Work Coordinate System (WCS) Offsets - AKA Work Offsets - exist to let the CNC Machine know the location of the G-Code program’s origin

• Without WCS Offsets, the machine does not know where the part is within the work envelope of the machine

Why not use the Machine's own WCS (G28) as the only WCS?

• G28 is inconsistent from one machine to another, as machines have different work envelopes, meaning part programs would have to be different for every single machine, even machines of the same type

WCS Offsets can be set anywhere, but best practice is to – whenever possible – set them in a consistent location that does not move/change, so that it does not have to be reset from one part to another

• Raw (unmachined) surfaces are typically bad WCS reference locations, as they change once machined, and therefore are no longer referenceable/consistent

• Workholding features, work stops & fixturing can provide consistent reference locations for your WCS offsets

• The key to note is that the location of the WCS is dependent on the program being run, and they MUST MATCH EXACTLY

Those are also important steps to consider when properly loading and locating parts in a vise or other workholding device on a CNC mill. Here is a procedure for doing so - by following these steps, you can ensure your setup is defect-free and ready to machine:

1. Ensure Vise Squareness: Before loading the part, verify the vise is properly squared to the mill table. This will ensure that the part is properly aligned with the spindle and tool axis. Adjust as needed and do not proceed until vise squareness is acceptable for the part being made.

2. Ensure Vise Cleanliness: Clean the vise thoroughly to remove any debris or chips that may interfere with the proper seating of the part. This will ensure that the part is securely held in the vise.

3. Ensure Parallel Cleanliness: If using parallels to support the part, make sure they are clean and free of debris or chips. Dirty or contaminated parallels may affect the accuracy of the machining process and compromise the quality of the finished part. Clean the parallels thoroughly before use and inspect them for damage or wear.

4. Ensure Part is Clean & Deburred: If not already done, deburr the edges of the stock to prevent interference between the stock and workholding device during machining, which can cause defects. Clean the stock thoroughly to remove any debris or contaminants that may interfere with machining.

5. Tighten the Vise: Use a torque wrench to tighten the vise to the recommended torque per the job/fixture specifications. Make sure the vise is tight enough to securely hold the part in place but not so tight that it distorts the part or prevents it from being held squarely.

6. Ensure Part if Seated Properly: Use a deadblow hammer to firmly tap the part against the parallels to ensure that it is properly seated and level. Try moving the parallels underneath the part - if they move, try seating the part again until the parallels no longer move - this means the part will be machined squarely.

7. Check Vise/Jaw Clearance: Check the clearance between the vise jaws and the part stock to ensure that the jaws are properly seated and the stock is held securely. Check your program/setup sheet for minimum clearance amounts between the part and the vise/jaws.

On the CNC Mill you've been assigned for this quarter, do the following:

• Set the offsets for each of the following tools:

  • (T1 = 2.0" FACE MILL, 5FL, IC)

  • (T2 = 0.375" FLAT EM, 3FL, SC)

  • (T3 = 0.500" SPOT DRILL, 2FL, SC)

  • (T4 = 0.3906" JOBBER DRILL, 2FL, HSS)

• Locate your WCS to the following specs:

  • (OP1 WCS = G54, TDC OF PART)

• Once done, upload documentation to your previously-created "CNC Mill Operation" Project page on your portfolio website, including:

  • Pictures(s)/Gif(s) and/or Summaries/Descriptions of:

    • Setting Tool Offsets

    • Setting Work Offsets

    • Descriptions/summaries of what you did/learned, including any mistakes/learning moments during this task