DUMMY BLOCKS

DUMMY BLOCKS

The dummy block is a critical element for extrusion quality and press performance. A dummy block is in direct contact with the billet. Therefore, its successful operation depends on several factors. The most important factor among them is its’ efficient interaction with a round, straight, thermally – and, therefore, dimensionally – stable container.

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RRB

Replaceable ring block for standard long stroke presses up to 100,000 psi. The combinations of the ring hoop strength and the yield strength of the mandrel and holder have been carefully designed. The ring expands to pre-determined size at a pre-determined pressure. It provides long-lasting dummy block elastic expansion and contraction.

RRB
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RRB

HPR

The HPR, high pressure ring block, is an evolution of the old favorite QEB, quick expansion block. The HPR has a similar expanding wear component. The full-length ring is relatively thin and of uniform thickness. It expands quickly, making it suitable for presses with rapid acceleration. The ring has an interference fit with the body or holder, which allows the pad to be very large. The large pad area reduces high pressure deformation.

HPR
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HPR

Marathon

This extra strong 2-piece block emphasizes quality of product plus length of operating life. The sturdy design provides excellent long elasticity life and rigidity.

Marathon
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Marathon

DUMMY BLOCKS

REPLACEABLE RING

RRB

Most wear naturally occurs at the front of the dummy block, on the outer lip of the shell. Castool provides an efficient and cost-effective expanding wear ring that is easily and quickly replaced. Most other components (holder, mandrel and wear ring) can be purchased separately. The economy of the replaceable ring block is soon apparent.
Replaceable ring block for standard long stroke presses up to 100,000 psi. The combinations of the ring hoop strength and the yield strength of the mandrel and holder have been carefully designed. The ring expands to pre-determined size at a pre-determined pressure. It provides long-lasting dummy block elastic expansion and contraction.

MARATHON (H-13 OR TUFF-TEMPER)

MARATHON

This extra strong 2-piece block emphasizes quality of product plus length of operating life. The sturdy design provides excellent long elasticity life and rigidity. Tuff-Temper is a patented steel developed by Castool. It has 3 times more Molybdenum than H-13. The amount of Molybdenum increases the yield strength from 156,000 psi to 165,000 psi, elongation from 6.5% to 8.5% and the ultimate tensile strength from 184,000 psi to 196,000 psi at extrusion temperature (800 oF).

This makes Tuff-Temper stronger and tougher for the dummy block. Tuff-Temper produces two times more carbides, so it has better wear property than H-13 as well. The single-use marathon dummy block has no replaceable parts and is not rework-able. It is simply replaced when it loses its ability to retract at the end of each cycle, and remains permanently expanded.

HPR

The HPR, high pressure ring block, is an evolution of the old favorite QEB, quick expansion block. The HPR has a similar expanding wear component. The full-length ring is relatively thin and of uniform thickness. It expands quickly, making it suitable for presses with rapid acceleration. The ring has an interference fit with the body or holder, which allows the pad to be very large. The large pad area reduces high pressure deformation.

The design features minimize plastic deformation and fatigue. This has been performed by optimizing all dimensions, angles and clearances using simulation and trials. Stresses have been distributed as evenly as possible between components and inside each individual component.

In the NEW HPR block, elastic recovery to original shape after each cycle is facilitated.

BAYONET COUPLING

Castool uses a unique bayonet-type coupling which locks the dummy block quickly and securely to the stem. This makes it much easier and faster to replace a very hot block than with a conventional screw-type or rod coupling. Castool uses a secondary stabilizing stud (behind the bayonet), to limit the amount of lateral movement of the block on the stem. The stabilizing stud can reduce the lateral movement from 0.7 mm to 0.2 mm.

STEM AND SPACER

SPACER

Existing stems can be adapted to the Castool bayonet system by attaching a spacer. The stem is cut and thread machined in the bore to accept the spacer stud. It is important that the stem and spacer faces match exactly, and that there are no gaps. A dowel pin must be installed on the diameter of the stem/ spacer to prevent rotation. If a gap develops between the stem and the spacer, the stud will then bear the full pressure of the ram, threads can foul and removal becomes difficult or impossible.

PURPOSE

  • Allow gases to escape during the combined process of billet upset, and burp decompression, reducing blisters
  • Maintain a minimal uniform skin of aluminum on the liner inner diameter reducing profile inclusions

FUNCTION

The function of the dummy block is the extension of the ram or stem, which pushes the softened alloy through the die. There are a number of functions that must be satisfied by an effective dummy block.

  • To repeatedly transmit the force of the ram, at high temperature, to the alloy
  • To expand to pre-determined size under load and maintain a secure seal with the container wall, leaving only a thin film of alloy on the liner
  • To separate cleanly from the billet at the end of the stroke
  • To contract immediately, and return through the container without stripping the film of alloy from the liner
  • To cause no gas entrapment that can result in blistering, or damage the face of the container and/ or dummy block
  • To compensate for minor press misalignment
  • To be quickly and easily removed and replaced
  • To function effectively until a production run is complete

BENEFITS

  • Reduce scrap, due to back end blisters and surface defects
  • Reduce cost of operation
  • Reduce downtime
  • Increase productivity
  • Increase operating life
  • Increase container liner life

With Dummy Blocks, Castool again sets a new standard of excellence in the extrusion industry.

Results may vary depending on individual press characteristics and setup.

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