Efficient Operation of JH21 Power Press: Proven Techniques & Guide

This is a complete JH21 power press service manual that will guide you on how to properly install and operate the press.

Keep reading.

I Summary

1. Working Principle and Application of Punch Press Machine
2. Working Environment and Conditions

II Specification

III. Preparation before the operation

1. Construction and Adjustment of Principle Units
2. Frame
3. Driving Parts
4. CIutch and Brake
5. SIide
6. Hydraulic Overloading Protector
7. Pneumatic System
8. Lubrication

VII. Foundation plan

VIII. Installation and testing

1. Installation of Punch Press
2. Installation of Moto
3. Horizontal Adjustment
4. Installation of air pipeIine
5. Testing
6. Operation Preparation
7. Running Preparation
8. Operation Preparation
9. Start and Stop of Main Motor
10. Daily checkup
11. Maintenance and Safety

XII. Troubles and Remedies

XIII. Easy wearing Parts List

XIV. Attached Figures

• Figure 1 Product Structure
• Figure 2 Frame
• Figure 3 Driving Parts
• Figure 4 CIutch and Brake
• Figure 5 SIide
• Figure 6 Pneumatic schematic diagram
• Figure 7 Lubrication schematic diagram
• Figure 8 Foundation plan
• Figure 9 Front Main Shaft Bushing
• Figure 10 Back Main Shaft Bushing
• Figure 11 Connection bottom bushing
• Figure 12 Connection upper bushing

This manual aims at the main performance characteristic, operation notice. The Figures are only for reference. The products are based on real presses.

I. Summary

Working Principle and Application

The JH21-80Ton (800kN) Open Back Fixed Bed Punch Press operates using a longitudinal crankshaft and crankshaft rod mechanism. The crankshaft rotates through two-stage speed reduction from the motor, which drives the reciprocating motion of the slide.

The press features a closed driving system and a stable operation with the use of a pneumatic clutch and brake, allowing the slide to stop at any position.

This universal press is ideal for sheet punching and pressing, including cutting, punching, blanking, bending, drawing, and stretching, but not coining. The nominal pressure of the press is 800kN, with a normal pressure stroke of 4.5mm.

The user should choose the pressure force based on the pressure curve, ensuring that the working pressure and its crank angle do not exceed the indicated range to prevent damage to the press.

Working Environment and Conditions

In order to ensure normal operation of the press, minimize maintenance frequency, and extend its service life, it should not be used in environments with excessive moisture, corrosive gases, liquids, or explosive gases. The air pressure must be at least 0.6 MPa, and the voltage should be 380±38V with a frequency of 50±5Hz.

II. Specification

III. Preparation before Operation

To ensure the proper functioning of the punch press, the user should follow proper procedures and consider the following factors before operating the machine.

Rated Load Capacity:

The working load must be kept within the nominal pressure limit. The overloading protection prevents overloading caused by mis-punching or sheets of non-uniform thickness during the process. It is not advisable to use the press with random overloading, as this can easily damage the machine. It is important to calculate the working load before starting work.

Torque Capacity:

The punching force will change with the position of the slide. The user should follow the stroke pressure graph that shows this change.

Sticking:

Sticking can occur if the working pressure exceeds the rated torque. Additionally, the punch press machine will become stuck if load is applied before the clutch is engaged. This can damage the clutch, so if this occurs during processing, the punch press machine must be stopped immediately and measures taken to prevent it from happening again.

Eccentric Load:

As a general principle, eccentric loads should be avoided, as they can cause the lower surface of the slide and bolster to become non-parallel and result in uneven forces on the slide gib, affecting precision. If an eccentric load cannot be avoided, it should be done according to the figure of the allowable distance that the load center deviates from the bolster to ensure precision and safety.

Single Turn on Frequency

In order to ensure the best performance and prolong the service life of the clutch and brake, it is important to adhere to the recommended single turn-on time listed in the main specification of the punch press. Exceeding the single turn-on time can cause abnormal wear and failure of the clutch and brake. The recommended single turn-on time for this press is not more than 25 times per minute.

IV. Construction and Adjustment of Principle Units

Frame (Figure 2)

The frame of the punch press is made of high-strength steel and is welded. The slide moves back and forth within the gibs. The screw on the right side of the frame is used to adjust the clearance between the gibs and the slide. The adjustment of the knockout rod will cause the punched parts to be pushed down as the slide approaches the top dead center. However, care should be taken to prevent the stripper from touching the bottom of the slide knockout rod groove to avoid accidents. The bolster of the frame is the basis for precision measurements. It should maintain a smooth and flat surface to avoid damage from tools and cutting tools.

Driving Parts (Figure 3)

The main motor drives the flywheel through a V-belt and stores energy in the flywheel, which is then transmitted to the gear shaft via a friction clutch and brake. The gear shaft drives the large gear in the oil bath, which then drives the crankshaft to move the slide up and down.

To adjust the V-belt, first loosen the four locknuts and turn the four adjusting screws equally. Apply 2 kg of force to the center of the V-belt, which will bend to 10 mm to achieve the proper tension. Then tighten the four locknuts. The new V-belt will stabilize after being used for a few days, but further adjustments may be necessary. The V-belt should be kept in a cool and dry place and protected from light and oil.

When replacing the V-belts, first loosen the adjusting screws, remove the old belts, and un-install the clutch brackets. It is important to replace all belts with new ones. Using both new and old belts will reduce the service life of the belts due to different tensions. Old belts should not be mixed with new ones, and it is important to note that belts of the same nominal dimension may have length variations of several centimeters. Belts in the same group should be the same length.

For automatic operation, the user can attach the auto feeder to the output shaft of the frame face (the output shaft is a special order and not included in ordinary products).

Clutch and Brake (Figure 4)

This punch press is equipped with a pneumatic friction clutch and brake, which is located inside the frame. (Please refer to the clutch manual for more information.)

Slide (Figure 5)

The slide is a critical component of the press and its precision directly affects the precision of the press.

This JH21 punch press features square hexagonal long gibs that provide good precision and stability.

The connection rod and ball-head screw are components that convert rotary motion into reciprocating motion.

The lower end of the ball-head screw is in contact with the ball-seat, which houses the hydraulic overload protector.

In the event of an overload, the protector will quickly release the oil in the hydraulic die cushion, send out an electric signal, and cause the press to stop immediately, ensuring the safety of the die and the press.

Once the issue has been resolved and the slide returns to the top dead center, the hydraulic die cushion will automatically rebuild the pressure, allowing the punch press to resume operation.

Users can adjust the die height. For instructions, please refer to the relevant electrical part operations in the service manual.

There are shims in the connection rod and cap. Over time, the clearance between the crankshaft and bushings may increase.

Users can remove shims to adjust the clearance between the crankshaft and bushings. (Normal clearance: 0.08-0.13mm)

4.1 Clearance Adjustment between Slide and Gibs

The distance between the slide and gibs must be appropriate to ensure smooth and reliable operation of the slide. If necessary, follow the steps below to adjust it properly:

(1) Loosen the screws on the gibs and the set screws on the right side of the frame.

(2) Adjust the left side gibs and tighten the screw.

(3) Adjust the right side gibs, and determine whether to add or remove shims based on the clearance.

After adjustment, tighten the front screws and the set screws on the right side.

(4) The clearance between the slide and gibs should be 0.03 to 0.05mm, but the total allowable value of front and back contact surface clearance should be 0.04 to 0.08mm.

Typically, the clearance between the upper and lower ends is greater. The measurement is accurate when the depth of the thickness gauge is over 30mm.

Note: The 0.03mm gauge should be in, the 0.05mm gauge should not.

(5) After the adjustment, check the clearance of each part and adjust again if needed.

4.2 Slide Knockout Device

The knockout force is 5% of the nominal pressure.

4.2.1 Structure of Slide Knockout Equipment

(1) It is composed of the knockout rod, knockout seat, and knockout bar.

(2) The knockout bar is located above the central line of the slide, crossing the slide.

(3) When the slide rises, the knockout bar touches the knockout rod, ejecting the punched parts.

4.2.2 Operation and Adjustment of Slide Knockout Equipment

(1) Unscrew the fixing screw of the knockout rod and adjust the knockout rod to the proper position. Note that the knockout rods on the left and right sides should be at the same height.

(2) After adjustment, tighten the fixing screws.

(3) The touch of the transverse bar and slide may cause noise when using the knockout bar.

4.2.3 Notice

When changing the die, make sure to raise the knockout rod to its highest position before adjusting the height of the slide to prevent striking the knockout rod during die height adjustment.

Adjust the position of the knockout bar so that the material is pushed when the slide moves close to the top dead center.

However, do not let the knockout bar touch the bottom of the knockout slot to avoid accidents.

4.3 Counter

The counter, which is installed in the electric panel, is used to keep track of and display the cumulative number of strokes.

The counter will record a count of 1 each time the slide moves up and down.

If resetting is required, press the reset button.

The counter can be used to calculate production output.

4.3.1 Panel of Counter

4.3.2 Operating Method

(1) Turn the switch to OFF and the counter will not function.

(2) Turn the switch to ON and the counter will function.

Note:

When resetting the counter, the slide must be stopped in the top dead center. If the counter is reset while the punch press is still in operation, it may damage the counter.

Hydraulic Overload Protector

The hydraulic overload protector can automatically detect the oil pressure of the slide’s oil hydraulic cylinder. If the pressure is insufficient, it can quickly supply pressure to maintain normal operation. In case of an overload caused by mis-punching or uneven sheet thickness during the process, the protector can unload immediately to protect the accessories and die from damage. The hydraulic overload protector is comprised of a pressurized cylinder, a pressure relief valve, and an inductive switch.

5.1 Preparation before operation of Hydraulic Overload Protector

• Check the oil level and ensure that there is enough oil in the air pump. If the oil level is low, loosen the screw of the pouring port and add antioxidant pickling hydraulic oil (ISO VG-32) or other hydraulic oil with similar performance.

• Ensure that the air gauge is normal.
• If the slide stops at the top dead center, press the reset button, and the air-operated pump will start working. After about 1 minute, the oil pressure will reach the specified value and the air pump will stop.
• If the slide does not stop at the top dead center, please follow the following procedures:

① Set the operation mode to “INCH” stroke.

② Use the operation button to inch the slide to a stop at the top dead center. (Be careful of the working height of the die for safety if it has been installed)

③ Once the slide reaches the top dead center, press the reset button, and the overload protector’s air pump will start working. After about 1 minute, the pressure will reach the specified value, and the air pump will stop automatically, and the overload indicator light will turn off.

④ The punch press can now be used in single or continuous operation modes.

⑤ The preparation for operation is now complete.

(6) Air Elimination of Oil Pressure Cushion in the Hydraulic Overload Protector

If there is air in the oil pressure cushion, the function of the hydraulic overload protector may not work properly and cause the air pump to run continuously.

To eliminate the air:

① Stop the slide at the top dead center.

② For safety, turn off the main motor. Wait for the flywheel to come to a complete stop. Then, use a hexagonal spanner to loosen the screw of the oil drainage hole on the hydraulic overload protector, allowing the oil to flow out.

③ If the oil flows out in a broken or bubbly manner, it indicates the presence of air.

Once the oil stops flowing out in a broken or bubbly manner, tighten the screw of the oil drainage hole. Check for any gas leaks from the joint between the pump and end plane of the oil box and ensure that the oil pipes are not leaking.

④ Air elimination is complete.

(7) Reset of Hydraulic Overload Protector:

If the punch press overloads, the overload indicator will light.

Operate it according to step (5) of the procedure.

5.2 Maintenance of Overload Protector

(1) Check for gas leaks in the tube connecting to the safety valve on a regular basis.

(2) Clean the oil filter periodically.

(3) Regularly check the tightness of the connecting part bolts.

(4) Check the oil level in the box regularly.

(5) Check the functioning of the electromagnetic valve periodically.

5.3 Common Failures and Trouble Shooting of Hydraulic Overload Protector

V. Pneumatic System (Figure 6)

The solenoid valve is the main execution component and has a self-control function. If one valve does not work properly, the other valve will release air, causing the clutch to disengage and the slide to stop, ensuring the safety of people and the press. The air source pressure should be between 0.55 to 0.6 MPa, and it is important to adjust it to the specified value. The lubricator should maintain a certain oil level, and the gas filter and air reservoir should frequently be drained of water and contaminants.

Air Consumption of Punch Press and Compressor

JH21-80 clutch air consumption: 0.18 m3/min. It is recommended to choose a 0.3 m3/min compressor for a single press.

Notice:

(1) When adding oil to the lubricator, the air pressure in the pipeline must be released to prevent an accident.

(2) The pressure of the counterbalance cylinder and the weight of the upper die can be adjusted according to the following figure. The maximum allowable working pressure of the counterbalance cylinder is 0.8 MPa.

(3) The electric relay interlocks with the electric circuit. If the pressure is too low, the circuit will not function. The pressure relay has been adjusted prior to being shipped from the factory; it should not be adjusted randomly.

VI. Lubrication (Figure 7)

The punch press machine adopts both intermittent automatic lubrication system and manual oil lubrication. The oil is pumped to all lubrication points through the oil-promoting distributor. The flywheel rolling bearing, rotating joint, and air cushion are lubricated using an oil gun.

The lubrication system is crucial to the crankshaft press. It reduces the wear and tear of accessories, increases the service life, ensures precision, and reduces power consumption and maintenance costs. Therefore, all parts in relative motion must be lubricated, except for the friction surface of the friction clutch and brake.

When operating the press, it is important to monitor the lubrication effect to avoid oil way blockages and to prevent the main bush, connecting rod bearing, and slide gibs from overheating and becoming damaged. The temperature should not exceed +70°C and should not be below -35°C. If the temperature rises, the punch press machine should be stopped immediately. The temperature of the main motor should not exceed +60°C (measured on the cover of the motor).

The lubrication oil in the gear case should be replaced for the first time after 3 months (approximately 750 hours) of use, and then every 6 months (approximately 1500 hours) thereafter. The gear case should also be cleaned every 6 months.

The lubrication of the flywheel bearing and drive shaft bearing is enclosed and should be filled with grease before assembly. The lubricating grease (3# lithium grease) should be refilled once every 2 months and checked every 6 months. When filling the grease into the bearing, fill 60-70% between the flywheel and the bearing.

The counterbalance cylinder uses both air lubrication and oil hand gun lubrication. To ensure the lubrication of the ball screw and ball seat, 100ml of 20# oil should be added before testing after installation. The lubricator should be filled with 20# oil and checked every week.

Note: Lubrication and oil changing should follow the lubrication directions indicated on the press.

Lubrication during Operation:

First, turn on the main motor and wait for 5 minutes for the lubrication pump to start working. Then, start operating the press.

When the press has been idle for 24 hours, the main motor should run for 10 minutes before starting production.

Lubricating Oil Reservoir:

Check the lubricating oil reservoir daily and refill as needed.

During the initial installation period, more oil is required and it should be refilled promptly.

Manual Lubrication:

Power must be turned off when lubricating manually.

Oil Replacement:

When replacing oil, it is necessary to thoroughly clean the interior of the oil reservoir and tubes.

Lubricating chart:

VII. Foundation plan (Figure 8)

Preparation before construction

1.1 Excavate according to the foundation plan.

1.2 If the soil is soft, pile driving must be done to reinforce it. (The soil pressure should not be less than 8 ton/m²)

1.3 Place rubble on the bottom to a height between 100mm and 200mm.

1.4 Leave holes in the base when pouring concrete.

• Prepare the concrete according to the foundation plan.
• After the concrete dries, remove the wooden sheet.
• When installing the punch press machine, assemble the press machine, anchor bolts, and horizontal adjusting plate in the pit. After adjusting the punch press horizontally, fill the concrete into the anchor bolts pit.
• Allow it to dry and then make repairs.

(1) Customers should prepare the footplate around the punch press machine using appropriate materials.

(2) If shockproofing is necessary, a layer of fine sandstone about 150mm wide should be added around the foundation.

VIII. Installation and Testing

Before adjusting the press, it is important to thoroughly understand its structure.

Installation of press:

Please prepare the foundation according to the foundation plan. If the soil is soft, reinforce it properly with iron reinforcement.

Once the press arrives at the factory, place it in a dry area for several days to check the electromotor and transformer before starting the installation process.

The punch press machine is coated with rust-preventing oil during transport, so be sure to wipe it off before installation. Pay special attention to cleaning the oil from the surfaces of the gibs and friction surfaces.

Measure the levelness of the press using a precision leveler, and fix the foundation bolts only when the level meets the required standard.

When adjusting the press, note that the levelness should be 0.3/1000 mm. Confirm that the bolster is fixed before measuring the levelness.

If the users opt to install the bolster themselves, they should ensure that the interface between the bolster and working table is clean and free of debris such as paper, metal scraps, gauges, washers, and dirt.

Installation of motor

The main motor is typically installed on the punch press machine. In case it has to be disassembled during transportation, it should be reinstalled as follows:

• Unpack the package and inspect for any damaged accessories.
• Clean the motor, belt pulley, flywheel groove, and bracket. Avoid getting any liquids on the electromotor. Clean the V-belt using a cloth and not a cleaning solution.
• Mount the motor to its joint position, but do not fully tighten the screws. Make sure to support the weight of the motor with a sling before tightening the screws.
• Align the reference line of the belt pulley groove and the flywheel groove, and correctly position the motor.

Note: Avoid letting any liquids come into contact with the electromotor.

If the reference line of the belt pulley groove and flywheel groove are not aligned, it may cause damage to the belt groove and motor bearing.

After aligning the reference line, tighten the screws of the motor bracket.

Move the motor to the flywheel and ensure that the V-belt does not have excessive tension when it is placed in the block.

Note:

Do not force the belt into the groove.

After installation, the belt tension should be about 10mm when pressed with the thumb.

Horizontal Adjustment

The levelness of the bolster is very important, and most presses come with a bolster. Before measuring, ensure that the screws are tightened. Begin by cleaning the bolster and placing a precision level gauge on the front, middle, and back of the bolster. Shims may be used to adjust the levelness of the frame.

Note:

① The shims must be large enough to ensure that the foot of the press bears weight evenly on the interface.

② Check the levelness after one month. If any errors appear, readjust the levelness. Check other items every six months and ensure the levelness of the press to maintain its performance.

Installation of air pipeline

The air line should be connected to the back of the press, with a required air pressure of 0.6 MPa. However, the distance from the air source to the press should be no more than 5 meters and the diameter of the pipeline should not be less than 1 inch. Ensure the channel is cleaned of dust and debris.

Testing

After installation, check the precision according to the certificate. During transportation, jostling and vibrations may affect the precision, so it may need to be adjusted. The punch press can only be used once the precision is correct. Before starting the press, clean any grease and dirt, especially the surfaces of the gibs and friction, and select the appropriate operating procedure based on the work requirements and prepare necessary tools. After installing the die, use an inch stroke and gradually move the slide to the bottom dead center.

Special Notice:

Do not let the dies collide with each other, and adjust the height of the dies manually.

After adjusting the dies, do not start single or continuous stroke.

Adjust the position of the knockout bar to allow for part ejection after the slide stroke has stopped (near top dead center).

However, when the slide moves to top dead center and the knockout bar is pushed to the bottom, be careful not to touch the bottom of the knockout bar groove and disturb its movement.

After adjustment, use inch stroke and progress step by step.

The single and continuous stroke can be performed once there is nothing preventing the press from functioning properly.

The air pressure of the punch press should be between 0.55-0.60MPa, and the maximum pressure of the safety valve should be 1MPa.

IX. Operation Preparation

Running Preparation

(1) Turn the air switch in the main control box to the ON position and ensure that the punch press machine is functioning properly.

(2) Close the door of the main control box.

Warning: For safety reasons, it is forbidden to open the door of the main control box while the press is in operation.

Operation Preparation

(1) Turn on the switch on the operation panel, and the power indicator (AC110V loop) will illuminate.

(2) Verify that the “Emergency Stop” button is not engaged.

(3) If the pressure is not within the normal range, the indicator will turn off and the punch press machine will be in an Emergency Stop state.

Correct the air pressure to the appropriate value and operate the press until the indicator is illuminated.

Start and Stop the main motor

The following steps should be taken to start and stop the main motor:

• Press the start button, the main motor will start and the main motor indicator will light.
• Note: the main motor will only run if the mode switch is in the “OFF” position.
• To stop the main motor, press the motor stop button. The main motor will stop running and the indicator will turn off.

It is important to note that the main motor will automatically stop in the following scenarios:

• The loop fuse in the main motor blows out.
• The thermal relay is in the protection mode.

X. Daily Checkup

Initial Checkup:

• Clean the bolster and ensure that nothing is placed on it.
• Drive the flywheel using the barring rod.
• Ensure that the power cable specifications meet the requirements.

Check after Opening Air Valve

• The air pressure of the clutch should be within the specified range of 0.55-0.6MPa.
• Air leaks are not allowed.
• No air leaks should be present in the clutch cylinder or rotator joint.

Check After Power On

• Turn the switch to ON, and the indicators for power and pressure should light.
• Set the mode selection switch to the “inch stroke” position. Press and release the “two-hand” operation button, check the solenoid valve action, and ensure air release and flexible motion of the clutch without interference.

Check After Starting the Main Motor

• Press the start button and the main motor will run, and the indicator will light up.
• Verify that the rotation direction of the flywheel is the same as marked on the press.
• Check the start and acceleration speed of the flywheel.
• The sound of the V-belt slipping should be normal.

Running Check

• During Inch Stroke, ensure that the press operates smoothly and without any abnormal noises or heaviness. To do this, keep the two-hand operation button depressed.
• In Single and Continuous Stroke, the motion should be normal. In Continuous Stroke, press the emergency stop button to ensure the clutch separates and the emergency stop button can be locked.
• In Single Stroke, the press should not run continuously when pressing the operation button. The stopping position should be between +5° and -10° of the top dead center, and any deviation is not allowed.
• In Continuous Stroke, pressing the stop button should result in the stopping position being between +5° and -10° of the top dead center. Any deviation is not allowed.
• In Continuous Stroke, pressing the emergency stop button should result in the punch press stopping immediately.

Checking When Adjusting the Slide

• Turn the slide adjustment switch to ON, the operation will be prohibited.
• Adjust the height of the die. When the slide reaches the upper and lower limits, the motor adjustment must be stopped.
• Check if the die height indicator matches the actual value.

XI. Maintenance and Safety

Operate strictly according to manual and safety procedures:

The clutch should be engaged after the motor starts and runs at full speed.

Maintain good equipment grounding and check it frequently.

Turn off the power when the operator leaves the press.

The working load of the press should be within the safe range.

Do not operate the punch press if the safety device is not assembled.

Punching two sheets is strictly prohibited.

If the slide falls freely or strikes irregularly with noise, stop the punch press immediately and inspect it.

Check the air pipeline frequently. If an air leak is detected, repair it before operating the punch press machine.

For the sake of personal safety, it is forbidden to place any part of the body into the dangerous area of the die. It is also forbidden to work or perform maintenance in the dangerous area before taking safety measures.

The photoelectric protector is optional. The press has connection points for the photoelectric protector.

XII. Troubles and Remedies

XIII. Easy Wearing Parts List

XIV. Attached Figures

Figure 1 Product Structure
Figure 2 Frame
Figure 3 Driving Parts
Figure 4 CIutch and Brake
Figure 5 SIide
Figure 6 Pneumatic schematic diagram
Figure 7 Lubrication schematic diagram
Figure 8 Foundation plan
Figure 9 Front Main Shaft Bushing
Figure 10 Back Main Shaft Bushing
Figure 11 Connection bottom bushing
Figure 12 Connection upper bushing