The name on your purchase order is not always the workshop that cuts, bends and welds your parts. That is the uncomfortable little sentence procurement teams learn after the first quality issue. For custom sheet metal enclosures, secret outsourcing can turn a controlled drawing into a guessing game: different bend tooling, different welding habits, different finish shop, different packaging, same invoice. Fun for nobody.
Quick answer: To verify a sheet metal enclosure factory is not outsourcing your order, ask for job-specific evidence: live video of your parts on the shop floor, job travelers, machine route records, material heat/lot traceability, in-process photos, first article inspection, packaging photos and a written rule that any approved sub-tier must be disclosed. MSTFAB manufactures custom sheet metal enclosure shells, cabinet bodies, panels, brackets, mounting plates and welded structures. We do not manufacture finished electronic, telecom, medical, battery or EV charging equipment.
First, separate honest sub-tier work from secret outsourcing
Not every outside process is a problem. Some special processes, such as plating, anodizing, passivation, heat treatment or certain powder-coating work, may be done by approved specialist sub-tiers. That is normal when it is disclosed, specified and controlled.
The problem is secret outsourcing of the core fabrication route: the supplier sells you “our factory” but sends your enclosure panels, cabinet shells or welded frames to another workshop without telling you. Now your DFM review, tolerance promise and quality agreement are attached to the wrong hands. That is how small quality surprises become repeat production headaches.
What should stay under factory control
The verification table buyers can actually use
| Verification point | Ask for this evidence | What it proves |
|---|---|---|
| Live shop-floor proof | Short video showing your part number or job traveler next to your enclosure panels on the laser, press brake, welding or inspection area. | The order is physically inside the claimed factory. |
| Machine route | Job traveler listing laser cutting, CNC bending, welding, hardware insertion, finishing and QC steps. | The process route is planned, not improvised through a mystery supplier. |
| Material traceability | Material grade, thickness, batch/heat/lot reference and photo of raw sheet or cut blanks. | Material was controlled before cutting, not swapped quietly. |
| In-process checks | Photos of bend angle checks, weld fixtures, door gap checks, PEM hardware and critical dimensions. | Quality is being controlled during production, not only after shipment. |
| First article inspection | FAI report or inspection photos tied to drawing revision and CTQ dimensions. | The supplier can prove the first part matches your drawing. |
| Approved sub-tier list | Named finishing or heat-treatment sub-tier, process spec and certificate requirement. | Outside processes are disclosed and controlled instead of hidden. |
How to catch secret outsourcing without flying there
You do not always need an expensive audit. Start with a simple request: “Please send a two-minute video showing our job traveler, our part number and the parts currently in your cutting, bending or welding area.” A real factory can usually do this. A reseller pretending to be a factory often becomes suddenly busy, deeply philosophical or allergic to cameras.
- Ask for a live video call, not only polished photos.
- Ask to see your drawing revision or part number in the frame.
- Ask for the process route before production starts.
- Ask for in-process photos at cutting, bending, welding and inspection.
- Ask for packaging photos before shipment, especially for enclosure shells and powder-coated panels.
- Ask whether any surface finish, plating or heat treatment is outsourced and to whom.
Evidence that matters for sheet metal enclosures
Enclosure work has failure points that flat brackets do not. A cabinet shell can be dimensionally close but still fail because the door rubs after powder coating, the gasket surface is warped, the mounting rail holes are off, the cable entry plate is awkward, or the welded frame twists. These are the exact things a hidden subcontractor may not understand if they only receive a rushed drawing and a target price.
| Enclosure risk | Evidence to request | Why it matters |
|---|---|---|
| Door and gasket fit | Door gap photos, hinge alignment check and coating allowance notes. | Prevents a nice-looking cabinet that cannot seal or close smoothly. |
| Rack rail or mounting plate alignment | Inspection photo with critical hole spacing and reference datum. | Controls assembly fit for the buyer’s internal equipment layout. |
| Welded frame squareness | Fixture photos and diagonal measurement after welding. | Reduces twist, rework and ugly field assembly fights. |
| Hardware insertion | PEM hardware photos, pull-out plan or torque check where required. | Stops loose inserts from becoming assembly line drama. |
| Finish protection | Masking plan, coating thickness check and packaging photos. | Protects threads, grounding points, visible panels and cabinet corners. |
Contract language that makes hiding harder
The contract should not pretend outsourcing is impossible. It should make hidden outsourcing unacceptable. Use clear language: core fabrication cannot be subcontracted without written approval; approved sub-tiers must be named; the supplier remains responsible for quality; the buyer can request job-specific evidence; and special process certificates must flow down to the sub-tier.
Buyer trap: “We control quality” is not the same as “we manufacture this order in-house.” Ask who cuts, bends, welds, inserts hardware, finishes, inspects and packs the parts. The verb matters.
When MSTFAB is the right fit
MSTFAB is a fit when you need custom sheet metal enclosure fabrication from drawings: electrical cabinet shells, telecom cabinet metalwork, PLC/HMI enclosure bodies, EV charger enclosure shells, solar battery enclosure metalwork, stainless panels, brackets, mounting plates and welded structures. The manufacturing scope is sheet metal: laser cutting, CNC bending, welding, hardware insertion, finishing coordination, inspection and export packaging.
MSTFAB is not selling finished certified electronic products. Your team or system integrator handles electronics, system integration, certification and end-use compliance. We make the metal shell and mechanical metalwork that those systems fit into.
Practical buyer checklist before the PO
- Confirm whether the supplier is a factory, trading company or hybrid.
- Request process route and job traveler example for your enclosure project.
- Ask which operations are in-house and which are approved sub-tier processes.
- Require written approval before core fabrication is subcontracted.
- Request in-process photos for first production batch.
- Tie inspection evidence to drawing revision and critical dimensions.
- Ask for export packaging photos before shipment.
Related buyer resources
FAQ
Is all outsourcing bad in sheet metal fabrication?
No. Approved specialist work such as plating, anodizing, passivation, heat treatment or some powder coating can be normal. The risk is undisclosed outsourcing of core fabrication or uncontrolled special processes.
How can I verify a factory without visiting China?
Ask for a live video call, job traveler photos, in-process production photos, machine route records, first article inspection evidence and packaging photos tied to your part number and drawing revision.
What is the fastest red flag?
A supplier that cannot show your job traveler or part number on the shop floor during production may not be making the order in-house. One vague excuse is normal; a pattern is not.
Can a factory use sub-tiers and still be reliable?
Yes, if the sub-tier is disclosed, approved, controlled by a written specification and supported by certificates or inspection evidence. Hidden sub-tiers are the problem.
Does MSTFAB make finished equipment?
No. MSTFAB manufactures sheet metal enclosure shells, cabinets, panels, brackets, mounting plates and welded metal structures. We do not manufacture finished electronic, telecom, medical, battery or EV charging equipment.
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