Machinery's Handbook, 31st Edition
MACHINING PLASTICS 605 Table 11. Suggested Approximate Speeds and Feeds for Milling Various Thermoplastics a
Roughing 0.250 in. Cut Depth
Finishing 0.050 in. Cut Depth
Material
Speed (feet/min)
Feed (in/rev)
Speed (feet/min)
Feed (in/rev)
ABS
600 600 450 800 500 600 450 800 450 800 450 600 600 450
0.018 0.012 0.012 0.012 0.012 0.010 0.010 0.018 0.015 0.018 0.010 0.012 0.010 0.012
480 480 360 480 450 480 360 620 360 620 360 480 480 360
0.008 0.005 0.005 0.005 0.005 0.004 0.004 0.008 0.006 0.008 0.004 0.005 0.004 0.005
Acetal (POM)
Acrylic (PMMA)
Polyamide, Nylon 6 / 6 (PA6)
Polycarbonate (PC)
Polyester (PET)
Polyether ether ketone (PEEK)
Polyethylene (PE)
Polyphenylene sulfide (PPS)
Polypropylene (PP) Polystyrene (PS)
Polytetrafluoroethylene (PTFE) Polyvinyl chloride (PVC) Ultem polyetherimide (PEI)
a 2-fluted, 1 in. end mill Milling of Plastics: Peripheral cutting with end mills is used for edge preparation, slot ting and similar milling operations; end cutting can also be used for facing operations. Some recommended approximate speeds and feeds are provided in Table 11 for periph- eral end milling of common thermoplastics; as per standard machining practice, speeds and feeds must be adjusted with observation of the machining relative to the quality re - quirements. Slower speeds are generally used for face and other milling operations, with some thermoplastics being machined at 300–500 ft/min (91–152 m/min), and some thermosets at 150–300 ft/min (46–91 m/min). Adequate support and suitable feed rates are very important. A table feed that is too low will generate excessive heat and cause surface cracks, loss of dimensional accuracy, and poor surface finish. Too high a feed rate will produce a rough surface. High-speed steel tools (M2, M3, M7, or T15) are gen- erally used, but for glass-reinforced nylon, silicone, polyimide, and allyl, carbide (C2) is recommended. Turning of Plastics: Plastics can be processed on commercially available lathes. A fine-grained, C2 carbide cutter, with a small cutting radius and broad-nosed finishing cutting edge, is recommended to avoid material build-up. Recommended approximate feed speeds are provided in Table 12. When feasible, turning at higher cutting speeds is recommended, using a cutting depth of at least 0.004 inch. Compressed air is a common and acceptable method for cooling, though misted and flooded coolants can be used if available. If the diameter of the plastic workpiece is small or workpiece rigidity is an issue, then a live center or lunette is recommended to stabilize the component and provide improved tolerances and surface finish.
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