Cutting HDPE(edited: to correct title)

[Robotboy86]

What does everyone use?

I have a dremel with a diamond cut off wheel, it somewhat works but it skips out a lot and doesn't seem to make a very clean cut.  I've tried around 20krpm and a bit lower and higher as the box suggests.  I tried a jigsaw but I had similiar problems with it not giving me a very clean cut.  I have only tried this on U shaped planks, (mcmaster item# 9928K58  and 9928K59) and they are about 3/8th 1/4" thick.  I don't have a very extensive set of power tools, just your basic dremel, jigsaw, and drill.  I just need to cut the planks into 2.5" sections each.    As for the sheet, its much thinner so I know I can just jigsaw/dremel that to shape. 


Thanks for any advice guys,

I'll upload pics of my walker's frame once i get clean cuts off these things


Appreciate it,


Dan

[HDL_CinC_Dragon]

You should be able to do fine with the Dremel... You just have to make sure your HDPE is firmly fastened to a sturdy surface and then make sure you grasp the dremel tightly and use as much support as you can such as branching out some of your fingers and pressing down hard so that 1) Your helping hold the HDPE down, and 2) You can make small precise movements with your hands to better control the dremel for a cleaner cut...

in the end it all comes down to having a sturdy cutting surface, your object that your cutting firmly held to the sturdy cutting surface, and a VERY steady hand...

Thats how I make my cuts an reshape things at will.

dont supposed youve got a heavy duty bench top clamp or something? perhaps a neighbor does?

[Soeren]

Hi,

Diamond tools are best used with very hard  materials - it grinds its way through and makes soft materials "furry" or how should I put it. for HDPE, I'd choose something that is cutting, like a (very) sharp circular saw, preferably tungsten tipped, or like my small table saw I have, where the entire saw blade is made of tungsten, then it'll keep it's sharpness for ages.

A router bit going full blast should also be a good solution - if you can control it, as it might tend to wander off any time you are less than totally concentrated.

Finally, a heat-knife might be useable, depending on thickness.

[Robotboy86]

Great stuff guys!!

Thanks!!

I was using a somewhat wobbly surface..  I will move it to a big metal table and grab a diffrent cutting wheel

Thanks again

[HDL_CinC_Dragon]

No problem, tell us how it turns out

[Gertlex]

One approach to take is to build a stand for your dremel.  I did a really simple one that you can see here:
http://www-personal.umich.edu/%7Eerelson/files/DremelMount01.jpg

For getting the fitting just right, a large toothed file works great on the wood.

On the other hand, my dremel is now kaputt at all but speed 10... I need to replace the carbon brushes (they're electrical contacts, I think) (and hopefully nothing else).

Of course... you might not have a right angle extension for the dremel (mine came with one). That just occured to me.

But as already mentioned, the router works nicely on plastic.

A hot wire cutter almost certainly won't work on denser plastics.  You need to burn some of the plastic away as you cut, or it'll just fuse back together as you go.  Still worth a try with HDPE... my experience with that particular problem is polycarbonate (Lexan).

[HDL_CinC_Dragon]

Dremeling lexan will get little fibers stuck in the drill bits head... but all you have to do is unscrew the screw on the top and slowly remove the cutter head and just take the fibers off and then your ready to go again... be very careful when cutting though because hot liquid lexan or plastic can stick to the dremel and then shoot off in whichever direction. And trust me, that HURTS =)



Interesting little stand youve built there, Gertlex

[dunk]

i would stay away from high speed power tools when working with plastics.
high speed tools will melt their way through rather than cut.

if you want to melt then use a tool designed to melt such as a heat-knife. as it won't vibrate like power tools so you will get far more accurate results.

if you want to cut instead of melt you need to use slower speeds.
this pretty much rules out using a dremel as they don't have much torque.

for drilling you need to use a sharp drill bit and use a slow speed. cut rather than melt.

for making cuts in material i find an old fashioned hand hacksaw best.
an electric jig saw with a fine tooth blade works too but you get a lot of vibration leading to less accurate cuts. again, use a slow speed.

dunk.

[JonHylands]

What you really need for cutting stuff like this is a milling machine - an end mill with really sharp teeth turning at 2-3000 rpm does wonders on most types of plastic.

- Jon

[Gertlex]

Milling machines are a great way to do a lot of stuff, but they're not cheap :p

(Didn't stop my friend, 19, with a coop at GM, from spending $1500 so far on a small mill and equipment for it)

I second dunk's opinion on hand tools being fine for this sort of thing.  Maybe the cuts will be a bit rough, but you can easily clean the edges up with a file or sand paper, or if you're in a real machine shop, a belt sander (I've never heard not to do that...).

[Robotboy86]

well I ended up using a jigsaw on a slow speed it didn't give me super clean cuts but I used the dremel to sand it smoother.  The biggest difference was clamping it down tightly to a sturdy table.  I then put a 35lbs weight on it to help reduce movement even more.  Worked great!

The cuts are relatively smooth, but still a bit wavy.  I am thinking about using alumium around the edges to give added strength as I am not terribly satisfied with its strength. 

[Admin]

I know you did it already but for future reference . . .

i would stay away from high speed power tools when working with plastics.
high speed tools will melt their way through rather than cut.

I agree with Dunk. Ive tried on many occasions to use a dremel on plastics and it always came out messy - uneven cuts or it melted. I recently did some touchup work on acrylic with a dremel, no melting, but still very uneven.

I find the best way to cut plastics (other than a CNC or a mill) is to use a bandsaw or scroll saw. For thin plastics, Ive successfully used regular scissors and metal shears (scissors for sheet metal).

You may also want a guide rail. Basically line up a big long block of wood to rest your part or tool against for a perfectly straight cut.

[JonHylands]

I cut a lot of Delrin plate on my little Sherline mill, and when I need a smaller piece that fits on the table, I generally cut it on my table saw. I have a decent carbide-tipped combination blade that cuts a 1/8" kerf, and it does a pretty decent job on the edges of the plastic. Of course, Delrin doesn't melt very much anyways, so it may not work as well for something like HDPE...

- Jon

[maverick monk]

im old fasioned, i use a box cutter, and just go over it again and again untill i can break it along the cut