Undercut shapes not cutting air when doing Opti-Rest.

[crazy^millman]

As some of you may know by now that do shapes where you rough out stock that have undercuts in them and then need to come back and finish them after a heat treat operations or maybe it is an assembly where you do this the Opti-Rest toolpaths even though it has a stock model defined with nothing in it will cut air from the top to the bottom ignoring your stock model in those voids. On a current part that this could create 20 hours of extra cut time that is unacceptable IMHO. What do you do to over come this. I will take an create offset surfaces, draft surfaces or many other tricks to create a set of check surfaces where needed. Sometimes I just make 3 or 4 HST operation and use the steep shallow controls and different boundaries for this task. Ran into one today where I have a rough shape with some pockets cut in on both sides and removing about 1" of stock after heat treat in certain sections. I only have reach 3.5" on my tool and need to eliminate air cuts, but also limit the cut to not cut deeper where it doesn't need to crash the holder into the stock, but still cut deep enough where it needs to. Trick I just figured out was to create an edge curve on the Rough Stock model in a front view. I have then made a single chain out of those edges. I have then offset the one chain a good distance in this case .200. I then create a draft surface and now have a very nice check surface that only allows the tool to go .2 deeper than the rough shape, but machine everything I need on the finish part leaving my desired leave stock of .02 for finish. In just 4 operations I have reduced the run time from 3-1/2 hours down to 1 hour and 8 minutes according to back plot and verify. Granted I have been messing with this for the better part of 4 hours trying to come up with the best process, but over 10 parts I think I will have save the customer well over 200 hours of run time. 

Want to test what I am saying. Make a mushroom shape and then cut of the mushroom off from the other side and cut from the top of the mushroom to the bottom using a stock model of the mushroom as your stock model shape. You will notice the toolpath used to cut the top of the mushroom will be the same all the way to the floor. Image a 20" or 60" tall part and every .75 depth of cut on a 20" diameter mushroom cutting air from 20" diameter to a 2" diameter stem you wanted to bring to 1.5" after heat treat? Yes seems extreme, but it gives you a good idea what I am seeing. Now create some check surfaces to control where and how the tool cut pasts the head of the mushroom and you now have a good understanding of what I am saying to control your undercut shapes using these check surfaces enough room to cut your finished shape where needed, but not cut air where it is not needed.

I have had conversations about this issue with QC and they are aware of. I am not bringing this up to bash anyone, but thought if others run into this until it is fixed they might like to know what I have found to allow them the way to make what I consider better toolpaths and have them efficient for running on the machine.

No I have not been drinking mushroom tea, but this shape is a good example to see what I trying to explain here. Sorry no sample file, too busy right now to make one up. Maybe in the next couple weeks or maybe someone got enough from this posting to come with a good example to share with others. Thanks for reading this hope this is a blessing to you in your work.

[Leon82]

I've had it happen a couple times. I made a path, then ghost it out to get what I wanted.

 

[?Mark]

I deal with this all the time. I revert to multiple stock models to avoid air cuts. I started a few threads complaining about the inability of MC to recognize "mushroom" shaped stock. I don't see it being fixed anytime soon though, lol

[crazy^millman]

Gcode and I talked this morning and I am going to external STL files, I have a 1gb file and I am dying on the vine watching the paint dry with this file. I run a file structure for every part I program like so.

C:\Customer\XXXXXXXXXX

XXXXXXXXXXX  <-- Part Number and CAM Program resides in the part number folder

    ARCHIVE

    NC CODE

    ORIGINAL MODEL

            REV A

            REV B

            ............

            REV R

    SETUP SHEETS

             ARCHIVE

    STOCK MODELS

    TOOLING

    NCSIMUL OR CAMPLETE OR VERICUT

You must add .stl to your Z2G list of extensions and I have also added tooldb and a couple other extensions to have them go along with a .z2g, but for sharing files I am going to give this process try and see if I don't loose a customer moving this way verse putting the Pmeshs on levels in the file. The stock model folder for this part is 1GB. The total folder with verification is over 10gb and this is for one part. I have some parts they are over 60gb.

 

[jlw™]

29 minutes ago, C^Millman said:

Gcode and I talked this morning and I am going to external STL files, I have a 1gb file and I am dying on the vine watching the paint dry with this file. I run a file structure for every part I program like so.

C:\Customer\XXXXXXXXXX

XXXXXXXXXXX  <-- Part Number and CAM Program resides in the part number folder

    ARCHIVE

    NC CODE

    ORIGINAL MODEL

            REV A

            REV B

            ............

            REV R

    SETUP SHEETS

             ARCHIVE

    STOCK MODELS

    TOOLING

    NCSIMUL OR CAMPLETE OR VERICUT

You must add .stl to your Z2G list of extensions and I have also added tooldb and a couple other extensions to have them go along with a .z2g, but for sharing files I am going to give this process try and see if I don't loose a customer moving this way verse putting the Pmeshs on levels in the file. The stock model folder for this part is 1GB. The total folder with verification is over 10gb and this is for one part. I have some parts they are over 60gb.

 

This is so close to what I do it's scary.  I also use external stl files.

[BenK]

2 hours ago, C^Millman said:

Gcode and I talked this morning and I am going to external STL files, I have a 1gb file and I am dying on the vine watching the paint dry with this file. I run a file structure for every part I program like so.

 

What's the reason for moving to the external STL vs saving to a level other than the obvious file size difference?

[crazy^millman]

23 minutes ago, BenK said:

What's the reason for moving to the external STL vs saving to a level other than the obvious file size difference?

My file is half the size now linking to external verses keeping them internal. Files start getting to 1GB and you hit the wall is what I am seeing. Why a project got broken in 10 files 2 years ago. Other thing you can change something in an operation and not have the whole thing go dirty. Now my stock models have no source operations and now any operation using them as the stock will not go dirty. Yes you seem to double up on work making the stock model. Then saving to an Pmesh or external stl to then go back and make that now the source file or model and get rid of all the source operations to make it stand alone, but just one or 2 times of everything gong dirty and you see why this method of approach on big files needs to be your process moving forward. Programmer does what they must to get the work done.

[BenK]

OK, reason I asked is I wanted to know if it helped with the undercut issue on rest paths cutting air. I agree, 1GB is the limit for a file.

[crazy^millman]

1 minute ago, BenK said:

OK, reason I asked is I wanted to know if it helped with the undercut issue on rest paths cutting air. I agree, 1GB is the limit for a file.

No it is really a separate conversation in this one, but lets be honest not to many people come to the emastercam forum to read about Mastercam. The only real traffic is in O/T.

[crazy^millman]

Well I was wrong after going to a linked STL process my file is now 1.2gb.

[Watcher]

On 18/08/2017 at 1:43 PM, C^Millman said:

No it is really a separate conversation in this one, but lets be honest not to many people come to the emastercam forum to read about Mastercam. The only real traffic is in O/T.

Not sure about that... Industrial forum is pretty active compared to any other CAM system... Heard from competitors that they monitor it closely... 

But I agree O/T is much hotter!