CNC splash containment enclosure: keep coolant in, controls reachable

Short answer: build the splash walls from 20 ga [0.9 mm] steel sheet, step up to 16 ga [1.5 mm] for the top cap, overlap the sliding doors 2 in [50 mm] at the meeting point so 1 in [25 mm] survives a drift, and hem the bottom 1/2 in [13 mm] inward so coolant runs back to the chip tray. Bolt the HMI and controls to a sliding door, and the electrical cabinet behind stays closed while the machine cuts. The splash sheet is guarding, not a rating; the sealed cabinet behind it does that work. The sections below cover wall height by droplet ballistics, door overlap arithmetic, roller sizing by beam deflection, and the flood test that proves the floor stays dry.

What do you need to build a splash containment enclosure?

You need 20 ga [0.9 mm] sheet for the walls, 16 ga [1.5 mm] for the top cap, 1 in [25 mm] square tube for the frame, and for each door two ball-bearing rollers on quarter-inch [6 mm] rod with a 3/4 in [19 mm] tube frame.

Stay inside the 16-20 ga band. On the Manufacturers' Standard Gauge for carbon steel sheet, 16 ga is 0.060 in [1.52 mm], 18 ga is 0.048 in [1.21 mm] and 20 ga is 0.036 in [0.91 mm]. Splash load is light; stiffness and handling set the gauge. A hemmed 20 ga wall shrugs off flood splash and chip spray, while the top cap and the cap over the cabinet take hands and leaning, so they get 16 ga.

How tall should the splash walls be?

Take the wall top 12 in [300 mm] above the highest point the tool reaches, or 18 in [460 mm] when the cutter slings coolant hard, and the arithmetic behind both numbers is droplet ballistics: a drop leaving at 2 m/s rises just 8 in [200 mm].

Rise is h = v²/(2g). At 2 m/s that is 2²/(2 × 9.8 m/s²) = 0.20 m [8 in]; at 3 m/s it is 0.46 m [18 in]. Gravity-fed flood and small nozzles throw drops near 2 m/s. A cutter whipping through a puddle at speed throws at 3 m/s and up, so watch your own machine throw against a scrap sheet and pick the line that matches. Chips leave faster but travel flat, and a wall that catches drops catches the spray too.

Clearance around the vise overhang, the spindle nose and a fourth axis is a separate sizing problem: CNC splash guard enclosure dimensions and clearances works those numbers. Make the door opening clear the largest workpiece plus fixture by 2 in [50 mm] a side, or the doors will never close over a big part.

How much overlap do sliding doors need?

Overlap the closed doors 2 in [50 mm] at the meeting point; that leaves a worst case of 1 in [25 mm] of lap when each door sits half an inch [13 mm] off its stop, which ordinary track wear produces inside a year.

Worked example. Opening 36 in [914 mm] wide, two doors on offset tracks. Door width w = (W + overlap)/2 = (36 + 2)/2 = 19 in [483 mm]. Check with overlap = 2w − W: 2 × 19 − 36 = 2 in [50 mm] closed on the stops. Let each door drift half an inch apart: 2 × 19 − 36 − 1 = 1 in [25 mm]. The seam stays covered, and the doors still park clear of the opening because they slide past the frame.

For a single door over a fixed wall, lap it past the opening edge by at least 1 in [25 mm] and leave parking space equal to its own width. At the seam between two doors, form a 3/4 in [19 mm] J-channel on one stile so the faces lap; splash that hits the joint hits metal twice before it passes. Set the two track planes one door thickness plus 1/4 in [6 mm] apart so the doors pass without rubbing.

How does coolant stay off the floor at the bottom edge?

Turn the bottom half-inch [13 mm] of every wall and door inward, end the walls 1 in [25 mm] inside the chip tray rim, and coolant that runs down the sheet drips back into the tray instead of onto the floor.

Doors slide on the dry side in most builds, so their own drips need a path. Under the door line, add a 1 in [25 mm] gutter flange sloped 1/8 in per ft [10 mm per m] back toward the tray, and hang each door so its bottom hem laps the gutter lip by half an inch [13 mm]. The hem itself stiffens 20 ga sheet, so the bend does two jobs. Soluble oil is water-thin and follows a 1% slope without pooling.

Put the doors on the coolant side instead and their drips land in the tray directly; the dry side then gets a fixed panel with its own inward hem. Both layouts work. The remaining paths — corner joints, the cabinet cap, hinge lines — get the full walk in how to contain machine-tool coolant at enclosure gaps.

What carries a sliding door without binding?

Run each door on two ball-bearing rollers over the quarter-inch rod, and size each roller at 3x its share of the door weight: a 19 x 24 in door of 20 ga steel weighs 10 lb, so a 15 lb rating carries it.

Door weight, shown. Skin: 19 × 24 = 456 in², at 0.036 in thick that is 16.4 in³, and steel is 0.283 lb/in³, so 4.6 lb [2.1 kg]. Frame: about 6.5 ft of 3/4 in tube at 0.6 lb/ft is 3.9 lb. Handle, latch and J-channel: 1.5 lb. Total 10 lb [4.5 kg], so 5 lb per roller and a 15 lb [7 kg] rating at 3x. In 16 ga the skin doubles to 7.7 lb and the door lands near 13 lb [5.9 kg]; the roller rating moves to 20 lb [9 kg]. The 3x covers the snatch when a chip-loaded door breaks free and drops its weight onto one roller.

The rod sags, and sag binds rollers. For a simply supported rod with the roller load at mid-span, sag = FL³/48EI, with E = 29 × 10⁶ psi for steel and I = 0.00019 in⁴ for the quarter-inch rod. At a 24 in span: (5 × 13,824)/(48 × 29,000,000 × 0.00019) = 69,120/264,480 = 0.26 in.

Keep the thin-rod bays at 12 in [300 mm]; for a clean 24 in span, 3/8 in [10 mm] rod sags five times less. Past about 1/16 in [1.6 mm] of sag, a ball-bearing roller squats in its bracket and rubs, so treat the table as a limit. Sealed races matter too: open bearings pack with chip dust within a month of flood work.

Where do the HMI and controls go?

Bolt the HMI and controls to the sliding door, run their cables as a hanging loop with a bend diameter of at least 10x the cable OD, and leave the electrical cabinet closed behind the splash wall; you reach everything while the cabinet stays sealed.

Jog, feed override and cycle start belong at the point of cut. You press them mid-cycle with wet gloves, and the cabinet behind never opens for it. The cabinet is the rated part: our 304 and 316L bodies are rated NEMA 4X / IP66 by the manufacturer; not UL listed, and that rating lives in the cabinet's gasketed door, its glands and its cutouts. The splash sheet carries none.

Size the cable loop from the door travel: 19 in of travel plus a 6 in [150 mm] droop is 25 in [635 mm] of slack. Clamp both ends. Cable makers publish minimum bend radii near 7.5-10x OD for flexing service, so a 0.3 in [8 mm] cord wants a 3 in [75 mm] loop diameter.

If you would rather mount the panel through the splash sheet into the cabinet's own door, the seal moves to the cabinet wall: mounting an operator panel in a cabinet door and keeping the rating shows that joint. The fundamentals behind every cutout sit in the cutouts, glands and HMI windows guide, and the cutout designer checks spacing and exports the layout with the quote. Whatever you cut, the gasket line has to stay continuous; what a NEMA 4 rating requires of gaskets, doors and hinges is the checklist to hold it against. If the cabinet is a 304 or 316L body ordered with factory cutouts, it is delivered in 10 business days from your approval of the drawing; custom stainless enclosures and cutouts lists the starting points.

Leave the splash sheet removable over the cabinet door's swing. A 16 ga [1.5 mm] cap on two quarter-turn fasteners comes off in seconds, and with the cap off the cabinet door still opens the 90 degrees that NEC 110.26(A) requires for equipment serviced while energized. A sliding or removable panel in front of energized gear carries its own code angles; custom MCC enclosures with sliding doors and their code requirements goes deeper.

How do you build it, step by step?

The build sequence below assumes the 36 in [914 mm] example opening with 19 in [483 mm] doors; scale every number by the arithmetic above and the order of work stays the same from a mini mill to a knee mill.

1. Scribe the height line on the frame: table top + tallest tool reach + 12 in [300 mm], or 18 in [460 mm] for the fast-sling case.
2. Cut the panels: walls and doors in 20 ga, top and cabinet cap in 16 ga. Deburr every edge before it moves.
3. Hem the bottom of each fixed wall and each door inward by half an inch [13 mm].
4. Square the 1 in [25 mm] frame; match frame diagonals within 1/16 in [1.6 mm] so the doors cannot rack.
5. Set the track planes one door thickness plus quarter-inch [6 mm] apart, and drill the rod supports on the 12 in [300 mm] bays.
6. Form the 3/4 in [19 mm] J-channel on one stile of each door pair.
7. Hang the doors and set the stops for the 2 in [50 mm] closed overlap; on this opening the doors measure 19 in [483 mm] wide.
8. Slope the bottom gutters 1/8 in per ft [10 mm per m] toward the tray, and hang each door so its hem laps the gutter lip by half an inch.
9. Bolt the HMI, pendant and keyboard to the door; make the 25 in [635 mm] service loop and clamp both ends.
10. Fit the removable 16 ga cap over the cabinet door swing on two quarter-turn fasteners.

Before any hole goes into the cabinet wall itself, lock out the machine and verify absence of voltage.

How do you check the finished enclosure?

Run flood coolant at full flow with the doors closed for 5 minutes at your top spindle speed, and a 6 in [150 mm] paper towel strip taped to the outside bottom edge comes away dry; that one test covers the walls, the seam and the gutters at once.

• Seam under drift: push each door half an inch off its stop and repeat the towel test at the meeting line; dry means the 1 in [25 mm] worst-case lap holds.
• Sag: at mid-travel, the gap between door hem and gutter stays within 1/16 in [1.6 mm] of the set hang height.
• Cycle: 20 full open-close strokes with the J-channel never dragging and the stops holding.
• Loop: door fully open, the 25 in [635 mm] loop hangs free at 10x OD bend diameter with no jacket kinks at the clamps.
• Cabinet: cap off, the cabinet door completes its 90 degrees of swing without touching the splash frame; cap on, it sheds what runs down the sheet.
• Return: the tray level rises and the floor under it stays dry.

Which mistakes cost you the containment?

Most failed builds fail at one of five details, and each failure has a measurement that catches it before the first flooded part: the seam, the rod span, the missing gutter, the misplaced seal or the rigid cable.

• Butt joint at the seam: splash walks straight through a flush meeting line. Form the 3/4 in [19 mm] J-channel and the lap ends it.
• Long rod span: the quarter-inch rod at 24 in [610 mm] sags 0.26 in [6.6 mm], the door squats, the lap drags and the seam opens. Support every 12 in [300 mm] or run the 3/8 in rod.
• Door on the dry side with no gutter: the hem drips onto the floor by itself. Add the 1 in [25 mm] flange at the 1/8 per ft slope.
• Sealing the splash sheet instead of the cabinet: guarding carries no rating, so the seals belong on the cabinet wall and its glands.
• Rigid cable to a moving door: conductors fail at the clamp within weeks of cycling. Give the loop its full 25 in [635 mm].
• Mist treated like flood: walls and laps stop drops; mist rides air through any opening. Close the top and lap every seam before you mist.

Build it this way and the containment survives drift, sag and a bad day at the coolant valve, with the cabinet sealed and reachable the whole time.

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.

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