VESPEL SP-1 Machining for Seals, Bushings and Insulators
VESPEL is DuPont's family of polyimide engineering plastics, and SP-1 is the unfilled base grade — the one with the highest strength and elongation and the best electrical and thermal insulation. We machine polyimide parts to ±0.01 mm with burr-free edges, low outgassing and documented inspection.
Why it is hard to machine
VESPEL is a polyimide, not a PTFE, and the difference matters when you specify a grade. SP-1 is unfilled: maximum physical strength, elongation and toughness, and the best insulation values of the family. SP-21 and SP-22 add 15% and 40% graphite for wear and friction duty; SP-211 adds 10% PTFE for the lowest friction coefficient of the family; SP-3 uses 15% molybdenum disulfide where graphite would become abrasive in vacuum. The family runs continuously from cryogenic temperatures to 288 °C, with excursions to 482 °C, and is used where outgassing, radiation or creep rules out thermoplastics.
Process controls that matter
Unfilled grades move differently
SP-1 has the highest elongation of the family, so the workpiece springs back as the tool leaves it. We take a finishing cut and let the part relax before the critical dimension is measured.
Filled grades cut differently from each other
Graphite-filled and PTFE-filled grades have very different chip behaviour. We set the same geometry and the same finish per grade, because a tool that suits SP-22 can smear SP-211.
Burrs are the failure mode, not the tolerance
Polyimide is slippery enough to push a burr over the edge rather than cut it. We use a positive-geometry, sharp-edged tool and clear the chip before it re-cuts.
Low outgassing is a process requirement
Vacuum and semiconductor applications cannot tolerate a part that sheds particulate. Parts are cleaned and bagged after machining, and critical features are verified on the CMM.
Tolerances, inspection and documentation
Typical applications
Rotary seal rings, thrust washers and discs, plain bearings and bushings, valve seats, thermal and electrical insulators, wafer guides and carriers, vacuum pads, die pickup collets, splined couplings and wear strips.