Practical Guide to Common Faults and Maintenance of Insertable Machines

As the core equipment responsible for the processing of internal keyways and irregular cavities in the mechanical processing workshop, the operational stability of the insertion machine directly affects the processing accuracy and production efficiency of heavy workpieces. Under long-term high-load operation, various faults are prone to occur in the mechanical transmission, hydraulic system and electrical control parts of the insertion machine. If they cannot be accurately and promptly identified and dealt with, it is very likely to cause the scrapping of workpieces, equipment shutdown, and even lead to safety accidents. Based on first-hand maintenance experience, this article systematically sorts out the frequently occurring faults, troubleshooting logic and standardized maintenance plans of the insertion machine, providing direct and practical operation references for the workshop operation and maintenance personnel.

Ⅰ. Mechanical transmission faults: Guardians of core precision

The mechanical part is the basic framework of the slotting machine. Long-term reciprocating impact loads are most likely to cause problems such as guide rail wear and excessive transmission clearance, which are directly reflected in the decline of processing accuracy.

1. Fault causes such as excessive surface roughness of the workpiece and uneven tool marks: Loose clamping or insufficient rigidity of the tool holder, resulting in slight swinging during operation; The oil supply screw of the main rail oil distributor was mistakenly closed, causing the rail to be scratched due to insufficient lubrication. If the gap between the slider inserts is too large or iron filings and impurities enter, jamming and vibration will occur during operation. Maintenance plan: Re-tighten the tool holder and appropriately thicken it according to the depth of insertion to enhance rigidity. Check the oil circuit of the oil distributor one by one, and tighten the adjusting screws of each lubrication point to the standard opening to ensure a continuous oil film is formed on the guide rail surface. Disassemble the slider guard cover to thoroughly clean the internal impurities, reapply the scraping inserts to ensure a standard gap of 0.04mm that does not penetrate the feeler gauge, and manually push the slider rest to move throughout the entire journey without any jamming.

2. Poor indexing accuracy and large backlash of the worktable during rotation. Fault causes: Under long-term heavy load, the annular guide surface of the worktable wears out, pitting occurs on the tooth surface of the indexing worm gear pair, and the rotation positioning locking mechanism wears out and fails. Maintenance plan: After removing the workbench, manually scrape the annular guide rail surface to ensure that there are 8 to 10 contact points within a 25×25mm range. Adjust the side clearance of the indexing worm gear pair. For severely worn tooth surfaces, repair them by scraping or directly replace them with brand new worm gear pairs. Re-grind the positioning lock pin to ensure that there is no shaking during locking after indexing, and the repeat positioning error during rotation is controlled within 0.03mm.

3. Abnormal noise and strong impact sensation occur during the reciprocating motion of the ram. Fault causes: Wear of the tooth surfaces of the gears inside the ram transmission worm gear box, and excessive transmission clearance. The steel wire rope of the balance hammer is loose or has broken strands, and the force on the up and down movement of the ram is uneven. Maintenance plan: Disassemble the worm gear box to inspect the wear of the gears. Replace the worm gears and worm shafts with excessive wear and adjust the meshing side clearance to 0.02-0.03mm. Check the tension of the steel wire rope of the balance hammer. Replace the broken strand steel wire rope directly and readjust the balance counterweight to ensure that there is no additional impact load during the full operation of the ram.

Ⅱ. Hydraulic System Faults: The core guarantee for smooth operation

The hydraulic type of slotting machine relies on hydraulic drive to achieve stepless speed regulation of the ram and is the most widely used type of slotting machine. Faults in the hydraulic system account for more than 40% of the overall operation and maintenance faults.

1.The causes of the automatic sinking and locking failure of the ram during operation: The sealing part of the piston rod at the upper end of the cylinder ages and leaks oil; the spring of the support valve is fatigued, resulting in insufficient pressure; air mixes into the hydraulic system, causing pressure holding failure. Maintenance plan: Disassemble the oil cylinder and replace it with a brand-new polyurethane seal. After replacement, conduct a pressure-holding test. Within one hour, the sink of the piston rod should not exceed 0.05mm. Adjust the preload force of the support valve spring. When the spring force is insufficient, directly replace it with a new spring of the same specification. Perform multi-point exhaust operations on the hydraulic system. After continuous no-load operation of the ram for 10 times, confirm that there is no sinking phenomenon.

2. Causes of rapid increase in hydraulic system oil temperature and equipment overheating alarm faults: Improper selection of hydraulic oil viscosity, scale blockage inside the cooler, long-term overflow of the relief valve, and excessive system pressure adjustment. Maintenance plan: When the ambient temperature is above 25℃, use 46 # anti-wear hydraulic oil; in low-temperature environments, use 32 # hydraulic oil. Disassemble the cooler to thoroughly clean the scale inside and unblock the cooling pipelines. Recalibrate the working pressure of the system and adjust the pressure of the relief valve to the standard value marked on the equipment nameplate to avoid long-term high-pressure overflow and heating.

3. The causes of the interruption of the automatic feed action of the workbench and the intermittent start and stop faults: The valve core of the feed hydraulic valve is stuck, the opening of the throttle valve in the feed oil circuit is blocked by impurities, and the contact point of the feed interlock device is displaced. Maintenance plan: Disassemble the feed hydraulic valve, clean the valve core and valve holes, and remove burrs and impurities on the surface. Disassemble the throttle valve to clear the blocked iron filings inside, and readjust the feed speed to the required process value. Check the contact positions of the feed interlock device. After adjustment, ensure that the manual feed and automatic feed switching interlock is reliable and there is no action conflict.

Ⅲ. Electrical Control Faults: The bottom line for safe operation

The aging and malfunction of the electrical system not only affect the operation of equipment, but also pose safety hazards such as electric shock and loss of control of movement. Therefore, it is necessary to strictly follow safety regulations for inspection and maintenance.

1.The cause of the direct high-speed reversing failure of the ram reciprocating motion without deceleration: The deceleration control module of the original G-M DC speed regulation system has aged and failed, the reversing limit switch has shifted or the contacts have been burned. Maintenance plan: Old equipment can be upgraded to an AC variable frequency speed control system to replace the original outdated DC speed control unit. Readjust the trigger position of the reversing limit switch, replace the eroded contacts, and ensure that the ram automatically triggers the deceleration action when moved forward by 100mm to avoid the impact of high-speed reversing.

2. Frequent overload protection shutdown faults triggered during equipment operation: The setting value of the thermal relay is too small, the motor bearing wears out causing the operating current to exceed the standard, and the distribution line has poor contact and false connection, generating heat. Maintenance plan: Recalibrate the protection setting value of the thermal relay according to the rated current of the motor, with the error controlled within ±5%. Disassemble the motor to check the condition of the bearings, replenish the grease or directly replace the worn bearings. Comprehensively sort out the circuits on the distribution board, re-tighten all the terminal blocks, clear the messy wiring, and avoid overheating and loose connections of the circuits.

3. The causes of faults such as the equipment casing being electrified and the leakage protection frequently tripping: Rust and poor contact at the grounding terminal of the equipment, damage and exposure of the insulation layer of the 36V safety lighting circuit, and insulation aging and breakdown of the motor winding. Maintenance plan: Re-grind the grounding terminal to ensure that the grounding resistance of the equipment does not exceed 4Ω. Replace the damaged lighting circuits. All mobile lighting must use a safe voltage of 36V or less. Use a megohmmeter to test the insulation resistance of the motor winding. When it is lower than 0.5MΩ, it must be dried and impregnated with paint. Only after the insulation meets the standards can it be put back into use.

Ⅳ. Acceptance after Maintenance and long-term Operation and Maintenance Norms

After all the faults have been repaired, acceptance must be carried out in accordance with the standardized procedures: Firstly, an 8-hour continuous no-load test run should be conducted, and there should be no abnormal noise, jamming or oil leakage in the equipment. Subsequently, a 48-hour full-load cutting test was conducted, and the precision of the processed specimens fully met the process requirements. Finally, organize the complete maintenance and debugging records and update the equipment operation and maintenance files. In daily operation and maintenance, a regular inspection mechanism should be established. The oil supply status of each lubrication point should be checked weekly, the guide rail clearance and transmission accuracy should be calibrated once a month, and the cleanliness of the hydraulic oil and the insulation performance of the electrical system should be tested every three months. Through preventive maintenance, the probability of sudden failures can be significantly reduced, the service life of the insertion machine can be effectively prolonged, and this old industrial equipment can continuously and stably serve production.