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Perhaps a video of the desired use case is helpful:
* https://www.instagram.com/p/CusUIbRIfxk/
This is a job that requires several operations to run to very nearly full length of the tool and there is only about 1mm before collision with the tool holder. The operator needs to check the tool length before the job, we also automate the post to run a tool length check on the machine to hopefully spot a problem, then we use probing to ensure that the Z height of the actual part is used (as the part to part Z height will vary)
It is certainly possible to have the operator setup accurate work stops before this job. It would also be possible to cut accurate softjaws to hold this part in a precise orientation.
However, the trend in manufacturing is to reduce setup times, setup costs and improve accuracy. This is a low volume part and we were able to hold it in simple softjaws. We didn't even need to set a workstop (which on this part saves setup time as the part is quite tall and prone to tip and be non vertical if we use a workstop).
This part is programmed in Fusion, with the WCS on the top centre of the part, against the fixed jaw, which allows very simple sanity checking of the program delivered to the machine. The WCS for the part is initialised at the start of each run FROM the corner of the Vice TO an offset location on the centre of the fixed jaw. This offset is read directly out of the CAD/CAM for the job. The corner of the vice bed is fixed and will be reprogrammed if the vice is ever removed and replaced.
This WCS will be specifically incorrect for each part, X is offset because no workstop is used, Y is offset because a given softjaw is not the same width as another (to the micron), the Z is incorrect because it's standing on a tail of stock which pushes it to different heights. However, probing brings in the precise location of the part for each run of the part, and we can even put a thread into it which starts at a precise angle (which requires Z to be carefully measured)
The offset function in this case was extremely useful to ensure that job setup required little more than checking there were some softjaws fitted to the machine, no other WCS setup was needed. However, the program is error prone in that if if the CAD is changed, the person doing that MUST remember to also update the manual offsets entered at in the manual NC program at the start
I believe many shops refuse point blank to allow manual NC operations and so the proposal above allows for a simple way to setup the offset WCS, through supported GUI operations in Fusion.
Fusion