Planning for Machine Setup Time
Operators need to plan ahead and devote time to stripping, cleaning and storing one set of rolls, then and loading and adjusting another set. The intensity and length of time dedicated to machine setup can vary based on the organization of the roll storage facility, the experience and awareness of the operator, and easy access to crane or hoist services when needed.
Tooling Time Requirements
The 1½” and 2” spindle mills that are changed over by stripping the rolls from the ends of the shafts can be setup in about 15 minutes per pass, both driven and idle. The 2½” and 3” mills require about 20 minutes per pass.
Additionally, if a cutoff is involved, about 15 minutes is needed to remove and replace the die, excluding any internal die changes. Length changes, which involve a mechanical method of length control, may require repositioning the cutoff target and, roughly, 5 to 10 minutes of time. If a system has an electronic method of length control, changing product lengths and or hole patterns can be accomplished on the fly, so halting the roll forming operation may not be necessary.
For a roll change in a large, wide (6” diameter x 60” wide) mill wherein roll and spindle assemblies are removed through the top of the housing and replaced with pre-assembled rolls and spindles, machine setup will require about 30 minutes per pass.
Cutting Down Machine Setup Time: Rafted Systems
In the situation where rafted roll formers are employed, the roll stand and tooling is mounted on a plate, typically referred to as a ‘raft’ or ‘cassette.’ The complete raft unit is removed and a second set of rafts with tooling in place are mounted on the machine. Though this setup requires greater capital investment, the changeover time is much faster and the operator does not need to physically remove or adjust the roll tooling.