Undercut with Lollipop Cutter

[Lee.]

Hi Guys,

 

I'm hoping someone can put there finger on my problem.

 

When I first told my customer I could do this, I drew the tool and the job and presto, exactly as I thought it would be a perfect toolpath.

 

Now we have the job to do, it will not work as it did before.

 

I can't get it to verify either so i'm scared to run the part.

 

it's a simple internal pocket that is shaped like a hockey rink ( oval ) 1/2" deep, open with a 16.7118 degree twist, so that two corners are undercut.

 

The tool will go in but when I backplot it looks very strange.

 

The path should constantly go down in z and gradually twist as it does.

 

The profile is constant as it goes down so that path should just twist, but it doesn't.

 

WTF.

 

Help Please.

 

Lee

[?Mark]

Only 2 toolpaths will do the trick: finish contour and flowline. If you're already using them and still get bad results then it's the parameter settings that are wrong.

hth

[Lee.]

Hi Mark,

 

Yes I am using finish contour and think i've tried most of the settings with no luck at all.

 

funny thing is, first time no problem.

 

Lee.

[?Mark]

How is your tool defined? Did you "allow" undercuts in parameter page? I go thru those setting automatically so I don't pay much attention to "nomenclature " :-)

Did you check your "z depths"?

I don't have a sim with me so I can't look at your file...

[Lee.]

Hi Mark,

 

I have no idea where the parameter is for allowing undercuts.

 

I changed the default lollipop file to suit my tool.

 

Lee.

[Lee.]

I can't figure out how to upload a picture, but could send you one.

 

It has the path on it.

 

Lee

[?Mark]

Use full editor and at the bottom there is "attach file" for pictures and so on...

[Lee.]

thx

[?Mark]

Is the tool defined correctly? (screen shot of main page would help)

Is the containment boundary set correctly? Offset it as necessary.

[Lee.]

please take a look

[Lee.]

boundary and settings

[?Mark]

Custom tool is the problem.

Use "auto" when undercutting.

Is it a lollipop or a keyseat style with full radius?

[Guest]

Lee,

 

I'd be happy to have a peek if you can share the file.

[Bruce Kanzelmeyer]

Your cutter is defined with a .75" flute length, but a .875" corner radius--can that work for a lollipop cutter?

[Lee.]

Hello All,

 

 

I cannot change the corner radius in that dialogue box.

 

It seems to default to half the diameter.

 

The cutter I need to use is 1.75 dia, with a corner radius of .375 and looks exactly like the picture above.

 

As I said when i first did it and told customer we can machine this part, it worked fine.

 

Still can't figure it out.

 

I will gladly share the files, please tell me how.

 

Lee.

[Lee.]

Mark,

 

If I use auto then it defaults to a full ball style lollipop.

 

That would not work for this job.

 

Lee

[?Mark]

It is defined incorrectly. Use keyseat type and set it to aute. With keyseat type you can't use a full radius. For example If the tool is .500 wide you have to input .250 radius at top and bottom instead of full radius in order for undercutting to work...

Bottom line: the tool definition is wrong in his example.

[Lee.]

Thanks Mark,

 

Didn't know that.

 

I'm giving it a try now.

 

Lee

[Lee.]

Mark,

 

Thank you so much.

 

It worked like crazy, again thanks.

 

Lee.

[?Mark]

<cheers>