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Torlon - Machining Tidbits
Torlon Machining Tidbits
• Torlon shapes are stronger and stiffer than most plastics, but considerably softer than most metals meaning fixturing is critical.
• All Torlon grades are more abrasive on tooling than softer plastics like nylon and acetal. This especially true of the reinforced grades such as 5030 and 7130. Carbide tooling can be used for short runs. Part geometry, tolerances and grade will also influence tooling selection. Polycrystalline (PCD) tooling should always be considered long runs, tightly tolerance parts and for reinforced grades.
• Torlon has lower elongation than many other plastics. Excessive tool rubbing during machining can cause material pullout that resembles localized porosity. Deep hole drilling without sufficient coolant can lead to cracking.
• All extruded Torlon shapes have a cured outer skin. This layer is 0,25 - 0,50 mm thick. It is harder than interior sections and can be machined off or left on. It does offer the best wear and chemical resistance.
• Coolant can be used while machining Torlon. Both water soluble and petroleum based coolants may be used although water soluble solutions are suggested. Those containing amine inhibitors should be avoided. Appropriate use of coolants will extend tool life and improve surface finish. Air, preferably from a cold air gun can also be used for small parts including those in which clean-up is difficult.
• Machined Torlon parts can be recured after machining if maximum wear resistance and chemical resistance is required. Contact Drake prior to ordering if a post cure is planned.
• Positive geometries with ground peripheries are suggested for inserts. Fine grained C-2 carbide or PCD inserts are best.
• 360° chuck pressure is suggested to avoid distortion. Pie jaws and or soft jaws should be used when turning thin walled tubular shapes.
• Low helix angle drill bits and flood coolant are best for holes below 25 mm diameter. Peck drilling is suggested for swarf removal.
• Larger diameter holes are best approached using a 2 step process incorporating a drilled pilot hole (12 mm diameter max) and a boring to finish diameter.
• Single point inserts with flood coolant should be used for threading. Two fluted, coated taps and suggested for tapped holes. Tapping should be done with coolant.
• Part fixturing is critical for milling as high spindle speeds and fast travel are preferred to minimize frictional heat buildup and material pullout. Cutters should be designed with positive geometry. Climb milling is recommended over conventional milling as it provides better chip removal, lower tool wear and better surface finish. End mills with 4 flutes should be used when possible. Generally during milling step overs should be limited to 25% tool diameter and depths of cut 50% of tool diameter to achieve an optimal surface finish.
• Band sawing is the preferred method of cutting Torlon shapes. It can be used for both straight and contoured cuts of plate in addition to rod and tubular bar. Saw blades should be chosen based on material thickness and precision and must have enough clearance to minimize heat build-up. Triple chip blades 2.5-3.5 teeth per inch are suggested. We have good results with .9 mm thick x 25 mm wide blades. Generally, fewer teeth per inch than metals require will help reduce heat build-up. We suggest 3 teeth per 25 mm at a band saw speed of 12.5 mm per second as a starting point. Coolant (fluid and or air) should be used.
• Table sawing can be used but care must be exercised to ensure safety. Residual stress within shapes can cause material to close in on the blade. When using a table saw partial cuts into the thickness are best. Rip and combination blades with carbide tips are suggested. We suggest fewer teeth per 25 mm than would be used on metals or wood. A 60 teeth 300 mm diameter rip and combination blade should yield smooth cuts on plates up to 12.5 mm thickness.
• Chop saws and radial arm saws may be used but care must be exercised to ensure safety. Residual stress within shapes can cause material to close in on the blade. When using a chop saw repeated partial cuts are required to minimize heat buildup when cutting cross sections greater than 50 mm. Rip and combination blades with carbide tips are suggested. We suggest fewer teeth per inch than would be used on metals or wood. A 60 teeth 300 mm diameter rip and combination blade should yield smooth cuts.