How to cut HDPE sheets - Router Forums
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post #1 of 27 (permalink) Old 01-10-2020, 12:24 AM Thread Starter
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Default How to cut HDPE sheets

Ok so its my first post on the forum....And I do know its a wood forum but when I googled this question this forum popped up so I thought I would ask my question here. I want to learn how to route HDPE sheets with a router as well to cut out basic shapes like squares out of 1/4 inch HDPE sheets of 4' x 8' material max 3/8 inch material...

So im just confused because I hear about deep feeding when cutting, cooling when cutting, certain rpms to it does not melt so im overwhelmed...

I just want an answer to these 2 questions

1. Then I want to know about cutting HDPE with routers like what drill bits do I need I keep seeing "O" flute and ball nose which I have no idea what it is... So ill be making basic square cuts in the middle of a sheet of HDPE so what type of bits and strategies/tips do you know..

2. Do I need to cool off hdpe while cutting? How can I do that?

Thank you guys in advance!
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post #2 of 27 (permalink) Old 01-10-2020, 01:25 AM
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I wouldn't recommend using a router to cut large HDPE sheets. A table saw is a much better idea. A negative rake blade is recommended. Regular wood blades with a positive rake will bite too deeply though I have to admit using an 80T plywood blade on 1/2" HDPE. It left a moderately rough edge.

For edging, profiling, general machining in a CNC machine, an O flute - a single flute bit - is recommended for any plastics. Fast feed and low router speed are the best strategy but the bit vendor will give you more detail. For hand routing, I would try to mimic the recommended feed and speed for CNC. Too fast router speed and too slow a feed will cause heat build up. I'm not sure you absolutely need cooling. Getting the optimal chip load will carry away a lot of the heat. Try a test piece.

Measure twice, cut once and CROSS OUT THE WRONG MARKS.

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post #3 of 27 (permalink) Old 01-10-2020, 06:51 AM
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Good morning,

I'm not claiming to be any expert on the cutting of the HDPE and have not cut lots but in my experience with it I have used both methods to cut it. Cutting it down to size I do also recommend the table saw. Yes negative hook blades may be best but I do tend to just put a good sharp blade on and cut it down. I have a veneer and plywood blade from Freud that has an extreme ATB tooth design that does a very clean job. (ATB= alternating tooth bevel) But any good blade and some care works.

As for cutting out the centers of your HDPE try a good spiral up cut bit from Freud and make a couple passes. (Yes this stuff can grab) Are you using templates or follow with guide bushings or ??? "Make sure the bit is designed for plunge application as well."
Heating is most generally caused by the chip load that is designed in to the bits themselves, and if you go to slow or to fast can cause heating up. As you route you can usually hear in your router's performance if your pushing it to hard. I would suggest testing and learning what speed works the best. RPM can also be adjusted if your router has the power to dial down a bit.

Also for profile cutting make sure your bits have enough shear built into them again I use 90 percent of Freud bits in all I do if I am running it on a router table or hand held router with part clamped down. Speed and RPMs again have a factor in the heating up. I typically don't have these problems so doubt you will either. Test and experiment and see what seems to work for you.
Best advice would be to run as much of this material on a router table for the safest and best control however.
I hope some of this helps and there may be other's give you some advice as well.

Kind regards,

Tim of ZWW&S
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post #4 of 27 (permalink) Old 01-10-2020, 07:39 AM
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Table saw..
High tooth count (80+), negative rake (-3 ~ -5°) MTCG, TCG, ATB, H-ATB, ATB-R OR H-ATB-R grind/hook angle..

Listed by preference:
MTCG - MODIFIED TRIPLE CHIP GRIND
TCG - TRIPLE CHIP GRIND
ATB - ALTERNATE TOP BEVEL
H-ATB - HIGH ALTERNATE TOP BEVEL
ATB-R - ALTERNATE TOP BEVEL w/ RAKER
H-ATB-R - HIGH ALTERNATE TOP BEVEL w/ RAKER

.
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post #5 of 27 (permalink) Old 01-10-2020, 09:25 AM
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Welcome to the forum
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post #6 of 27 (permalink) Old 01-10-2020, 11:30 AM
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Welcome to the form N/a, I have cut HDPE ,(Starboard) for my boat and used the same power tools as for wood cutting. Regular router bits cut it fine and so do saw blades,and drill bits. Screws do not hold very well, and neither does calking. Cutting makes a big mess, white sawdust and chips everywhere. The material I used was 1/2" thick and 1" thick. The tablesaw blade was a 10" X 60 tooth carbide blade, regular straight and 1/4 round carbide router bits. I used the router table, freehand w/ templates and a straight carbide bit with a pilot bearing. Laid the full sheet on a sawhorse and broke it down with a skillsaw. It is heavy and full sheets are hard to handle alone. Never needed any cooling, drills with regular drill bits,cuts like butter.
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post #7 of 27 (permalink) Old 01-10-2020, 12:15 PM
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Lots of specialized terminology so far. Rake is pretty important. Here is a diagram that explains rake. I have cut this stuff on my table saw (table saw zero clearance inserts), and it is pretty messy. Just don't let it linger on the blade, keep it moving forward into the blade, but don't push it too hard. Haven't used a router on it, but if I were going to, I'd use an up spiral bit. This bit is ground so it lifts the chips up and out of the cut. Other types of bits might quickly wind up with the plastic melted onto the flutes (cutting edges) and be all but impossible to remove. Same would apply to a saw blade. The negative rake is something you have to double check on any blade you are considering. It is not always obvious just looking at it.

More teeth on an 8 inch saw blade makes for a smoother cut. At any given speed, more blades will mean smaller spaces between each tooth's cut, thus smother. The illustration also reveals the difference between crosscut (across the grain) vs. rip (with the grain). The large gaps (gullets) between the rip blade's teeth, let it carry off very large amounts of sawdust or waste. Crosscuts produce less sawdust per inch.

Tooth shape matters. Flat top teeth make for a flat bottom groove when you don't cut all the way through. This is very useful if you are cutting a groove in your workpiece into which something will be fitted. The smooth bottom makes for a stronger glue joint. But if you're using it for a through cut, the raked, or top at an angle tooth makes for a very clean slice through the wood or other material. Through cut just means cutting all the way through a piece (cutting it shorter for example).

I've also attached a short pdf on saw blades that lays out the big facts on sawblades.

Hope this is helpful. There were a lot of tech terms flying around the responses.
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post #8 of 27 (permalink) Old 01-10-2020, 07:08 PM Thread Starter
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Wow thank you all for your replies. I am basically building a cage for an animal so id literally just cut a 4' x 8' sheet into 4 x 2 sheets with a circular saw(Dewalt 60v 7 1/4 inch) and then I would use the hand router to cut out a square through the material for example if i had a 4' x 4' square piece then I would make a 3' x 3' square cutout through the hdpe out that 4 x 4 piece.

So I called some plastic company that are local to me. They told me for the circular saw to use a saw blade with 40-60 teeth and bigger flute to allow air through so the plastic does not melt..... As for the router he could not offer much advice...
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post #9 of 27 (permalink) Old 01-10-2020, 07:13 PM Thread Starter
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Quote:
Originally Posted by PhilBa View Post
I wouldn't recommend using a router to cut large HDPE sheets. A table saw is a much better idea. A negative rake blade is recommended. Regular wood blades with a positive rake will bite too deeply though I have to admit using an 80T plywood blade on 1/2" HDPE. It left a moderately rough edge.

For edging, profiling, general machining in a CNC machine, an O flute - a single flute bit - is recommended for any plastics. Fast feed and low router speed are the best strategy but the bit vendor will give you more detail. For hand routing, I would try to mimic the recommended feed and speed for CNC. Too fast router speed and too slow a feed will cause heat build up. I'm not sure you absolutely need cooling. Getting the optimal chip load will carry away a lot of the heat. Try a test piece.
HI appreciate the reply. I have an example of what I would be doing with this HDPE and router.. Picture a 4' x 4' square piece of HDPE and then I wanted to cut a 3' x 3' square through the 4 x 4 piece so its empty inside(would hold glass piece with hinges) What type of hand router would you ideally use (plunge or basic hand router) Type of bit?

And then the rest is just dependent on the feed speed and the rpm of the router to avoid melting. stalling etc.... Thats how I figure out the chip load??
Thanks again bro for the response...
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post #10 of 27 (permalink) Old 01-10-2020, 07:36 PM
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Quote:
Originally Posted by angel619392 View Post
HI appreciate the reply. I have an example of what I would be doing with this HDPE and router.. Picture a 4' x 4' square piece of HDPE and then I wanted to cut a 3' x 3' square through the 4 x 4 piece so its empty inside(would hold glass piece with hinges) What type of hand router would you ideally use (plunge or basic hand router) Type of bit?

And then the rest is just dependent on the feed speed and the rpm of the router to avoid melting. stalling etc.... Thats how I figure out the chip load??
Thanks again bro for the response...
Hmmm, I'd be temped to use a jig saw (or plunge/ track saw) to rough out the inside square and then edge trim it with a router. Doesn't matter what kind. Slowest speed on the router and feed it as fast as you can with it not feeling forced.

If you use a router to cut out the inside square, I'd worry that by making contact on at least 1/2 of the bit circumference, you will get a lot of heat buildup. If you have to do it that way, I'd take shallow cuts, maybe 1/4" or less each pass.

Measure twice, cut once and CROSS OUT THE WRONG MARKS.

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