Medical Device Machining Materials
The metals and polymers that the vetted Vietnamese shops in our network machine for surgical, orthopedic, dental and diagnostic components, with the standards you would put on the drawing, how each grade behaves at the machine, and what to watch in the design.
Grade designations at a glance
Medical drawings usually call a material by its ASTM surgical-implant or instrument specification. The table cross-references the common designations so a buyer in Europe or Japan and a mill in Asia are talking about the same alloy. Values are typical; the governing document is the standard named on your drawing.
| Material | UNS | EN / ISO | JIS | Typical medical spec |
|---|---|---|---|---|
| Stainless 316L | S31603 | 1.4404 / ISO 5832-1 (implant) | SUS316L | ASTM F138 (implant bar), ASTM A276 |
| Stainless 17-4 PH | S17400 | 1.4542 | SUS630 | ASTM A564, ASTM F899 (instruments) |
| Ti-6Al-4V ELI (Grade 23) | R56401 | ISO 5832-3 | - | ASTM F136 |
| Ti-6Al-4V (Grade 5) | R56400 | 3.7165 | TAP6400 | ASTM F1472, ASTM B348 Gr 5 |
| CP titanium Grade 2 | R50400 | 3.7035 / ISO 5832-2 | Class 2 | ASTM F67 |
| CoCrMo (wrought) | R31537 | ISO 5832-12 | - | ASTM F1537 |
| PEEK (implant / long-term contact) | - | - | - | ASTM F2026 |
| UHMWPE | - | ISO 5834-1/-2 | - | ASTM F648 |
| PEI, PSU, PPSU | - | - | - | Medical grade per resin maker datasheet |
| Nitinol (NiTi) | - | - | - | ASTM F2063 |
Background reading: Ti-6Al-4V on Wikipedia and ISO 10993 (biological evaluation).
Stainless steels: 316L and 17-4 PH
Stainless is the default for instruments, trays, cannulas and many equipment parts. The two grades solve different problems: 316L for corrosion resistance and formability, 17-4 PH for strength and hardness after a simple ageing treatment.
316L (and 316LVM)
Austenitic, non-magnetic in the annealed state, not hardenable by heat treatment. It work hardens fast, so shops use sharp positive tools, constant chip load and avoid dwelling in the cut. Vacuum-remelted 316LVM is specified for implants where inclusion cleanliness matters. Typical finish route: machine, deburr, passivate per ASTM A967 or electropolish for a smoother, cleanable surface.
17-4 PH
Martensitic precipitation-hardening grade. Usually machined in condition A or an aged condition, then aged to the condition on the drawing: H900 gives roughly HRC 40 minimum, H1025 roughly HRC 35, H1150 lower hardness with better toughness. Ageing causes a small, predictable shrinkage, so finish-critical bores are sometimes left for after heat treatment. Magnetic, which matters near MRI equipment.
Titanium: Ti-6Al-4V ELI, Grade 5 and Grade 2
Titanium is chosen for strength-to-weight, corrosion resistance and a long clinical record in orthopedic and dental devices. It conducts heat poorly, so heat stays at the cutting edge: shops run lower surface speeds than for steel, high-pressure coolant, rigid holding and fresh edges. Galling and thread tearing are the usual failure modes on fine threads.
| Grade | Typical tensile strength (annealed bar) | Where it is used | Machining and design notes |
|---|---|---|---|
| Ti-6Al-4V ELI, ASTM F136 | 860 MPa min | Bone screws, plates, spinal hardware, dental implants and abutments | Lower interstitials than Grade 5 for better fracture toughness; ask for the ELI certificate, not just "Grade 5" |
| Ti-6Al-4V Grade 5 | 895 MPa min | Instruments, trial implants, housings | Same machining behaviour as ELI; fine for parts that are not permanent implants if your file allows |
| CP Ti Grade 2, ASTM F67 | 345 MPa min | Housings, cases, non-load-bearing parts, dental components | Softer and gummy: burr control on thin walls and cross holes is the main cost driver |
Color anodizing of titanium (used to code screw sizes and instrument sets) is available as a secondary process. The color is produced by oxide thickness, so agree a physical color reference at FAI.
Cobalt-chromium alloys
Wrought CoCrMo to ASTM F1537 is used where wear resistance and stiffness beat titanium: articulating surfaces, some spinal rods and dental frameworks. It is one of the harder alloys to machine conventionally. Expect low cutting speeds, carbide or ceramic tooling, more tool changes and a higher price per part than the same geometry in Ti-6Al-4V. Cast CoCrMo (ASTM F75) parts arrive near net shape and only need finish machining of datum and mating features. Grinding and polishing of bearing surfaces is a separate specialist step and is confirmed per drawing.
Medical polymers: PEEK, UHMWPE, PEI, PSU and PPSU
Polymers move under heat and clamping, so tolerances are looser than for metals and stock preparation matters as much as the program. Shops buy annealed stock where available, rough and stress relieve on thin or long parts, and avoid coolants that could contaminate the surface. Typical achievable tolerance on plastics is about ±0.02 to ±0.05 mm depending on size and wall thickness, confirmed per drawing.
| Polymer | Typical use | Steam sterilization | Machining notes |
|---|---|---|---|
| PEEK / PEEK-CF | Spinal cage trials, instrument handles, wear parts, radiolucent components | Repeated autoclave cycles | Stiff and stable; sharp carbide, annealing between rough and finish on precision parts |
| UHMWPE | Bearing inserts, liners, guides, low-friction parts | Limited; check your grade | Very soft, low stiffness: support thin sections, very sharp tools, generous tolerances on large flats |
| PEI (Ultem type) | Sterilization trays, handles, housings | Repeated autoclave cycles | Amber, rigid, machines cleanly; sensitive to some cleaning chemicals, check compatibility |
| PSU / PPSU | Instrument handles, trays, fluid-path housings | PPSU high cycle count; PSU fewer cycles | Tough and transparent options; stress cracking if over-tightened inserts or wrong solvents |
| POM / PTFE | Diagnostic housings, manifolds, valve seats | Generally not for repeated autoclaving | Good machinability; PTFE creeps, so avoid tight press fits |
Nitinol notes
Nitinol (ASTM F2063) is superelastic and shape-memory, and that is exactly why it is hard to cut: it springs back from the tool, work hardens and wears edges quickly. Stents, guidewire components and baskets are made by laser cutting tube, centerless grinding, EDM and heat shape setting, not by general CNC milling. What does fit this service is the tooling around nitinol: shape-setting fixtures and mandrels in stainless or tool steel, and simple turned nitinol features when the drawing allows generous tolerances. Send the drawing and we say plainly whether it fits.
Choosing a material: quick guide
The table is a starting point for a conversation with your design team, not a design recommendation. Final choice depends on your device classification, contact duration, sterilization method and test results.
| If the part needs | Usual first candidates | Trade-off to check |
|---|---|---|
| Permanent implant, load bearing | Ti-6Al-4V ELI, CoCrMo, 316LVM | Fatigue data, MRI behaviour, cost of CoCr machining |
| Reusable cutting or gripping instrument | 17-4 PH, 420 / 440 series as specified | Hardness vs corrosion after repeated reprocessing |
| Instrument body, cannula, tray part | 316L | Lower hardness, electropolish for cleanability |
| Radiolucent or lightweight handle | PEEK, PPSU, PEI | Material cost, autoclave cycle count |
| Low-friction bearing or liner | UHMWPE | Dimensional stability, creep |
| Equipment housing or fixture | 6061 / 7075 aluminum, POM | Anodize color and cleaning chemistry |
Design for manufacture: material-related notes
Specify the standard, not just the alloy
"Ti-6Al-4V" can be bought to several specifications. Write ASTM F136 (or ISO 5832-3) and the condition on the drawing so the mill certificate can be checked line by line at goods receipt.
Think about bar size early
Implant-grade bar is stocked in fewer diameters than commercial grades. A part designed 1 mm over a common bar size can force a larger bar and more scrap. We flag this in the DFM notes returned with the quote.
Design for cleaning
Blind holes, deep narrow slots and sharp internal corners trap soil on reusable instruments. Radii, through holes and access for brushes make reprocessing validation easier on your side and deburring easier on the shop's.
Material certificates show what the mill tested. Biocompatibility, cleaning and sterilization validation, and the regulatory file stay with the device maker. No FDA registration or ISO 13485 certificate is claimed on this site. See quality & documentation for what ships with each lot.
Related pages and guides
- Tolerance window, finishes and secondary processes
- Applications: surgical, orthopedic, dental, diagnostic and fixtures
- Titanium Grade 5 vs Grade 23 for medical machining
- Cobalt chrome vs titanium for orthopedic components
- PEEK vs PPSU for reusable instrument handles
- Sourcing medical-grade bar stock in Vietnam
Material questions
Can the shops supply implant-grade bar with certificates?
Yes, when the drawing names the standard. Ti-6Al-4V ELI to ASTM F136, CP titanium to ASTM F67, 316L to ASTM F138 and CoCrMo to ASTM F1537 are bought from mill or distributor stock with a mill certificate traceable to heat number. The certificate is checked against your drawing at goods receipt and ships with the lot. Availability of small diameters varies, so it is confirmed at quote stage.
Who decides whether a material is biocompatible for my device?
You do, as the device maker. Biological evaluation under ISO 10993, the choice of grade, and any testing on finished parts belong to your design file. The shop machines the grade your drawing specifies and documents where the material came from. No material on this page is presented as approved for a particular device.
Do you machine nitinol?
Rarely, and only for simple turned or milled features. Most nitinol device components are made by laser cutting tube, grinding, EDM and shape setting, which is specialist work. Send the drawing and we tell you honestly whether a shop in the network fits. Fixtures and mandrels for nitinol shape setting are a common machined request and do fit.
Which plastic should I use for a reusable instrument handle?
For handles that see repeated steam sterilization, PPSU, PEI and PEEK are the usual candidates. PSU tolerates fewer autoclave cycles than PPSU. POM (acetal) is cheaper but is generally not chosen for repeated autoclaving. Confirm the cycle count and chemical exposure in your own validation; the shop machines the grade you specify.
Send your drawing with the material spec
Upload STEP, PDF or DWG with the material standard and condition. We check certificate availability for your bar size and reply with matched shop options, pricing, lead time and DFM notes.
First response within 24 business hours. No phone calls, everything in writing.