bit and it was a bit under. I put brand new bit in that was 0.25" and ran two test cuts and they both came out exactly 0.50" Thanks for the tip. I usually only do wood and this aluminium thing is new to me so yes I need to watch the wear on my bits.

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@MikeH, @cyberreefguru.

Thanks for the link post and the procedure for the calibaration. Seems like it was bit diameter was a bit under due to wear. But I will be doing the cybereefguru calibaration.