Bolster extensions are roller platforms at the front or back of the press bolster. A forklift sets the die on the rollers, and the die is pushed into the die space over the die lifters. They bring quick die change to presses that don't have a die cart.
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How Bolster Extensions Work
Bolster extensions maximize efficiency in quick die change when fork trucks are used to transport and load dies. The die is staged at the front or back of the press with a fork truck, then pushed into the die space over the die lifters in the bolster. Sub-plates under the lower die are required so the die can ride on the rollers.
Green Valley describes them as a platform for depositing and aligning the die before it is moved into the press, giving low-friction transfer and bridging the gap between the press and rail-bound die carts or shuttles. They are usually supplied in pairs. Lift-off and folding models come off or fold out of the way between die changes.
Green Valley calls them bolster extensions. Pascal calls its equivalents pre-rollers and also builds a portable pre-roller stand. The lifters inside the press are covered in the die lifter guide, and the full changeover in the quick die change guide.
Equipment That Works Together
Green Valley Bolster Extension Styles
Built to the press, the dies and the layout. Green Valley's gallery runs from 2,500 lb to 30,000 lb, and any design can be built for more or less capacity.
| Style | Capacity shown | Features |
|---|---|---|
| Lift-off (hanging) | 2,500 to 6,000 lb per pair | Hang on press-mounted brackets and lift off between changes. Inline gravity rollers; 11" to 40" long; gravity die stop; extra support leg on heavier pairs. |
| Press-mounted | 4,000 lb per pair to 30,000 lb | Stay on the press. Adjustable support leg and fail-safe gravity die stop; heavy units add side guide rollers and high-capacity die rail rollers. |
| Folding | 4,000 to 10,000 lb per pair | Bolt to the press through a flange and fold or pivot against the press when not in use. Support leg and gravity die stop. |
| Swing or fold-over with lock | 8,000 to 15,000 lb | Swing-type frame or fold-over pivot that locks in place, with high-capacity rollers and a support leg. |
Examples from Green Valley’s bolster extension gallery; “per pair” where Green Valley states it. Green Valley die tables can also carry folding or swing-away bolster extensions.
Pascal Pre-Rollers and Pre-Roller Stands
Pascal's pre-rollers mount on a block at the edge of the bolster. Each is rated by allowable load per pre-roller, and the rating drops as die travel gets longer; choose enough pre-rollers that the allowable load times the quantity is greater than the die weight. Pascal recommends removing pre-rollers during stamping, because press vibration can damage them, which is why the removable and folding styles exist.
Pascal recommends the pre-roller stand when the die weighs over 2 tons, is wider than 1,300 mm and travels more than 1,250 mm. Pascal's operating conditions for pre-rollers are a die loading speed under 50 mm/s and a transfer speed under 100 mm/s. Ratings are from Pascal's published pre-roller catalogs; confirm them with PRI when you quote.
How to Choose Bolster Extensions
- 1Die and sub-plate weightAdd up the die and sub-plate weight. Extensions are rated per pair and pre-rollers per unit; the total rating must exceed the die weight.
- 2Front, back or bothDecide where dies are staged. Extensions at the front and the back let the old die go out one side while the new die waits on the other.
- 3Die travelMeasure how far the die travels from the extension to its place on the bolster. On pre-rollers, longer travel lowers the allowable load.
- 4Mounting and storageLift-off and detachable units come off between changes; folding and swing units stay on the press and fold out of the way. Note anything near the bolster edge a folding unit must clear.
- 5Match the liftersRoller height has to meet the die lifters in the bolster, and the sub-plate has to cover the rails. Plan lifters and extensions together.
- 6Consider a stand, table or cartFor heavy, wide dies with long travel, a portable pre-roller stand can serve several presses. Where forklift staging is slow, a die table or die cart may fit better.
A bolster drawing answers most of these:
- Press make, model and tonnage
- Bolster drawing: size, edge details, T-slots and height from the floor
- Die and sub-plate weights and footprints
- Die travel from the bolster edge to the die position
- Front, back or both sides
- Lifters in the bolster today (type and roller height)
- Lift-off, folding or fixed preference
- How dies are staged: forklift, crane or cart
Bolster Extension Brands PRI Offers
Help From PRI
PRI's Application Engineers check the bolster, the lifters and the dies, then size the extensions or pre-rollers and how they mount. PRI coordinates installation with the manufacturer and stays your contact for parts and support afterward. See PRI services.
Frequently Asked Questions
What is a bolster extension?
A roller platform or arm mounted at the front or back of the press bolster. The die is set on it with a forklift, aligned, then pushed into the die space over the die lifters in the bolster.
Do I need sub-plates to use bolster extensions?
Yes. Sub-plates under the lower die are required so the die can ride on the extension rollers and the lifters in the bolster.
What is the difference between a bolster extension and a pre-roller?
They do the same job. Green Valley calls its units bolster extensions; Pascal calls its roller arms pre-rollers and also makes a portable pre-roller stand.
Can bolster extensions stay on the press while it runs?
Pascal recommends removing its pre-rollers during stamping, because press vibration can damage them. Lift-off, detachable and folding designs let you remove them or fold them out of the way between die changes.
How much weight can bolster extensions hold?
Green Valley's gallery runs from 2,500 lb per pair to 30,000 lb, and it builds to the capacity you need. Pascal rates pre-rollers per unit: up to 25 kN (about 5,600 lbf) for its standard types and 35 kN (about 7,900 lbf) for the heavy-load PRC, depending on die travel.
Related Guides
Quick Die Change · Die Lifters · Die Carts · Die Storage Racks & Tables · Die Clamps
Send us your bolster drawing, die weights and how you stage dies. PRI will recommend the extensions or pre-rollers and quote them.
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