“Mask the contact areas” sounds specific until a finisher asks where each area starts, which side of the panel it occupies and what surface condition must remain underneath. On an enclosure with several electrical and mechanical interfaces, that missing detail can stop a batch after fabrication is already complete.
For custom aluminum sheet metal enclosures, masking should be a drawing-defined operation with an inspectable boundary. It should not depend on a supplier recognizing the purpose of every hole in a CAD model.
Separate masking from the final surface requirement
Masking prevents or limits a process in a particular zone. It does not, by itself, specify what finish that zone should have. An area may need to remain untreated, receive a specified conversion coating or follow another approved route. Those alternatives have different requirements.
Name the applicable finish specification and the required state of each zone. Do not describe a surface only as “conductive” without an agreed acceptance criterion and responsibility for verification. The OEM determines the electrical function; the metalwork drawing must communicate the physical and process requirements supporting it.
Make every zone identifiable without interpretation
Use controlled views, dimensions or model annotations that locate the boundaries from stable features. Identify both faces when a thin panel has different requirements on each side. If a mask edge may vary, specify the permitted boundary condition rather than expecting an infinitely sharp transition.
The AAC guidance on specifying anodized finishes reinforces the importance of material and process specification. Project-specific masking details still need agreement with the actual finishing supplier; an anodized finish name alone does not define them.
Put the zone information in one usable schedule
| Zone | Drawing information | Acceptance question |
|---|---|---|
| Contact pad | Face, location, extent and finish | Is the intended mating area exposed in the approved state? |
| Threaded hole | Thread identity and protection requirement | What inspection confirms the finished thread? |
| Sliding interface | Protected extent and dimensional requirement | Is the complete travel surface covered by the instruction? |
| Visible exterior | Cosmetic class and transition location | Is the permitted mask edge acceptable to the buyer? |
| Rack or handling contact | Approved location if relevant | Can the process leave a mark in this region? |
A zone schedule is especially useful when two visually similar panels have different finish requirements. Connect the schedule to the part number and revision instead of relying on color coding that may disappear in a printed drawing.
Review masking access before releasing the geometry
Deep narrow recesses, closely spaced holes and boundaries crossing a bend can complicate the operation. Ask the finisher how the zone will be protected and inspected. A modest design change may simplify the process, but it must not compromise the required contact or mating geometry.
Also decide which surfaces must remain accessible after hardware installation. If a captive fastener covers part of a contact zone, the process sequence and inspection plan need to account for that obstruction.
Avoid creating conflicting corrosion and bonding instructions
One team may request electrical contact while another requests isolation between dissimilar metals. Both concerns can be legitimate, but the same interface cannot be left for the fabricator to reconcile by intuition. Identify intentional bonding points and protected mechanical attachments in the approved design.
The companion galvanic-isolation guide discusses why fastener, washer, coating and environment decisions belong together. Masking should implement that approved interface plan, not silently redefine it.
Check the first finished parts against the zone map
Review the actual boundaries, residue, protected threads and any agreed measurements. Keep coating records separate from electrical or functional acceptance records. If an interface is reworked, assess the resulting surface condition and update the disposition rather than simply removing an inspection hold.
Send DRAmetal the finish specification, annotated zone map, hardware sequence, critical dimensions and required records. A complete package lets the fabrication and finishing teams review feasibility before a batch reaches the masking station.
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