Am I rest machining correclty?

[jon1 (Jon)]

Hello,

This is likely a “me” thing, but its costing me a fair bit of time and I’d like to try make it better.

I have a house which I’ll use a 1/16 bit on:

I want to refine some of the smaller areas with a 1/32 bit. I put in the following for rest machining:

I would expect there to be a lot less work to do as seen below. The 1/32 bit requires 645 mins vs the 192 mins for the initial 1/16th pass.

Am I doing something wrong or misunderstanding how rest machining works?

Greatly appreciate any tips or tricks to make these jobs run a bit faster.

[Jeffish (Jeff de Ruiter)]

Looks to me like you are doing it correctly.
The image has a lot of detail. The 1/32 endmill is going to get to the places the 1/16 couln’t and that’s going to take a lot of time. Also your cut is 5mm deep which is a lot for small endmills.
I’d clean up a lot of the “noise” in the image and go with outlines of things like bushes and windows The finer details can be cut separately with a much shallower pass, maybe 1mm ish. The main outlines of the image can be cut deeper to give the main viewing definition.

[jon1 (Jon)]

Thanks for taking a look Jeff. Ya, the work is a little on the small side. Really like the suggestion of outlines.

Without risking a perma ban, I generally try a contrasting epoxy (urgh I know lol), which is why I like the 5mm. Helps with any warping for flattening etc.I’ve had times where a high spot with a 2-3 mm pocket starts to wear, this is likely the result of me wanting the piece too perfect…

After some google / AI help I did notice that I can tweak some settings to help, step over and plung rate. Would be nice for it not to repeat as much though.

[Jeffish (Jeff de Ruiter)]

I haven’t tried epoxy yet… but after seeing the first pic I get it now. All the “noise” actually looks good when it’s filled in. I like to use shallow outlines on the signs I made recently to breakup the different colors of paint I used on the images. If you zoom in on the eagle in the link below you can see them. [What did you cut on your Shapeoko/ Nomad today? - #5301 by Jeffish]

[mhotchin (Michael Hotchin)]

If you are seeing that your smaller bit is going over areas that have already been done by the larger bit, you may be running into this bug:

CC 805 PRO - Rest machining doing WAY more work than needed

Windows 10 Pro, CC 805 Pro I’m testing some lettering for an epoxy sign I’m making, and I’ve found a case where pocket REST machining is doing way more work than needed. The intent is that of an Advanced VCarve, but I’m using appropriately spaced vectors to Pocket the bulk of the work to reduce time. Pocket is 1/4" - 2mm - 1mm REST machining. The 2mm pocket is cutting areas already cleared by the 1/4" bit. I’ve verified the geometry of the 2mm and 1mm bits, the diameter is correct on both. …

As a work-around, try this:
Instead of entering the the actual size of the previous bit, try entering (previous size - current size). In this case, since you are going from 1/16 to 1/32, change the previous size from 1/16 to 1/32 (i.e, half of what you have now).

[jon1 (Jon)]

Yep, that worked. Thank you so much. My search for rest machining didn’t pick up that previous thread unfortunately.

Looks way better now.