Safety: Always wear safety glasses when cutting polyethylene or any material. Hearing protection is advisable when using power equipment. Respiratory protection should be used when a dust producing operation is being preformed, such as sanding. Gloves or tongs should be used when thermoforming to prevent burns.

General Machining Characteristics: Polyethylene is machinable using standard wood and metal working equipment. In some cases, certain adjustments must be made in cutting speeds and feed rates for lower heat distortion temperatures to avoid heat build-up from tool friction. For optimum tool life and accuracy, carbide or diamond tipped tooling is recommended. Tools should be kept sharp and smooth, with good side clearance angles. Water-soluble coolants may be used. Material to be machined should be supported and clamped to minimize vibration (which can cause chipping and rough edges).

Saw Cutting: Polyethylene can be cut with all types of saws. Handsaws, hand power saws, jigsaws, band saws and table saws. The optimum circular saw blade for cutting polyethylene is a 1/ 16" kerf, carbide tipped, 1.25 tooth per inch saw blade. Slower feed rates will minimize chatter marks on the cut edge. The index surface of the material (that which is in contact with the saw table or base) should be protected from abrasion with wax, tape or chipboard. Cutting of polyethylene does not produce noticeable airborne dust.

Laser Cutting: Polyethylene can be successfully cut with a laser. Testing the laser on the material to be cut is recommended because the power of the laser must be matched with the thickness of the material for a crisp clean cut. Complex patterns can be cut from a CAD file with remarkable accuracy.

Water Jet Cutting: Polyethylene can be successfully cut with a water jet. As with a laser the water jet should be tested on the thickness of the material to be cut.

Die Cutting: Polyethylene can be successfully die cut in thicknesses up to ¼". When the material is die cut, the top edge is slightly eased and the bottom edge is slightly sharp but not commercially unacceptable. The material should be tested first. The number of parts that can be cut at one time depends upon the thickness of the material, the pressure exerted by the die cutting machine and the design/strength of the steel cutting rule. This is a high-speed way to produce large quantities of the same part.

Routing: Polyethylene can be routed with hand held and CNC routers. High-speed steel or carbide tipped cutters quickly remove material leaving a crisp slick edge. Good material hold down is essential. Routing is used for cutting out irregular shapes, edge profiling, milling and engraving.

Shaping: Polyethylene panels can be run through a shaper to profile edges. High-speed steel or carbide tipped cutters quickly remove material leaving a crisp slick edge. Good material handling and material surface protection is essential.

Turning: Polyethylene can be satisfactorily turned on a lathe. Cutting tools with negative back rake and front clearance will give the best results. Feed rates of 0.02 to 0.10 inches per revolution and turning speeds of 250 to 750 surface feet per minute give the best turning results.

Drilling: Polyethylene can be drilled by hand, with hand power drills, drill presses or CNC drilling. The faster speeds produce holes with slick interiors and crisp clean edges w/ no surface deformation. Virtually any type of drill bit works. Drilling is required when using mechanical fasteners. Recommended feed rate is .004 to .020 inches per revolution, deep holes require backing drill out of hole periodically to remove chips. Drill specifications for optimum results are as follows:

DRILL ANGLES DRILL SPEEDS
Spiral Helix Angle 22° to 45° Up to 0.093" Dia. 5,000 rpm
Rake Angle 0 to 5° 0.094" to 0.125" Dia. 5,000 rpm
Point Angle, Small Drills 60° to 90° 0.126" to 0.187" Dia. 3,000 rpm
Point Angle, Large Drills 90° to 118° 0.188" to 0.224" Dia. 2,500 rpm
End Angle 120° to 135° 0.226" to 0.312" Dia. 1,700 rpm
Lip Clearance Angle 12° to 18° 0.135" to 0.375" Dia. 1,300 rpm
0.375" to 0.500" Dia. 1,000 rpm
0.500" Dia. and over use fly cutters

Milling: Milling at 500 to 1000 sfpm should give good milling results

Reaming: Fluted reamers are recommended. Speed is approximately the same as for drilling.

Tap & Die: Threads both male and female can be successfully cut into polyethylene. Generally tap and dies of 2 or 3 flutes and a slightly negative rake work best. While operating, the tap or die should be periodically backed off to clear chips from the threads.

Deburring: Polyethylene can be deburred with a deburring tool. The deburring tool is an inexpensive hand tool that bevels edges, working best on interior curve edges.

Edge Planing: Polyethylene can be planed with hand and hand power planers. These tools are useful for beveling or easing edges to relieve the edge sharpness left by most cutting operations. Planes are also useful for reducing the width of panels by slight amounts.

Thickness Planing: Polyethylene can be successfully thickness planed with a knife or abrasive planer. Begin by reducing the thickness by no more than 0.010" per pass. Depending upon the type of knife planer used, the surface may show knife marks.

Sanding: Polyethylene can be sanded for decorative effect, to remove or hide scratches and in surface preparation. Hand sanding is often used for small area surface preparation when adhesives are going to be used. Hand held electric or air sanders are used for sanding large and/or irregular shaped areas. Wide belt sanders or abrasive planners can be used to create a brushed look. CNC sanding can be used to apply a consistent swirl pattern and sand blasting is an efficient way to cover very large areas quickly. Coarse grit such as 40, 60 or 80 will produce a suede like finish. By stepping up the grits, by no more than 100 at a time a very smooth surface can be achieved with 600 grit. All sanding produces airborne dust.

Polishing: Polyethylene can be polished. As the final step after sanding to 600 grit, hand or power buffing using an automotive or plastic buffing compound will result in a high polished surface. Edge polishing can be achieved with a cloth buffing wheel. To polish and ease edges at the same time, 2 or more cloth buffing wheels may be ganged on the same arbor.

Decorating: Polyethylene can be decorated with ink or paint. Silk screen inks and paint have been developed for polyethylene but all require that the surface of the polyethylene be treated to allow adhesion of the ink or paint. Plastic decorating is widely used in the automotive industry. Surface treatment is called oxidation and this is accomplished by any one of the following:

1. A blue flame passed over the entire surface to be decorated. The flame must pass by fast enough not to distort the material and it must be the blue portion of the flame.

2. Sulfuric acid w/ specific gravity of 1.82 (must be contained in glass bottle to be strong enough) bath, dip or application w/ polyethylene or polypropylene bristle brush. Allow to stand for 5 to 10 minutes before rinsing off with water.

3. Corona treatment of the surface using an electrical discharge. This method is only practical with extruded polyethylene because consistent thickness and surface properties are required.

4. Another method of surface preparation is plasma etching.

Mechanical Fasteners: Screws and bolts are a common and very successful fastening method. Polyethylene is denser than wood and does not have cells that collapse to accommodate fasteners. It will also melts slightly as a fastener is forced through it, then cool around the fastener securing it in place. Because of this, fasteners will actually hold better than in wood but pre-drilling is recommended to avoid surface deformation or splitting of the material over time. Nails and staples work but are not recommended for high quality results. Properly installed threaded inserts are a good way to firmly secure polyethylene to many other materials.

Laminating: Polyethylene can be laminated to itself and other substrates. When laminating to wood or any other material, abrade the side of the polyethylene to receive the adhesive with a 36 to 80 grit paper. Apply a good grade of contact cement per the label directions. With contact cement lamination, the seams can still be welded using adhesive or heat. The highest quality lamination of polyethylene to polyethylene is in a compression molding press. With this method several thicknesses of material can be laminated together to form a 100% bond. When different color panels are used, the laminated panel becomes suitable for engraving or edge profiling. This method of lamination requires no surface preparation. The various adhesives tested and approved for use with Origins are:

1. 3M # 4693 Contact Cement, quick, visible glue line - http://www.3m.com

2. Loctite Super Bonder Products #414, 416, 454 w/ #770 primer, a cyanoacrylate, invisible glue -
   http://www.henkel.com/cps/rde/xchg/henkel_com/hs.xsl/12165_COE_HTML.htm

3. 3M #DP-8005 Scotch-Weld Structural Plastic Adhesive, invisible glue line - http://www.3m.com

Edge Gluing: If strong watertight bonds are required for edge gluing, there is no adhesive that would work as well as 3M #DP-8005 Scotch-Weld Structural Plastic Adhesive.

Tack Welding: Polyethylene tack welds with a plastic welder, a soldering iron, a wood burning tool and even a clothes iron. Tack welds are produced when the hot tool is run along the seam where 2 pieces of polyethylene are touching producing a thin film of polyethylene joining the two pieces together. Tack welding is not strong and is used primarily for positioning to allow another fastening method to be used.

Welding: Polyethylene can be welded using a plastic welder. There are several type of plastic welders available. A polyethylene welding rod is required. The joints made with a plastic welder are as strong as the material itself and are highly recommended for edge joints. In some cases the plastic welding rod can be cut from the material to be welded, which allows for the weld joint to become invisible. The simplest type welder produces a stream of hot air and can accept various different types of welding tips. Another welder heats up the edges of each material and injects heated welding rod into the joint. Some plastic welding suppliers are:

1. Seeley Inc., hot air type, requires electricity and compressed air @ 800-258-2936

2. Kamweld Products Co Inc hot air type, requires electricity and compressed air - 781-762-6922 - http://www.kamweld.com/

3. Drader, injector type, requires electricity and compressed air @ 780-440-2231 or http://www.drader.com.

4. Abbeon Cal Inc, distributor of plastic fabrication equipment @ 800-922-0977

Forming: Polyethylene can be thermoformed and vacuum formed. Experimentation is required to achieve the correct balance of material thickness, heat and timing. Thermoforming can also be achieved with a 2-part mold, where both surfaces of the heated material are pressed between two molds and allowed to cool.

Repairing: If repairing becomes necessary, it can often be accomplished with a variety of materials. Many of the above listed adhesives will work including auto body putty. A minor scratch can often be repaired by simply rubbing the scratch with a spoon. More serious scratches can be repaired by carefully applying heat from a plastic welding torch to cause the material to "flow" back together. A large scratch or gouge is best repaired with a plastic welder and then sanding and buffing the repaired area to match the surrounding area. If welding is not practical, mars can be repaired with epoxy glue. Drill a few 1/ 32" holes in the deepest parts of the area to act as anchors for the adhesive. Then cover the surrounding area with wax or very thin tape. Mix up a small batch of 5-minute epoxy and tint it with color pigment or plastic dust if desired. Add the mixture to the depression, being careful to fill up the cavity and the anchor holes. Place a waxed piece of a hard material with a texture like the marred surface, over the epoxy and clamp or apply weights in order to apply as much pressure as possible to produce some adhesive squeeze out. This will insure a similar texture on the repair’s surface. When the Epoxy has set, remove the clamps or weight and peal off any thin layers of adhesive squeeze out and clean off the wax. Trim with razor if necessary. When done correctly, it will be difficult to detect the marred area.

Please contact us if you need further information or help with a specific application.