Dangers of doing the VCarve before cutting the Pocket?

Excuse the Noob question, but I haven’t found a topic that covers this.

I’ve been making some signs out of MDF with fair results. One of my early issues was that the 1/4" endmill was beating up my masking. I noticed that the vee bit was much easier on the mask, so I started using advanced VCarve without a pocket to score the mask, then run the VeeCarve with the pocket enabled. This has provided excellent results, but is very time consuming.

Is someone able to explain the dangers of running the VCarve option BEFORE hogging out the Pocket? Is this just an issue with tear-out? Or should I be using a downcut bit to save my mask?

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so the V bit is not as good a cutter generally than your flat endmill… by doing the flat endmill first the V bit has to basically only cut half the material compared to the other direction

you can do it the other sequence order, but I would slow down the feedrate of the V bit by… probably half given that it’ll cut basically twice as much material

(and you can break out the toolpath in pieces using GcodeSplit - Split gcode files by toolpath browser based tool and just run the gcode in a different order)



I get that the endmill is the better cutter, but it is rougher on the masking than the Vee bit. I’m not cutting very deep (in this instance) but I want to learn more about why one tool is chosen over another.

Is your suggestion to slow the feed rate based on the Vee cutting both sides of the initial contour? Do you generally slow your feed rate on VCarve-only toolpaths?

Also, thanks for the GcodeSplit reference - I broke my toolpath apart manually and it took a while. I’ve started trying to minimize cutting times, and found dividing Adv. VCarve into groups can save a lot of that time, but CarbideCreate inserts two tool changes for each toolpath, so I’ve bundled the Pockets and VCarves together, then set the VCarve to run first.

if you flip the order, the V bit will have to cut the material on both sides of it’s “center axis of the point” while if you ran the normal endmill first, the inside half of that was already cut away… so “thumbs in the air math” says “have to cut 2x the material” which translates to “run half the speed or half the depth of cut” to keep the forces/etc on the V bit roughly the same,…

(since if you double the forces the quality of cut goes down)

if I had to pick I would maybe lower half depth-of-cut but many others here will point at feedrate


Brian, if your using masking tape I can see that this would be a problem. If not using Oramask or similar this may help your issue. Somewhat thicker and more ridgid than masking tape and it cuts smoother- using the v-carve bit as the primary cutter lifts up the debrie that was cut lower in the v trough. This is what is causing the issue as the v carve bit must eject the cut material to clear the path. Using the mill first as noted above allows the debre to exit more freely. Just a though. I am also a nuebe, still learning and still struggling often times. Just got to set it side and think about it. Tom

Thanks, Tom. I’ll see if I can dig up photos of my earlier examples. I am using Oramask, and while much cleaner than painters tape, it tends to “stretch” when using a flat endmill to hog out the pocket first.

Now - (new issue) - if anyone wants to help me figure out how to fix formatting issues when manually editing a .nc file - I’ll gladly start a new topic.

on .nc editing… I tend to write software to do it for me instead :wink:

if the splitter doesn’t do what you want, it might be an easy feature add to make it do what you’d want

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