Double-Head Spot Welding Machine for Compressor Housing Oil Baffles

Six Weld Points On A Compressor Shell: Two Heads Fire In Turn, The Housing Is Clamped Once

Application story  ·  Double-head spot welding of the oil baffle on a compressor housing - sequential heads, one clamp-up, six welds per part

A compressor housing is a drawn steel can with a baffle inside it, and that baffle is what decides whether the oil stays in the sump or travels round the circuit. Six spot welds hold it. Six is also six chances to burn through a thin wall - and there is no second attempt, because the part is loaded once, welded, and if one point is missed the housing is scrap with the baffle already inside it.

The machine: two pneumatic welding heads on one vertical frame, copper secondary arms, fixture at working height, swing-arm operator box and two-hand start on both sides

The Part: A Thin Shell And A Baffle That Has To Stay Put

The housing is drawn from steel sheet and the wall is thin enough that a spot schedule has to be respected - too much current and the electrode leaves a crater on the outside face, too little and the baffle is held by nothing. The baffle itself is a formed sheet-metal part, and its position inside the housing is set by the fixture, not by the operator's hand.

That is the whole reason this is a dedicated machine and not a hand gun on a bench: the six points are in fixed places on the housing, the same six places on every part, and the fixture has to hold the housing so that the electrodes come down square to each of them.

The housing: drawn steel shell, thin wall - the baffle is welded to it at six points, and the outside face has to stay clean

Two Heads, Firing In Turn - Not Together

The machine carries two welding heads on one frame, and they do not discharge at the same moment. They fire in sequence: one head closes, welds, opens, and only then the second one comes down. It looks like a small detail and it changes the result, for two reasons.

The first is current. Two heads closing on the same part at the same instant split the secondary current between two loops, so neither joint gets the schedule that was set for it - one comes out cold and the other expels. The second is force. Two cylinders pressing on a thin shell at the same time bow the wall between them, so the second electrode lands on a surface that has already moved. Sequencing removes both problems: every weld is made with the full current of the transformer and with the part in its natural shape.

The two heads seen from the working side - copper electrode arms angled down to the lower electrode, each head with its own pneumatic cylinder and its own stroke

One Clamp-Up, Six Points

The fixture holds the housing for all six welds - the operator loads once, starts once and unloads when the sequence is finished. Between welds the part stays clamped, which is the point of the design: every re-clamp is a chance to introduce a fraction of a millimetre, and six re-clamps on a thin shell add up to a baffle that is not where the drawing put it.

The welding sequence is stored, so which head fires first, in what order the points are made and how long each one is pressed are all settings. A different housing with a different baffle is a different program and a different set of jaws - not a different machine.

Inside a welded housing: the six weld marks left by the electrodes - the pattern the fixture and the program have to reproduce on every part

A Short Secondary, And Water Where It Matters

The frame is a vertical welded steel structure with the transformer and the secondary built into the throat, so the copper path from the transformer to the electrode is short. On a spot welder that matters more than the transformer size: a long secondary loses current and adds impedance, which is why two machines with the same kVA do not weld the same.

Both secondary arms are water-cooled, and the cooling circuit runs through a manifold with individual flow meters on the side of the frame - a restricted circuit is visible as a low reading rather than as a burned electrode tip a week later. Air comes from a receiver mounted on top of the frame, so the press force does not drop when another machine on the same line draws air.

Machine and control cabinet: welded vertical frame, copper secondary in the throat, water manifold with flow meters on the frame side, air receiver on top

What The Operator Actually Does

01   Load the housing into the fixture and seat it against the locating stops

02   Fit the baffle into its seat in the housing

03   Close the clamp - the part is now held for all six welds

04   Start with both hands; the first head closes, welds one point and opens

05   The second head follows in sequence; the fixture presents the remaining points in the stored order

06   Sequence ends, clamp opens, housing out, next one in

Between the first point and the last, the operator does nothing to the part. That is what makes the cycle time repeatable - the welding time is set by the schedule for six points, and the only variable left is how fast the operator loads.

Fixture and start buttons: the housing is clamped at working height, and both hands are on the buttons when the heads come down

Why The Welds Come Out The Same

Three things do the work. The frame is rigid enough that the electrode force goes into the joint and not into the frame. The fixture holds the shell without distorting it, so the wall does not bow between the electrodes. And the sequence keeps one weld independent of the next, so a point that needs a little more current does not steal it from the point beside it.

The result on the bench is a housing that comes off the fixture with six marks in the same place as the last one - which is what a compressor line needs, because the next operation (leak test, painting, assembly) assumes the outside face is flat and the baffle is where it was designed to be.

Baffle bracket welded inside the shell - the joint the six points are there to make

Two machines built together before dispatch: same frame, same fixture, same sequence - one setup, repeated

Key Specifications

Where It Welds

•   Refrigeration and air-conditioning compressor housings with an internal oil baffle

•   Accumulator and oil separator shells where a baffle plate is welded inside

•   Compressor shells with brackets, terminal seats or mounting plates welded on

•   Thin-wall steel vessels where several fixed points are welded in one clamp-up

•   Any part with a fixed pattern of welds that must repeat part after part

The fixture and the electrode arms are built from the customer's housing drawing and a sample. We weld the first parts in our workshop and set the sequence and the schedule on the real housing before the machine ships.

How A Custom Machine Is Built

01   Housing drawing, baffle drawing and weld-point layout review

02   Weld trial on sample housings - nugget and appearance on the outside face

03   Process proposal - head arrangement, transformer size, sequence, cycle estimate

04   Fixture, electrode arm and lower electrode design in 3D

05   Frame, secondary and pneumatic/water circuit build

06   Weld control and operator box integration, sequence programming

07   Assembly and run-off on customer parts before shipment

08   Delivery, installation and commissioning on site

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

Talk to Pudian Technology

Guangdong Pudian Automation Technology Co., Ltd builds resistance and laser welding equipment in-house - transformers, controllers, fixtures and complete machines - one team, one solution. Send us the housing, the baffle and the weld-point layout, and we will weld sample parts and send them back with a parameter sheet.