Seal it. A shop that has you blowing the PC out every 2-3 weeks is telling you two things: the dust is fine and metallic, and it is everywhere. A filtered dust cover loses that race; its media loads on the same clock, and the particles that slip past are conductive. Put the computer in a sealed stainless enclosure and give the walls a second job, dumping the heat. A 150 W desktop load needs about 2.7 m² [29 ft²] of stainless wall to hold a 15 K rise over 25 C (77 F) shop air, and a 40 x 32 x 16 in box carries 3.14 m², so the air inside lands near 38 C (100 F). Below, the dust decision, the wall sizing, the sealed entries and the order line.
Where a filtered fan still works
Filtered air is a service contract. The fan pushes shop air through a media patch every hour the PC runs, and everything the media catches has to come off before it chokes the flow. In a light, clean space — an office floor, a packaging line — that service is a monthly rinse, and the filter fan is the right, cheap answer. In metal grinding, plasma cutting or machining, the mat builds on the same 2-3 week clock that clogs the bare PC, and intake air starts finding the gaps around the filter frame.
Your cleaning interval is the measurement. A PC that needs compressed air every 2-3 weeks loads a small intake filter at least that fast, because all its cooling air now squeezes through one patch. Miss a round and flow falls while the fan spins harder. The box runs hot exactly like the filtered cover you already retired. The fix in those shops is not more media; it is no intake air at all, which is how a plasma-table computer enclosure handles the same conductive dust at the source.
Blow the old dust out at a bench vacuum or outdoors, never over the open shop floor: a compressed-air blast lifts a cloud, and aluminum grinding dust is combustible.
| Environment | Dust you fight | What holds up |
|---|---|---|
| Office, dry assembly area | light, non-conductive | filter fan, cleanable media, monthly rinse |
| Wood shop, extraction at each machine | chips and fines | filter fan on a fixed media-change interval |
| Metal grinding, plasma, machining | fine conductive metal dust | sealed box, walls as the heat sink |
| Metal shop with coolant mist or washdown | conductive dust, wet | sealed 316L box, sealed cooler if it runs hot |
| Any shop above about 27 C (81 F) ambient | any, at a 150 W load | sealed box plus a heat exchanger or air conditioner |
Where the table points you at a filter fan, size it from the heat load rather than the box volume, and pick media that survives rinse cycles. Watch the media instead of guessing at it: clogging shows up as rising temperature before it shows as dust on the board, so a monthly log of the enclosure's internal temperature tells you when the filter is done. If a sealed box is new to you, the same sealed-versus-vented fork applies from the vented side: any opening you add lowers the assembly's rating to that part's own.
The rating that stops metal dust
Metal particles need dust-tight, not dust-resistant. Under IEC 60529, first digit 5 lets some talc through as long as it cannot interfere with operation; first digit 6 lets nothing through. The wall-mount stainless enclosures we build are rated NEMA 4X / IP66 by the manufacturer; not UL listed. The first 6 is that dust-tight chamber. The second 6 is the powerful-jet test, a 12.5 mm nozzle at 100 L/min — cover for the day someone hoses the floor. The 4X half is the corrosion margin: the same gasketed seal, stainless instead of painted steel. NEMA writes the type definitions and tests nothing itself, and the NEMA 4X versus IP66 guide walks through what each designation covers.
Every hole you cut later carries its own rating, and the lowest one becomes the box's. A gland, a button or a vent each sets the assembly rating where it sits, which is why the entries below are all sealed. For the digit-by-digit meanings of dust and water side by side, the IP rating chart keeps them on one page.
Sizing a 40 x 32 x 16 in box for a 150 W PC at 25 C shop air
The inputs, and where each one comes from:
- Heat load, 150 W. An assumed desktop with a mid-range GPU under load; such towers draw roughly 100-200 W at the wall when busy, and an office desktop sits nearer 50 W. Replace it with a plug-meter reading at your own workload, because every watt that enters the box leaves as heat.
- Wall value, 3.7 W/m²K for stainless. The natural-convection-plus-radiation figure the sizing guides use for a sealed stainless wall.
- Shop air, 25 C (77 F). A conditioned workshop; hot shops get their own decision below.
- Ceiling, 40 C (104 F). The ambient rating most drives and electronics carry unless a datasheet allows more. Allowed rise: 40 − 25 = 15 K.
The rule in words: a sealed box rejects heat through its surface, heat = wall value × area × rise, so area = heat ÷ (wall value × rise).
Area = 150 W ÷ (3.7 W/m²K × 15 K) = 150 ÷ 55.5 = 2.70 m² [29 ft²].
The surface of a rectangular box is 2 × (H×W + H×D + W×D). For 40 x 32 x 16 in [1016 x 813 x 406 mm], that is 2 × (0.83 + 0.41 + 0.33) m² = 3.14 m² [34 ft²], which at a full 15 K rise carries 3.14 × 55.5 = 174 W. Run the same numbers backwards for the real rise: 150 ÷ (3.7 × 3.14) = 12.9 K. With the shop at 25 C, the internal air sits near 38 C (100 F), about 2 K under the rating.
The decision, with the thresholds attached:
- Hold this design while shop air stays at or below about 27 C (81 F) and the load stays under about 175 W. Those are the same 174 W of capacity and the 12.9 K rise, read from both ends.
- Every 10 W you add costs about 0.9 K inside. Ten watts through 11.6 W/K of wall.
- At 35 C (95 F) shop air the same box reads about 48 C (118 F) at 150 W, and passive walls alone are done. Holding a 5 K rise at that load would take 150 ÷ (3.7 × 5) = 8.1 m² [87 ft²] of wall. The largest size in the wall-mount range, 60 x 36 x 16 in, offers 4.8 m². Take one of two outs: cut the load or seal in a cooler.
- Cut the load first. A fanless industrial PC drawing about 40 W lifts the internal air just 40 ÷ 11.6 = 3.4 K, so it holds the 40 C rating even with 35 C shop air. Pick one whose own enclosure rating survives the dust in the first place, and check its datasheet's ambient limit the same way.
- Or cool it sealed. A heat exchanger or an air conditioner moves the heat with closed-loop fans and no shop air in; the crossover between them lands by heat load and ambient, with the air conditioner winning once shop air approaches the target internal temperature.
An internal circulation fan trims the board-to-air gradient a few degrees at most, but the wall stays the bottleneck, so it never replaces area. Bolting the box flat against a cool masonry wall adds a conduction path on top of these convection numbers. When the box also carries terminals and wire, the enclosure sizing guide adds the electrical side: fill, bending space, working clearance.
Leave room for the machine. A mid-tower case lists at about 8 x 18 x 19 in on most spec sheets, and laid on its side it drops into a 40 x 32 x 16 in box with at least a 2 in [50 mm] air gap on every face. Measure your case before you settle the depth, and keep the mounting panel 2 in off the back wall so air washes the whole surface.
Sealed entries: power, USB and the switch
Glands, not grommets. Fit one sealed cable gland on the bottom wall and run the power cord and a USB extension through it. The gland holds its rating only where the elastomer grips the cable jacket, so match the gland's clamping range to the cords you measured and seat it on a flat area. Leave the PC's own ports inside the box and bring a USB extension out through that same gland instead of cutting a rectangular port cutout you cannot seal.
The power switch is the other hole, and it has a sealed answer: an actuator extension over a single round cutout presses the board-level button through the wall and keeps the manufacturer's rating, at the cost of a few newtons of extra thumb force. Keep every entry round, bottom-mounted and sealed; that is the shape a gasket can hold for years. For the cutouts themselves, work from the cutout, gland and HMI window guide so the hole sizes match standard gland threads.
What to order
Settle the size from wall area, then put the entries on the drawing. The stainless size finder filters the lines by outside size, so you can see a 40 x 32 x 16 in box next to your case's numbers. The enclosure selector narrows the choice by environment and DIN module count if the box will carry more than the PC. We cut, fold and weld to your dimensions and deliver in 10 business days from drawing approval, anywhere in the world.
| Order line | Take this | Number behind it |
|---|---|---|
| Material | 304 stainless | dry dust service; 316L under coolant mist or washdown |
| Rating | NEMA 4X / IP66, manufacturer-rated | dust-tight first digit, hose-down second digit |
| Outside size | 40 x 32 x 16 in | 3.14 m² of wall against the 2.70 m² a 150 W load needs |
| Mounting panel | removable, set 2 in [50 mm] off the back | keeps air moving over every face |
| Entry | one sealed cable gland, bottom wall, sized to cord OD | elastomer on the jacket, round hole |
| Switch | sealed actuator over one round cutout | presses the PCB button with a few newtons extra |
| Fit | tower on its side, 2 in clear all round | an 8 x 18 x 19 in mid-tower fits with margin |
The decision in one line: dry shop, conductive metal dust, PC at or under 150 W, shop air at or below about 27 C — order the sealed 304 stainless box sized by wall area. Shop air regularly above that, or a load near 175 W in the example box — the same sealed box with a fanless PC inside or a sealed cooler bolted on. Coolant mist or hose-down in the mix — the same box again, in 316L.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 60 × 36 × 16 in | 304 stainless | 60 x 36 x 16 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 12 × 10 × 6 in | 304 stainless | 12 x 10 x 6 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 16 × 14 × 8 in | 304 stainless | 16 x 14 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 20 × 16 × 8 in | 304 stainless | 20 x 16 x 8 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
How hot will a sealed box get with my PC inside?
The internal air sits 12-13 K above shop air for a 150 W tower in a 40 x 32 x 16 in stainless box: about 38 C with the shop at 25 C and about 48 C with the shop at 35 C. Most electronics carry a 40 C ambient rating, so passive walls alone suit shop air up to about 27 C at this load; above that, cut the load with a fanless PC or add a sealed cooler.
Can I add a fan filter to a sealed enclosure for extra cooling?
Yes, and it stops being a sealed enclosure: the filter fan becomes the weakest opening and its own rating sets the assembly's. Most filter-fan datasheets stop at IP54 - splash-protected, dust-protected, not dust-tight - so conductive metal dust reaches the PC. In a shop that clogs the bare PC every 2-3 weeks, expect to service the filter at least weekly; skip a round and flow falls while the fan spins harder.
Which rating keeps grinding dust out?
Dust-tight is the first digit 6 under IEC 60529: nothing passes the talc chamber. The second 6 in IP66 is the powerful-jet test, a 12.5 mm nozzle at 100 L/min, so a hosed floor is covered too. Any entry you add - gland, button, vent - carries its own rating, and the lowest one becomes the assembly's.
Is 304 stainless enough, or should I order 316L?
For dry shop air and steel filings, 304 is the right grade. Move to 316L when coolant mist, chloride-bearing fluids or washdown touch the box, because 304 pits under chloride deposits even at room temperature. Both grades share the same roughly 60 C (140 F) chloride stress-corrosion threshold, which dry dust service never approaches.
How do I switch the PC on without drilling the box?
Fit a sealed actuator extension over one round cutout: the boot rides the board-level power button and holds the manufacturer's IP66 rating, at the cost of a few newtons of extra force. Power and USB leave together through a single sealed gland on the bottom wall, clamped to the cords' measured outside diameter.
