Automatic Roller Seam Welding Machine for Oil Radiator Brackets

An Oil Radiator Bracket Is One Long Seam: The Rolls Travel The Whole Length, The Part Is Clamped Once

Application story  ·  Automatic seam (roller) welding of a sheet-metal bracket for oil-filled radiators - two copper rolls, a chain-driven slide, one unbroken seam per pass

A bracket for an oil-filled radiator is two thin steel sheets folded into one long profile, and what holds them together is a line, not a point. Along that line a spot welder leaves a row of dots with cold metal between them; a seam welder leaves one unbroken join from the first millimetre to the last. On a part that has to carry a radiator full of oil, the gaps between the dots are exactly where the fold starts to open.

Automatic seam welding machine: vertical frame, two copper roll electrodes at the throat, chain-driven slide underneath, control cabinet with touch screen at the side

The Part: Two Sheets, One Folded Profile

The bracket is a long piece of formed sheet metal. Both ends carry a drawn boss - a raised round seat with a hole through it - and the middle is stiffened by a rib pressed along its length. Between the rib and the edge the two sheets lie flat on each other, and that overlap is the joint: it runs the full length of the part, in a straight line, at a fixed distance from the edge.

That geometry is what decides the process. The joint is long and narrow, so a spot gun would need dozens of strokes and would still leave gaps; and the flange is too narrow to carry a spot electrode without marking the visible face. A pair of rolls rolling along the overlap lays one continuous nugget instead, with the mark confined to the edge that nobody sees.

The bracket on the machine: drawn bosses at both ends, a rib along the middle, and the folded overlap the rolls run along

Two Copper Rolls, Both Touching At Once

The welding head carries two copper alloy rolls on parallel shafts. One is driven by a gear motor, the other turns with the work. The part's flange passes between them, so the current goes in through one roll, across the overlap and out through the other - and because the rolls are turning while the current flows, the contact patch is never the same copper twice. That is the difference between a roll and a tip: a tip craters, mushrooms and has to be dressed; a roll wears evenly and can be skimmed and put back.

Pressure comes from the pneumatic cylinder on top of the head, acting straight down on the roll block through a guided slide. A pilot pin mounted beside the roll drops into the boss hole before the rolls come down, so the part cannot creep sideways once the seam starts - which matters, because on a two-metre run a millimetre of drift at the start is a millimetre off the edge at the end.

The head: copper roll on its shaft, pilot pin beside it, pressure coming down from the cylinder above - the part's boss hole is seated before the rolls close

The Slide Carries The Part, Not The Operator's Arm

Under the head there is a slide, and the slide is pulled by a chain inside the yellow guard. The part is clamped on the slide and the slide travels the length of the seam at a set speed, so the rolls are doing what rolls do: turning in place while the work goes past them. Feeding by hand would work for a sample and fail in production, because seam quality depends on travel speed staying constant - slow down and the nugget grows and expels, speed up and the weld goes cold.

Because the travel is mechanical, the seam is straight, the overlap is held at the same width for the whole run, and the current is applied for the same length of time at every point along it. The operator's job is reduced to loading, seating the part and pressing start.

Working side: chain-driven slide and its guard at the bottom, rolls and copper busbars above, water hoses looped clear of the weld zone

Loading, Locating, Unloading

The part goes on from the front, boss end first, and drops onto the slide until the drawn boss seats in its pocket. That seat is the datum: it sets the distance from the end of the part to the start of the seam, so the seam begins in the same place on every bracket whether the operator is fast or slow. A clamp holds the part flat against the slide so the flange cannot lift as the rolls pass.

Then the cycle runs: rolls down, slide forward, seam welded along the full overlap, rolls up, slide back, part out. One bracket in, one bracket out, and nothing in between that depends on how steady a hand is.

Loading at the working height: the bracket is laid on the slide and pushed until the boss seats - the rolls come down behind the operator's hands, not in front of them

Why The Same Seam Comes Out Every Time

Three things carry the repeatability. The frame is a welded steel structure rigid enough that roll force goes into the overlap instead of flexing the machine. The rolls and the copper busbars behind them are water-cooled, so the contact face stays at a stable temperature through a shift and the seam does not drift hot towards the afternoon. And the fume hood beside the head pulls the smoke away at the arc, which keeps the roll face and the part clean enough that the next pass starts from the same condition as the last.

What comes off the slide is a bracket with one continuous seam, an edge that has been rolled rather than stitched, and a visible face with no electrode marks on it - which is what the next operation, painting or assembly, is expecting to receive.

Machines built and run off in the workshop before dispatch - the seam is proved on the customer's own brackets, not on a test coupon

Key Specifications

Where It Welds

•   Oil-filled radiator brackets and frames - the folded overlap seam along the length

•   Radiator end plates and mounting rails where two sheets are joined edge to edge

•   Convector and panel heater frames with a long straight overlap

•   Sheet-metal profiles where the seam has to be continuous rather than a row of spots

•   Any narrow flange that must be joined without marking the visible face

Rolls, anvil and slide are built from the customer's bracket drawing and a sample part. We run the first brackets in our own workshop and set pressure, speed and current on the real part before the machine ships.

How A Custom Machine Is Built

01   Bracket drawing, material and seam length review

02   Seam trial on sample parts - nugget width, edge set-down, marking on the visible face

03   Process proposal - roll size, pressure, travel speed, cycle estimate

04   Roll, anvil, slide and fixture design in 3D

05   Frame, transformer, secondary and pneumatic/water circuit build

06   Weld control and touch-screen programming, seam parameters per part

07   Assembly and run-off on customer brackets before shipment

08   Delivery, installation and commissioning on site

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

Talk to Pudian Technology

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