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Custom Cavity Mill Operation stepovers

Experimenter
Experimenter

Using Cavity Milling as a primary roughing strategy, and haveing lots of issues with getting consistent stepovers.  Mostly job shop one off parts, mostly alloy steel in the 500-10000# range.  most roughing is being carried out with either highfeed type mills or midsize button cutters(4" dia 8 T .300" DOC).

 

when setting maximum stepovers the outputted paths sometimes leave uncut areas in areas for a few cut levels,(for simplicity say cut levels 1,2,&3) then on cut level 4 mills the entire area( cutting length on tools is defined as .375, so it knows it cant cut at 1.2" DOC, and in verification it shows this way, after levels 1,2,3 there is a large chunk of material left, as level 4 is cutting it goes "under" the island area, and leaves a "floating" island of material in the IPW.   

 

The stepovers are even more confusing.  If i set the max stepover to 1.5", it should only cut with 1.5" of the cutter engaged.(these are all open areas, nothing closed) But when run in verification, and on machine (using internal 10.0.03 verification not after post) it will consistently overengage, and at times full slot(4"WOC).

 

Any suggestions on either of these? 

 

I can try to add a file if needed, but Im not sure how to upload such a large file.

5 REPLIES

Re: Custom Cavity Mill Operation stepovers

There are 2 issues here:

 


TNTCUSTOM wrote:

 

when setting maximum stepovers the outputted paths sometimes leave uncut areas in areas for a few cut levels,(for simplicity say cut levels 1,2,&3) then on cut level 4 mills the entire area( cutting length on tools is defined as .375, so it knows it cant cut at 1.2" DOC, and in verification it shows this way, after levels 1,2,3 there is a large chunk of material left, as level 4 is cutting it goes "under" the island area, and leaves a "floating" island of material in the IPW.   


This is PR 7785318, which is being looked at by devlopment. In this particular case, follow periphery does not show the problem, so that may be a workaround for this part. You should be notified when the problem is fixed.

 


TNTCUSTOM wrote:

The stepovers are even more confusing.  If i set the max stepover to 1.5", it should only cut with 1.5" of the cutter engaged.(these are all open areas, nothing closed) But when run in verification, and on machine (using internal 10.0.03 verification not after post) it will consistently overengage, and at times full slot(4"WOC). 


Follw part and follow periphery are traditional cut patterns, created by offseting from the part or bounds of the cut region. For these, stepover is the distance between successive cuts. There are many cases where the actual engagement exceeds this, such as a channel or any inside corner. There are tools like corner rounding and feed optimization to minimize the effects of this, but is is the nature of any pattern that follows an inregular shape with "parallel" cuts.

This is what led to the development of newer cut patterns to avoid this - starting with trochoidal, and recently the adaptive pattern, which does not use parallel offsets. I think you will be pleased with the results of our adaptive milling operation, which constantly adjusts to avoid over-engagement.

Mark Rief
Retired Siemens

Re: Custom Cavity Mill Operation stepovers

Experimenter
Experimenter

Mark, 

 

Thank you for your response.  The fisrt issue i agree that follow periphery does do better on this particular part, Are there a set of rules for when to use Follow Part versus Follow Periphery? This is something that we have struggled with several times.  We have issues and after discussing with Gtac they suggest trying whichever one we aren't using at that time, and sometimes it makes it better, sometimes not. 

 

The second issue with the stepovers, I am a little confused here.  I agree any "stepover path" will "overengage" in inside corners.  100% onboard with that philosophy.  The stepover violations we are seeing is not in inside corners or a channel.  The stepover are being exceeded in large open areas.  say cutting a 12" dia hole with a 4" cutter, that is being cut into a ring, with a 16" od, and a 10" id as a blank.   Trochodoil seems to be for "channelling" mostly, from my playing with it in NX10, and we did try that on this part, and it did some really weird stuff in the "open areas".  I agree Adaptive may help.

 

I have a call with Gtac Tommorrow to discuss that option.

 

Thanks

Tom

Re: Custom Cavity Mill Operation stepovers

Valued Contributor
Valued Contributor

Mark,

are you implying that adaptive roughing is already available? If so, where and how?? If not, how long until it will be?

Thanks/Harri

Re: Custom Cavity Mill Operation stepovers

Esteemed Contributor
Esteemed Contributor

Adaptive milling is planned for NX 11.0.1 or later, based on the last rumors.

Stefan Pendl, Systemmanager CAx, HAIDLMAIR GmbH
Production: NX10.0.3, VERICUT 8.0, FBM, MRL 3.1.4 | TcUA 10.1 MP7 Patch 0 (10.1.7.0) | TcVis 10.1
Development: VB.NET, Tcl/Tk    Testing: NX12.0

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Re: Custom Cavity Mill Operation stepovers


hjoy wrote:

Mark,

are you implying that adaptive roughing is already available? If so, where and how?? If not, how long until it will be?

Thanks/Harri



Adaptive milling is available only to those customers involved in the EAP (Early Adopter Program) who are testing it and providing feedback to development. you can see some of the details from 6 months ago in this thread.  It will not be released for production in NX 11.0.1, but may be available as a preview to let more customers try it out. We'll anounce something when NX 11.0.1 is released. 

Mark Rief
Retired Siemens

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