Slitting HDPE Plastic

I have sliced HDPE with a 7 1/4" hand held circular saw with a 60 tooth carbide blade designed for slicing aluminum. I have had good smooth edges with this setup.

With a thin sheet like you have, I would want to try two rolling round knives against each other, like rolling scisors. Set the knives to cut a 4 " strip. When the roll is completed, reposition the roll and cut another 4" strip. Good luck.

I did try the circular saw with plywood finishing blade, but is was not consistently straight. I am going to experiment with the circular knife or slitter blade, but I was wondering his had been tried successfully. Thanks for the advice!

Ain plastics, US plastics both have saw blades listed in their books designed for cutting plastics. There was another plastics company that was brought up on this forum that had a much better selection. I think the company name was a California city name. Do you want me to try to search it?

I like the rolling scissors approach. A reasonable test of the suitability of the process is to use hand metal shears on the product. If you can shear it by hand you can certainly shear it by machine. I can't imagine 1/16" HDPE being difficult to shear.

In production, you probably want to gang the knives, so that you get your strips in one pass. Depending on tolerance requirements, you could get either 11 or 12 strips across a roll: run 50', stop, crosscut, run 50' more, etc.

You can shear it by hand shears. I am not sure that I undersand the rolling scissors idea. How would you arrange the blades to meet?

The rolling scissors idea. Picture a rolling pizza cutter. Now imagine another one right next to it. Do you see how the two blades overlap, similar to looking at the Master Card logo. If the sheet of HDPE was pulled in a way that it was trying to fit between the blades at a 90* angle. Have I made that clearer yet?

Exactly.

In some slitters (search rotary slitters) the blades are square-edged (like a sheet metal shear) and in others the blades are flat on the side that touches the other blade and beveled on the other sides to sharp edges.

If you've seen pasta being made at home, the attachment that cuts the flat sheet into strips of linguine works on this principal, with square edges.

you need to roll it to sheet form.clamp the roll construction such that even after spliting you dont have any spring back problem. feed the roll to high speed splitting saw (mettal cutter), you can use coolant ( to avoid burrs) it works.

I hope the point is useful.

With Regards,

Shivakumar

I can see where coolant would lubricate and make it much smoother

Hi Not sure of your budget but we use a Gerber GTXL CNC machine to cut various types and thicknesses of material, it can be loaded on the front of the machine in roll form and is held onto the cutting surface by a vacume. Ours cost approx £75K but we have achieved remarkable results in comparrison to cutting by hand.

Maybe worth checking out their web site.

Cheers

when you cut vinyl siding for houses you take a veneer blade in a circular saw and run it backwards. The resulting cut is very smooth. Doesn't sound right but it works.

I'm guessing having it custom cut instead of a standard roll size would be prohibitively expensive, but the supplier probably cuts 48" rolls from a much longer size. Ask them how they cut it. If it's not too exotic, you may be able to emulate them.

Have you considered a gang saw set to cut the HDPE on the roll as it is being un-spooled. If the saw is placed before the tangent point where the material is being un-spooled, the 1/16" material will be quite stiff. The depth of cut could be just slightly over one material thickness.

Then again, if the diameter of the roll is great, it might be possible to cut to a depth that would slit the entire 50' length. A gang saw could be used, or a single saw could be indexed across the roll. Spool off and cut the 50' lengths, then repeat the process until the full spool is cut.

I know that a hot knife is used to cut parisons in EBM equipment, but I dont think the cut will be clean enough.

The rolling blade is probably the best idea, but it will need to have an anvil behind or the plastic will distort as cutting pressure is applied.

The shearing action of the "scissors" type set-up sounds to me like you are inviting problems as the blades start to wear.

When I worked for Alcoa Kama (Elyria, OH), we split extruded plastic routinely. We could provide a coil 4" wide or cut it to any length you want. Try them.

Sheet metal shear. Deburr edges with a Routaburr type deburring tool. Noga makes some great ones jsut for plastic.

There are bandsaw blades made specifically for cutting plastics.

look at your office schreader!! and up size!!

Thanks for the great input. So far I built a homebuilt splitter using a circular saw with plywood blade cutting directly into the roll with limited success. Yesterday I bought an electric sheet metal shear and mounted it in a saddle 4" from the edge and pulled the plastic thru it by hand . It worked pretty well but it seems to me that the gang saw approach is probably going to be best. Perhaps with a spring loaded pressure roller in front of the blades to hold the plastic down and and a crank operated roller clamps to the beginning of the plastic and pulls it across the blade.

I need to find a way to gang the saw blades 4 inches apart. Maybe threaded rod? I will also have to find a motor and pulley strong enough to power thru it.

When you cut into the roll, was it rotating?

When building your gang saw, stack the blades with spacers between the blades and use one nut to lock the whole assembly together. For the threaded rod, I would use an ACME thread. The table the blades will go through could be made of plywood or Melamine as it has a slippery surface and use the blades to cut through the table. Because the material is thin, I agree that a roller or presser foot is required to both hold the plastic down entering and leaving the blade. I would minimize the distance the saw blades penetrate through the sheet.

Blade selection: Choose higher tooth counts for thin or brittle materials, lower tooth counts for thicker or lower melting point materials. Too many teeth may cause excess friction, causing melting, blade gumming and rough cuts. Check out http://www.professionalplastics.com/SAWBLADES

Good luck.