Key takeaways
- Keep the finished panel within 482.6 mm +0/−0.4 mm and hold flatness to 0.8 mm across the width, or stacked panels show light gaps and rattle.
- On 1.2 mm CRCA keep the inside bend radius at 1.2 mm and holes at least 4.2 mm from a bend line; a 1U face has only about 20 mm of flat height to work with.
- Perforated airflow panels need a ligament of at least one material thickness, so 6 mm holes on a 7.2 mm pitch give about 55% open area on 1.2 mm sheet.
- Specify the latch retention force, typically 30–50 N per panel, and test it with a force gauge; a latch specified only as tool-less is the one that drops out in transit.
- Blank at 1.2 mm on a 40 tf press once volume justifies a progressive tool; below that the laser and brake route avoids tooling entirely.
A blanking panel is the cheapest part in the rack and the one most likely to be returned. It has 44.45 mm of height to work with, two folds, a latch and a powder coat, and it has to sit in a stack of identical panels without a visible gap, a rattle or a jam. Data centre blanking panel design is a fit-budget exercise in 1.2 mm CRCA, and almost every complaint traces to one of four numbers: the 482.6 mm width, the fold depth against a 44.45 mm unit, the latch force, and the coating thickness.
The panel also does real work. Empty rack units let hot exhaust air travel back to the server intakes, so a row of open 1U spaces quietly raises inlet temperature at the top of the rack. A panel with a 2 mm gap around it and a bowed face does not close that path; a flat panel with returns and a positive latch does.
What follows is the geometry that fits, the forming limits on 1.2 mm sheet, the perforation arithmetic, the latch specification that survives transport, and the inspection that catches a bad batch before it is boxed.
What has to be true for a 1U panel to fit?
Four things: the width must be inside 482.6 mm, the height must clear 44.45 mm including coating, the mounting holes must land on 465.1 mm centres, and the panel must stay flat enough that a stack of twenty looks like one surface.
The width is a one-sided tolerance. A panel that measures 482.9 mm will not enter between the rails, while a panel at 482.2 mm fits and simply leaves a small gap at each ear. That asymmetry is why the drawing should read 482.6 mm +0/−0.4 mm rather than a symmetric tolerance, and why the measurement is taken over the ears after coating, not on the flat blank.
The height is tighter than it looks. One rack unit is 44.45 mm, and the panel has to slide in with the panel above and below already fitted. If the top and bottom returns are 12 mm deep, the flat face left between them is about 20 mm, and every feature, from the latch pivot to the finger slot, has to live in that band.
Blanking panel dimensions and the limits we hold
The values below apply to a 1U panel in 1.2 mm CRCA with 12 mm returns, which is the common configuration for airflow blanking in a 19-inch rack.
| Feature | Typical drawing callout | Ganesh limit or note |
|---|---|---|
| Overall width over ears | 482.6 mm | 482.6 mm +0/−0.4 mm, measured after coating |
| Height | 44.45 mm | 44.45 mm −0.2 mm; coating adds about 0.14 mm to the edges |
| Mounting hole centres | 465.1 mm | ±0.3 mm; the same pattern as the rack rails |
| Material | 1.2 mm CRCA | 1.0–1.5 mm; 1.0 mm drums under fan airflow, 1.5 mm is harder to fold |
| Return depth | 12 mm | 10–15 mm; deeper returns hit the rail and the latch arm |
| Inside bend radius | 1.2 mm | 1.2 mm minimum on 1.2 mm sheet; 1.5 mm avoids a sharp outer corner |
| Hole-to-bend distance | 2.5t + R | 4.2 mm; closer and the mounting hole pulls oval |
| Face flatness | 0.8 mm | 0.8 mm across 482.6 mm; twist within 0.5 mm |
| Perforation | 6 mm holes, 55% open area | Ligament at least 1t: 6 mm holes on a 7.2 mm pitch |
| Latch retention | 30–50 N | Measured with a force gauge on the first and last piece of each batch |
| Powder coat DFT | 60–80 µm | 70 µm nominal; ear faces and EMC contact strips masked |
| Panel mass | 0.25 kg | 0.22–0.28 kg in 1.2 mm CRCA; check the flat pattern on the weight calculator |
Forming a 1U panel on 1.2 mm CRCA
The panel starts as a flat blank roughly 40 mm high and 482.6 mm wide. Two folds at the top and bottom create the returns that give the 20 mm face its stiffness, and the mounting holes are cut or pierced in the ears that extend sideways at each end.
Four forming rules keep it straight:
- Inside radius at least 1t. On 1.2 mm sheet that is 1.2 mm. A 0.8 mm radius at the fold puts the outer fibre into a strain that shows as a line of orange peel on a powder-coated panel.
- Holes at least 4.2 mm from the bend line. The ears are narrow, and the distance from the mounting hole to the return fold is the first thing a designer shrinks to gain space. It shows up as an oval hole and a panel that sits at an angle.
- Fold both returns before piercing the latch slot, or pierce before forming if the tool sequence allows, so that the latch slot stays parallel to the face. A slot cut into the flat and then bent moves with the bend allowance.
- Deburr the finger slot. The slot is where an installer's finger goes, and a laser-cut edge at 1.2 mm with a burr on the underside is the one defect that gets a panel rejected by the person fitting it.
Long, thin panels bow during forming because the brake ram deflects and because the blank is not perfectly flat. On a 482.6 mm panel the bow is small, but on a 600 mm panel bent in the same setup it is visible. Bending in the middle of the bed and using a stored programme per part number keeps the angle consistent across a batch; that is the same discipline described for rack frames and cabinets.
Perforation, open area and the airflow variant
A perforated blanking panel does a different job from a solid one: it fills a unit and still allows a controlled amount of air through, which is useful at the top or bottom of a rack where some bypass is wanted. The design question is open area, and open area is limited by how thin a ligament 1.2 mm sheet can hold.
The rule is a ligament of at least one material thickness. On 1.2 mm CRCA that means 1.2 mm between holes, so a 6 mm hole needs a 7.2 mm pitch. Square pitch open area is π/4 × (hole ÷ pitch)², which for 6 mm on 7.2 mm gives 0.785 × 0.694, or about 55%. A 5 mm hole on the same 7.2 mm pitch drops to 38%, and a 6 mm hole on a 6.5 mm pitch reaches 67% but leaves a 0.5 mm ligament that will distort in the press and tear in service.
Two practical consequences follow. First, the perforation wants a progressive tool with a staggered pattern so the punch load per station stays inside the press rating. Second, the perforated zone must stop at least 6 mm short of the fold line, because a hole adjacent to a bend distorts and a distorted hole on a visible face is a reject.
Where the panel is solid, the airflow argument depends on the fit, not on the material. A solid panel with a 2 mm gap top and bottom has the same leak area as a small perforation pattern, so the returns and the latch matter more than the sheet.
Latches, fasteners and the retention force
The latch is the part that fails first, and it is the part most often specified in one word: tool-less.
A tool-less latch is a spring clip, usually 0.8 mm stainless, that hooks over the rack rail or engages a slot in the panel. What the drawing needs to state is the retention force it must hold, not the mechanism. We work to 30–50 N per panel: low enough that an installer can pull it out with two fingers, high enough that a panel does not walk out of a rack in transit or during a seismic event.
Three details decide whether the latch works after coating:
- The clip must contact bare metal or a masked face. A clip that grips a powder-coated edge loses about a third of its friction and creeps over time.
- The engagement depth must survive tolerance stack. If the rail slot is 5 mm deep and the clip engages 5 mm, a panel at the low end of its width tolerance engages 4.6 mm; that is the difference between a latch and a rattle.
- The pivot or rivet must be set after coating, or the coating must be removed at the pivot. A rivet squeezed onto cured powder crushes the film and flakes it around the head.
Captive screws are the alternative for panels that are rarely removed. A spring-loaded captive screw in a 1.2 mm ear needs a 4.2 mm hole with a swaged collar, and the collar has to be set before coating so the powder does not bridge the thread.
Coating a panel that has to slide into a gap
Coating a blanking panel is straightforward until the fit budget is applied. At 60–80 µm per face, a 1.2 mm panel becomes a 1.34 mm panel, and the returns grow by the same amount on their outer faces.
The masking schedule is short and specific: the mounting ear faces where they touch the rail, the latch contact zone, and any EMC contact strip if the panel has one. Everything else takes the full coat, including the returns and the inside faces, because those are the surfaces a hand touches and the surfaces that rust first in a dusty hall.
Colour consistency across batches is a real acceptance criterion on a visible part. Panels are stacked in a row where a shade difference between a batch from January and a batch from July is obvious under LED lighting, so the powder batch should be recorded against the panel part number and a retained sample kept.
Adhesion is checked with cross-hatch to ISO 2409 on the first part of each shift. On a formed return, the powder is thinnest on the outside of the bend, and that is where a chipped edge starts.
Inspection: what a panel batch is checked against
A blanking panel inspection is quick if the gauges are right:
- Width gauge over the ears at 482.6 mm +0/−0.4 mm, on the coated part.
- Flatness on a surface plate with a dial indicator, 0.8 mm across the face and 0.5 mm of twist.
- Hole position on the same 465.1 mm pin gauge used for the rack rails.
- Latch force with a spring gauge, first and last piece.
- DFT and adhesion, with a cross-hatch on a sample return.
- Visual: burr in the finger slot, die marks on the face, colour against the retained sample.
PPAP and first article reports are available where the customer's system asks for them. For a part this small the first article record is mostly a record of the tool, because a progressive tool that is right produces a million correct panels and one that is wrong produces them wrong just as consistently.
What Ganesh runs for blanking panels
At volume, panels run in a progressive tool built in our own tool room, on the mechanical presses from 20 T to 300 T. The arithmetic is modest: a blank perimeter of about 1,100 mm in 1.2 mm CRCA at 300 MPa shear needs roughly 40 tf, so the tooling decision is about tool life and hole quality rather than press size. Below the volume that justifies a tool, panels are laser cut on the 12 kW machine, formed on the 200 T 5-axis brake and finished on the seven-tank line.
Panels are part of the data centre rack range, which also covers 19-inch frames, mounting rails and cable management. The forming and piercing operations behind a panel are explained in blanking, piercing and forming, and the wider enclosure family sits in the data centre and enclosure hub.
The rack load calculator is the wrong tool for a 0.25 kg panel and the right one for the rack it goes into, which is usually the number that decides how many units get blanked.
What to put on the panel drawing
- Overall width and height with one-sided tolerances, and the note that they apply after coating.
- Mounting hole pattern: 465.1 mm centres, hole size, and the ear geometry.
- Return depth and bend radius, or a note allowing the supplier to choose within the 44.45 mm envelope.
- Perforation: hole size, pitch, open area and the unperforated border width.
- Latch type and retention force, with the rail interface it engages.
- Coating: colour, gloss, DFT and the masked zones.
- Marking and packing: panels scratch in a carton, and a stack packed face to face without interleaving arrives with rub marks.
When a fabricated panel is the wrong answer
Extruded aluminium panels with a plastic end cap and a moulded latch are a different manufacturing route, and we do not extrude or mould. If the design depends on a polymer latch, the metal part is still a folded panel, but the latch has to come from the moulding supply chain and the interface has to be toleranced across two suppliers.
EMC blanking panels with a knitted gasket or a finger strip need the gasket bonded after coating, and the bond is only as good as the surface preparation underneath it. We can mask and coat, but we do not bond conductive gaskets or test shielding effectiveness, so that step belongs with the panel assembler or the customer.
Very shallow panels with a 6 mm return are also a poor fit for press braking at 1.2 mm, because the punch and die cannot reach the fold without marking the face. Those designs are better as a flat plate with a formed edge on one side only.
A drawing with the coated width tolerance, the return depth and the latch force on it is enough to quote a panel that installs first time. Send the revision and the annual quantity through the RFQ route, and the quotation will separate the laser route from the tooled route so the crossover is your decision rather than an assumption.
Frequently asked questions
What size is a 1U blanking panel?
A 1U panel is 482.6 mm wide over the mounting ears and 44.45 mm high, matching one rack unit. The mounting holes sit on 465.1 mm centres to match the rack rails, and the panel body is usually folded back 10–15 mm top and bottom to give it stiffness.
How thick should a blanking panel be?
1.2 mm CRCA suits most 1U panels and holds flatness within 0.8 mm across the width. Below 1.0 mm the panel drums when a fan pulls air past it; above 1.5 mm the returns become hard to form cleanly in a 44.45 mm height and the weight goes up without benefit.
Do blanking panels actually save energy?
They stop hot exhaust air from recirculating into server intakes through empty rack units. The saving depends on the rack layout and the containment, so the panel is a airflow control measure rather than a guaranteed energy figure; the design requirement is a close fit with no open gaps.
Why does the powder coat make the panel hard to fit?
Two faces at 70 µm add about 0.14 mm to the panel thickness, and the returns sit in a 44.45 mm gap that other panels are stacked against. Coat the face and the returns but keep the mounting ear faces and any EMC contact strip masked, which is where the fit and the bonding actually happen.
What is the difference between a blanking panel and a filler panel?
Both fill an unused rack unit. A blanking panel is usually the airflow part with returns and sometimes perforation, while a filler panel can be a flat plate with a simple latch. The fit tolerances are the same; the stiffness requirement is not.
Sources and further reading
- IEC 60297-3-100 — 482.6 mm (19 in) series mechanical structures: basic dimensions · reviewed 3 Nov 2026
- ISO 2768-1 — General tolerances for linear and angular dimensions · reviewed 3 Nov 2026
- ISO 2409 — Cross-cut test for paint adhesion · reviewed 3 Nov 2026
Need blanking panels to a drawing?
Send the panel drawing, colour, latch requirement and annual quantity. We quote the laser route and the progressive tool route separately so the crossover is visible.
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