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PixelCNC: CAM For Artists

CAM software developed by artists for artists to create unique and original works on a 3-axis CNC router or mill. · By Deftware

Pocket vs Horizontal Milling

A topic by valhallaCNC created Dec 28, 2021 Views: 102 Replies: 4
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What is the difference between these two ?  After Medial - axis operation, I tried clearing the pocket with both. Only pocket milling has the offset to leave the angled sides but still leaves uncut areas inside the pocket. Its always in the very center of the pocket, like it needs another pass to clear. The horizontal tool path clears better but there is no offset so its unusable for pocket clearing.


Pocket milling just re-produces the same set of cuts down to the Max Depth, where each set of cuts is Cut Depth lower than the previous set. It is good if you absolutely must have a pocket with vertical walls as it only contours the canvas at the specified Z and uses that to generate the cuts.

Horizontal milling, on the other hand, generates a new set of cuts at each cut level, rather than using the same contours for all cut levels. It re-contours the canvas at each cut depth to determine where to remove material from to re-produce the canvas' shape without cutting into the canvas.

Pocket milling doesn't care about the canvas' shape after the initial contours are generated.

The Profile Milling operation behaves the same as the Pocket Milling except that instead of removing all of the material inside of the waterline contoured Z level down to Max Depth it instead just follows the contour, and can include a Cut Width (i.e. total spacing from inner-most to outer-most cut) as well as including a waterline contouring offset. I'd suggest using the profiling operation with a Cut Width (don't forget a stepover!) to get the tricky spots.

Hope this helps!

 - Charlie

Im really confused now, My Medial-axis operation was done with a 15 degree V bit which left me with sloped walls. which is what i wanted. When  I do Horizontal Milling with a 1/16 inch EM I get perfect vertical walls, exactly opposite of what your saying. When I Pocket Mill and use an offset it leaves the Medial wall cuts alone and just flat cuts , and removes material left over to clear the bottom of the V.


So the horizontal milling follows the contours of the canvas. If your canvas has sloped walls (i.e. draft angle) then it will follow that The Pocket Milling operation contours the Contour Z height you specify and uses that to generate a set of cuts down to the Max Depth, at Cut Depth increments for each cut level.

The Medial-Axis Carving, Pocket Milling, and Profile Milling all derive a contour from the canvas at a specified Z plane, their Contour Z. For a pyramid this means that a higher Z means a smaller square will result for the cutpaths to be generated around.

The Horizontal Milling operation, in contrast, does not use a fixed Z plane that the user specifies to generate its cutpaths. Instead it generates multiple planes of cuts that conform to the canvas at each of those planes' Z depth.

For example, here's the canvas I'll be demonstrating with:

Here's a Pocket Milling operation that is using a Contour Z of 75% (0.375" from the bottom for a 0.5" thick canvas):

Here's the same canvas and same Pocket Milling operation but with a Contour Z set to 25% (0.125" from the bottom for a 0.5" thick canvas):

The Contour Z parameter is what is important to the three operations I mentioned.

The Horizontal Milling operation, by comparison, will adhere strictly to the canvas (along with whatever Leave Stock is included, but for demonstration purposes I'm using a Leave Stock of zero):

Does this help make things clearer? If I'm missing something I think if you could share some screenshots that show operation parameters that would help clear up any misunderstanding on my part. :)

 - Charlie


Thanks Charlie,  I've got a handle on it now.  I'm used to thinking top down, need to flip my thinking to understand Contour Z . Great examples.