FAQ
Custom precision ceramic CNC machining FAQ
Answers for ceramic RFQ preparation, material choice, green vs hard machining, tolerances, surface finish, micro-holes, inspection, and acceptance criteria.
RFQ and engineering questions
Use these answers to reduce ambiguity before sending a drawing for quotation.
What information should be included in a ceramic CNC RFQ?
Send material and grade, blank or sourcing requirement, drawing revision, STEP or IGES files, functional datums, GD&T, critical faces, quantity, lead time, surface finish, inspection scope, and application constraints such as temperature, media, wear, vacuum, or insulation.
How can I reduce quote back-and-forth?
Mark the functional faces and datums, define surface finish per face, list micro-holes or thin-wall features, state edge condition, and specify how each critical requirement will be inspected.
What are the main cost drivers in ceramic CNC machining?
Cost is usually driven by diamond grinding or lapping time, micro-features, tight GD&T across multiple faces, low Ra requirements, brittle failure risk, inspection time, and blank availability.
When does green machining reduce cost or lead time?
Green machining may reduce shaping cost before sintering when a suitable preform route and shrinkage data are available. Tight seal faces, bearing fits, or datum faces usually still need post-sinter finishing.
When should a drawing use as-sintered dimensions?
Use as-sintered dimensions for non-critical surfaces and moderate tolerance features. Use post-sinter grinding or lapping for seal faces, bearing interfaces, flatness, parallelism, and measurable datums.
What lead time should be planned?
Lead time is estimated after review of blank sourcing, customer-supplied material status, preform route, post-sinter grinding, lapping, polishing, micro-hole work, and metrology scope. Inspection often controls schedule for tight parts.
What should be specified for ceramic plungers, sleeves, and pump parts?
State the media, pressure or flow role, mating seal or sleeve, OD/ID fit, roundness, straightness, Ra, chamfer, cleaning, packaging, and inspection evidence. For dispensing or injection-pump parts, do not quote only by outside dimensions.
How should quotes from different suppliers be compared?
Normalize material grade, route, datum scheme, tolerance map, Ra per functional face, inspection method, documentation, and packaging requirements. Low quotes often exclude finishing or evidence.
Which ceramics are commonly machined?
Common precision ceramics include alumina, zirconia, silicon nitride, silicon carbide, aluminum nitride, boron nitride, fused silica, and selected machinable glass ceramics.
How do I choose between alumina and zirconia?
Alumina is often used for insulation, wear resistance, and cost efficiency. Zirconia is often chosen when toughness and reduced chipping risk matter more.
When is silicon nitride a strong candidate?
Silicon nitride fits bearing, wear, and thermally cycled parts where strength retention, shock resistance, and lower chipping risk are important.
When should SiC be considered?
SiC fits extreme wear, high temperature, and chemical service, but it is very hard to finish. Apply tight tolerances and low Ra only where function requires them.
What counts as a micro-hole in ceramics?
A micro-hole is any small-diameter or high-aspect-ratio hole where diameter, depth, edge integrity, breakout, taper, and position become yield-limiting.
What causes chipping around micro-holes?
Entry and exit fracture, tool wear, local thermal shock, poor support, aggressive feed, and missing edge-break rules can all create chips or cracks.
What tolerances are realistic?
Tolerance feasibility depends on material, size, geometry, and process route. Tight values may be feasible on accessible, finished faces, but price and risk rise sharply when multiple faces require precision without stable datums.
How should surface finish be specified?
Surface finish should be reviewed per functional face. Ground surfaces fit many wear and datum needs; lapping can improve flatness and Ra; polishing is used only where very low Ra or sensitive surfaces justify it.
How should datums be defined?
Define datums on stable, finished, inspectable features. Avoid using rough as-sintered surfaces as primary datums for tight grinding relationships.
Can ceramics be threaded?
Threads may be feasible after review of material, size, wall thickness, and load direction, but they are fragile and expensive. For load-bearing joints, consider inserts, brazing, metallization, or compression-dominant clamping.
Can sharp internal corners be machined?
Internal corners are limited by tool geometry and stress concentration. Use radii where possible and define chip criteria if a sharp transition is function-critical.
What inspection methods are common?
CMM, optical measurement, microscopy, pin gauges, profilometry, flatness mapping, density checks, leak checks, or CT may be specified depending on feature size, risk, and available inspection route.
What can CT scanning prove?
CT can validate internal geometry and detect defects above the scan resolution threshold. It cannot prove that no defects exist below that threshold.
What should acceptance criteria include?
Tie tolerances to datums, define maximum allowable edge chip size by zone, specify Ra per face, state crack criteria, and select inspection method and sampling plan.
How should packaging be specified?
Use individual cushioning, protected edges, face separators, and controlled orientation for fragile parts. Avoid loose packing for precision faces and micro-features.
What if the exact ceramic grade is not known?
Send the failure mode and environment: temperature, media chemistry, wear, insulation, thermal conductivity, load type, dimensional stability, and inspection needs.
How do I avoid over-specification?
Apply tight tolerance, Ra, and geometric controls only on functional interfaces such as seal lands, bearing fits, datum faces, alignment features, and inspected bores.
Ready to send a ceramic RFQ?
Send drawings, material, quantity, target lead time, and acceptance requirements. After review, we respond with feasibility notes, questions, or quotation details.