1. Knocking appears during press operation.

     The reasons of the knocking can vary from wear-out of bronze bushings to screwing off the ram cushion pins. It is required to check tightening of cushion fixing pins periodically. The wear of bronze bushings and inserts is checked by lifting the ram by hydraulic jack.

     Knocking can also appear due to enlarged clearance in press slides. Overall clearance of slides should be in the range of 0.05-0.1 mm. Decreasing the clearance leads to heating and seizing of ram slides.

        2. Heating of sliding bearings located in shaft supports and drive shafts of the press.

     Heating of sliding bearings shows the lubrication system disorder – the lubrication is not supplied, work must be terminated till the problem is solved. Mechanic, who is taking care of the particular press should periodically check the sliding bearings- he should touch the covers.

        3. Problems of clutch and press brakes.

    All presses which are used In India have either separate or rigidly constructed clutches of dry friction brake. Clutch and brake start up is controlled pneumatically. Press clutches and brakes are designed for the work at the pressure of 4-4.5 bar, if you use bigger pressure it shows incorrect work of brake or clutch. Malfunction of clutch and brake switch manifests unstable ram stoppage in top position.

     It is important to follow the plant-manufacture recommendations regarding installing the valves of clutch and brake pneumatic control. All presses are using pneumatic regulators model U7122 or seldom U7124 (these regulators are almost the same, except supplying hole diameter, all other components are completely interchangeable ). These regulators are usually being changed because of unstable work, but this is not always correct. The regulator structure is very simple. 90% of all disorders are connected with control valves malfunction. We recommend installing control valves make “CAMOZZI” - the valves in general shows very good work capability – no one failure during a year. When using other valves, they should be chosen according to the air consumption ratio and not pressurewise. The regulator should be placed as close to the brake as possible, as the pipeline makes additional resistance to the compressed air flow. Brake is operating from the compression springs so increasing the actuation time affects badly on the longlife of brake friction material.

     Presses produced in the end of 70th have so-called diaphragms in clutch and brake. Diaphragm material and roughness of the surface of the components susceptible to friction affect the long term service. Diaphragm lifetime is increased by using reinforced plate made from oil-resistant rubber.

     Defect of control unit

     There is defect of control unit which by mistake can be taken as defect of clutch and brake. During press operation the reliable fixing of control unit should be checked. This is manifested in unstable stoppage of ram in the upper position – upper dead point.

     Oil comes to the friction material of brake.

     The same can occur when oil comes to the friction material of brake. Oil entry should be avoided by placing extra oil collectors and oil reflector. Clutch disorders do not affect critically on the press operation –accidents occur very seldom. Wear of friction elements leads to ram stopping under pressure when flywheel continues rotation.

     and brake piston move adjustment

     For all clutches there is provision of clutch and brake piston move adjustment. Move of 2.5-3 mm is considered to be normal. Ram stoppage can be caused by belts slip, in this case flywheel stops. Special attention should be paid on ram stoppage during trial forging of new components as it can show press torsion moment overload. It is required carefully follow the recommendations of manufacture pointed out in press manual.

        4. Ram.

     Main unit of the press is ram which parts require constant attention. As the specific loads are very high only recommended materials can be used for repair. Press shafts are manufactured from steel 40 Cr (chromium) - preferably forged, with normalization and induction hardening on the depth of 1.5-1.8 mm, while repairing shafts the attention should be put on above. To repair these shafts false centers are to be produced for grinding large shaft diameter. Particular attention should be paid on crossing of shafts of small and large diameter. Bushings and inserts of bronze on ram unit of cold extrusion and coining presses are made of bronze mark Аl Fe Ni 11-6-6 (Al 10,5-11,5, Fe 5-6,5, Ni 5-6,5 rest Cu) usage of softer bronze will cause plastic deformation of inserts and sticking of bronze to the press shafts that will disable the press. If the press is overloaded this bronze gets destroyed –it crackles.

     In general Russian presses have good margin of strength of the basic components and indeed provide long service life. Hope that our recommendations will help you in your work. If you have any specific problems in your press maintenance we invite you to contact us and our experienced engineers will help you.

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