Medical Device Enclosures
IEC 60601-1 is a standard written around electrical safety, not sheet metal. But most of what determines whether a medical device housing passes or fails on metalwork is decided long before anyone touches a multimeter: how the chassis is bonded, where the ports are, how big the openings are, how the shield is terminated. Get the metalwork right and certification becomes a paperwork exercise. Get it wrong and you pay for a re-spin of tooling, a re-test, and a delay you cannot recover.
We are a Ningbo sheet metal factory, not a regulatory consultancy. What this page does is set out the sheet metal decisions that carry electrical-safety consequences, so that when you send us a drawing we are arguing about the right things on the first exchange rather than the fifth.
What the metalwork actually controls
Four things on a housing drawing have direct electrical-safety consequences. Everything else is mechanical, cosmetic or commercial.
| Metalwork decision | Why it carries safety weight |
|---|---|
| Chassis bonding and protective earth | The PE path has to be continuous from the earth terminal to every exposed conductive surface. Whether that is a welded strap, a bolted stud or a press-fit contact changes the drawing, the weld map and the inspection points. |
| Port openings and their size | Openings determine ingress protection and, for apertures in certain positions, the permissible leakage. A ventilation slot that is cosmetic on a drawing can be the single item that changes the device’s classification. |
| Creepage and clearance on the mounting plane | These are distances across the enclosure between conductive parts and between parts and the patient or operator. Sheet metal gauge, flange width and standoff height all move them. |
| Shield termination | An RF shield that is bonded at one point, or bonded after painting, or bonded to a surface with a thick coating, behaves differently from one bonded properly at low impedance. This is decided by how the part is designed to be assembled. |
Material choice for a medical housing
Three material families cover almost all of what we build. Each one makes a different set of the decisions above cheaper or harder.
- Cold-rolled steel, powder coated — the default for carts, stands and non-patient-contact housings. Strong, stiff, cheap to tool. Needs a weld map that keeps flatness so doors seat without gaps, because a warped door is a leak path.
- 304 / 316 stainless — where cleaning is aggressive or the environment is wet. Gaining is harder than on steel, so we plan the bend sequence around the part rather than bending it in the order it is drawn.
- Aluminium — where mass matters or the heat has to leave. Light, conductive, and it moves dimensionally more than steel, so the assembly tolerances need to be looser or the fit-up needs features that absorb the difference.
| Material | Where it fits | What we watch |
|---|---|---|
| CR steel, powder coated | Carts, stands, general housings | Flatness after welding; coating runs off the weld if it is not dressed |
| 304 stainless | Wet and washdown environments, patient-contact furniture | Grain direction, surface finish on visible faces, contamination control |
| Aluminium 5052 / 5754 | Lightweight and thermally conductive housings | Creep and springback; anodising mask areas |
Shielding that works, and shielding that only looks like it works
Most shield problems we are asked about are assembly problems, not sheet metal problems. Three patterns cause almost all of them:
- Bonding fingers that are formed but not plated, so the surface under them is the mill finish with whatever oxide and shop dust is on it
- A bond specified from the paint, where the coating is still on the contact face
- A single-point bond on an enclosure that is expected to carry RF current back to the chassis
We would rather see the bond as a machined or plated land on the part, with the coating masked out, than as a note on the assembly drawing that says “bond to chassis here”. The second version is where the certification problems come from.
Openings, filters and ingress protection
If your housing breathes, something has to be in the opening. We build the frame, the filter seat and the mesh retainers, and we are explicit about which of those we machine and which we supply as customer-specified parts. Where a device needs a specific filter class, we machine the seat to the filter you nominate and we check the fit with a sample before the batch runs.
Ventilation that has to pass acoustic or EMC screening is a tolerance question as much as a materials question, and it is easier to solve at drawing review than after the first article.
What we can and cannot do here
We build and inspect metalwork. We do not certify anything, and nobody in this factory will tell you that a part is compliant before your own test house has been through it. What we do is build to the drawing, flag the metalwork decisions that carry safety weight, inspect against the drawing, and produce the records your incoming inspection will ask for.
| In our building | Partner / customer supplied | |
|---|---|---|
| Laser cutting (3 machines, 2× 3,000 W + 1× 6,000 W) | Yes | |
| CNC bending (4 press brakes, 250 t each, 3,000 mm bed) | Yes | |
| Welding (10 stations) | Yes | |
| Hardware installation, assembly | Yes | |
| Powder coating | Audited partner lines we specify and inspect | |
| Wet paint to a named two-component system | Routed to a controlled applicator, told to you at quotation stage | |
| Electrical safety testing, type testing | Stays with your test house or notified body |
Documentation your incoming inspection will ask for
- Material certificates for the sheet we actually cut, matched to the batch
- First article report against the drawing revision quoted
- Film thickness records per batch when coating is in scope
- Third-party audit references available on request under NDA: TUV Rheinland MIC-ASI243729 and Bureau Veritas MIC-ASR263630
Our quality system is documented to ISO 9001. We do not hold a third-party ISO 9001 certificate and we will not claim to; the two audit references above are the evidence we can actually put behind that sentence.
Lead times, stated properly
| Stage | Typical |
|---|---|
| Simple samples | 3–7 days |
| Complex first article | 15–20 days |
| Production batch | 25–35 days |
| Tooling — simple | 7–15 days |
| Tooling — complex | 30–45 days |
Questions we get asked about medical enclosures
Do you hold an ISO 9001 certificate?
No, and we would rather tell you now than have your supplier audit find it. Our quality system is documented to ISO 9001, and we have two third-party audit references — TUV Rheinland MIC-ASI243729 and Bureau Veritas MIC-ASR263630 — that we can put under NDA. If your customer’s supplier qualification requires a certificate rather than an audit report, we are not the right supplier and you should know that before you spend a week on us.
Can you make the housing to an IEC 60601 drawing we issue?
Yes. Send the drawing in STEP plus a 2D PDF and we will come back with a manufacturing view, flagging anything we think affects bonding, openings, creepage or clearance. We do not sign off compliance — that is your test house’s job — but we will tell you early if a metalwork decision is going to make your certification harder.
What tolerance can you actually hold?
Most sheet metal features we hold comfortably in the range your mechanical drawings assume. Where a drawing asks for something tighter than our process can hold, we tell you at quotation stage. We measure with height gauges and coating thickness gauges and we do not have a coordinate measuring machine, so we will not claim measured positions we cannot actually verify.
Do you powder coat in-house?
No. Powder coating runs on audited partner lines that we specify and inspect. We set the pre-treatment and film build, approve a drawdown panel before the batch runs, and measure film thickness on receipt. If a specification calls for a named two-component wet paint system, we say so at quotation stage and route it to a controlled applicator rather than substituting powder.
Can you protect the earth bond from coating?
Yes, and we prefer to do it as a designed feature rather than a note. Masking the bond land keeps coating off the contact face; where the bond needs a defined stiffness we can machine or form the land. Tell us how the housing will be assembled and we will design the bond for that assembly.
Will you sign a first article report?
We inspect the first article against the drawing revision we quoted and issue a report with the measurements we took. It records what we measured and how, not a blanket conformance statement, which is what most incoming inspection systems actually want.
Send the drawing and get an answer
Send STEP and a 2D PDF. We will flag the metalwork decisions that carry electrical-safety weight, tell you what we can hold and what we cannot, and quote. If your project is not a fit we will say so in the first reply.