Mechanical Press Use & Care Guide

I. Proper Use of Mechanical Presses

The press is one of the basic equipment for stamping production. Whether it is used and operated correctly is directly related to product quality, production efficiency, the technical condition of the press, the service life of the mold, production costs, and a series of important issues such as personal and equipment safety.

To use the press properly, the following tasks should be performed at different times.

1. Preliminary Technical Preparation

(1) Be familiar with the stamping process procedures, prepare for production according to the stamping process card, and guide production.

(2) Remember the safety production norms, regulations, and rules for stamping.

(3) Understand the structure, performance, and technical parameters of the online press.

(4) Before stamping operations, organize the environment around the press, and lubricate at fixed points, with fixed quality, at fixed times, and in fixed quantities.

(5) Clarify the functions and operation adjustment methods of various switches, buttons, indicator lights, and meters.

(6) Before starting, check for any abnormal conditions in the press, such as whether the positions of various knobs are correct, and whether the position of the feeding device is correct. The clutch must be in a non-working state before the motor is started.

(7) The slider can only be started after the motor flywheel reaches the rated speed.

(8) If the motor does not rotate when the start button is pressed, immediately press the stop button to prevent the motor from burning out.

(9) The installation and adjustment of the die should be carried out by a dedicated adjuster, stamping technician, or a qualified senior stamping worker. Small and simple structure dies can be adjusted under the guidance of the above-mentioned adjusters and qualified personnel. The closing height of the press must be greater than the closing height of the die.

Also, measure the closing height when the slider is at the bottom dead center. When adjusting the die on a press without a fine-tuning device, control the number of operations to prevent the clutch and brake from overheating. Use a torque wrench for die installation and adjustment.

(10) Before starting stamping operations, run the press empty for 5-10 minutes to check for any abnormal sounds. Start production only after confirming normal conditions.

(11) The installed and debugged die can only be handed over to the stamping worker for production after the trial-stamped parts pass inspection. Stamping workers must be trained before taking up the post and operate the stamping machine with qualified certification.

(12) Stamping workers should operate fixed machines at fixed positions, so they can familiarize themselves with the structure and master the operation techniques. This also facilitates cleaning and maintenance according to the structural characteristics and tonnage of the press. They should purchase and make complete sets of handheld tools as needed, such as hooks for removing workpieces from the die, feeding tongs, and cleaning scrapers.

(13) During stamping, materials, dies, and equipment all need lubrication. Stamping workers should know in advance that different lubrication objects require different lubricants and lubrication methods. They should understand the lubrication methods, tools, and containers in advance. Some lubricants need to be prepared by themselves, so they must know the lubricant formula and preparation method.

(14) During stamping, workers should conduct self-inspection of the stamped parts, so they should be equipped with basic measuring tools: steel rulers, vernier calipers, feeler gauges, etc., and know how to use them.

(15) Wear personal noise protection devices, such as earplugs and noise-canceling hats.

2. Key Points for Stamping Workers During Production

(1) Fully understand the technical requirements of the stamped parts and the quality indices given in the drawings. Master the key points of processing the stamped parts. Check whether all equipment, dies, and materials meet the requirements according to the stamping process card and ensure the production of qualified stamped parts.

(2) If strip material is used, manually feed the material after cleaning the surface, measure the strip dimensions, and ensure no positive deviation in the width of the strip material. Remove burrs from sheared strips in advance. The strip surface should be free of rust, dirt, and unevenness. If conditions permit, level the strip before stamping.

(3) The operator must not leave the workstation, must stay focused, and constantly monitor the press operation. If a malfunction is detected, stop the machine immediately and start troubleshooting.

(4) The material must not be fed crookedly or overlapped, and there should be no debris, rust, or scrap between the upper and lower dies.

(5) Special care must be taken to protect the working surface, sliding surface, and protective devices of the press, such as ladders, railings, and guards. Protective devices must not be moved or removed arbitrarily.

(6) Check whether the oil supply at each lubrication point is adequate and whether the vernier or oil level indicator is within the specified range. If abnormal sounds, smells, or gauge readings (such as oil pressure, air pressure, current, etc.) are detected, stop the machine immediately and have a maintenance worker inspect and repair it.

(7) When reverse operation is needed, wait until the motor has completely stopped before reversing. Do not reverse while the flywheel is rotating.

(8) Regularly check whether the bolts fastening the die are loose, and tighten them with a torque wrench.

(9) All buttons and switches must be operated correctly. Do not press switches with wooden sticks or iron blocks, and do not kick manual buttons with your feet.

(10) After replacing the friction block (piece) of the clutch, control and reduce the number of single strokes.

(11) If the slide stops and the downward distance is too large (braking angle is large), have a maintenance worker adjust the brake to prevent personal and equipment accidents.

(12) During production, the stamping worker must self-inspect the stamped parts without stopping the machine and observe the operation of the press. If any abnormality is found, stop the machine immediately.

3. Work to be done after production stops

(1) Check for any scratches on the sliding surface of the press.

(2) Keep the press tidy and clean regularly.

(3) Check the technical condition of the die and any existing problems to determine if sharpening or repair is needed. If the technical condition of the die is poor, record the problems in the plan and repair sheet, and fill out the die life card.

(4) If the technical condition of the die is good and no sharpening or repair is needed, clean it, apply anti-rust oil, attach the last stamped sample, and fill out the stamping record and die life card before sending it to the mold library.

(5) Take the last stamped workpiece, attach the stamping part drawing, stamping process card, and production plan task sheet, and send it to the inspector. Wait for the inspection report to confirm that the stamped workpiece is qualified, check the technical condition of the die and any existing problems, and draw a conclusion before removing the die.

(6) Sort and send the stamping scrap frame and punching waste to the scrap library according to the categories and grades of steel and non-ferrous metals.

(7) For stamped parts that need to be processed in the next sequence, transfer them according to the production dispatcher’s instructions or the process route shown on the process card, or send them to the semi-finished product library.

II. Troubleshooting of main components of mechanical presses

Mechanical presses in poor technical condition should be stopped for inspection to promptly detect and quickly eliminate problems, avoiding small faults from developing into major equipment accidents, causing greater losses and affecting production.

There are many types of presses with different structures, and the faults that occur during production are also varied. Here, only some common fault phenomena, causes, and troubleshooting methods of typical structural components are provided. Common faults of the key clutch are shown in Table 1. Common faults of the friction clutch are shown in Table 2. Common faults of the slider mechanism are shown in Table 3. Common faults of the drawing pad are shown in Table 4.

Table 1 Common faults of the key clutch

Table 2 Common faults of friction clutches

Table 3 Common faults of the slider mechanism

Table 4 Common Failures of Deep Drawing Pads

III. Proper maintenance of mechanical presses

New mechanical presses from the factory are strictly inspected according to national standards and higher enterprise standards. To maintain the factory condition of the press for stamping and extend its lifespan, proper maintenance is required after the new machine is put into production.

Under normal circumstances, Chinese-made mechanical presses are used online for about 10 years before the first major overhaul. After the overhaul, the press loses its factory technical condition and precision. If the press is to continue in service, it can only be used at a downgraded level. Routine primary maintenance of the press is generally carried out by stamping workers in collaboration with professional maintenance electricians and machinists, with the main items listed in Tables 5 and 6.

Table 5 Primary maintenance of open presses

Table 6 Primary maintenance of closed press

IV. Maintenance and troubleshooting of medium and large closed presses

Closed presses, especially multi-point closed presses, are large and medium-sized modern stamping equipment on the outer covering stamping production lines in the automotive industry (mainly car manufacturing). They have complex structures, complete functions, and a high degree of automation.

Among them, the multi-link closed four-point mechanical press not only has a multi-link transmission system but also is equipped with a hydraulic unloading safety device with pre-selected tonnage. The workbench is a semi-automatic mold change trolley, and the upper and lower molds use electric or hydraulic clamping devices. The lubrication system uses a PLC-controlled quantitative oil supply system, and the drawing pad system uses a pure air type.

This type of high-tonnage, advanced design press has a stamping frequency of 3.2 times/min on the production line. With three shifts and continuous production without stopping, it works 22.5 hours a day, with 4320 stampings per day, and an average downtime rate of less than 5%. After 5 million stampings, and up to a maximum of 12 million stampings, various faults begin to appear in this type of press, necessitating necessary repairs. See Table 7 for details.

Table 7 Common Faults and Troubleshooting Methods for Multi-Link Closed Four-Point Presses