CamBam - Tutorial : Pocketing

Open a cad file. I’m using phillby’s love2.dxf

NOTE: This file was causing me some grief as it has a number of unclosed polylines that had a last point very close to (but not the same as) the first point. CamBam now detects these (to within the tolerances set in Options->GeneralTolerance) and removes these end points and closes the polylines.

BEFORE you open this file, go Tools->Options and set GeneralTolerance to 0.001 (The default is 0.00001 which will not auto close the polylines in this particular file).

If you have a drawing open with polylines you want to tidy, you can change the Closed property for the selected polylines and also use Edit->Polylines->Remove Duplicate Points.

Select just the text polylines using a click+drag rubber rectangle.

Make sure all the selected polylines show Closed=True in the object properties.

Now select Edit->Regions->Convert to Region.

All being well, all the text objects should remain selected and be changed to Region types.

A region is basically a polyline with a list of contained polylines that denote inner ‘holes’.

Now select CAM->Pocket.

Set ToolDiameter=3, TargetDepth=-3, also set the Stock property to 0.3 (that’s Stock and NOT StockSurface).

Right click on the mop and select generate toolpath. (This will take a little time to complete (CamBam is not so good at feeding back that it is busy at the moment).

If it has worked, you show see some toolpaths that fill the letters.

Click on the machining object in the file tree and (toward the bottom) set ShowCutWidths to true.

This shows a filled pattern that indicates where the toolpaths will remove stock.

This was a very quick and dirty feature I added to help highlight toolpath problems. It only works when you view the drawing in the XY plane (ie no view rotations).

You will immediately see that there is missed stock around the inner holes.
This is intentional (yeah right!). My thinking was that sometimes it’s more efficient to do a rough pocketing operation and then tidy up the inner faces with a profile mop but if enough people moan at me I may reconsider this.

Select the Pocket mop (to also select the geometry). Now do CAM->2.5D Profile.

Set ToolDiameter=3, InsideOutdside=Inside. Set Target Depth=-3 and DepthIncrement=3.
Note this will do just one profile pass at the target depth.
This should be OK as it is only removing the left over stock from the pocketing operation.
This should also leave a nicer finish than multiple depth passes. (Multiple depth pass profiles could still be used if you wish).

Generate the toolpaths again and it should now show all the regions filled.

Try changing the Pocket mop’s steover distance to 0.8 and regenerate the toolpath.

You show now seem some small gaps of remaining stock starting to appear.

At the moment I haven’t got a way of ensuring these are removed. If you see any gaps, try reducing the stepover distance until the remaining stock is acceptable.

I am currently working on linear and spiral pocketing patterns which should be immune to these problems.

If you have been taking brave tablets and actually try this gcode out on your machine (or perhaps more sensibly a simulator), you’ll see that the toopath order isn’t the most efficient. I haven’t put much effort into optimisation yet but it’s on the TODO list.

Good Luck!