Komatex

[3d_danny]

I had a client stop by yesterday with a couple of 6mm Komatex 4 x 8 sheets and wants me to cut a variety of shapes out of it.

I understand that this is a PVC material of some sort.

I primarily cut wood on my bot so I am not familiar with cutting anything "foreign".

Is it possible to cut this material with a wood down-spiral bit? Could someone please give me a starting point for speed and feed numbers?( I have a 3hp spindle)

I was hoping to get by without buying a bit just for plastics which would delay the job ( customers always wanted it yesterday ).

Any help is greatly appreciated.

Dan

[Brady Watson]

Dan,
I would not use a down-cut spiral to cut Komatex. You will get a lot of chip welding and the results will be less than desirable. If you want to hit a home run with the customer order an Onsrud double spiral-O bit from MSC. Depending on where you live, you should be able to get it the next day. I use an Onsrud 52-624 1/4" to cut all types of PVC sheet. The difference in quality is unreal. MSC #: 06051692 and they are $22.19ea. Get 2 of them and they will last you though many many jobs. (IE - I have used the same bit to run over 60 sheets of 18mm Komatex and the bit is still sharp!

While I think it is a good quality to be frugal when it comes to consumables, that doesn't override the fact that your cutting bit is where the rubber meets the road. Don't cheese out on your cutting tools!

For holding the material down I have found that vacuum works best, and carpet tape if you don't have a vac setup. Screws don't adequately hold the material down and the material can lift and cut quality will suffer. Depending on your hold down method and shape of your parts, you may want to cut it in 2 passes. Komatex is a little spongy and running the tool thru it in one pass can cause material distortion and work against your hold down method. You'll see what I mean when you cut it


I would try around 13,500 RPM @ 2 IPS as a start. Remember that you want nice big chips coming off the bit like soap shavings. If by chance you cannot get the Onsrud bit in time, you can use a NEW/sharp standard end mill/upcut spiral at the same speed. The end mill will leave some climb marks on the material, but depending on what you are cutting, it may not matter.

Hope that helps!
-Brady

[3d_danny]

Hello Brady,

Thank you. I just ordered a couple of the bits and should be here tomorrow. Off to the "depot" for some carpet tape. I'll let you know how it works out.

Again, thanks,

Dan

[jhicks]

Dan, I agree with Brady and have used both 2 flute and single up cut "super O flute" (Super polish and sharp)from onsrud with good results. Depending on the size and detail with a 1/8" or even a 1/16" bit we cut in the same range from 12,000 rpm to 13,000 rpm at 1.5 to 2.0 IPS. The slower move speed and smaller bits do seem to provide a cleaner edges for us.

[mikejohn]

Brady
Promoting a product from the largest European plastics manufacturer, Kommerling?
I am suprised at you


..............Mike

[Brady Watson]

Mikey...It's a good product! Who can argue with that?


-B

[mikejohn]

Brady
I was actually being cheeky.
Kommerling have a PVC manufacturing plant in the USA!
(but the profits still end up in Germany
)

[wcsg]

I get a nice edge with 7,900 RPM's at 1.3"IPS using a single flute upspiral Belin bit which is comp to onsrud. PVC is so soft going to fast in RPM's can cause you problems. I use to go 15,000RPM's and 2.5"IPS but I see a better edge now on slower speeds. It depends to, alot of times I laminate aluminum or acrylics to the surface of PVC and at that point I change speeds.

[Brady Watson]

Erik,
2 things to tuck under your hat: 1) Your spindle makes it power ideally between 12,000 & 18,000 RPM. Running it slower will not necessarily hurt it, but it is not designed to cut production runs at that speed. (Never stopped me b4, but figured I'd share that) 2) A double edge spiral O-flute will let you move at 2X the speed as the single flute @ the same RPM, and in my experience will give you a better finish than the single flute tool.

-Brady

[wcsg]

All that you say is true but....the Belin bits that I am totally sold on only makes Single flute for their specialty tools 9Acrlyic & Alum). 18k is the optimum speed for the 3hp.

Also from my understanding double and triple flute create more heat no?

[Brady Watson]

If you are happy with what you are using, roll with it!


I wouldn't say that 2 or 3 flute cutters create more heat than a single, unless you run it at the same RPM & Speed. If you run lower RPM OR faster move speed, then it is not a problem. It all comes down to chipload and pulling the heat away with the chip.

-B

[jhicks]

I have been looking over/using the shop bot chip load calculator download for some time now and wonder if anyone has one that calculates higher feed rates? The shop bot download seems to stop at 24,000 rpm which is OK but max move speed is 4IPS. Seems lots of folks are running faster than that and it would be nice to have a handy calculator to monitor the chip load at higher move speeds.
Any one out there with such a quick reference calculator download?

[wcsg]

Spiral bits ALum, Copper, Brass, Bronze (Wood)

for 1/8" CED bits

.00005 x rpm x Z(#flutes)x25.4 = IPM/60 = IPS

1/4" Bits

.0002 x rpm x Z x 25.4 = IPM

Spiral Plastics PVC, Acrylic, Poly-carb, foam board

1/8" CED

.00015 x rpm x Z x 25.4

1/4" CED

.0004 x rpm x Z x 25.4

example for cutting acrylic with 1/4" bit double flute and you want to go 12,000RPM's

.0002 x 12000 RPM's x 2(2Flutes) x 25.4 = 243.84" IPM or 4"IPS

[3d_danny]

Brady,

Thanks again for the help

All went well cutting the Komatex except for a slight problem using the carpet tape. About half way through the cut the bit starts getting
gummed up with the adhesive from the tape. Could be the tape I used...Home Depot

Anyone have better luck using a particular brand of tape as a hold down?

Dan

[Brady Watson]

Dan,
Tape gum is a downside of using tape to hold stuff down. It cleans right off with acetone, but *slightly* deglosses the finish. For most people, they don't know the difference. As a less effective but totally inert alternative you can use denatured alky to clean it off as well. Use a lot of it and keep the surface wet.

-B

[robtown]

I use double sided masking tape. I will screw down a pc of solid surface (or melamine) to the spoilboard, and tape the pcs down to it. No problems with gum, holds great, and it comes off with little problem. It's sometimes referred to as double sided paper tape, McMaster has it in two flavors regular, and for "smooth surfaces".

[artisan]

We cut Komatex sign blanks regularly here to wholesale to the local vinyl shops. I probably average a dozen sheets every week and it's a handy side business. They deliver the sheets and pick up the blanks. I charge them 35.00 per sheet to cut any shape blanks they want.

I just screw two diagonally opposing corners down and occasionally the middle if needed. I run Komatex at just 1 ips and this gives a much cleaner edge than at faster speeds. PVC does not seem to like a very fast feed rate in my experience and this puts no pressure on the sheet to move. I generally get 8 or 10 sign blanks from a sheet with the classic rectangular-with-an-oval-on-top being the most popular style. This is cheaper for them than buying the individual blanks by about half. Even at 1 ips, it takes just 15 minutes to do a sheet as they are pretty basic shapes.

I enjoy driving around my town and looking at all the various shaped "for sale" signs that I've cut for the vinyl guys....maybe it could be an easy side business for other Botters....D