REST machining and multi-pass toolpaths

[Anonymous]

I'm working with a morph toolpath over a sculpted surface. I'm using 3 axial offset passes with a max stepdown of .125 in. The two higher (in Z) toolpaths do a lot of "air cutting". I've tried various settings for the rest machining parameters, but none seem to get me there.

Thanks

[randyT9V9C]

Without seeing your model this is only a guess. What if you create some boundary sketches around your high areas. Rough them using one operation. Next, rough the lower sections using another, set you top height below your high areas so they become islands. Once your roughing operations are done finish the entire model.

After thinking about it some more... 

How do you have your stock defined? Did you try selecting the body as stock? Sometimes I will create a body in my model to represent the rough stock and then select that body as my stock on the operation. Then it will only machine the stock.

[Steinwerks · Accepted solution]

Axial offset passes are just that, an offset. If you want to utilize the Rest Machining in 3D toolpaths it's best to split them into multiple toolpaths and use the Stock to Leave settings for your first operation.

Here are a couple quick differences.

Axial offset using Rest Machining from Job Stock:

First toolpath with Rest Machining using Job Stock and Stock to Leave:

Follow-up toolpath (duplicated) utilizing Rest Machining from Previous Operations:

It can be seen where the toolpath has been trimmed in the second operation where the tool has cut previously, whereas the first screenshot is clearly just an offset of the second.

[Anonymous]

As you suggest, there are many strategies to manually create toolpaths that do less air cutting. The adaptive roughing will also do a pretty good job. My question is directed at automatic strategies, specifically whether there are REST settings that can be applied to a multi-pass toolpath to prevent air cutting on the higher passes.

[Anonymous]

Thanks, Neal. It's unfortunate that REST doesn't provide a means to cut relative to the previous layer, but your solution is relatively simple to implement. For anyone reading this thread, I want to emphasize Neal's point that the REST setting is relative to "stock", otherwise you will likely get the default "Previous Operation", which may do nothing to trim the path depending on what you're trying to do.

[Steinwerks]

For what it's worth as most of the 3D operations are considered finishing operations, it is unlikely that Rest Machining inside the toolpath will be implemented unless it is a simple thing to do. However, I do think it could be considered a valuable feature, so I'd suggest submitting an Ideastation post here: https://forums.autodesk.com/t5/hsm-ideas/idb-p/231

[Anonymous]

you're absolutely right that most of these operations are intended as finishing operations and thus multiple passes, other than rough + finish are not likely to be very common. In retrospect, my desire to avoid an adaptive roughing cut to avoid a tool change (I have no tool changer on my router) is probably silly.

My specific use case was solved using the approach you suggest above, but required multiple operations. Depending on how the toolpath generation and REST were implemented, I can imagine that it would not be too hard to implement a multi-pass that respects the tool stock specification, removing the need to create a operation with offsets. I will post this to IdeaStation, as you suggest.

[Steinwerks]

Are you using a ball tool? Because you can use that with Adaptive and it will work just fine 

[Anonymous]

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@Steinwerks wrote:

Are you using a ball tool? Because you can use that with Adaptive and it will work just fine 

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Yeah, I kind of figured that out once I decided I was being silly to avoid using the same ball tool. (I originally programmed the adaptive for a larger ball tool). But I think there are still times when a finishing style path at multiple depths would be preferred to adaptive, mainly when working in wood and tear-out is a concern.