Confused About Stock Model

[Bill H]

I'm programming a flat part that's machined on a fixture.  A blank is placed on the fixture, located with dowel pins, and held in place with some screws while the first operation is machined.  It then gets turned over on the same fixture and is held in place with clamps while the second operation is machined.  All of the components - fixture, part, clamps, etc. - are modeled in Mastercam, so I can make sure that there are no conflicts with the toolpaths.

I created a stock model at the end of the first operation and saved it out to an STL file.  I then imported the STL file back into Mastercam onto its own level.  It came back in a crazy location, so I manipulated the STL model into the proper location and orientation on the fixture.  So far, so good!  Now, at the beginning of the second operation, I created another stock model by selecting the STL model in the graphics area, but the stock model toolpath is in the original (pre-manipulated) position.  Why?  Obviously a plane problem, but I can't figure it out.  Can someone help?

[JParis]

Save the Stock Model as a Pmesh, they are WAAY easier to work with...

[Bill H]

19 minutes ago, JParis said:

Save the Stock Model as a Pmesh, they are WAAY easier to work with...

JParis:  I'm not seeing this as an option anywhere.  How do you do it?  I'm using MC2019.

[Chally72]

Hey Bill,

This has to do with the Plane Transform options of Stock Model and it's difficult to explain, so I'm posting two videos below on how this is usually accomplished. Basically, you have two initial approaches that decide how you handle stock models and plane choices. Let's go over these first to better understand how/why that stl location changed.

When programming a single part, multiple fixture/multiple vise setup, we have two choices:

• Have one master model of the part, and "rotate" the fixturing around the part in space to represent Setup 1 and Setup 2. (In this case, a twin vise setup would have one vise at "top" orientation and one vise at "bottom" orientation in space- so if you turned on all levels at once the vises wouldn't actually look like they were side by side like they would be in the machine) The benefit of this method is that all your toolpaths are on the single master model and any changes to your part model in the future need only be made in one place.
• Have multiple models of the part, and change/transform the location and orientation of each to fit it in fixturing you have modeled. (Such as twin vises sitting side by side) The advantage of this is you physically see the multiple fixture/multiple pocket setup as you would bolt it to the machine table in real life, but now you have multiple copies of the master model geometry and if you did something like change a chamfer width on the part, you'd have to do it in two places.

Now, the plane transformation options in Stock Model operations exist specifically for the latter scenario here- where we have to move the part stock in space between pockets on a tombstone or fixtures on a table. That Plane checkbox, in my mind, should remain off at all times unless you run into a specific scenario where you need it on.

Otherwise, what you do when you turn that checkbox on for the first stock model operation is "Create" the stock in a specific plane, or coordinate system. And if you ever change that plane, (IE, save the stock out to a STL,) it has to translate that to the world coordinate system. This is why you see it in a different position, but then when you recreate the stock model and reselect the STL and apply the same plane transformation to it, it snaps back to the original location. 

 

Here are those videos on the two types of part flow and maintaining stock model associativity. Apologies for the quality of the first video. Let me know if you have questions on what I cover in them. The second video covers scenarios where you'd be moving stock between pockets and even between machine groups and between machine types, such as moving lathe stock to a mill fixture and continuing on with perfect associativity.

 

 

 

[Bill H]

Chally72:  Dylan, thanks so much!  These were the two most informative, understandable, and well-presented videos I've ever watched.  Bravo!!

[Bill H]

Dylan:  I have a follow up question about the Plane Transform option that you've demonstrated in the Part 2 video.  I can only get the Transform to work properly if the Op 1 coordinate system is the same as the World Coordinate System.  Am I doing something wrong? 

[Chally72]

5 minutes ago, Bill H said:

Dylan:  I have a follow up question about the Plane Transform option that you've demonstrated in the Part 2 video.  I can only get the Transform to work properly if the Op 1 coordinate system is the same as the World Coordinate System.  Am I doing something wrong? 

Hey Bill, if you've got multiple parts/fixtures you're transforming the stock between, this is what I touch upon in the second half of the second video. If you've got a single part location, then just uncheck that Planes option in every single stock model as it's not necessary.

If your situation was the former, this starts to become a complex scenario because your planes are just applying relative transformations, or XYZ and rotational deltas, to move the stock from one area to another. So if you started from a solid body, which is located in World coordinates, but your setup 1 origin was not in the exact same place as World coordinates, it can get difficult to visualize. Here's another (poorer quality) video I made a while back to try to explain this. This is a difficult concept and I wish it was easier/clearer to the user that the entire use of those planes is just to apply relative transformations to the stock position.

 

 

[Bill H]

Dylan, thanks again!  I think I get it now.  

[Bill H]

Dylan, can I bother you with one last question?  In the case of the single part location scenario shown in your Part 1 video, how would you get the vises to be visible in simulation to make sure there aren't conflicts with the jaws?

[crazy^millman]

36 minutes ago, Bill H said:

Dylan, can I bother you with one last question?  In the case of the single part location scenario shown in your Part 1 video, how would you get the vises to be visible in simulation to make sure there aren't conflicts with the jaws?

Turn on the levels in the Simulator Options that has the vices and jaws in them and then they will show up in the simulation when using Mastercam Verify.

[Bill H]

6 minutes ago, crazy^millman said:

Turn of the levels in the Simulator Options that has the vices and jaws in them and then they will show up in the simulation when using Mastercam Verify.

millman: In Dylan's video, one vise is used in Op 1 and a different vise is used in Op 2.  How would you control that visibility in Verify?

[crazy^millman]

35 minutes ago, Bill H said:

Dylan, can I bother you with one last question?  In the case of the single part location scenario shown in your Part 1 video, how would you get the vises to be visible in simulation to make sure there aren't conflicts with the jaws?

In one machine group you will have to go through the Simulator options and pick that level for each verify. With 2 machine groups one for each operation then you would do it for each group. Many ways to accomplish the process. I would put each vice on their own level to have that type of control. I do this when programming in one machine group for many different parts that will be run on one machine.

I make up stock models for each part and don't define a stock in the Machine group when programming this way. In the Simulator I Pick the stock model I want to use for that part and then I am good to go.

The limitation of the simulator options to to one machine group. Be great to assign simulation options to sets of groups, but that is where making each new Machine group does accomplish the task, but does break the process for simulation/verify. If we had a way to make simulation options per operation group inside of one machine group then it would be a cleaner process. Currently the simulator options in the current process is limited and requires the programmer to pick what they want for each operation if they are in one machine group.

[Bill H]

4 minutes ago, crazy^millman said:

In one machine group you will have to go through the Simulator options and pick that level for each verify. With 2 machine groups one for each operation then you would do it for each group. Many ways to accomplish the process.

Millman:  That doesn't help here.  In Dylan's example there is only one machine group with two toolpath groups.  One vise is used in the first toolpath group and the other is used in the second.

[Chally72]

On 12/30/2021 at 3:26 PM, Bill H said:

Millman:  That doesn't help here.  In Dylan's example there is only one machine group with two toolpath groups.  One vise is used in the first toolpath group and the other is used in the second.

In the case of two setups in a single machine group, you'd have to simulate them separately and change both the fixturing and the starting stock to reference Setup 2 conditions when simulating Setup 2.