Motionwell designs and builds automation equipment that has to run inside a classified cleanroom. The cleanroom automated test equipment carries 4 to 6 fan filter units in its own ceiling and holds ISO Class 7/8 over the test fixtures. The GMP liquid filling and sealing machines use SUS316L product-contact surfaces electropolished to Ra 0.4 um with ASME BPE welds and FDA 21 CFR 177.2600 gaskets. This page is about the machine, not the room: what changes in the frame, the drives, the cables, the lubricant and the enclosure when the equipment has to hold a particle class while it is moving.
That last part is where cleanroom machine design gets interesting. A machine is a particle source that you are about to place inside the one space you spent money keeping clean. It has bearings that wear, belts that shed, cylinders that exhaust, cables that flex, and an operator who opens it. Every one of those is a design decision made months before anyone runs a particle count.
What makes a machine cleanroom-compatible?
Four properties, and they pull against each other.
It does not generate particles. Anything that slides, rolls, meshes or flexes wears, and wear becomes airborne. This is the constraint that reshapes the mechanism.
It does not outgas. Plasticisers, uncured adhesive, standard grease and some cable jackets release volatiles that condense on product surfaces. Nothing is visibly dirty. Yields drop anyway.
It can be cleaned. Every external surface has to survive being wiped with isopropanol or a quaternary disinfectant, several times a shift, for years. Blind holes, exposed bolt heads and lap joints are places a wipe cannot reach.
It does not wreck the airflow. A machine standing under unidirectional downflow is an obstruction. Flat tops create recirculation. Deep external recesses hold what the airflow was supposed to sweep away.
For scale, ISO 14644-1 allows 352,000 particles at 0.5 um and larger per cubic metre at Class 7, and ten times that at Class 8. A factor of ten between two adjacent classes sounds generous until you realise the machine itself has to fit inside that budget alongside the operators, the product and the facility. Getting the mechanism right early is the cheapest lever you have, which is the same argument that runs through our approach to custom special purpose machine design generally.
How does cleanroom class change the machine design?
The class does not change what the machine does. It changes what the machine is made of, how tightly it is closed, and how much of the mechanism has to be hidden behind a seal.
| Design aspect | ISO Class 8 | ISO Class 7 | ISO Class 5/6 |
|---|---|---|---|
| Frame | Anodised aluminium or SUS304 | Anodised aluminium or SUS304/316 | SUS316L, or SUS304 electropolished |
| External finish | Smooth and wipeable | Smooth, crevices designed out | Electropolished |
| Cable routing | Enclosed trunking or conduit | Sealed conduit, individually glanded entries | Fully sealed, low-outgassing jackets |
| Pneumatics | Standard cylinders acceptable | Cleanroom-rated cylinders, exhaust filtered | Exhaust ducted out of the clean zone entirely |
| Motors and drives | Standard servo motors | Sealed motors, drives moved outside the enclosure | Enclosed motors, mechanism behind a barrier |
| Lubrication | Standard grease, used sparingly | Cleanroom-grade grease in sealed bearings | Low-vapour-pressure grease or dry lubrication |
| Documentation | Operating procedures | Cleanroom handling protocols, particle records | Full qualification package |
Two entries in that table cost the most money. Moving the servo drives outside the enclosure means a longer, shielded motor cable and a separate control cabinet, which changes the footprint. Ducting pneumatic exhaust out of the clean zone means every cylinder gets return tubing back to a manifold instead of a muffler on the port, which changes the pneumatic schematic and the cable carrier fill.
Do not over-specify. If the product only needs Class 8, buying Class 5 sealing buys you a machine that is harder to maintain for no yield benefit.
Materials, coatings and surface finish
Metals. Anodised aluminium (6061-T6, hard anodise on wear surfaces) and stainless steel carry the structure. Bare aluminium sheds oxide. Mild steel corrodes under the cleaning chemistry and then sheds rust, so it does not belong anywhere a wipe reaches. Where product touches metal, it is stainless.
Polymers. PEEK, POM, UHMWPE and PTFE behave. Nylon is hygroscopic and swells, and standard rubber outgasses and sheds. Static seals are typically Viton or EPDM, chosen against the cleaning agent rather than against the process fluid, because the disinfectant is what attacks them daily.
Coatings and adhesives. Powder coat is fine on a Class 8 enclosure and a liability above it, because chipped coating is a particle source that grows over the machine’s life. Anodise the aluminium, passivate or electropolish the stainless, and keep adhesives low-outgassing and fully cured before the machine ships.
Geometry. Cleanability is drawn, not cleaned in. No blind holes. Generous internal radii instead of sharp internal corners. Countersunk or counterbored fasteners rather than exposed bolt heads. Welded seams ground flush, with no lap joints forming a crevice. Unused threaded holes plugged.
What surface finish do we actually specify?
On the GMP liquid filling and sealing machines, product-contact surfaces are SUS316L electropolished to Ra 0.4 um, with ASME BPE welds on the fluid path. On the tray filling platform, contact surfaces are SUS304/316 at Ra 0.8 um in an IP65 washdown build. Those are two different answers because the cleaning method is different: one is a validated CIP-and-swab regime, the other is a hose.
The general rule is that the finish follows how the surface gets cleaned and how much residue is allowed to survive that cleaning, not the ISO class number by itself.
Where do the particles actually come from?
Guides, screws and belts
Linear guides, ball screws, timing belts and gear trains generate particles by design. In a normal factory nobody cares. Inside a classified zone the options are: enclose the mechanism in a sealed housing with local extraction, move it below the product plane so downflow carries debris away from the part, or select a low-particle variant with sealed wipers and cleanroom grease. Bellows over a ballscrew are cheap. Reworking a gantry after the first particle count is not.
Pneumatic exhaust
A standard cylinder with a muffler on the exhaust port vents oil-laden air into the room on every stroke, at the exact moment and location the tooling is over the product. This is usually the single largest particle source on a machine and the easiest to miss on a drawing, because the schematic looks identical either way. Cleanroom-rated cylinders from suppliers we already buy, such as SMC and Festo, plus exhaust routed back to a manifold outside the clean zone, solves it.
Motors, drives and the enclosure boundary
Motor cooling fans move unfiltered air. Servo drives have their own fans and heatsinks. The usual answer is a boundary: particle-generating hardware on one side, product on the other, with panels gasketed continuously and fasteners captured so a screw cannot drop into the process. Where an axis must cross that boundary, it crosses through a sealed bellows or a glanded penetration, not an open slot.
Vision hardware needs the same treatment. Keyence and Cognex cameras and their lighting run warm and often have their own airflow, so on cleanroom builds they sit behind a sealed window rather than in open air. The optical trade-offs of doing that are covered in our machine vision inspection guide.
Cables, drag chains and lubricants
Cabling in a cleanroom machine is a contamination question before it is a tidiness question.
- Jacket material chosen for low outgassing and low particle shedding; PTFE and FEP for the tightest classes, PVC acceptable in Class 7/8 builds.
- Individually glanded cable entries. One large cutout backfilled with silicone is not a seal, it is a future leak path.
- Continuous-flex cable inside energy chains rated for the travel. We standardise on igus chain and flex-rated cable so the jacket does not craze after a few million cycles.
- Stainless cable ties, not nylon zip ties, which shed as they are tensioned and again as they age.
- Bend radius respected. A jacket cracked at a tight bend becomes a particle source that no wipe-down will fix.
- Permanent laser-etched or engraved labels. Paper labels and printed tape shed fibre.
Lubricants matter for the same reason and get overlooked more often. Standard machine grease outgasses and can migrate to product surfaces. PFPE greases sold for cleanroom and vacuum service are the usual substitute, applied to sealed bearings in small quantities. Over-lubrication is a contamination source in its own right, so the maintenance instruction has to specify a quantity and an interval, not “grease as required”.
When is a fan filter unit better than a cleanroom?
When only the process needs classified air and the rest of the building does not.
Fan filter units mount in the machine’s own ceiling, push HEPA-filtered air down over the process area, and let it exit through filtered vents at the base. The clean zone travels with the machine. You are buying filters, a gasketed ceiling panel and pressure monitoring instead of building construction, facility HVAC capacity, gowning airlocks and the recurring cost of maintaining a classified room around equipment that only needs a clean envelope over one fixture.
The design work is in the airflow. The FFUs have to move enough air downward to sweep particles off the product before the machine’s own motion stirs them back up, and the internal layout has to leave that downflow a clear path. Tall fixtures, overhead tooling and a poorly placed cable tray all create a shadow where the flow does not reach. Positive pressure inside the enclosure has to be maintained relative to the factory, or the room leaks into the machine every time the door seal moves.
It is not the right answer everywhere. If your product needs classified air along its whole route, not just at one station, you need the room.
How the fan filter units are integrated into the test equipment
The cleanroom automated test equipment for electronics and semiconductor customers carries 4 to 6 fan filter units sealed into the enclosure ceiling with continuous gaskets, holding ISO Class 7/8 over the test fixtures and the part handling area while the machine sits in a normal factory bay with no classified facility around it.
Getting that to hold in production needs a few things designed in from the start: an unobstructed downward path over the fixtures, filtered return at the enclosure base, differential pressure monitoring so anyone can see the enclosure is still positive, and sampling ports so a particle counter can verify the class without dismantling anything. The build is described further in the cleanroom ATE case study.
How does wipe-down change the enclosure design?
Wipe-down is a daily mechanical event that the machine has to survive thousands of times, and it drives more geometry than most specifications admit.
Every external surface has to be reachable in one pass with a wiper, which rules out deep recesses, ledges and exposed fastener heads. Cleaning chemistry attacks seals and labels, so gaskets are selected against the disinfectant and labels are etched rather than printed. And because a wipe-down cannot reach inside the enclosure, maintenance access has to be planned: put service points on the non-clean side wherever the mechanism allows, and where an access panel must open into the clean zone, it gets a documented re-clean and re-qualification step. Every maintenance event that breaks the boundary is a contamination event unless someone wrote the recovery procedure down.
The same thinking applies to guarding. Interlocked doors, light curtains and access panels are safety hardware and contamination boundaries at once, which is why the guarding layout and the airflow layout have to be resolved together rather than in sequence. Our approach to that is set out under machine safety and compliance.
How do you prove the machine holds its class in production?
At rest, almost any machine passes. The number that matters is the particle count taken while the machine is running at production speed, with the axes moving, the cylinders firing and the operator doing what an operator does.
That is why particle count verification belongs in performance qualification rather than at handover. The counter samples at defined points around the process area during a real production run, and the result either shows the mechanism stays inside the particle budget under motion or it shows which axis does not. For regulated customers this sits inside the wider IQ/OQ/PQ package, which we cover in detail under computer system validation and equipment qualification.
The design consequence is simple: decide the sampling points and the acceptance criteria during concept, not after the machine is built, because they influence where you put the access ports and how the enclosure is divided.
Which cleanroom machines has Motionwell delivered?
Electronics test with on-board clean air. Automated test equipment with 4 to 6 fan filter units integrated into the machine ceiling, holding ISO Class 7/8 over the test fixtures without a classified facility.
Medical device rotary assembly. A 12-station rotary syringe assembly machine running a 15 second cycle with in-line vision inspection for a global medical device manufacturer. The design work here is the usual cleanroom compromise: high-rate indexing motion and enclosed, wipeable structure in the same footprint. The build is written up in the medical rotary assembly case study, and the wider context sits on our medical device automation page.
GMP liquid filling and sealing. SUS316L contact surfaces electropolished to Ra 0.4 um, ASME BPE welds, FDA 21 CFR 177.2600 gaskets, servo ceramic piston pumps holding plus/minus 0.5 percent of target volume from 5 to 500 mL, and an 8-head rotary format running 120 bottles per minute at 100 mL, with IQ/OQ/PQ documentation. Related work on pharmaceutical packaging lines covers the downstream side.
Laboratory and QA environments. Repeat work across the QA lab transformation programme put mobile robots, a collaborative robot and vision into a controlled laboratory space, where the constraints on transport, cabling and surface finish overlap heavily with cleanroom builds. That work is described under automation for laboratory and QA environments.
Five mistakes that show up on the first particle count
Designing the machine, then making it cleanroom-compatible. Cleanroom requirements sit in the frame, the fasteners, the cable route, the motor choice and the pneumatic schematic. All of those are early decisions. Revisiting them late means redoing the frame and rewiring the machine, which is most of a rebuild.
Treating wear debris as a maintenance problem. Guides and belts shed because that is what they do. Either enclose them, drop them below the product plane, or specify low-particle variants. No cleaning schedule compensates for a mechanism that sheds into the product path.
Leaving pneumatic exhaust on the cylinder. A failure that recurs. It is invisible on the schematic and obvious on the particle counter.
Building a flat-topped, recessed enclosure. Under unidirectional flow, a flat top creates recirculation and external recesses trap what the airflow should carry away. Slope the top and keep the outside geometry simple.
Assuming maintenance is somebody else’s problem. If a bearing change requires opening the enclosure inside the clean zone and nobody wrote the re-clean procedure, the machine goes out of qualification the first time it is serviced.
Specifying a cleanroom machine
To get a useful design proposal rather than a generic one, we need three things from you:
- The particle class the product actually requires, and where. Over the whole process, or only at one station? That single answer decides between a facility cleanroom and machine-integrated fan filter units.
- The cleaning regime. What chemistry, how often, by whom. This sets the surface finish, the seal material and the label type more directly than the ISO class does.
- The qualification scope. GMP, ISO 13485 or a customer protocol, and whether particle counting under motion is part of acceptance. This changes the documentation effort and the sampling port layout.
Send those along with your cycle time and part description through our contact page and we will come back with a design approach, including an honest view of whether you need a classified room at all.