Pocketing routines and cusps

[neurosis]

Are there any 2d pocketing routines that are intelligent enough NOT to leave cusps when using a tool with a corner radius? I have .26 of flat on the bottom of my tool and I am machining a decent size pocket. I have to bring the step over down to .15 for it to clean up all of the little xxxx that it leaves behind which adds several more passes. It is very obvious which areas are going to have these cusps just by looking at the cutter path in backplot.

 

Ive tried constant overlap spiral, parallel spiral, and even parallel spiral clean corners and NONE of them work without leaving small cusps.

 

Do the SHS paths work any better? I hate to have to create a bunch of surfaces just to machine a 2d pocket but this is getting ridiculous.

[jeff]

I have the same issue with Dynamic Facing, and yes it's very annoying.

[Guest CNC Apps Guy 1]

Pretty simple really... get and use CATIA. Of course... with what you gain in features, you loose in productivity.

[neurosis]

I have catia, just not catia mfg. I also have Cimatron and Esprit. How many cad/cam systems do I need to machine a simple pocket without leaving cusps? Maybe I need to look in to a 3rd party 2d pocket addon. <grin>

[neurosis]

I thought that I hit the jack pot with 2d area clear but it seems to have done exactly the same thing that the 2d pocketing paths do. I can set a min and max step over which I thought would hold the max step over until it hit the areas that needed a tighter path but it appears to have just held ALL of the step overs to the min value which is exactly what I had to do using the 2d pocket to get the cusps out.

[peon]

Neuro, I feel your pain. The Hurco's conversational pocket toolpath creates an efficient pocket toolpath, but this expensive software can't. Try explaining that to da boss. You're correct by noticing it in the area clearance path and the HST Horizontal path is the same. You can only stepover at 45% with a .060" CR cutter.

[CJep]

You need to allow for the radius in the stepover percentage.

[peon]

Cj, even allowing for the corner radius, the stepover required to clean the cusps is still inadequate. A 1/2 bnem with a .060" CR equals to .38" flat cutting surface. Stepping over .225" (45% of the cutter diameter) just to clean cusps is not acceptable. If I define my cutter with corner radius, the toolpath should stepover the distance I specify and automatically adjust in the areas to clean the cusps. Lets say I want to stepover at 70% of that .38" diameter I stated above. That would equal to a .266" stepover, but yet this software (on most occasions) can't make a clean pass even at that stepover. I gave an example using a 1/2" cutter. Now just think how much more inefficient it is to use 1.0"-2.0" diameter cutters!! The bullnose support in any kind of pocket type or dynamic mill routines in this software is ridiculous! Most folks I know, including myself, use corner radius cutters for roughing because the cutters last much longer than using a flat endmill. I don't understand why CNC didn't address the bullnose problem with the introduction of the dynamic and optirough toolpaths.

[neurosis]

You need to allow for the radius in the stepover percentage.

 

 

I am machining the pocket with a 1/2" dia endmill with a .12 corner rad. That leaves a .26 flat on the bottom of the endmill. I programmed my step overs to .225 to allow for some variation. @ .225 step over it left .02 high cusps in several areas ( it is a strange pocket profile ). I had to drop my step over down to .15 to get it to remove all of the cusps from the pocket floor.

[CJep]

I know, I've seen this as an issue with highspeed toolpaths as well.

[Jon @ NOWHERE]

I don't think I have had that problem with volumill, but can't remember if I have ever used a bullnose with it.

[neurosis]

Jon,

 

I have never had an issue with volumill while using bullnose endmills. I use them with volumill all the time. I never use volumill to finish cut however.

 

 

 

I just played with the 2d area and it leaves just as many cusps as the 2d pocket. Im going to try shs horizontal area and see if that does the trick. After that I will try shs area. If those dont work I guess that I will just have to use a .15 step over. Terrible!

[neurosis]

None of them worked.. ALL of the paths left cusps unless I reduced the step overs to .15 or less.

[peon]

Try creating a custom tool on a level and see what happens. I have not tested it on a pocket routine, but just thinking out loud.

[CJep]

I think this has quite a bit to do with the geom driving the toolpath. (I know that sounds like an asinine statement )

 

I just used the 2D area mill with a .250 bullmill .062 rad with a 35% stepover it cleaned up with no cusps in the verify.

 

I used the same stepover for a standard pocket using parallel spiral as the cut method and got the same results.

 

Does it help if you change where the toolpath entry is ??

[neurosis]

Entry doesnt help. With 2d area clear it enters in a few different places because I have islands that I am avoiding (bolts).

 

Here is a picture showing the pocket and the areas that cusps are left. This is being machined on a Mori NH4000 with Look ahead turned on so it is not over shooting!

 

I am using a .24 step over which is smaller than the width of the flat on the endmill and a .174 min. If I leave the max at .24 and reduce the min to .12 it helps some of these areas but leaves cusps in others. There is a strip on the left that gets completely avoided which leaves a .025 cusp about 4" long.

 

The area clear path is far more efficient than the pocketing paths but the cusp issue is as bad or worse in some cases. I am leaning toward using the area clear path and then adding some geometry to come back and get rid of the cusps. This really does seem like a horrible waste of my time. It would be nice if this issue would get resolved!

[peon]

This issue has been apparent for a very long time.

[CJep]

This issue has been apparent for a very long time.

 

I'm aware of that, I dealt with this when I was programmin', just trying to work out a solution, till the toolpath will recognize bull mills.

[neurosis]

The boss came out and said "It looks like you have a t!tty garden growing in that pocket!" haha!

[J Coulston]

Back plot, save as geometry, add geometry to eliminate cusps, re-chain using wait, post. Beat head on desk wondering why a simple task is such a pain. Feel happy that there is a work around and then remember why you love MasterCam.

[CJep]

My supervisor used to draw udders on the stock if it had been sitting in the machine more than 15min without making chips.

[gcode]

For one off parts I just deal with the small stepover.

 

For production programs I do a pocket routine with 60 or 70% stepover,

 

Then backplot and save the geomtry, edit it to remove the cusps and drive a centerline contour to give me posted code.

It can be a ton of work to get some efficient code

Mastercam's 2D pockect routines have not had a significant workover in a decade.

Its time we had some intelligent pocketing routines..

Dynamic stepover sounds like a good name..

Smart enough to steop over 70% where is can and kick down to 15% where it needs too.

[Mic]

The boss came out and said "It looks like you have a t!tty garden growing in that pocket!" haha!

 

[Cannon]

CNC has requested that this unauthorzied link not be posted on the fourm..

and yes.. I know its a link to an offshore Mastercam dealer

edit by gcode

 

 

The links says that X6 should have bull nose support for 2d milling. Actually I didnt even know it doesnt support them now.

[neurosis]

For one off parts I just deal with the small stepover.

 

For production programs I do a pocket routine with 60 or 70% stepover,

 

Then backplot and save the geomtry, edit it to remove the cusps and drive a centerline contour to give me posted code.

It can be a ton of work to get some efficient code

Mastercam's 2D pockect routines have not had a significant workover in a decade.

Its time we had some intelligent pocketing routines..

Dynamic stepover sounds like a good name..

Smart enough to steop over 70% where is can and kick down to 15% where it needs too.

 

 

I agree. One offs I could care less about a smaller step over. Production runs are a different story. Adding geometry is ok for a must have work around but it can become time consuming if your part has several odd shaped pockets. Some times the cusps are very hard to see or I cant see them at all in verify so I have to run a part, figure out where these cusps are, then go about creating the geometry. You can see how many cusps I have circled in this pocket. There were SEVERAL.

 

I dont understand why this problem has not been addressed after so many years? It is not like this issue only affects a single person or just a few.

 

We have a customer that makes another - number of the same part for us. They are obviously using different software because their parts come back to us showing a much greater step over then we are able to get away with and the cutter path is very uniform inside of the pocket.

 

 

 

And I have to ask, does anyone really use the morph spiral pocket routine? What situation is that good in? Ive tried it several time just to screw around and it is a real time waster. I would be willing to give that one up for a good constant overlap path that doesnt leave cusps.