Medical-Grade Silicone Parts: 10 Questions Beyond ISO 13485
ISO 13485 certification is the entry ticket, not the proof. When you audit a medical-grade silicone parts manufacturer, the certificate tells you the quality system exists; it does not tell you how clean their molding area is, how traceable their material batches are, or how deep their validation goes. Ask these 10 questions instead — they separate suppliers that stamp certificates from suppliers that can actually support a medical device through design, validation, audit and scale-up.
TL;DR — The 10 Questions
| # | Question | What it verifies |
|---|---|---|
| 1 | What cleanroom class is the molding area? | Particle control where parts are actually made |
| 2 | Can you trace every batch from raw material to finished part? | Material genealogy and lot control |
| 3 | What biocompatibility testing do you have — and on what? | USP Class VI / ISO 10993 coverage |
| 4 | Which cure system do you use for medical parts? | Platinum vs peroxide — residues matter |
| 5 | What process validation (IQ/OQ/PQ) exists for my part? | Evidence the process is controlled |
| 6 | What mold steel, polish and cavity marking do you use? | Tooling quality and part-level traceability |
| 7 | What post-processing and cleaning do you perform? | Post-curing, deflashing, cleanliness |
| 8 | What inspection equipment and reports can you provide? | Metrology and DHR documentation |
| 9 | How do you manage material and process changes? | Change control that protects your file |
| 10 | Can you support audits and provide batch records? | Documentation depth for your own audits |
Why ISO 13485 Alone Isn't Enough
ISO 13485 certifies that a manufacturer operates a documented quality management system for medical devices — a genuine achievement and a necessary baseline. But a certificate is awarded to the system, not to your project. Two ISO 13485 factories can differ enormously in:
- Cleanroom class of the actual molding area (certified system vs certified cleanliness)
- Batch traceability depth (raw material → compound → molded part)
- Validation evidence (a documented procedure vs executed IQ/OQ/PQ records for your part)
- Change control rigor (a policy vs a demonstrated notification history)
The questions below test the difference.
The 10 Questions
1. What cleanroom class is the molding area?
Ask for the class of the room where molding actually happens — not just the plant's overall certification. ISO Class 8 (per ISO 14644) is common for medical molding; Class 7 is tighter. Also ask what is molded inside the cleanroom versus outside, and where post-processing (deflashing, packaging) occurs — contamination risk lives in the secondary operations too.
2. Can you trace every batch from raw material to finished part?
For medical parts you need material genealogy: the compound batch, raw-material lot numbers, cure date, mold cavity number, and final inspection status — all linked to a batch/lot number on the finished part. Ask to see a sample Device History Record (DHR). If the answer is "we can find it when needed," it is not traceability.
3. What biocompatibility testing do you have — and on what?
Two different claims get confused:
- USP Class VI — a material-level test (cytotoxicity, implantation, acute systemic toxicity) that classifies a material, not a part.
- ISO 10993 — a risk-based biocompatibility evaluation series (cytotoxicity, sensitization, irritation, and more depending on contact duration), which is what regulators increasingly expect.
Ask whether reports cover the raw material or the finished, molded part, how old the reports are, and whether they match your material grade. A supplier should hand you reports you can put in your own file — not a wall of certificate photos.
4. Which cure system do you use for medical parts?
Platinum (addition) curing is the standard for medical silicone: clean, no by-products, low extractables. Peroxide curing leaves residues and requires post-curing to drive them out — acceptable for some industrial parts, rarely for implant-adjacent or long-term skin-contact devices. For medical-grade LSR, platinum-cured two-part liquid silicone is the norm. Confirm the cure system on your material, not "what we use generally."
5. What process validation (IQ/OQ/PQ) exists for my part?
For medical components, process validation is not a sales pitch — it is evidence:
- IQ (Installation Qualification) — the machine and tooling are correct and calibrated
- OQ (Operational Qualification) — process parameters (temperature, pressure, cure time) produce consistent parts across the operating window
- PQ (Performance Qualification) — repeated runs confirm stability under production conditions
Ask which parameters are monitored and recorded per shot/cycle (many LSR lines log temperature, pressure and shot weight automatically), and whether a validation package can be delivered with your first production order.
6. What mold steel, polish and cavity marking do you use?
Tooling determines both quality and traceability:
- Steel — hardened tool steel (e.g., S136, 718H, NAK80) for wear and dimensional stability
- Polish — mirror polish where parts must release cleanly and meet surface requirements
- Cavity marking — each cavity should be identifiable so defects can be traced to a specific cavity
An in-house tooling center is a strong signal here: the manufacturer controls mold repair, modifications and cleaning schedules instead of waiting on an external mold shop.
7. What post-processing and cleaning do you perform?
Medical silicone parts often need:
- Post-curing — drives out volatiles, stabilizes hardness and compression set
- Deflashing/deburring — flash from parting lines must be removed without damaging the part
- Cleaning and packaging — cleanliness level and packaging environment (e.g., double-bagged, cleanroom-adjacent)
Ask where these steps happen and under what conditions — secondary operations are a frequent source of contamination and foreign-material complaints.
8. What inspection equipment and reports can you provide?
Verify dimensional and material claims with real metrology:
- CMM (coordinate measuring machine) or optical/projection measurement for critical dimensions
- Tensile, tear and hardness testing (ASTM D412, D624, D2240) on molded samples
- Durometer checks and visual inspection with defined criteria (AQL or 100%)
- A per-batch inspection report you can attach to your incoming inspection
Ask for sample reports in the RFQ stage. If the supplier cannot produce a report example, they will not produce one for your part either.
9. How do you manage material and process changes?
This is where medical suppliers live or die. Ask:
- Will you be notified in writing before any material, mold or process change?
- How far in advance, and what documentation accompanies the change?
- Do they understand that a material change can affect your FDA 510(k) or CE technical file?
The right answer is a formal change-notification procedure with a defined lead time — not "we'll let you know if it matters."
10. Can you support audits and provide batch records?
Eventually your own auditor will visit, and your file will need records. Confirm:
- The supplier accepts customer audits (on-site or remote/virtual)
- DHR batch records are complete, legible and delivered per batch
- CAPA (corrective and preventive action) records exist and are shared appropriately
A supplier that treats audits as routine — rather than as a disruption — is a supplier you can scale with.
Red Flags
Walk away — or escalate — if you hear:
- "The certificate covers the whole plant" (without a cleanroom-class answer)
- "We can find the records if you need them" (without a demonstrated DHR)
- Biocompatibility reports that are raw-material-only, expired, or from an unrelated material grade
- No change-notification procedure
- No example inspection reports
- Validation described as "our process is stable, trust us"
Medical-Grade Silicone Material Essentials
- LSR vs solid silicone: LSR (liquid silicone rubber) dominates medical molding — two-part platinum-cured, injectable, precise, fast cycles, ideal for complex geometries like seals, valves, diaphragms and pump components. Solid HCR suits larger or extruded parts (tubing, sheets). A manufacturer running both lines can recommend without a tooling bias.
- Hardness: Shore A 10–80 covers nearly all medical parts; soft (10–30A) for skin contact and seals, mid (40–60A) for general components, harder for structural parts.
- Transparency and color: medical parts are often clear or lightly tinted; material cleanliness and molding control determine optical clarity — ask how colorants are validated for biocompatibility (medical-grade pigments, not generic ones).
FAQ
Is ISO 13485 required for silicone parts used in medical devices?
For medical device components, an ISO 13485-certified supplier is the expected baseline in most markets. But certification alone does not guarantee cleanroom conditions, traceability or validation depth — verify with the 10 questions above.
What is the difference between USP Class VI and ISO 10993?
USP Class VI is a material-level test (cytotoxicity, implantation, systemic toxicity). ISO 10993 is a broader, risk-based biocompatibility series (cytotoxicity, sensitization, irritation, etc.) tailored to how long and how the device contacts the body. Regulators increasingly expect ISO 10993-based evaluation.
Can silicone parts be sterilized?
Yes — silicone withstands autoclaving, ethylene oxide (EtO) and gamma sterilization, which is one reason it is chosen for medical devices. Confirm sterilization compatibility with the material grade and design.
What is the difference between platinum-cured and peroxide-cured silicone for medical use?
Platinum (addition) curing produces no by-products and low extractables, making it the standard for medical and food-contact parts. Peroxide curing leaves residues that require post-curing and is less common for medical applications.
How do I verify a supplier's cleanroom claim?
Ask for the ISO 14644 cleanroom class of the actual molding area, what is processed inside versus outside, and recent particle-count reports. Audit or video-verify if the part warrants it.
Conclusion
ISO 13485 gets a supplier into the conversation; the 10 questions above decide whether they stay in it. The differentiators that matter for medical parts — cleanroom discipline, batch traceability, biocompatibility evidence, process validation, change control and auditability — are all verifiable before you commit. A manufacturer that answers all ten with documents, not promises, will carry you from prototype through validation to volume.
Evaluating a supplier for a medical-grade silicone component?
NEWTOP CUSTOM SILICONE is a 15-year custom silicone manufacturer serving medical device OEMs, with dual LSR and ISO 8 cleanroom and an in-house CNC tooling center. Our engineers will answer these 10 questions directly — with records, not slogans.
