When To Re-Select Geometry After a Model Change

[xanderluciano]

Overview
Inventor HSM, HSMworks, and FusionCAM all work great with parametric modeling environments when it comes to changing or updating geometry. After changing your model you can simply regenerate your toolpath at the touch of a button. No need to reselect all your geometry and reinput all your settings.

However, sometimes a model will be modified in such a way that the previously selected geometry is no longer valid, no longer exists, or has changed. How do you know when you need to reselect geometry?

Modifying Dimensions
Geometry will rarely need to be reselected after a dimension is modified.
For example, you change a pocket from a depth of 10mm to 15mm, you increase a slot's width by 5mm, or reduce the width of a pocket all without having to reselect geometry.

Deleting Features
After a feature is deleted, if it has any connection to a toolpath, the geometry tab will show a missing geometry message. At this point you can simply delete the old references, and the toolpath will usually generate without error (so long no invalid geometry is created).
For example, if you have 1 hole that is 50mm wide and 10mm deep, and then create another hole on top of it that is 100mm wide and 20mm deep, deleting the 100x20mm hole will not make the CAM engine select the 50x10mm hole. You would have to manually reselect it.
You should verify toolpath(s) after deleting features.

Adding Features
After a feature(s) is added, if the resulting geometry interferes with an existing toolpath, it may need to be reselected. In this the instance of adding and deleting geometry, it will depend on how the geometry was selected originally.
You should verify toolpath(s) after creating new model geometry.

Recreating Sketch Entities
If a sketch entity is deleted and recreated, the geometry will need to be reselected. When a sketch entity is deleted, the toolpath loses it's connection to that sketch entity and it will not be reconnected. Therefore anytime you delete and create a new sketch entity, you will need to reselect your geometry.
For example, if you have a 50mm slot in a part, and you delete the slot, then create a new 75mm slot, you will need to reselect the slot for your toolpath.

3D Toolpaths are Flexible
Alright so those guidelines aren't too complicated, and are easy to pick up after the first few times, but what if I told you 3D toolpaths were way more flexible. They are so flexible that you don't even have to select geometry. They will automatically find features and generate toolpaths with minimal input. 3D toolpaths can be leveraged more than 2D toolpaths, allowing users to quickly create large roughing and finishing operations with minimal geometry selection. Combined with confinement sketches, 3D toolpaths can usually handle large changes in geometry without issue.

Summary
To sum everything up cleanly in a short description, for 2D toolpaths, if the existing geometry is simply modified by a changed dimension (e.g. an extrusion is made shorter, a circle diameter is increased, etc.) then usually it will regenerate without issue. However, if the geometry is changed (e.g. another hole is cut in the body) it will likely need to be reselected. For 3D toolpaths, it will regenerate without issue.

For 2D Adaptive/Pocket, regeneration will largely depend on which geometry was originally selected. Lastly, if features/Sketches were changed/added/removed, you should check your toolpaths, as it's likely you will need to reselect or remove previously selected geometry.

TL;DR: If dimensions are modified, toolpaths will regenerate without error. If features/Sketches were changed/added/removed, check your toolpaths, as it is likely you will need to reselect/remove previously selected geometry.

- Xander Luciano

[ArjanDijk]

Nice writeup!

It generally is dependend on what you want.

If you work with a single product that changes, then its ok to work with 3d and 2D toolpaths and handle the comments you describe.

If you want to do something like product configuration for product families you need to be smart about selecting geometry.

For example: If you have a product that can have 4 different shapes of pockets you can increase the total product size, put all the 4 pockets in there, program them with 2D pocket.

If you then tell the product by parameters which pocket to use it will suppress the other ones and that operations become invalid and wont be posted out to NC code.

If you do the same with 3D pocket, after the geometry is disappeared, it will then machine the complete part, which is not what you want. 

TLDR:

Be smart about using 2D and 3D operations if you work with product families.

[xander.luciano]

Well said! I could write pages about how to select geometry, and how different changes will produce different outcomes. The best way to learn the in's and out's of how CAM works is to just start messing around and getting that first hand experience!

[al.whatmough]

This write up was so good we hired the kid (see the initial post was he was not an employee and now he is one already)

Good job Xander on taking the initiative to do this!

[Bartlett-Pentagon]

Great writeup. I have found there are situations where geometry selection has to be reslected on every tool path edit, even though no geometry has changed.

http://forums.autodesk.com/t5/support/horizontal-cant-remember-machining-boundary-between-adjustment...