Centroid Community CNC Support Forum

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I have been using my Acorn equipped lathe with 8 position turret for some time and am very impressed with ACORN and CNC12 software. I have notice that tool offsets change. I have an optical eyepiece used to set the tools and the offsets. I will set all 8 tools for a job and then run multiple parts of the job. At the end of the day I reference to zero and shut the machine down. Start up the next day reference to zero. I will check all tools and the offsets are slightly off. If I check the offset at the end of the day before shutting down the offsets are correct. I use tool 1 as my master tool then set the other to that tool. The position for tool 1 will be slightly off because mounting the optical eye piece to the spindle housing and I expect that. The offsets for the remaining tools are slightly different (varies but up to .010”) and is not consistent with each tool. I do not move or remove the optical eye piece until I set all tools. The Lathe runs great and holds tolerance well as long as I check tool offset and “Z” zero every day at power up (but that is time I would like not to have to spend).
Has anyone seen something like this? Is it a mechanical problem, hardware problem or software problem? I am running Acorn Board, DYN4 SERVOs, CNC12 V4.5, Report is attached as well as picture of the optical eye piece.

What is the repeatability of your optical eye? What is the accuracy of your optical eye?
Do you use the optical eye to set your part x and Z with tool number 1 at the start of your machining?

Can you also describe how your machine homes? The tool offset error could be due to homing variances plus repeatability errors on the optical positioner movement.

I would never use the homing switches to set my X,Z zeros as they are never repeatable unless you have like a 1000 dollar sensor with repeatability to .00001 in. I ALWAYS make a test cut with my reference tool to set my part x and Z zero. All other tool offsets are referenced to the reference tool and should never change unless something moved or is falling apart on the tool post.

The machine homes to a proximity sensor (15 ipm) then it indexes to a ZRI pulse in the servos at (.001 ipm). The repeatability for the optical eye piece is probably about .1". I only use the eye piece to set the tool offsets not to set any work piece or machine position. The repeatability (or lack of) for the eye piece I don't think is an issue. when i use the eye piece I set tool 1 and record x and y position. I then check everything against that position and never touch the eye piece until I am completed. All Tools offset then should be relative to tool 1. The accuracy for the eye piece is easily with in .0005".

the accuracy of the eye piece against the tool is easily .0005" when mounting the eyepiece that repeatability on the spindle housing is about .1". reading it back I just wanted to clarify.