Open pocket starts inside...

[William Grizwald]

Simple bottle shaped chained 2d curves using "Pocket-Open". The small end is the opening. No matter how I slice it or dice it, the tool wants to plunge into the large area of the pocket then finish at the narrower open end. The tool is a 3/4" EM. The narrow end of the pocket is .875 wide. The widest area is 2.5" across. S/B plenty of room to enter from the narrow area without having to plunge into the part first. What gives?

 

__________

|---------

|----------__________

| * Plunges here ------- <-- Open here

|---------- __________

|----------/

|---------/

|________/

 

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Bill

[Guest]

In the tool parameters, do you have use open pocket method checked?

[William Grizwald]

Yep. Pocket Open, "Use open pocket cutting method"...

 

I used closed with a start point to get it done. Still, it should have worked.

 

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Bill

[Guest]

Open pocket does work the way you describe, I do this a lot. If you want to send your file or place it on the FTP I'll get a look and see if I can tell you why.

[Kannon]

try selecting "constant overlap spiral" in your pocket roughing and finishing parameters, and see if that changes it.

It works for me.

[William Grizwald]

John,

Thanks for the help. Can't really send the file (hush hush and all that...) but I will try more later using different curves (and the machine is not waiting for my program).

 

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Bill

[Mike Whitten CAD/CAM Contractors]

It would be a good idea to send the file or a modified test file that is similar to [email protected]

 

Mike

[Kyle Waters]

I am not at work, but can't you select "use start point" in the lead in-out?

[William Grizwald]

Kannon, The cutting style is locked when using open pocket.

 

Kyle, Use start point on open pocket gives the "can't cut island boundarys (or somthing like that) which makes sense.

 

John et all, I sent the file to QC but it's occurred to me that really the purpose of Open Pocket is to allow one to define a pocket boundary with an open side (hence the overlap value adjustment feature). Perhaps it's not designed to nessessarily start at the open end. It's just for selection purposes? We'll see.

 

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Bill

[Guest]

I start from the open end ALL this time, just finished 4 separate parts that all had open pockets. The rough and finish passes all began out side of the boundary.

[Mike Whitten CAD/CAM Contractors]

If the "open pocket cutting method" is used, it should start from the open end.

 

From Help:

----------------------------------

Machining open pockets

Open pockets are created from chains that do not have the same start and end point. Mastercam calculates the distance between the start and end points of the chain and treats the chain as if it was closed geometry. For this type of geometry, you can use the Open pocket cutting method, which starts the toolpath at the open end of the pocket and cuts from the inside to the outside. To create an open pocket, select Open from the Pocket type list in the Pocketing parameters tab.

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Mike

[William Grizwald]

John,

 

I'm going for the day (finally) but... draw a simple shape where the main shape is wider than the opening of the pocket. Perhaps that is the issue?

 

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Bill

[Guest]

I am doing that, tool size seems to be the issue, it it is too close to the narrow end size it starts inside I think because that where it sees more stock to cut

[Mike Whitten CAD/CAM Contractors]

Bill,

 

I did a test on my end and had the same problem as you. The work around was to turn off "open pocket cutting method" and add a chained point which is I believe what you had to do. It looks like a limitation in open pocket.

 

Mike

[Guest]

You still have access to ramped and helix entry so you could enter the material that way as well

[Kyle Waters]

Bill,

I created a bottle shape similar to yours, using a 3/4 tool, and everything worked fine. On the roughing/finishing parameters page, if zigzag or one way were selected for roughing, it did start on the inside of the pocket. All of the other methods started from outside the boundary. Is this the same issue that you are having?

[mcpgmr]

I have this problem occasionally. Try changing your geometry at the opening. Maybe there is cutter diameter conflict even though the opening is wider than the tool. Sometines decreasing the step over amount will fix it too.

[heavychevy2155]

I like using open pocket, I just wish they would add options like rapid between cuts, or high speed loops. Like they have in the facing toolpath.

[William Grizwald]

I just used closed pocket/start point. Moving on...

 

Thanks all.

 

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Bill

[P_Scott]

William

Grizwald,

 

I believe mcpgmr may be on to something with this statement:

quote:

---

Sometines decreasing the step over amount will fix it too.

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If there's a large stepover amount (>50%) and a large stock to leave value, the Open Pocket could simply be entering wherever it finds enough room for the tool. Changing those two values should help as well as using the "Start Point" method described without using the "Open Pocket Roughing" technique.

 

QC may not consider it a "bug" because the toolpath is simply trying to do what you ask while considering all the values of the parameters. A good test would be to use a smaller diameter tool with the same parameters as the first toolpath. If the smaller tool does it the way you intend, the original tool is too big to do it the same way. HTH

[William Grizwald]

Peter,

 

Sorry, I didn't see this thread still going...

 

You may be right in that it's as designed because of the step over amount. That said, in a previous life, the system I used would know that and not step over where it can't but would where it could. No worries.

 

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Bill