multysurface pocket

[gmenzies]

i gouge a part the other day. the area i was machining was a slot, inside a cavity . with many surfaces surounding it. i biult a boundary and machined the slot. it has two drafted surfaces open to the cavity on both ends. thinking the tool should be contained inside the boundary. it seammed okay. i did select all surfaces . i ran through metaview

verification and it machined the surfaces perfectly. but it hit the side walls of my cavity. after re-examining the tool path in mastercam backplot. the toolpath actually went to the center of the tool along the boundary . and not the OD of the tool.

1) should i have used check surfaces ?

2) should i have biult containment walls to prevent the tool from leaving the slot ?

3) should i have use another package (just a joke dave)

using level 3 ( 7.2c)

[rteagan]

In multisurf rough pocket, the tool center does go to the boundary, while in 2-D pocketing the whole tool is contained inside the boundary (why is that, mastercam?). Also in multisurf rough pocket, you are not allowed to use check surfaces (also why is that, mastercam?). I think you have fallen victim to a discrepancy between the two differant pocketing routines.

[gmenzies]

yup .

so biulding extra surfaces that contain the slot is the correct answer ? and using a boundary does not always work like a 2d pocket. and after looking at the dialouge boxes in mastercam (rough pocket). prompt for tool center boundary is very clear and the check surfaces is blanked out.

does level 8 fix these types of problems ?

[Allan Brown]

Sorry to hear about the gouge Gord. Did Metacut View show the problem once you knew exactly where to look?

Using a containment boundary and recognizing that it is a "Tool center boundary" is really the easiest and most reliable way to handle this situation. The tool center boundary *never* works like 2D Pocket. The toolpath is always contained to the tool center. I believe this is the standard for surface work in CAM packages. Imagine having to offset curves on a core or boss just to get the tool to move to the edge of a piece when using a containment boundary.

I typically create edge curves on the surfaces (unless my own wireframe was used to create the surfaces and is still there). I set the Z depth above the part and use the squash.dll C-Hook to create flat, easily chainable geometry for use as a tool center boundary.