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  #1  
Old 05-02-2014, 12:20 PM
Jadendo Jadendo is offline
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Default Chatter marks on cutting acrylics

I need help guys. The Acrylic that I cut have chatter marks on the Y direction.
The X direction cuts smooth. Does this mean my machine does not hold the Y direction tightly?

I use 1/4" All Purpose O-Flute Spiral Upcut tool, 1/4" cast acrylic, down pass of .060".

Thanks.
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Old 05-02-2014, 02:54 PM
Xray Xray is offline
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I take it you are referring to a profile cutout.
What thickness of plexi ? Feed speeds ? What is your holddown method ?
New bit, or has it been used some, and on what ?

Don't mean to bomb you with questions but the problem is most likely due to one of the above rather than mechanical ,,, Would be advisable to post a pic if able.
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Old 05-02-2014, 05:12 PM
Jadendo Jadendo is offline
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Default ......

Thanks for asking the questions.

Thickness: 1/4" cast acrylic
Feed speed: 100 in/m
RPM: 16,000
Bit: fairly new single O flute
Suction hold down with Hurricane.

I am thinking the piece is moved while it's cutting in the Y direction.
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  #4  
Old 05-02-2014, 05:19 PM
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Gary Campbell Gary Campbell is offline
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Jadendo...
IF you are getting chatter when moving in the Y direction, most likely there is a mechanical looseness in the X axis. The invers is also true. In either case, check belt tension, gear to rack clearance (spring tension) and look for debris in the rack gears for both. Plastic is famous for loving to stick in the gears.
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Old 05-02-2014, 05:52 PM
Jadendo Jadendo is offline
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Default ...

Thanks Gary. I'll check. My Stinger III is 1 month old.
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Old 05-02-2014, 06:19 PM
Xray Xray is offline
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Might want to try screwing directly into spoilboard and see if situation changes. 2 screws kitty corner should do.
Even when screwed thin plexi can easily lift, especially with an upcut bit. This lifting/flexing will always cause chatter/nicks/rough edges.
Feed seems about right, though I sometimes slow to 50 with the thin stuff ... Also reduce RPM's if possible, just to avoid any melting issues.
If problem persists I'd try a downcut bit.
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Old 05-02-2014, 06:22 PM
Jadendo Jadendo is offline
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Should I try 12,000 rpm with 50in/min feed?

Also from Vectric, how do I program it to perform the complete rough cut and then run one final profile with tool at full thickness and a .015" step over?
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Old 05-02-2014, 07:50 PM
Mark Johnston Mark Johnston is offline
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Just create another toolpath right behind the first cutout and do an allowance offset of -0.015 if you want it to cut a little more off. Since your going to cut with the same tool you can save both toolpaths as one and it will cut one right after the other.

Mark
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Old 05-02-2014, 07:57 PM
Jadendo Jadendo is offline
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Got it. So I would have to do 2 separate tool paths with the 2nd one -.015" offset.
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Old 05-02-2014, 08:08 PM
Mark Johnston Mark Johnston is offline
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Quote:
Originally Posted by Jadendo View Post
Got it. So I would have to do 2 separate tool paths with the 2nd one -.015" offset.
Yes, but as I said you can combine the toolpaths so they run as one because your using the same bit.

Mark

If the first toolpath didn't cut all the way through the material you can have the second toolpath cut all the way through in on pass since your only removing .015.
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Last edited by Mark Johnston; 05-02-2014 at 08:10 PM.
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