polycarbonate cutting question

[muntin chops]

So the manual says that cast acrylic or polycarbonate (lexan) can be cut with the CW.

I need to cut knife templates for moulding knives (example attached).

I found three options on McMaster-Carr's website (all clear polycarb, 12"x12"x1/4"). One of the options show operating temperatures of 240 degrees Fahrenheit ($12ea). I assume this helps in preventing melting during the cut. The second option shows an additional 10 degrees (250F total) for op temp but is twice the price ($22ea) as the first. The third one, though $45ea, claims 'static dissipation' which sounds like a nice piece of insurance when cutting plastic on a piece of electronics-dependent machinery. It's operating tempurature is only 180F.

My question is which of these is the best option?

Cost is always a consideration...business is business. The cost of material counts but so does cost of replacing a circuit board. Has anyone really had problems with static or even thought it might be a problem?

I can get get anywhere between fifteen and thirty templates per square, depending on the profile size, so the materials cost gets manageable.

I'm not an engineer so below are the specs they offer on the website for the materials. Maybe there's something there that I'm missing entirely.

Any advice that you can provide would be more than appreciated.

I'm just tryin' to measure twice so i can cut once! :rolleyes:

Cheapest
Part Number: 8574K28
$11.61 Each
Material-Polycarbonate-Polycarbonate Material
Backing-Plain Back
Shape-Sheets, Bars, Strips, and Cubes
Sheets, Bars, Strips, and Cubes
Type-Square Sheet
Thickness-1/4"
Thickness Tolerance-+0 to -.026"
Length-12"
Length Tolerance-+.625"
Width-12"
Width Tolerance-+.625"
Clear-Clear with No Tint
Operating Temperature Range--40° to +240° F
Performance Characteristic-High Impact Strength, Weather Resistant
Tensile Strength-9000 psi
Impact Strength-12 ft.-lbs./in.
Tolerance-Standard
Hardness-Rockwell R: 118
Specifications Met-Underwriters Laboratories (UL)
UL Rating-UL 972, UL 94V0

Most Expensive
Part Number: 8184K15
$45.12 Each
Material-Polycarbonate
Polycarbonate Material-Static Dissipative Polycarbonate
Backing-Plain Back
Shape-Sheets, Bars, Strips, and Cubes
Sheets, Bars, Strips, and Cubes
Type-Square Sheet
Thickness-1/4"
Thickness Tolerance-±.014"
Length-12"
Length Tolerance-+.062", -.25"
Width-12"
Width Tolerance-+.062", -.25"
Clear-Clear with No Tint
Operating Temperature Range-Up to +180° F
Performance Characteristic-High Impact Strength, Static Dissipative
Tensile Strength-9500 psi
Impact Strength-16 ft.-lbs./in.
Tolerance-Standard
Specifications Met-Not Rated

[hotpop]

muntin chops,

Looking at the Specs I would choose the the cheaper product. The thickness tolerance is .026" while the more expensive product is .028" total. I've machined poly-carb many times. I've never had it melt during machining all though I haven't used it on the CW many others have. Also the cheaper product has a UL 94V0 rating. This is good, as the product flame resistant. The other product is not rated.

You might also check out the CarveWright Store. They put Corian on sale about a week ago. I don't know how the prices compare. Also put a "Wanted" ad on www.craigslist.com for your area. There is a possibility you can get some Corian scraps real cheap.

[muntin chops]

that the cheap option is a suitable option. Thanks for the help on that. I also never would have known what those ratings meant.

Everyone here seems to like corian a lot. my only challenge is that i need a rigid material that will last when the knife-cutting stylus passes over the plastic. Creating the knife blade with the template is one thing but that same knife will be sharpened with every use, meaning that the plastic template will be needed indefinitely.

Is corian just as rigid as poly carb?

[Router-Jim]

Have you looked at your local building supply stores? I priced 1/4" acrylic last week. 2' x 4' sheets $34. It cuts real clean.

[muntin chops]

Router-Jim Have you looked at your local building supply stores? I priced 1/4" acrylic last week. 2' x 4' sheets $34. It cuts real clean.

from McMasterCarr's website:

Acrylic Material
Cast Acrylic: Often used to replace glass, provides outstanding optical clarity even at greater thicknesses. Has a smooth surface for use as windows and signs, but is less impact resistant than polycarbonate.

I would still probably go with the polycarb just because it gives me the impression that it would last longer. And in my application, that counts big since consistent accuracy is critical.

also, the cast acrylic they offer, priced against the polycarb, actually came out a touch more expensive (they could just be ripping me off, who knows). What's more, it doesn't have a 'fire resistant' rating, or any rating for that matter, like hotpop pointed out. it also looks to have worse tolerances.

The next step up in quality has military spec, but is $45 per 12"sq piece.

Thanks for bringing up the acrylic option though Router-Jim. I hadn't even known it was an option before you said something. :)

Part Number: 8560K354
$18.10 Each
Material-Acrylic
Acrylic Material-Cast Acrylic
Backing-Plain Back
Shape-Sheets, Bars, Strips, and Cubes
Sheets, Bars, Strips, and Cubes
Type-Square Sheet
Sheet Style-Standard
Thickness-1/4"
Thickness Tolerance-+.023" to -.042"
Length-12"
Length Tolerance--.125"
Width-12"
Width Tolerance--.125"
Clear-Clear with No Tint
Operating Temperature Range-+40° to +170° F
Softening Point-239° F
Performance Characteristic-Weather Resistant
Tensile Strength-10,000 psi
Impact Strength-0.4 ft.-lbs./in.
Tolerance-Standard
Hardness-Rockwell M: 94-103
Specifications Met-Not Rated

[hotpop]

muntin chops

I don't know of anyone else on the forum doing what you are doing with the CW.

I afraid your going to have to do some experimenting. I would start with the cheaper poly-carb because it has a slightly tighter tolerance although I don't think you will really care about the exact thickness.

I was wondering how you make the blades. What type of steel is used? Do you use EDM to cut the profiles or are they machined? Do you need to heat treat?
Do you make carbide blades?

[muntin chops]

I was wondering how you make the blades. What type of steel is used? Do you use EDM to cut the profiles or are they machined? Do you need to heat treat?
Do you make carbide blades?

the steel type is a T1 bar steel (that's the best info i got. i'm sure that if you needed more info i could dig into it). apparently there are lesser grades that are softer and easier to grind knives out of but they don't last long in a moulder when it comes to larger quantities of moulding. I believe its high carbon, but not a carbide blade.

EDM? I'm not sure what that means. The process i'm dealing with starts like this:

1. a custom moulding is needed. I'm given a sample of an existing profile or its designed on the fly.

2. if its an existing profile, I scan it with a 2D color scanner at high res.

3. I use autoCAD to trace the image (.tif) to make an exact vector file (no vector imports for Designer yet, such a bummer).

4. I give a printout of the profile to my moulding guy, he then hand cuts the plastic profile out to make a template. This is one of the many reasons i'm trying to take advantage of the CW. Carvings and small mouldings are also on the punch list with that machine.

5. that template is then mounted onto a commercial knife grinder (over-sized key maker, in my opinion)

6. the T-1 bar 'blank' is then mounted onto a 'moulder head' (over-sized router bit) and then mounted onto the grinder.

7. based on the template (which is why i need the accuracy and stamina), the steel blank is carved into, making the knife (2 knives are made, actually, since it's a 4-head moulder head. 2 slots for the profile, 2 slots for straight blades).


I know this idea may be off the beaten path for the CW but i see potential. based on everyone's experience at this site (unless that bass wasn't actually 400 pounds and six feet long! ;)) the machine really seems to be a real trooper, assuming good care & maintenance.

without the CW, a new knife template could take as many as 4 man hours. with the CW's help, I could knock that down to an hour tops for any profile. maybe better. I could even cut a 1" sample out of something like poplar to show a customer for approval before bothering with a knife template, etc.

[Router-Jim]

I have been making router templates with the CompuCarve using 1/4" acrylic. I have no doubt they will hold up for your application. The machine cuts it very cleanly. The most time you will spend will be in the designing phase.

[muntin chops]

I have been making router templates with the CompuCarve using 1/4" acrylic. I have no doubt they will hold up for your application. The machine cuts it very cleanly. The most time you will spend will be in the designing phase.

Then I'll be sure to also buy acrylic when i buy the polycarb. no reason i can't try both, right? Awesome.

[TIMCOSBY]

a radius at any corner, even using the carving bit, so some hand filling will have to be done. i think the corian would hold up to depend on what the stylus is made of. maybe add a corian tip to the stylus???

[muntin chops]

a radius at any corner, even using the carving bit, so some hand filling will have to be done. i think the corian would hold up to depend on what the stylus is made of. maybe add a corian tip to the stylus???

I see where you're getting at with the corian and the stylus. I think i'll add corian to my materials list too ( this is my 'project development' anyway, budgets can be busted!).

I realized the filing would be necessary. our knife guy is relieved, though that he doesn't have to cut out the entire profile now. He's fine with filing, sanding.

I could eliminate even more finishing on the template if i could just finally get a way to smoothly throw vector files from ACAD to Designer. wishlist i guess :rolleyes: