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Working with Tivar«

Machining Processes

Sawing: For circular sawing, carbide-tipped blades give the best results. A 300-355mm diameter blade should have approximately 24 teeth. Feed speeds can range from 3 metres to 12 metres per minute. For band sawing, a blade with three teeth per 25mm, raker set and positive rake angle are recommended. Feed speeds range from 3 to 12 metre per minute.

Turning: HSS tool bits with 10║ front and side clearance and 15-30║ rake. Lower cutting speeds of between 180 and 300 metres per minute are required. However, it is often necessary to run at higher rpm to keep chips clear of the machine. Cutting fluids are not necessary, but a blast of compressed air will sometimes aid in chip removal. When trying to achieve close tolerances or a very thin walled part, machine in passes. Remove most of the material in the first pass, then let the piece sit and rest overnight.

Milling: Cutters designed for machining aluminium give the best results and cutting speeds of 180 to 550 metres per minute with a feed rate of 0.25mm per revolution are recommended. Router bits work well for slotting and light milling.

Planing: Wood planers readily reduce the thickness and true-up the surface although in most instances TIVAR« is already planed. A rigid machine with sharp blades will give very efficient stock removal and good surface finish. To minimize the potential to warp when machining, plane on-half the desired thickness from each side of the sheet.

Drilling: Conventional high-speed drills are adequate for most drilling applications however, for optimum performance, use special low helix drills with polished flutes. Drilling pilot holes prior to drilling a large hole is not recommended for TIVAR« because its properties cause the drill to grab and pull itself into the material.

Grinding/Sanding: Due to the abrasion resistant properties of TIVAR«, grinding and sanding are usually ineffective. In fact, grinding may cause the material to melt and smear, resulting in a clogged grinding wheel.

Forming and Welding

Tivar« can be hot-formed on the job to make simple bends and angles that facilitate installation. No matter which method is chosen-torch, electric heater, oven or bath - caution should be used and every effort made not to overheat the material. TIVAR«, like any plastic, will burn under proper conditions. In addition, the complete cooling cycle will be somewhat longer than the heating cycle due to the high heat retention characteristics of TIVAR«. Cooling should not occur on concrete or metal surfaces because the process will be too rapid and may introduce additional stress into the material. An additional recommendation is to cover the material with an insulation blanket made from a material such as fibreglass.

Cold-forming TIVAR« is often pre-formed when there is a need to fit curves and angles. Whether using a brake-press, rolling, hand-forming or using bolts to draw and form the piece in place, the angle and curves must be over-bent by as much as 75-100% to compensate for the spring-back effect of TIVAR«. The potential for stress cracks can be reduced by using sheets 10mm or thinner when cold-forming.

Spin or friction welding can be achieved using a standard machine lathe capable of 550 to 650 rpm with the ability to stop turning the instant the brake is applied, and, a metal backup plate of 6mm steel, with a diameter of slightly less than the flange OD. This kind of weld needs 48 hours to fully crystallise before the pipe can be put into service.

Butt, or hot plate welding to join flat sheets into long pieces or coils, requires the use of a heating tool of metal, coated with a non-stick agent, capable of reaching the necessary temperature to the bring the polymer to a molten state. This process requires the use of special welding equipment to achieve uniform welds with strength of between 85 and 100% of the original material strength.

Adhesives

The low coefficient of friction, non-porous surface of TIVAR« makes it difficult for any adhesive to penetrate into the polymer and form a bond. Consult your adhesive supplier for recommended procedures to bond TIVAR« to various substrates although mechanical bonding or fastening is highly recommended.