Issue #1: Different depth between rough pass and detail pass. I placed an “X” on a corner I knew wouldn’t be carved to set my Z axis. So I would be to be consistent between passes. There was a deeper cut with the rough pass (1/8" down cut bit) than the detail pass (1/16" down cut bit). This has not been an issue in the past.
Issue # 2: Movement of the piece, it appears my piece may have moved during the rough pass. I had 7 clamps (XCarve clamps) on all corners and sides. Any suggestions on any additional clamp types to use to help a larger piece stay put?
I use a 1/4" down cut bit on red oak at 72 ipm. On the last or 2nd to last circle it grabs the piece and rips a large chunk out of it. This is usually when it has cut thru the piece and is cutting into the sacrificial piece below.
another thing to be cognizant of is the Z axis possibly bottoming out. It doesn’t look to be the case with this particular carve, but if you were to use shorter bits or thinner stock, this issue could come into play and it’s good to know about it…
One thing I highly recommend is to forget about hold down clamps and stars figuring out areas in your work piece that can safely be secured with wood screws directly to the spoil board. I still use clamps for specific applications but with hardwoods like oak and large pieces I allow for additional material when preparing the plaque. I had the same problem where my pieces moved on me and when I started using index and hold down holes my pieces vastly improved.
one thing that might help is to create a template of all the threaded inserts of your spoil board if applicable. This way when you’re figuring out your design in CAD/CAM you know which spot can be used to secure the piece.
In your piece I see the corners would be a good place to drive in a screw. I would drill a pilot hole first.
Another issue I was having was the router physically bumping into something, whether it’s the dust shoe bumping against the clamps or the Nema motor bumping against a piece of wood I forgot next to the table that cause my machine to loses steps.
I hope this helps. Let me know if you have any questions.
In the picture you can see two options, a wood screw straight into the MDF spoil board or an M5 threaded bolt into the hold down inserts. I try and get all corners or two sides or places to keep the piece flat. Just be very careful where you place your screws.