Semi-Automatic Projection Spot Welding Machine for Hinges on Sheet-Metal Cabinet Doors

Hinge Projection Welding Cell for Sheet-Metal Cabinet Doors: A Head At Every Hinge, Spacing Set By Hand

Application story  ·  Semi-automatic projection welding of hinges onto enclosure door panels, manual load, independent heads on a common rail

A cabinet door is a folded sheet, up to 795 mm by 1,140 mm in this build, and it carries three hinges down one edge. The hinge only sits square if the door is held flat while each boss is welded - and a door that has already moved by the third hinge is a door that will hang on the frame and never line up again. This cell was built around that one problem: hold the door flat, weld the hinges where they belong, and make the hinge spacing a setting instead of a fixture.

The cell: projection welding heads on a common rail over the door support table, each head with its own pneumatic cylinder and water-cooled copper secondary loop, on a welded PDKJ frame with adjustable feet

The Door Is Long, Thin And Easy To Twist

The part is an enclosure door: a folded steel sheet with a reinforcing rib pressed into the inside face and an M6 earth stud near the bottom edge. The rib runs the full height - up to 1,140 mm - which stiffens the door in one direction and does nothing at all in the other. Laid flat on a bench and welded by hand, the panel springs between the welds, and the hinge line comes out with a bow.

So the cell is laid out along the part. A support table carries the door over its whole length, the hinge edge runs parallel to the welding rail, and the door is pushed against stops that set both its position along the rail and its distance from it. The operator slides the door in; the machine does the holding.

Support table in aluminium profile with ball-transfer and roller units - a door of the full cell length slides into position without being lifted

The Hinge Carries A Boss, So The Process Is Projection Welding

Every hinge in this application has a raised boss on the face that meets the panel - a ring or a set of dimples pressed into the hinge. That boss is the process. The head brings the electrode down and the boss is the only part of the joint in contact, so the current goes there first, the boss heats and collapses, and the nugget forms underneath it: one discharge, one hinge, no filler wire and no mark on the visible face of the door.

It also keeps the heat where it is useful. The energy is spent collapsing the boss rather than running along the surface, so a thin door skin does not take the full heat of a spot cycle and the outside face stays flat enough to paint. Because the boss collapses by a fixed amount, the hinge lands at the same height on every door - the weld sets the dimension as well as the joint.

Heads on the rail: pneumatic cylinder on top, water-cooled copper secondary loop behind, brass electrode holder and hinge jaw at the bottom; each head is switched and set on its own

A Head At Every Hinge, And The Spacing Is A Setting

A three-hinge door needs three welds at three positions, and the positions change with the door. Instead of one head and a moving part, this cell puts a head at each hinge position on one rail: every head has its own pneumatic cylinder, its own secondary loop and its own weld schedule, and every head can be switched off on its own. A door with two hinges runs two heads and leaves the third idle.

The spacing is not built into a fixture. Each head rides on its own carriage on the rail, is positioned by hand and locked; changing from one door width to the next is a matter of releasing, sliding and re-locking, not of ordering a new fixture. The original process proposal for this project was written for two heads with adjustable spacing - the rail is what lets that number follow the product instead of the other way round.

Head close-up: upper electrode on the hinge boss, lower electrode backing the panel from below, air lines and water circuit routed to the moving head

What The Operator Actually Does

01   Slide the door onto the support table and push it against the stops - position and hinge-edge distance set

02   Fit the hinges onto the panel at the marked positions, boss side against the sheet

03   Press start: the heads come down together and press each hinge flat onto the panel

04   Each head discharges once - one projection weld per hinge, schedule per head

05   Heads lift; the operator checks the hinge line and lifts the finished door away

06   Next door of the same size needs no setting change - same stops, same heads, same schedule

The cycle is semi-automatic in the strict sense: the machine welds, the operator loads and unloads. That is the right split for this part - a door is light enough for one person to handle and too long to feed automatically without a conveyor, and keeping the load manual keeps the cell small enough to stand next to an existing assembly line.

Cell as installed: welding rail and heads on one side, ball-transfer table on the other, so the door is supported right up to the hinge edge

The Rail, The Table And The Frame

Underneath it all is a welded steel base with adjustable feet - one flat, rigid surface that carries the rail, the heads and the support table at the same height, so nothing moves relative to anything else when a door is dropped onto the table. Air lines and water hoses run in a cable carrier along the rail instead of hanging loose where they can be caught by a door edge.

The heads and the transformer loops sit above the working height, the electrodes come down to the hinge line, and the support table is open from the front, so the operator can see the hinge sitting in the jaw before starting the cycle. Water cooling for the secondary circuit is piped through the frame; the machine is delivered as one unit, assembled, wired and run off on sample parts before it leaves the workshop.

Shipped assembled: the cell leaves the workshop as one unit and is lifted onto site in one piece

Key Specifications

Where It Welds

· Electrical enclosure and control cabinet doors with welded hinges

· Distribution box and panel doors, single and double leaf

· Machine housing and equipment covers with hinge reinforcement

· Tool cabinets, storage cabinets and locker doors

· Appliance and sheet-metal doors where the hinge boss is the weld point

The fixture is built from the customer's door drawing and the hinge part number. We run the first doors on the machine and set the head positions and the weld schedule on the real part before it ships.

How A Custom Cell Is Built

01   Door drawing, hinge part number and boss dimensions review

02   Weld trial on sample hinges and panel material in our workshop

03   Process proposal - head count, spacing range, cycle estimate

04   Head, jaw and support table design in 3D

05   Frame, rail, pneumatic and water circuit build

06   Electrical build and weld control integration

07   Assembly and run-off on customer doors before shipment

08   Delivery, installation and commissioning on site

09   Operator training, then after-sales service and spare parts

Talk to Pudian Technology

Guangdong Pudian Automation Technology Co., Ltd builds resistance and laser welding equipment in-house - frames, fixtures, welding transformers and controls - one team, one solution. Send us the door drawing, the hinge and the spacing you need, and we will weld a sample door and send it back with a parameter sheet.