Document KJJrL172zyw0xd01ZZbporoa0

COLD FORMING OF METALS spected at intervals determined by the type of service of the presses. Inspections should be quarterly or at the most semiannually for presses in frequent use A good sched ule is to inspect the dutch brake mecha nisms whenever the dutch bearings are lubricated. The unit should be inspected for loose bolts and nuts, broken parts, lubrication leaks, air leaks, faulty or loose lining, ex cessive accumulation of partldes on the friction lining, and broken springs The inspection should indude the action of the dutch and brake, both at rest and m motion. The travel on the friction disks will indicate the amount of wear Adjust ment should be in accordance with the man ufacturer's instructions It also is important that the brake be ad justed to stop the press on top center or within S degrees of top center, or as sjiecified by the manufacturer The dutch and brake should operate smoothly and engage and disengage quickly, with little or no coasting on die press slide when the brake engages In units with separate brakes, the brake and dutch must never engage simultaneous ly Sliding surfaces that maintain parts in alignment should be checked for excessive wear, to prevent parts from coclang or wedging Inspection of air friction dutch and brake units will readily disclose leaks in air cylin der packings and in air glands To increase the life of these packings, air line strainers, lubricators, and moisture traps should be used Traps and strainers should be checked frequently and foreign matter removed On air pressure regulators, the regulator dia phragm and air pressure gauge should be checked for looseness and malfunction Valves on air friction dutches and brakes are usually the solenoid-operated type and may be either direct acting or pilot operat ing Through constant use, the mounting brackets, operating levers, and mounting bolts may loosen To operate properly, the valves must be ngidly mounted Hammer ing of the solenoid magnet fidd surfaces or residual magnetism in the field may cause the solenoid to stick Inspection of air valves should include checking for Excessive scale or moisture in air lines. Damaged parts, particularly packings. Overiubncation or other improper lubricating practices Solenoid failure or damage Loose parts Incorrect piping Electric controls are not usually a part of dutch and brake units, but do affect opera tion. Pushbuttons, limit switches, relays, and contactors should be inspected for ex cessive wear, broken springs, loose parts, loose or broken wires, peened magnet field surfaces, badly burned contacts, poor con tacts, dirt, any of which may contribute to faulty operation Since redressing of con tact points produces only temporary benefit, faulty contacts should he replaced At inspection tune, all guards on power presses should be examined Guards not in good repair should be reconditioned or re placed. Pressure pads and die cushions should be checked for material between the pressure pad and the bolster plate, likewise for faulty air packings, air leaks, loose nuts or screws on die supporting rods or plates Metal Shears Squaring shears The knife head, on both foot and power operated shears, should be equipped with a guard which will keep the operator's fingers away from the cutting edge This guard should extend across the full width of the table and m front of a hold-down (Fig 23-39) The guard may be a fixed barrier at least % in. away from the shear and set not more than % in above the table, or it may be a self-adjusting barrier which will auto matically adjust itself to the thickness of the material to be cut, with a limit of % in above the table (Fig 23-40) The guard should be high enough so that the ojjerator cannot reach over it and under the knife The barrier may be slotted or perforated to allow the operator to observe the cutting edge of the knife, provided that the openings do not exceed % in The hold-down can be guarded either separately or as a part of the knife guard When helpers and take-away men work at the rear of the machine, the back of the kmfe should be guarded so that the men cannot get their fingers under it Chutes or 23-38