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Feature Request: Equivalent Chip Thickness/ Chip Thinning Control

11 REPLIES 11
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Message 1 of 12
jesse.lamphere
353 Views, 11 Replies

Feature Request: Equivalent Chip Thickness/ Chip Thinning Control

How difficult would it be to implement a feedrate control method for adaptive toolpaths (or any milling, really) that specifies the equivalent chip thickness (ECT), rather than the feedrate? 

 

For a good explainer, see Harvey Tool's article: https://www.harveyperformance.com/in-the-loupe/combat-chip-thinning/

 

Tools will probably need another entry field for ECT in the "Cutting Data" tab, and a checkbox would likely need to be added for the operation's "Tool" tab. Then, the system could do one of two things:

1. Calculate ECT based off commanded stepover ("Optimal Load" for 2D Adaptive, for example) which would be somewhat ignorant and risky. This is effectively what I do now, manually.

2. Dynamically calculate ECT based on the cutter's actual conditions line-by-line. This runs the risk of being slow to compute, but could be a good time-saver. This method should probably have a user-adjustable maximum feed setting in the tool's "Cutting Data" tab, since you probably don't want the feed trying to approach infinity on very fine stepovers.

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Message 2 of 12
bedfordpro
in reply to: jesse.lamphere

This is quite an issue. I support machining facilities with tooling and processes. I have actually downloaded this product since many of my newer customers are using it. The chip thickness, feed rate, control while cutting inside radiuses is a major issue if anyone is planning to utilize high flute count end mills effectively. 

The current Fusion360 does not have a mechanism for automatically adjusting basic feed rates on inside (or outside) arcs in the roughing processes. There is the "feed optimization" but this is user driven and not variable based on how tight the centerline arc radius is at any given cut.

Here are some basics that would help.

1st - have software calculate feed rate at cutting edge of tool and not the centerline of tool

2nd - could have a chip thickness selection box, but need #1 before you can do this

3rd - have an option in adaptive milling (both 2d and 3d) for tool radius engagement (a radial amount of tool that would contact the cut.) Example; 15% of tool to be engaged selection. In small centerline radius cuts the actual stepover would be very little to keep only 15% of the circumference of the tool engaged in the work piece. as you go straight cuts or larger radiuses it would be more stepover engaged. 

 

Just some more thoughts to this request. There are so many people who "hate" certain tools stating they break, etc. and it is this issue here that actually is breaking the tools. (mostly speaking to end mills with 6 or more flutes.

 

Best Regards, John 

Message 3 of 12
DarthBane55
in reply to: bedfordpro

I think it does #3 already, but internally.  You can see that internal radius get a gradually smaller and smaller radial engagement, and opposite, external corners get bigger stepover.  It is already doing that.  However we cannot specify the tool engagement angle, the calculation is probably done internally from the stepover.

For the multi-flute endmills, I have a 7 flutes roughing endmill that can only go 0.03" radially before it blows up, so I put 0.025" in the radial stepover, and the tool never breaks.  So I can only assume that the radial engagement is calculated internally and maintained, even in tight corners.

That means, they could probably very easily add a field to input the tool engagement angle instead of a stepover value, to the user's preference (use either or).  For me, the maximum stepover works fine, even on 7 flutes endmills.  As an example, Helical Tool has a tool called "machining advisor pro", in which both the tool engagement angle and the stepover are shown (see picture below).  These 2 are tied together, so they could give us a field to use the one we want.

1.png

Message 4 of 12
bedfordpro
in reply to: jesse.lamphere

Based on what I see posting there is no account for radial engagement. I understand this as it is a more complex calculation for determining stepover. I am including a quick sketch to give sight to those who may not realize what they are loosing in cutting efficiency. as @DarthBane55 mentioned you can play with your stepovers until you can get something to cut without destroying a tool. This example will let you see what you are giving up by not having a variable feed rate. (example is starting a helix cut out from a 1.0" drilled hole with a .50" diameter cutter and an example of your linear cut (which is basically what Fusion360 is currently calculating)

If you play with your numbers to get a good cut at the start you will be under feeding by almost half by the time you get to cutting straight lines in your pocket roughing. This addition I feel is critical for these tools to be utilized as they were designed. Hopefully this is already on the list of updates for Fusion 360.

(I will note that there are some long standing well known CAM packages that do not have this option)

 

RADIAL CHIP EXAMPLE IN POCKETS.PNG

 

Message 5 of 12

These are great replies; thanks all!

 

Based on these additions, I'm realizing that while I was asking for dynamically-adjusted feed rates, having dynamically-adjusted stepovers is also very important. I don't do a lot of high-MRR work right now, but I'm seeing that there is apparently a considerable demand in the community for these features.

 

Suggestions:

Dynamic stepover: Have max and min limits on cutter engagement percentage, with a targeted engagement percentage. Having max and min values will allow the Adaptive roughing cycles to work their magic with smoothing toolpaths to more-or-less morph to the final shape.

 

Dynamic feed (Equivalent Chip Thickness): Specify a chip load and a max-permitted feed rate. The system will calculate chip thickness based on tool path and cutter engagement percentage.

 

At 5% stepover, feeding .05" per tooth of feedrate is reasonable.At 5% stepover, feeding .05" per tooth of feedrate is reasonable.At 25% stepover, feeding .05" per tooth of feedrate is very much not reasonable.At 25% stepover, feeding .05" per tooth of feedrate is very much not reasonable.

 

Ideally, stepover amount would be calculated first, then an appropriate feedrate would be calculated to support it.

Message 6 of 12

mcam already has RCTF, and theoritically all you need to do in fusion is find your parameters once and save as template.

Could possibly also use the equations of optimal stepover / tool dia = engagement x feed multiplier IF you guys really want to get into this. 

Please click "Accept Solution" if what I wrote solved your issue!
Message 7 of 12

That's what I think most people are doing now, and it works for straight cuts. It changes dramatically, however, on curved toolpaths. Even with a constant stepover value, the amount of cutter engagement can vary wildly between concave cuts versus convex cuts.

Message 8 of 12

Thanks for raising this often overlooked aspect of machining efficiency. It's long been an annoyance for some customers as well as developers. We're well aware of this deficiency and are regularly tossing around ideas on how to best implement this.


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 9 of 12

Thanks! I know you all are really cranking out the improvements and fine tuning, and I for one really appreciate it!

 

I'm glad to hear that this is being discussed and kicked around. I suspect that it's even more complex than I am considering, so it's good that real consideration is being given to it.

Message 10 of 12

I've opened up CAM-48807 to capture all this feedback, thank you all for chiming in and sharing your thoughts!


Seth Madore
Customer Advocacy Manager - Manufacturing
Message 11 of 12
bedfordpro
in reply to: seth.madore

I ma available for any questions. I make my living with machine optimization. I would love to see some of these enhancements in Fusion360.

John
Message 12 of 12
seth.madore
in reply to: bedfordpro

@bedfordpro on one of your points; Adaptive does maintain a consistent engagement angle, it's not performing just a stepover calculation.


Seth Madore
Customer Advocacy Manager - Manufacturing

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