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Old 03-21-2008, 07:32 PM
Matt Zettl mzettl is offline
Join Date: Mar 2006
Location: , Morehead City NC
Posts: 84
Default ? Cutting Coroplast

A sign shop has contacted me wanting to know if I can cut some shapes out of Coroplast for them. They will apply vinyl graphics to them, and want to do a trial run of about 50. If they are successful with the idea, then they would need many more.

I have searched the ShopBot forums on this subject, and what I've found is not encouraging. The most recent posts are from about a year ago, and it would seem that the best bits would be either a Belin O-flute, or an Onsrud double spiral O-flute. Brady Watson mentioned a triple spiral, but did not mention the manufacturer. I could not find any information about how long any of these bits would last before the cut degraded to the point of being unacceptable.

I tried a few a test cuts in some material they gave me, using bits that I had on hand. The best cut I got was with a new 1/4" Centurion down cut spiral at 120 in/min and 18,000 RPM. I have included a photo of the cut. The cut is clean on the top and bottom skins, but the feathering of the interior ribs is the problem, as has been noted in previous posts.

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I was wondering if anyone has any new information or suggestions. Alternatively, is there another material that would be easier to work with and comparable in price? These are going to be used outside, so they need to be waterproof.

Old 03-21-2008, 10:40 PM
Jay Nicolaides signsbyjay is offline
Join Date: Feb 2007
Location: Highland, IL
Posts: 71

Coroplast cuts better if you cut counterclockwise.

I use a 1/4" 2 flute straight bit.

Old 03-22-2008, 07:09 PM
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Brady Watson bradywatson is offline
Senior Member
Join Date: Jan 2004
Location: iBILD Solutions - Southern NJ
Posts: 6,526

I doubt you will find a cheaper plastic substrate to cut. I've had excellent results with a 4-flute downcut bit. I don't remember where I got it...but it worked best out of everything I tried...Or just use a straight bit as Jay indicates.

Old 03-23-2008, 01:41 PM
Jerry Hicks jhicks is offline
Senior Member
Join Date: May 2004
Location: Lyons Illinois
Posts: 859

Matt, I agree with Jay. Take a look at the other side of your cut edges on the scrap and I think you will find the edge quality is much better. Keep in mind these are used for cheap signs that often sit on wire frame holders and the sign shops have no way to cut any shapes except squares or rectangles. They use a razor blade for straight cuts or a scroll saw for curves so your curved cuts will be superior regardless. Just try to cut a circle in that stuff with a razor blade and you'll see how impossible it is to go throuh the corregated cells.
Try the reverse cut direction with a small 1/8" bit, hold with a vac system, and you should get what you want.
Dont prejudge the customers reception to the edge. I think they will be happy they found someone who can do shapes and be much more forgiving on the edge than you might suspect.
BUT if it simply isnt good enough, maybe a Sintra sheet stock will work. More costly though.
Old 03-23-2008, 04:51 PM
Matt Zettl mzettl is offline
Join Date: Mar 2006
Location: , Morehead City NC
Posts: 84

Thanks for all of the suggestions. I've tried conventional (counterclockwise) and climb (clockwise)cutting, and there's no doubt that counterclockwise is better. Jerry, you bring up a good point regarding customers being more forgiving. I am too much of a perfectionist for my own good sometimes. I'm going to continue some experimentation with different types of bits, and will eventually report back on my results. Appreciate the help.

Old 03-23-2008, 05:58 PM
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Mark Tucker tuck is offline
Senior Member
Join Date: Feb 2004
Posts: 627


I have encountered this problem myself. My solution was to burn (melt) off the feathers with a propane torch. It goes fast but won't be much fun if you have 1,000 of 'em to do.

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