Transfer Stamping System

Overview

A transfer stamping system is a mechanical press that runs several separate forming operations in one machine and uses a mechanical transfer mechanism to carry each part from one die to the next. A flat blank is fed in at one end, and after passing through a line of die stations it leaves as a finished pressed part such as an oil pan, a structural bracket, a wheel half, or an appliance shell. The machine does the work of what would otherwise be a row of single presses plus the loaders and conveyors between them, in one frame on one cycle.

The system is built around the Stamping Press, which supplies the forming force, and the Transfer Mechanism, which moves the parts. Blanks enter through the Destacker, pass through the Transfer Die Set with the help of any Idle Station reorientation, and leave on the Part Unloader. The Die Change System system swaps the whole tooling line for a new part, and the Control System keeps every motion locked to the slide.

How the transfer differs from a progressive die

This is the point that sets the machine apart. In a progressive die the part stays attached to a continuous strip of coil stock, and the strip itself indexes forward through one large die one pitch per stroke. The carrier is the metal. In a transfer system there is no strip. The blank is cut loose first, and discrete loose parts are physically picked up and walked through the line by the Transfer Mechanism. The carrier is the machine.

That difference is why transfer suits large, deep, or three-dimensional parts. A deep-drawn shell cannot be left hanging on a strip, and trimming away a strip carrier on a big panel wastes too much metal. Carrying loose blanks also frees each station to be a complete part, so the dies can be turned over and worked on more than one face, which a progressive die cannot do. The cost is mechanical complexity: the transfer must place every part within a fraction of a millimetre, every stroke, in time with a slide that does not wait.

The press

The Stamping Press is a straight-side mechanical press. A motor spins the heavy Flywheel, storing energy that the Clutch-Brake Unit releases into the Eccentric Drive for each stroke. The eccentric shaft drives the Slide down through two Connecting Rod links, and all die stations close at once because they all hang from the same slide. The Bolster takes the load below, the Slide Gib ways hold the slide square under the off-centre loads that come from working several stations of different force at once, and Counterbalance Cylinder cylinders offset the slide weight. The Tie Rod members clamp the frame so it stays stiff at full tonnage. A press in this class runs 630 to 1600 tonnes at 15 to 40 strokes a minute.

The three-axis transfer

The transfer is the defining subsystem. Two Transfer Rail beams run the length of the die line, one on each side, carrying Finger Tooling set at the station pitch. The motion has three axes. The Clamp Drive moves the rails together so the Gripper Finger sets pinch each part. The Lift Drive raises the rails so the parts clear the lower dies. The Advance Drive moves the rails one station downstream, the rails lower to set the parts in the next dies, unclamp, and return empty for the next stroke. Edge-gripped parts use fingers; flat or faced parts ride on Vacuum Cup tooling and locate in a Part Nest.

The rails must never be over a die while the slide is down. The Sync Cam reads the press angle and feeds it to the transfer servos so the motion profile stays clear of the closing dies. Older machines drove the three axes off mechanical cams geared to the crankshaft; servo machines use a Servo Cam Box box per axis, which lets the curves be retuned for a new die set from the control screen.

Blank feeding and die stations

Blanks start as a stack of precut sheets. The Destacker lifts one at a time with its Vacuum Head, while a Magnetic Fanner and a Sheet Separator keep two sheets from coming up together, checked by a Double-Blank Detector. The Stack Lift raises the pile so the top sheet stays at pickup height.

The Transfer Die Set is a line of single-purpose dies. A typical order is draw, trim, pierce, flange, restrike. The Draw Die forms the flat blank into a shell over a Draw Punch while a Binder Ring controls metal flow. Later stations Trim Die, Pierce Die, and Flange Die cut and bend, and the Restrike Die coins the part to final form. A Die Cushion under the bed supplies blank-holder and knockout force. Where the part must be worked on a new face an Idle Station flips it with a Rotary Actuator before the rails pick it up again.

Materials, variants, and use

The press frame and slide are cast steel, the eccentric shaft is forged alloy steel, and die working surfaces are tool steel, often coated for the abrasive high-strength grades. The system runs mild, high-strength low-alloy, and stainless steels and aluminium from about 0.6 to 3.0 mm. Variants split mainly on the transfer drive, mechanical cam versus servo, and on bed size and station count, from compact four-station lines to long eight-station automotive lines.

Changeover speed is what keeps the machine economical, so a Die Change System system with a Moving Bolster rolls the whole die line out and a preset one in, clamped by Die Clamp units. The Part Unloader carries finished parts out on its conveyor. The Control System ties it together: the Line PLC times the cycle, the Servo Drive units run the transfer axes, the Die Protection Module module stops the slide on a mislocated part, and Light Curtain guards protect the operator. These machines run automotive body and chassis pressings, appliance panels, and large housings, the medium-to-high volume parts too big or too deep for a progressive die.