# ABS plastic is MUCH easier to work with than HDPE...



## lunchmoney (Dec 27, 2007)

Started work on the baffles for my mids tonight...

My first attempt was with 3/8" thick HDPE cutting boards... what a pain that stuff is... when I tried to cut out the circles with a jigsaw, the plastic would melt and "heal" itself back up right behind the blade.

I then tried some 1/4" ABS plastic, because we had some lying around at work... this stuff is MUCH easier to work with... it has a much higher melting point than the HDPE, so it doesn't melt when you cut/machine it, and yet it's not brittle the way Acrylic or Polycarbonate is.

It's just as heavy as the HDPE, and just as stiff if not stiffer.

I highly recommend the ABS if you're looking for material to make baffles out of.


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## Infinity (Jun 28, 2005)

ABS/PVC is damn nice to work with, it's also much more expensive when you can buy a cheap HDPE cutting board for a buck or two. I'd love to CNC mill an entire enclosure from a block of Delrin, just to say I did it.


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## jj_diamond (Oct 3, 2007)

lunchmoney said:


> My first attempt was with 3/8" thick HDPE cutting boards... what a pain that stuff is...


i cut some of the same 3/8" HDPE this morning. smooth as a hot knife thru butter.


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## bobditts (Jul 19, 2006)

the trick with working with any plastic is not trying to cut it too quickly. You need to slow down the blade and find a speed that actually cuts it instead of melting it. 

I could be wrong, but I think HDPE is denser than ABS so it is much better for using as a baffle.


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## lunchmoney (Dec 27, 2007)

jj_diamond said:


> i cut some of the same 3/8" HDPE this morning. smooth as a hot knife thru butter.


Weird... I wonder why I had so much trouble. Maybe the jigsaw blade was too dull.


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## bobditts (Jul 19, 2006)

lunchmoney said:


> Weird... I wonder why I had so much trouble. Maybe the jigsaw blade was too dull.


I think your jigsaw was sawing too fast.


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## lunchmoney (Dec 27, 2007)

bobditts said:


> I think your jigsaw was sawing too fast.


Very likely. But I didn't have the same problem with the ABS.


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## bobditts (Jul 19, 2006)

right. The ABS must have a higher resistance to heat than the HDPE as you mentioned earlier. As the saw blade rubs against the plastic it creates heat (friction). If you slowed the blade down a bit, less friction would occur. Less friction = less heat = less melting. I highly dont recommend trying to cut either of the plastics with a dremmel and cutting wheel. That hot plastic flies all over the place and it hurts a bit when it lands on your face, arms, and legs. haha


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## lunchmoney (Dec 27, 2007)

From Matweb.com

ABS Density: 0.0280 - 0.0462 lb/in³	

HDPE Density: 0.0333 - 0.0383 lb/in³	

Hard to say which is more dense, since the range of density of the two materials overlaps. Looks like ABS _could_ be denser, who knows. I was suprised to see how much the density varies.


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## lunchmoney (Dec 27, 2007)

bobditts said:


> right. The ABS must have a higher resistance to heat than the HDPE as you mentioned earlier. As the saw blade rubs against the plastic it creates heat (friction). If you slowed the blade down a bit, less friction would occur. Less friction = less heat = less melting. I highly dont recommend trying to cut either of the plastics with a dremmel and cutting wheel. That hot plastic flies all over the place and it hurts a bit when it lands on your face, arms, and legs. haha


LOL... yeah, I know that feeling... like hitting yourself with tiny bits of napalm...


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## tyroneshoes (Mar 21, 2006)

Might as well get the abs precut baffles seen all over ebay.


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## ErinH (Feb 14, 2007)

Target cutting boards FTMFW! That is all.

Also, Bob is right. The faster you cut plastics the more likely you are to get it to melt back with each other. Plexi is notorious for this. If you can throttle the blade down you'll get much better results, but I guess it doesn't matter at this point since you've already cut the ABS.


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## jj_diamond (Oct 3, 2007)

lunchmoney said:


> Weird... I wonder why I had so much trouble. Maybe the jigsaw blade was too dull.


fairly new blade. i use them sparingly. jigsaw at full throttle. the HDPE does curl at the edges, but it's easly removed by rubbing with your finger or chiping it away with a small flathead. if what your cutting _seems_ to dense or it feels like the jigsaw is having trouble, change the blade.


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## Whiterabbit (May 26, 2006)

lunchmoney said:


> It's just as heavy as the HDPE, and just as stiff if not stiffer.
> 
> I highly recommend the ABS if you're looking for material to make baffles out of.


welp, since I was on the google train to material properties, I figured we could give this one a whirl, too:

ABS: Modulus 2.3 GPa, UTS 40 kPa, density 1.04 g/cm^3
HDPE: Modulus .8 GPa, UTS 15 kPa, density .96 g/mL

Given that baffle performance relies on density alone the data only marginally agrees with you (slightly less than 10% improvement). Given that a stiff baffle is also acoustically beneficial (debateable) then it's a slam dunk (almost 300% improvement).


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## OldOneEye (Jun 16, 2005)

You want to use a jigsaw blade that is designed for metal:










See how it has lots of really small teeth? On the other hand, if the blade you are working with looks more like the yellow or green one, which is designed for rough cutting, you could have issues:


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## FoxPro5 (Feb 14, 2006)

IME Bob is exactly right. It's all about the blade and speed you are going at. I've used HDPE and PC and PC melted like butter and reformed right away until I switched to the blades in the second picture above. In essence, you don't want to fine cut it, you sort of want to chip it instead. Cutting, IME = melting. Same thing with HDPE - a rougher blade worked better.


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## stryke23x (Jun 22, 2007)

The other thing you can do is cut it with a spiral upcut router bit. There are ones specific to cutting various plastics like these:

http://www.harveytool.com/products/...amily=Plastic+Cutting+End+Mills&category_id=1

You just need to make a template you can follow with your router.


John


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## Whiterabbit (May 26, 2006)

the important thing to look for in a blade is the "hook" angle or "rake"

A negative hook is desired. rather than aggressively taking bites of material, it scrapes the surface. All the blades pictured above have positive hooks. none are the ideal for plastic.

Note with circular saws and the like, negative hook is easy. but when the blade spins backwards, the hook is positive. For reciporcating saws like a jigsaw, its important to make sure the hook is negative on both strokes. Note for all the blades pictured that during the UPward stroke the rake is negative. the downwad stroke is all positive hook. 

the appropriate blade will be triangle shaped.

I'm not saying positive rake WONT work, I'm saying positive rake will tend to burn meltable plastics, and crack and chip brittle plastics.


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## Infinity (Jun 28, 2005)

To be honest, I had my best luck using a Rotozip and the bits that were recommended- pretty sure it was teh Sabrecut bit. Cheap and quite effective on both ABS and HDPE. There's also router bits available for it, but I haven't used them.


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