Abstract: Explain the meaning and value of overhaul of die-casting machine, and explain in detail the whole process of die-casting machine repair, including pre-repair inspection, data preparation, parts preparation, disassembly process, installation adjustment and result verification. Explain the general precautions, key points, and difficult treatments, analysis and explanations during the overhaul of this type of complex equipment of the die-casting machine.

Keywords: die casting machine overhaul repair process

In die-casting factories, die-casting machines are generally the key equipment of a company, with high value and low substitutability. In order to ensure the normal operation and safe production of machine tools, the implementation of planned and preventive maintenance of equipment is an important part of industrial equipment management, and it is more important for die-casting machines.

Die-casting machine production environment is relatively poor, soot, lubricating oil, release agent water mist, coupled with high temperature, high humidity, machine tool wear and corrosion in this environment is much stronger than other environments (such as other machining machine tools), plus die-casting The machine produces 24 hours a day, daily maintenance and spot inspection maintenance, many times due to poor production, the design life of the die-casting machine is generally 12 years, 20-hour work system, it is precisely this kind of production has a greater impact on the surface of the mechanical structure. The internal quality, such as metal fatigue, stress, etc., has not reached the level of exchange, and the maintenance of the die-casting machine is very cost-effective.

Die-casting machine overhaul has a large workload and a long repair period. For the equipment itself, it is necessary to fully or partially solve, replace or repair mechanical parts, electrical parts, adjust and repair electrical systems, assemble and debug the whole machine, in order to achieve a comprehensive cleaning and overhaul Before repairing, restore the specified performance and accuracy, grasp the existing technical status of the equipment before repairing, make a practical repair plan, fully prepare for the technology and production, and actively adopt new technologies, new materials and Modern management methods, do a good job in technical, economic and organizational management to ensure repair quality and reduce repair costs.

Talking about the method and process of overhaul of die casting machine

1. Inspection and preparation before maintenance

1.1 Preparation of data before maintenance

Check the manual of the repaired model, PLC memory card, and other memory cards. In addition, whether the manual is consistent with the model, the date of machine factory serial number, the content of the manual, such as electrical control circuit diagram, program ladder diagram, hydraulic lubrication principle diagram, position diagram, mechanical structure and layout diagram, operation instructions and alarm table, etc. .
What are the maintenance changes during use and whether the data is recorded. Generally speaking, during the production and use process, there will always be maintenance and repair. Whether the results of these maintenance processes are recorded, especially whether the program changes are recorded in the manual, memory card Has it been corrected.

Check the wiring carefully, especially whether there is terminal identification for the changed wiring, whether the relay added by the change is defined, and if there is no identification, it is necessary to make the wiring clear later. On-site inspection and maintenance, there are many such situations, and special attention should be paid.

1.2 Appearance and defect inspection

Whether the appearance is clean, the die-casting machine has been working in a poor environment for a long time, and the surface of the machine tool has oil stains, aluminum chips,
How many parts are missing, what are the piping and wiring loose, broken, temporary treatment, etc., in the production operation of the die-casting machine, it is easy to miss the cover plate, the missing screw, and the switch of the operation panel to be damaged.

1.3 Gap check

Detection of clearance between moving template and large pole

The gap between the moving template and the large rod must be checked in the adjusted position first. The moving foot of the moving template can be adjusted in height, whether the large rod is in the middle of the bushing of the moving template (can be measured with a feeler gauge), in the upper and lower gaps In the case of balance, the gap between the moving template and the large rod is tested, and the measured value obtained is an effective detection of the wear of the large rod of the bushing. The detection position method is as shown in the figure:

Test data for recording

Analyze based on the above recorded values. Generally speaking, the copper sleeve of the moving template needs to be exchanged; the large pole is re-grinded and chrome-plated, and then the large pole is inspected.

1.4 Check the gap between the connecting pin and the bushing at the elbow

The gap between the LINK PIN and the bushing at the elbow part affects the clamping force of the machine tool, parallelism and noise during movement.
According to the figure, check the gap between the connecting pin of the mold opening and closing mechanism and the steel sleeve with a feeler gauge, and check four positions for each pin.

Check location map

Location map zoomed in

Connection pin clearance data:

When the connecting pin is checked, the mold opening/closing is in the no-load mold clamping state. As the equipment to be overhauled, it is generally required to exchange the steel sleeve of the connecting pin. When testing, pay special attention to whether the connecting pin is rotating during the movement. The single side of the steel sleeve has been worn through, which damages the ear hole of the template. If necessary, the pin must be removed for testing, which is related to the processing workload and quotation.

1.5 Other clearance checks

Crosshead guide rods and bushings, ejector guide rods and bushings must be checked and recorded, and exchanges are required under normal circumstances.

1.6 Mobile template, fixed template plane detection

In the use environment of the die-casting machine, the template plane is used for a long time with the same mold, and there is generally high temperature during use, or acidic release agent corrosion, the plane will be corroded and dented. Flying material, the casting pressure required for the product is greatly reduced, and the product will have quality problems. Whether the template needs to be processed, first check the flatness, and proceed according to the diagram. The detection position method is as follows:

After testing, perform data recording:

1.7 Pressure system inspection

Die-casting small machines generally use double vane pumps. Take the Toshiba DC350J die-casting machine as an example: the pressure value of the high-pressure low-flow pump PF1 is generally required to be 15MPA, and the low-pressure large-flow pump PF2 is 14.5MPA, if it is a medium-sized machine 500/650 /800, there is also a large flow pump PF3 with a pressure value of 7MPA, so that the machine tool can continuously and stably move the actuator. Under normal circumstances, when the pressure of the low-pressure pump reaches the set value of the load relief valve URG1, PF2 is relieved, and the overflowing hydraulic oil will be cooled by the cooler, plus other actions to return to the oil for cooling, so that the temperature of the operating oil is dynamic balance. If there is internal leakage of the seal or valve body in a certain position of the system and the system pressure cannot reach the pressure setting of the overflow valve, there will be no hydraulic oil overflow. The cooler has no cooling effect because there is no hydraulic oil entering, and the oil temperature rises. , The viscosity decreases, and the system pressure does not reach the set value, resulting in a vicious circle, causing the machine tool to work under extremely unstable conditions, resulting in an increase in product defect rate and even failure to produce. The system pressure is poor, generally speaking, the seal is poor, the internal leakage of pumps and valves must be handled properly, and the system pressure must be checked. The following is a brief description of the pressure system check:

1.8 Lubrication system inspection

Preliminary inspection of the lubrication system of the die-casting machine is time-consuming to check whether the lubrication point has a quantitative overflow.

1.9 Inspection of electrical components and wiring

Record the model of the missing part, whether the wiring needs to be exchanged, etc. for detailed records. In the process of using die casting machine, compared with metal processing machine tool, because of dirty, oil, moisture, high temperature and other harsh environments, the probability of causing accidents is higher.

1.10 According to the customer’s site and production management, make a detailed understanding of the injection performance of the die-casting machine. 

In normal work, what are the alarms of the die-casting opportunity, what problems are generated, what is the injection performance, especially the high-speed speed and the supercharging effect. What areas need to be improved, whether there have been any changes in the past, and so on. So that during the maintenance process, special targeted treatment can be achieved to achieve a targeted and improve maintenance effect.

1.11 Coordination of peripheral devices

Investigate the peripheral devices carefully to see if the peripheral devices are intact, whether the action is stable, whether there is any abnormal sound, whether the piping is deformed, the wiring is not exposed, or the ends are broken.

2. Based on the above inspection, negotiate with the customer to determine the maintenance plan and sign the contract

The main schemes determined are:

●On-site maintenance or factory maintenance.
●Adjustment of production plan and determination of maintenance schedule
●Contract signing (contract text, attachments to technical conditions, attachments to construction matters, etc.)

3. Preparation for maintenance

Based on the above inspection, the following preparations should be made

3.1 Parts preparation

Through the pre-maintenance inspection, the parts are scheduled to be exchanged. The parts have a procurement cycle. It is difficult to accurately and comprehensively reserve these parts. Therefore, you must check before the maintenance to be accurate and targeted.

3.2 Tool preparation

According to the maintenance plan, determine the required tools, including ordinary tools, special tools (such as steel sleeves, copper sleeves inserted into tooling), etc.

3.3 Preparation for hoisting and preparation for reinstallation of basic components

Determine whether the factory’s on-site driving is applicable, whether special relocation and hoisting tools are required, etc.
When reinstalling, the original installation basic components may not be usable, and the basic installation components must be prepared.

3.4 Processing preparation

Coordination of processing units and confirmation of processing capabilities, such as template processing, large rod repair, etc.

3.5 Transportation preparation

Both on-site and factory maintenance require transportation. After the weight is determined, contact the transportation vehicle.

4. Break down

4.1 Normal decomposition.

 Under normal circumstances, follow the steps and decompose step by step. Similar or the same parts in different parts must be recorded and marked so that the position of the parts can be clearly known during installation, and the installation is convenient and smooth. In the high temperature or corrosive environment of the die-casting machine, the nut is easy to be seized by corrosion, and some of the thread is damaged due to being smashed. It is very difficult to disassemble the nut. Some parts are difficult to decompose. There are some methods to spray the corroded nut. Appropriate loosening agent can be twisted by tapping lightly with a hammer.

Vibrate under the applied force, heat the nut with a blowtorch, make it expand by heat, and turn it quickly

4.2 Destructive decomposition

During the decomposition process, some nuts and screws cannot be decomposed at all after a long time trap. They may be destructively decomposed. Use a blowtorch to heat the nuts, make them expand by heat, and twist them quickly.

4.3 Parts re-inspection

Some of the decomposed parts are clearly unusable, and some need to be tested.

4.4 Re-preparation of parts

In the process of disassembly, it may be found that there are unscheduled parts that need to be replaced during the preliminary inspection. At this time, it is necessary to confirm all replacement parts. Taking into account the delivery date of the parts, the delivery time for machine tool repair may be delayed. This must be coordinated with the customer’s instructions. The requirement must be stated when the contract is signed.

5. Processing after decomposition

5.1 Template processing, die-casting machine in the use environment, the template plane due to long time use of the same mold, the mold is generally high temperature during use, or there is acidic release and corrosion, the plane will be sunken, if it reaches a certain level, it will appear. The phenomenon of flying materials, once the materials are flying, the casting pressure required for the product is greatly reduced, and the new product will have quality problems. In addition, due to the problem of the lubrication system, the lubrication cannot be supplied in time and effectively at the rotating or sliding parts, causing excessive wear, and even unilateral wear of the bushings, and damage to the template ear holes. Repairs must be made at this time. The repair method is generally increased Ear holes as large as a certain value (usually 5MM on one side), matching tolerances of inserts to connecting pins, tolerances of specific processing methods, and positioning base points, as shown in the figure:

6. Installation

6.1 The installation of mechanical parts must comply with the assembly process

Follow the assembly process and the possible conditions on the site are limited. The parts must be clean and clean; the copper sleeve and steel sleeve should be cooled with dry ice for 24 hours; the copper sleeve and steel sleeve should be installed with tooling, and carefully clean and check the lubricating oil hole.

6.2 Lubrication system installation

The lubrication system should be installed according to the original installation path, not easily changed, the hose hard pipe joints should be tightened, and the torque should not be excessive, because the diameter of the lubrication pipeline is relatively small and cannot withstand a large torque.

6.3 Installation of seals and valve body

Seals and valve body clean

7. Adjustment and inspection

7.1 Level detection

7.2 Inspection of the big pole and the mobile template.

Testing and recording as mentioned above

7.3 Adjustment and inspection of template parallelism

(Toshiba die casting machine DC350J as an example)

Precautions for this inspection: The measurement under no-load conditions can also be selected under the 10% clamping force standard.

7.4 Inspection of clamping force

The main detection maximum clamping force is generally more than 110%, the deviation range between the major rods does not exceed ±5%, and the standard mold base is required to be tested.

7.5 Inspection of tailboard swing

The tailboard swing is mainly due to the clamping force and the possibility of swinging.

7.6 Security Check

According to the safety checklist

The safety components of the main die-casting machine are effective, interlocked between actions, and the die-casting machine is interlocked with peripheral machinery, and the inspection items are recorded.

7.7 Lubrication system inspection

After starting the oil pump, check whether the lubrication pressure rise pressure, overpressure time, pressure relief time are within the allowable value range, whether the pipe joints are tight, the lubrication hard pipe hose and the fixed, whether there is any interference with the movable parts, especially check each lubrication Point quantitative overflow lubrication lubrication point.

7.8 Trial operation and casting

Before starting, confirm whether the water, electricity, gas, operating oil, lubricating oil, grease, nitrogen, release agent, punch oil (lubricating particles) of the die-casting machine are in place. After starting, confirm whether it is running, emitting, dripping or leaking

After installation, make an inspection report according to the checklist form before maintenance

7.9 Injection performance inspection

For a die-casting machine, the main set parameters and actual casting parameters are compared and recorded.

Low-speed speed, low-speed acceleration speed, high-speed, high-speed acceleration, high-speed range, deceleration, casting pressure.

7.10 Dynamic parameter check

Such as system pressure, operating oil temperature, ACC pressure, ACC pressure change, ACC filling time

8. Summarize,

 issue an adjustment report and related materials, record the above inspection results, form a table, prepare the materials, and deliver them to the customer.

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