Backplot Drill Cycle

[Paul McGarr]

Hi,

 

When I backplot a drill cycle that uses a ball endmill, why does the tool appear to go too deep by the radius of the ball? I've had this problem as long as I can remember, but I figure there must be something I am doing wrong because I would think this would have been fixed long ago.

 

If I am not mistaken, this happens in verify also.

 

Mastercam Mill 9.1 SP1 / Windows XP

 

Thanks,

 

Paul McGarr

[mayday]

do you have tip comp turned on in your opp?

[Keith Graydon]

is "TIP COMP" turned on? per chance? just a thought.

[Keith Graydon]

ey MayDay, nice Tractor.... Farmall?

[Paul McGarr]

No, tip comp is not on. The value displayed in the status area is correct, and the value output in the program is correct.

 

Paul

[Keith Graydon]

try changing

 

[COMP]

tip

center

 

< shrug >

 

where are you in Mass. Paul?

[Paul McGarr]

Where would I change Tip/Center compensation in a drill cycle? I don't think you can.

 

Paul

[Paul McGarr]

I'm in Chicopee MA. Near Springfield.

[mayday]

quote:

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ey MayDay, nice Tractor.... Farmall?

 

---

nope '51 Case DC

[Keith Graydon]

quote:

---

I don't think you can.

---

Sorry, i was thinking off the top of my head. Perhaps the tools settings in verify. try changing from auto to custom or visa versa.

 

quote:

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I'm in Chicopee

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My sister lives in Newton, and I have other relatives in Fall River and that general area. and many in Rhode Island.

 

 

quote:

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nope '51 Case DC

---

looks like a Farmall C ~1955

[Henk]

Hi Paul,

 

I have the same with bullmills, set on tip and no tip comp. Only the backplot is wrong, the NC-file is correct

 

Henk

 

V9.1SP1 Mill 3

[P_Scott]

Paul,

 

The toolpath that Mcam generates is always from the center of the tool for XY. Ball mills are generally considered milling or "contour" tools. In drilling the feed motion is calculated from the tip of the tool. Change the depth to a value above the bottom by the radius of the tool to get your desired result. This also means you will have to touch off the tool and then adjust the length offset for that tool's radius. It's as if you were drilling from the center instead of the tip. Or you could just be aware of it and know that the code will be correct without changing the depth for the radius of the ball. Ball mills typically aren't center cutting. Matter of fact, there's usually no land at all in the exact center of a ball mill so there's no cutting edge like there is on a drill. Have you ever tried to drill a hole with a drill that comes to a needle point? Some would argue that the center of a ball mill doesn't actually spin either, that's why it can't cut at the precise center. I hope this helps to clarify things a little.

Give us a call if you have any questions regarding Mastercam. I played pool at a team tournament in Chicopee once. I forget the name of the place but I'm sure I would remember if I heard it. I had my biggest screw up ever in APA league history. But that's another story.

 

[ 08-22-2003, 11:30 AM: Message edited by: Peter Scott ]

[Thad]

quote:

---

I've never tried using a ball mill for a drill cycle because ball mills typically aren't center cutting.

---

Peter,

 

It's interesting that you say that because the only ball endmills (carbide) that I've seen that aren't center cutting are the resharps that have been hacked up by the cutter grinder. In fact, using a ball nose is our preferred method of adding a forgotten start hole (for wire EDM) to hardenend steel. Bump it a few times to get it started straight and then it cuts like butter.

 

Thad

[Paul McGarr]

I understand what you are saying. It does not make sense to me though. If I do the same operation without using a drill cycle, backplot and verify work fine. When using a drill, it works fine. Why does Mastercam care what the shape of the tool is?

 

I'm not looking for a technical answer as much as a logical answer. If I plunge a 1/2" ball endmill 1" deep into my part, backplot should show me a ball endmill going 1" deep into my part...not 1 1/4" deep. Does this bother anyone else?

 

Programming the tool shallow and setting it deep sounds like a work around. I guess I would like to see tip comp for drill cycles.

 

quote:

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I played pool at a team tournament in Chicopee once. I forget the name of the place but I'm sure I would remember if I heard it. I had my biggest screw up ever in APA league history. But that's another story.

---

You were probably at Market Square.

 

Thanks,

Paul McGarr

[Paul McGarr]

Just to comment, because I forgot in my last post, all of my ball endmills are center cutting. I actually tried to find one that is not, and I failed.

 

I guess that in the "absolute" center of the ball, the SFM would be "zero".

[P_Scott]

Paul,

 

Yes the tourney was at Market Square. My teammates pulled me through after the screw up and we went on until the end of the day for the semi-finals. I redeemed myself by kicking a$$ for the rest of my matches, beating out some tough competition. I even disappointed one opponent's girlfriend after hearing her ask him if she could use his stick when he won.

 

On another note. The ball mills I remember weren't used as drills for the simple reason that they didn't have any flute or relief at the tip and would gall up if used in that manner. Maybe they were regrinds. It wouldn't surprise me because the company was too cheap to get new ones. My referring to these tools as not typically "center-cutting" was a misuse of jargon and technically they are center-cutting.

This does nothing to explain why Mastercam Backplots a ball mill differently than a drill. Only know that it does, so if you want the tool to Backplot correctly, what I suggested works. If you want the output for a ball mill used as a drill to be correct, call it a drill in a drill operation and touch it off at the tip. The Backplot will LOOK bad but the code will be OK. The code is the true test of the program. Mcam only Backplots and Verifies NCI data, not code. HTH

 

[ 08-25-2003, 04:57 PM: Message edited by: Peter Scott ]