machining laminate sheets

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Rob Davis
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machining laminate sheets

Postby Rob Davis » Thu, Jan 22 2009, 10:59PM

Any suggestions on feed rates or other useful ideas on how to machine a sheet of lamiante, standard grade, 0.063" thick? We are using a 1/4" straight bit and feed of 400 with machine adjustment to about 60% feed rate (240 ipm feed). We are having trouble keeping the sheet on the table as once we start cutting through the sheet we tend to have the sheet lift up and lose suction and slide around and ball up on us. We are cutting 48 "holes" of 8"x11" into a 61x121 sheet and we get most of them in and then the sheet lifts up and we are done. We are gettign 27 on the suction gage so we are getting good vacuum until we start cutting a bunch of holes. The sheet wants to curl up and come off the table as we get along becasue the pieces left in the holes curl and come off the table, get chips under them and leaving exposed spaces so the suction drops to about 20 or less.
We are thinking a sharp bit is critical, and maybe slower speeds so we don't push the sheet with the bit. If we go real slowly and use a piece of slat to hold the sheet down while cutting, we can improve things. But is it OK to go that slowly cutting laminate or will we just dull the bit terribly? Any opinions from you gurus out there?

Nemanja Vujkovic
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Re: machining laminate sheets

Postby Nemanja Vujkovic » Fri, Jan 23 2009, 7:24AM

Rob,
have you tried double sided tape. Taping the eges of the laminate sheet tom the CNC table might help to. You can machine laminate a lot faster than that and get a nivce edge. Try 24000rpm and 700-800ipm. It's been a long time since i machined a sheet of HPL by itself, so numbers might be off a little. Good luck with your project.

Nemanja

David Hall
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Re: machining laminate sheets

Postby David Hall » Fri, Jan 23 2009, 7:34PM

My suggestion(s) really depends on how many of these you must cut, and if they're all the same.

1. Use a freshly machined waste board.

If you're not already, Flip the sheet so the center of the sheet wants to pop-up, instead of the edges curling up. (In my experience this has always been face side up)

You also might consider using a down shear tool. (helps push the part against the wasteboard, but I doubt this alone will solve the problem)

If you have 50 to do that are all the same, it's time to make a dedicated fixture with gaskets holding both the part and the off-falls in place. And then crank up the feed speed and make-up for the time you invested in the fixture.

For a shorter run, double sided tape was mentioned. You might also consider stapeling the off-fall to a 3/8" wasteboard prior to machining. I would program some shallow drill marks in the off-fall areas to mark the ideal staple positions. Send the spindle home and add a pause to the CNC code. Staple down the off fall, and resume machining. If editing CNC code is not your thing, then one program to mark the staple positions, and another to machine the parts would get er dun. Or even just laying one of those messed-up parts on top before you start will give you a good idea where to shoot the staples, screws, brads... with a 6 x 9 block of 1/2" whatever between the screw and the laminate.... whatever's handy.

Again depending on quantity, you can leave a skin on the window cuts. ( say .010 or .007) and with a good pair of gloves on, touch-up the openings with a little sandpaper. Don't forget the gloves. (My customers tend to frown on bloody parts.)


What's your vaccum reading with nothing on the table? With just a wasteboard?

Regards,
Dave
David Hall
Hall's Edge Inc.
eCabinets Machining Services
http://www.HallsEdge.com

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Damon Nabors
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Re: machining laminate sheets

Postby Damon Nabors » Fri, Jan 23 2009, 9:08PM

I cut 5 x 12 P-Lam on my router all the time. Normally it comes coiled up in a roll and wants to spring back on you when unrolled. I normally have to remove the brackets for the flip op jig so it will lay flat. (If you do this, be sure to notice that there are some shims in place and you will want to put them back exactly like they came off or your fixture will not be in align properly.) I usually lay it out in the sun flat for a few hours so it will relax and lay flat. For me the money side face down on a newly flycut waste board and a down cut spiral works for me. The back side seems to be too rough and will not suck down to the table as well. Sometimes on a small piece, I will stop the machine with the feed overide and then tape the part down on three sides to prevent it from sliding and then finish the forth side.
Damon Nabors

Rob Davis
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Re: machining laminate sheets

Postby Rob Davis » Mon, Jan 26 2009, 9:06AM

Thanks for the help guys. We have 50 of these to do but aren't building a fixture. We got new bits (1/4 straight shank), slowed it down versus speed it up, and as bit dulls, use two sided tape. the problem is that when we are done, most of the sheet is gone and suction is not enough to hold it all down. Once it catches the edge of the sheet, it peels it up without any trouble. Bit has to be sharp and can't push the material.
We do lamiante sheets often also but this one is cut out big time.
Just fly cut waste board and cut it to 1/8 thick.
Suction before sheet is 16, with sheet on it before cutting is 24, and after cutting is 19.
We also added a step to machine the outside ones first and work our way to the center of the table. As the outside ones get cut, we cover them in shrink wrap plastic or with 1/2 melamine and that works better for holding them down.
THis is definitely a small part, suction at edges, issue. We have a 50 sq foot sheet (5x10), we are cutting out 8"x11" squares 48 of them, which do NOT stick down once cut out, so we cut out 30 sq feet and have only 20 left to hold down, and this is 3" wide banding between holes.

Thanks for the ideas.

Gary Urlacher
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Re: machining laminate sheets

Postby Gary Urlacher » Mon, Jan 26 2009, 2:29PM

Judging by the numbers you posted, Your vacuum is good. It looks like you have a CFM problem.

Here are my suggestions:

A - Use a down cut bit, not a strait bit.

B - Your spoil board (waist board) is to thin. This allows air
to go through the board faster than a thicker board. I sugest a 3/8" waist board
then plain both sides flat then you should be left with a board just over 1/4".
This should help with your CFM issue.

C - If you have a large distance between parts, this means that you are cutting 1/2" of material away between any
two parts if you use a 1/4" bit. Set your space between parts to just over a 1/4" then the bit will share cutting area between parts.
if your part gap is smaller then you are saving vacuume becouse your bit is not taking a full 1/4" around every part.

Keep us all posted.

Gary

Dennis Englert

Re: machining laminate sheets

Postby Dennis Englert » Tue, Jan 27 2009, 8:29AM

Since your spoilboard or wasteboard is already marked with the cut positions lay down some gasket material to capture the vacuum for those points. You can purchase some thin about 1/4" wide weatherstripping at just about any hardware store or building supply. This works well and since all of your operations appear to be a through-cut, it does not affect the depth of cut for dadoes, etc. It's also easy to apply, does not require routed grooves, and just scrapes off or can be flycut when you're done.

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Dale Wills
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Re: machining laminate sheets

Postby Dale Wills » Thu, Jan 29 2009, 12:10AM

In the past couple of years I have successfully machined laminate on a regular basis. Although this was on a Procam CNC, the machining principles all still apply on Thermwood CNC's. We found using a straight bit worked well and also a freshly flycut wasteboard was critical. We also left a collar of 50mm min around the sheet to stop corners curling up. On small parts we added in part clearance. As dust is minimal in machining laminate we also turned off all dust extraction to minimise parts be potentially sucked off the table.

Dale

Rob Davis
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Re: machining laminate sheets

Postby Rob Davis » Thu, Jan 29 2009, 3:36PM

Gents, job completed. We ended up being very efficient in accomplishing this. We used our thin wasteboard, freshly flycut, barely cut through the parts (-0.0015) but we did it in two steps. First was to cut one half the sheet while we had some melamine on the other half (5x4.5) for weight to hold it down. Plus as we cut, we would cover the spaces we could with melamine pieces to hold it in place and get some suction. After it got done with first half of sheet, we stopped (feed to 0%) and moved the 5x5 sheet onto the cut half which since we were using melamine, got held down with suction while we cut the other half. We did have to put boards around the outside to hold the edges while we cut but worked out and worked great. My operator thought about using some boards because it would work fine for most of the sheet until it started to bubble up due to reducing suction around teh outside.
The issue we struggled with was the natural curve of the sheet. Sheets were 5x10 so big to handle and expensive to replace if we screwed them up. Some of these we machined face up and some face down (symetric parts luckily) because the sheets would curl based on how they were shipped on the skid and the vacuum couldn't pull the curl out of them at the edges without the help of a little weight and stiff board.
We did not use 2 sided tape but that was our next step. We don't like it because we have to do 50 sheets and byt he time you ge tmultiple sheets, you have to replace the stuff and it is dusty and so on. Sometimes necessary but not our preferred method.
The forum is great and thanks again for all the help! You guys are a huge resource. We love Thermwood and its members!
Rob

Nemanja Vujkovic
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Re: machining laminate sheets

Postby Nemanja Vujkovic » Fri, Jan 30 2009, 7:26AM

Rob
I am glad eveything worked out for You!
Now we all expect our royalties to be sent immediately to us!!! :lol: :beer:

Rob Davis
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Re: machining laminate sheets

Postby Rob Davis » Fri, Jan 30 2009, 9:39AM

Nemanja,
We will send the royalties by putting your name on preferred stock in one of these bailed out banks or perhaps an automaker! Unfortunately not worth the papaer they are written on!!!! :(
What have we Americans gotten ourselves into?
Saying "Thanks for the help" may be worth more than the other!

Nemanja Vujkovic
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Re: machining laminate sheets

Postby Nemanja Vujkovic » Fri, Jan 30 2009, 9:56AM

You are right, Thank You is sufficiant. :D

Bob Gregory
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Re: machining laminate sheets

Postby Bob Gregory » Wed, Feb 04 2009, 11:48AM

Rob I have solved this problem by using an O flute down cut spiral tool. My favorite is a Vortex 5730H. I have also used this tool to cut over 125 sheets of an art type acrylic composite with the top surface colored epoxy and the substrate clear acrylic. Its rather brittle and easily damaged and at $900 per sheet I really did not want any part movement or delamination.
Bob


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