All-in-one machine control enclosure: PC, drives and VFD

Short answer: yes, one enclosure can carry all of it, and heat — not noise — sets how big it must be. A 24 x 24 x 12 in wall-mount box holds a control PC, three servo drives, the breakout board, the 80 VDC supply and a 2 hp VFD, with room to work inside. Three rules make your build behave. Keep every low-voltage signal loom 8 in [200 mm] away from VFD and servo motor leads, and cross them at 90 degrees where they must meet. Land every shield and ground on one bonded bar. Size for about 175 W of heat: filter fans in a clean shop, a sealed NEMA 4X box with an air-to-air exchanger where washdown rules.

What the gear turns into heat

Every watt a part draws without delivering to a motor or a screen becomes heat inside the box, so you size from heat rather than from the parts list. The figures below are worked-example values for a bench CNC conversion. Swap in the loss figures from your own datasheets where you have them, because one bigger drive moves the total fast.

Two anchors keep the example honest. Hold the interior at or below 40 °C (104 °F), the ambient most drives and electronics carry unless a datasheet allows more. And watch the spindle: a 5 hp drive at the same 3 % assumption adds about 112 W, close to the heat of all three servo drives together.

What the walls shed and when fans take over

A sealed stainless wall moves heat out in proportion to its area and the temperature difference across it. The figure this site's sizing guides use for stainless is 3.7 W/m²K, so the arithmetic is heat = 3.7 × area (m²) × ΔT (K). For the wider method, the enclosure sizing guide walks the whole calculation.

That example box has 2 × (24 × 24) + 4 × (24 × 12) = 2,304 in² of wall, about 1.49 m². At 35 °C ambient with the interior held to 40 °C, ΔT is 5 K: 3.7 × 1.49 × 5 = 27 W. In a 25 °C shop the same wall sheds 3.7 × 1.49 × 15 = 82 W. Both fall far short of 175 W, so a small sealed box cannot cool your gear by itself.

Stepping up to a 48 x 36 x 12 in box gives you 2 × (48 × 36) + 2 × (48 × 12) + 2 × (36 × 12) = 5,472 in², about 3.53 m². At a 15 K difference it sheds 3.7 × 3.53 × 15 = 196 W, which carries the 175 W load and settles the interior just under 40 °C in a 25 °C shop. At 35 °C ambient the same box manages 65 W and cannot hold the line.

Where walls fall short, move air, with the fan-maker sizing rule CFM = 3.17 × watts / ΔT(°F). For 175 W at a 20 °F rise that is 3.17 × 175 / 20 = 28 CFM; a 50 CFM filtered exhaust with a filtered intake opposite holds the rise near 11 °F (6 °C). At 287 W, the 5 hp example, the same formula asks for about 45 CFM. A second fan in series moves the same air — the flows do not add.

The catch is the rating: the weakest part sets the rating of the assembly. A filter-fan kit is commonly IP54 (dust-protected, splashing water) on its datasheet, and the vented build takes that rating. For a single drive in its own box, the VFD enclosure guide to rating, size and cooling works the same numbers per drive.

The rating call, shop by shop

The rating you end up with depends on what lands on the outside of the box, because that is what the type protects against.

These are manufacturer ratings — NEMA 4X / IP66 across the stainless wall-mount range — and the boxes are not UL listed. On US jobs, NEC 110.28 says IP ratings are no substitute for enclosure type ratings, so a specification that calls out Type 4X needs the type written down, with the IP code alongside it.

Exchangers keep the seal intact, and their datasheets rate them in W/K, which makes the choice arithmetic: a 15 W/K unit across a 15 K inside-to-outside difference moves 225 W, clear of the 175 W load. A sealed build stays sealed — a plain drain hole or an open louvre sets the rating of the whole box, so an exchanger does the air moving instead. In a dusty cell the sealed box also spares you clogged filters; keeping a cabinet clean in a dusty machining cell covers the habits that decide upkeep.

A layout that keeps the PC quiet

VFD output leads and servo motor leads are the transmitters; the PC and its DC leads, the breakout loom, the analog lines and the encoder cables are the receivers. Space and right-angle crossings are the cheapest cure, and they cost nothing when the layout drawing shows them on day one. Servo drive and computer wiring separation in one enclosure treats the subject in depth; the working rules for one box are:

• Keep 8 in [200 mm] of air or steel between any signal loom and any motor or drive-output lead.
• Where a run must pass the power zone, cross it once, square, at 90 degrees.
• Where a motor lead must run parallel with signal wiring past 12 in [300 mm], double the gap to 16 in [400 mm] or take the run outside the box.
• Leave 2 in [50 mm] above and below each drive frame as a layout placeholder, then fit the drive's own drawing before the cutout drawing goes final.

In the example box (inside 23.88 x 23.88 x 11.88 in) the PC sits across the top of the backplate with the breakout board beside it, the ground bar runs down the left edge, and the power gear fills the bottom: servo drives bottom right, VFD bottom left, the 80 VDC supply between them. That gives roughly 10 in of clear separation between the signal zone and the drive zone, above the 8 in floor, and the encoder cables cross the boundary once, square. If you are wiring two servo drives behind one breaker and filter, two servo drives in one enclosure walks that chain, and the CNC sizing walkthrough shows how wiring room grows a box.

Shields, grounds and one bar

Size the wire for the noise it lives next to. A major drive maker's application note on VFD wiring calls for 20 AWG shielded cable on analog signals, 16 AWG on other control wiring and 14 AWG on relay contacts, and those sizes hold up beside switching electronics.

Terminations decide whether the shield works:

• Run VFD output in shielded motor cable and land the shield in a screen-termination gland; tightened, it grips the shield around its full 360 degrees. VFD motor cable entry: locking connector or conduit compares the entry hardware.
• Clamp each encoder shield 360 degrees at the drive end of its run.
• Bond the backplate, the door (a strap across the hinge) and every shield to one ground bar. NEC 250.96(A) (2020 edition) requires metal parts acting as equipment grounding conductors to be bonded so they can carry the fault current likely imposed on them; the grounding and bonding guide carries the detail.
• Route the PC's own supply leads away from its audio and USB wiring; switching supply noise in an enclosure explains why small supplies whine into analog lines.

The 24 VDC side of the breakout board and the PC is a low-voltage build in its own right; wiring a 5-24 VDC low-voltage system safely covers the separation and fusing that side wants. One safety line belongs here: the 80 VDC bus counts as live, so lock out the machine's mains disconnect and read 0 V across the bus terminals with a meter before your hands go in.

What goes on the order

Draw every opening once, on one layout, and send the drawing with your order. The cutout designer lays out fan openings, glands and any display cutout, checks the spacing and exports the drawing; the box itself is delivered in 10 business days from your approval of the drawing.

For a dry dusty shop that skips the fans entirely, the passive pick is the 48 x 36 x 12 in 304 wall-mount enclosure. Where the machine outgrows the catalog grid, custom enclosures take your width, height, depth and every cutout as a one-piece build, and the wall-mount range lists each standard size with its inside dimensions.

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.

Questions