The Fixed Dummy Block maintenance  

Fixed dummy blocks must be properly sized for the press and aluminum alloy being extruded, and they should expand and contract a fixed amount on each pressure stroke. Single cell ovens should be used to preheat the fixed dummy block, and, while in service, the dummy block can be kept at temperature by advancing the presses ram to bring the dummy block into the container whenever the press is stopped.

The fixed dummy block should be inspected daily. It should be visually checked for aluminum build up on the face and the land. The land should also be checked for evidence of explosions. The mandrel should be free and forward from the face of the dummy block.

Once each week, the dummy block should be removed from the press and cleaned in caustic. It should be visually inspected for signs of wear, and measured accurately across the face. The dimension should be recorded and compared to the diameter of the block when it was new, since the dummy block will eventually grow to take up a permanent set.

As the diameter of the dummy block increases, blisters will form on the extrusion. Machining the land to the original diameter can prevent these blisters and extend the dummy block’s life.