What factors will affect the service life of three-axis injection molding robot?

The core factors that affect the service life of the three-axis injection molding robot are concentrated in four dimensions: the configuration and selection of the equipment itself, the operation specifications for daily use, the adaptation and protection of the production environment, and the later maintenance. At the same time, the technological characteristics of injection molding (such as the frequency of picking up parts and the change of load) will also directly affect the loss speed of the robot. If some detailed factors (such as the weight of fixture and signal linkage) are not properly controlled, they will accelerate the aging and wear of components and greatly shorten the service life of the equipment. The following are the core factors sorted from high to low, which are easy to understand and can be avoided in accordance with the actual production scene of the injection workshop:

First, the core hardware configuration and processing technology (innate basis, determines the lower limit of equipment durability)

Hardware selection and manufacturing accuracy of manipulator are "innate conditions" for its service life. Poor matching and inferior parts will directly lead to early failure, which is the core factor affecting its service life:

Quality of driving and transmission parts

Servo motor (Panasonic/Delta/Mitsubishi and other first-line brands), ball screw and linear guide rail (Shangyin/THK/PMI) are the core vulnerable parts. The materials and machining accuracy of miscellaneous/non-standard parts are poor, and the screw is easy to have gaps, the guide rail is easy to wear, and the servo motor is easy to overload and burn. Moreover, the assembly accuracy of transmission parts is insufficient (such as coaxiality deviation and poor parallelism of guide rails), which will lead to jamming and uneven stress during operation and accelerate the aging of parts.

Design matching of load and shaft body

If the steel strength and structural reinforcement design of the shaft body do not match the rated load, long-term full load/overload operation will lead to bending of the shaft body and cracking of the joint; Moreover, the safety factor of the three shafts is not reserved enough (for example, the load only leaves 20% margin), and the inertia force during high-speed movement will aggravate the loss of transmission parts.

Selection of pneumatic components

If the pressure regulating valve, solenoid valve and cylinder are made of inferior products without brand name, the seals are easy to age and leak pressure, and the valve core is easy to get stuck, which not only affects the stability of taking parts, but also leads to too many start-stop times of equipment due to frequent failures and accelerates the loss of electrical components.

Second, the actual use of the operation and working conditions match (the day after tomorrow, the most likely to accelerate the loss of equipment)

The actual use habits and working condition matching in injection molding workshop are the most critical acquired factors that affect the life of the manipulator, and most of the early damage of the manipulator comes from this:

Super-parameter illegal operation

Long-term overload pickup (such as rated load 5kg, actual pickup+fixture weight 7kg) and overspeed operation (increasing the three-axis operation speed to catch up with the beat, exceeding the design limit) will lead to the servo motor, screw rod and guide rail being overloaded for a long time, and the wear speed will be increased by 3~5 times; And frequent emergency stop and rapid acceleration (such as pressing the emergency stop button frequently during operation) will produce instantaneous impact load and damage the connecting structure and electrical components of transmission parts.

Matching deviation between picking process and manipulator

The weight of the fixture exceeds the standard (if the fixture is made of cast iron, the weight accounts for more than 60% of the rated load), which will increase the running load of the three shafts; In addition, frequent collision with the die and die table (such as inaccurate stroke debugging and no recalibration after die changing) will lead to deformation of the joint between the shaft and the fixture, displacement of the sensor and even damage to the brake mechanism of the servo motor.

Production beat and equipment start-stop frequency

If the running rhythm of the manipulator does not match the mold opening period of the injection molding machine, the equipment will start and stop frequently and idle, and the electrical components (such as contactors and relays) will be ablated due to frequent on-off and the temperature rise of the servo motor will be too high, which will affect the service life.

Third, the adaptation and protection of the production environment (environmental impact, easy to be ignored but the loss continues)

There are many harsh environments such as dust, oil pollution, high temperature and humidity in the injection workshop. If there is no targeted protection, it will continue to corrode and wear equipment parts and accelerate aging.

Erosion of dust and oil pollution

Plastic scraps produced by injection molding, oil stains of mold release agent and dust in the workshop will mix with grease to form sludge if they enter the guide rail, screw rod and bearing of the three shafts, which will aggravate the abrasive wear of the guide rail and screw rod; At the same time, oil and dust adhere to the surfaces of electrical components and sensors, which will lead to poor contact, signal drift and even short circuit burning.

The influence of high temperature and humidity

If the manipulator is installed next to the barrel of the injection molding machine, it will be exposed to high temperature radiation for a long time (ambient temperature > 60℃), which will lead to excessive temperature rise of the servo motor, aging of the insulation layer and hardening and cracking of the seal (rubber/silica gel); However, the workshop is wet and dewy, which will corrode the terminals and metal parts of electrical circuits, produce rust, and affect the transmission and conductivity.

Unprotected outdoor/dusty workshop use

If the manipulator is installed outdoors (without rain and sun protection) or used in workshops with high dust such as grinding and polishing, the corrosion and wear speed of equipment components will be greatly increased due to the lack of protective devices such as fully enclosed shields and dust scraping strips.

IV. Daily maintenance (post-guarantee, which determines the upper limit of equipment service life)

Manipulator belongs to precision automation equipment. Without maintenance and nonstandard maintenance, minor faults will accumulate into major faults, which will greatly shorten the service life. On the contrary, scientific maintenance can prolong the service life of equipment by more than 50%:

Lack and irregularity of lubrication maintenance

Transmission parts such as screw rod, guide rail and bearing need to be filled with special grease regularly. If they are not lubricated for a long time, dry grinding will occur and the wear rate will increase sharply. And filling the wrong grease (such as replacing the special grease for precision equipment with ordinary butter) and filling too much/too little grease will affect the lubrication effect and aggravate the wear.

Failure to replace wearing parts in time

Wearable parts such as vacuum sucker, seal (sealing ring of cylinder and solenoid valve), sensor head, cable sheath, etc., if they are aged or damaged and not replaced in time, will lead to parts leakage, pneumatic pressure leakage and signal failure, which will lead to frequent equipment failures and illegal operations, and indirectly accelerate the loss of core components.

Lack of maintenance of electrical system

Failure to regularly clean the dust in the electrical cabinet, check the looseness of the terminal and test the temperature rise of the servo motor will lead to short circuit and poor contact of electrical components, and even burn the core electrical components such as servo driver and PLC; Moreover, the oil-water separator of hydraulic/pneumatic system fails to drain water in time, which will cause compressed air to contain water and corrode the internal structure of cylinder and solenoid valve.

Lack of equipment calibration

Failure to re-calibrate the stroke and positioning accuracy of the three axes in time after mold changing, equipment shifting and collision will lead to uneven stress on the manipulator during operation, which will lead to "crawling" and "jitter" and aggravate the wear of transmission parts.

Five, electrical and linkage system adaptation (system compatibility, indirectly affect the stability of equipment)

The adaptability and linkage stability of the electrical system will not directly wear the mechanical parts, but will lead to the start-up and maintenance of the equipment due to frequent failures, which will indirectly affect the service life:

Does not match the linkage signal of injection molding machine.

If the PLC linkage signal between the manipulator and the injection molding machine (such as mold opening in place and the completion of taking parts) is delayed or triggered by mistake, it will lead to unsynchronized equipment actions, mold collision, empty take and other problems, which will lead to frequent emergency stop and fault maintenance.

Arrangement and protection of electrical circuits

If cables and gas pipes are not routed by towing chains, or the specifications of towing chains are poorly matched with cables, the cables and gas pipes will be pulled and entangled for a long time, and the outer skins will be worn and the internal wires will be broken, which will lead to equipment failure; And the wiring is not waterproof and oil-proof, which will lead to poor contact.

Operation and maintenance of control system

Failure to back up programs regularly, random modification of equipment parameters (such as speed and load limit), and non-professional operation and programming will lead to disordered operation of equipment and even program errors, which will lead to misoperation of equipment and damage of components.

Six, fixture and additional tooling matching (matching details, indirectly increase the equipment load)

If there is any irrationality in the design and matching of fixture and additional fixture, it will indirectly increase the operating load of the manipulator and accelerate the loss:

The design of fixture is unreasonable.

The deviation of the center of gravity of the fixture (if the picking point is not in the center of the fixture) will lead to the eccentric load when the manipulator is running, which will aggravate the uneven stress of the shaft and transmission parts; Moreover, the redundant parts on the fixture are not simplified (such as unnecessary cylinders and brackets), which will increase the overall weight and improve the running load.

Improper installation of additional tooling

Additional equipment, such as pneumatic scissors, rotary cylinders, and distributing tools, will cause vibration when they are installed, which will be transmitted to the three-axis transmission parts and aggravate wear. Moreover, the pressure leakage of pneumatic pipeline with additional tooling will lead to frequent start-up and stop of equipment and affect the service life of electrical components.

Key points to avoid: the key method to prolong the service life of manipulator

Selection stage: First-line brand core accessories are selected first, sufficient load and speed safety factors are reserved, and protective devices (such as fully enclosed shields and dust-proof scraping strips) are customized according to the workshop environment;

Use stage: Run strictly according to the rated parameters to prevent overload and overspeed, recalibrate the stroke after the mold is changed to avoid collision with the mold, standardize the operation and reduce emergency stop;

Protection stage: in view of dust/oil pollution/high temperature environment, install protective cover, oil-water separator and high-temperature insulation layer, and regularly clean the dust and oil pollution on the equipment surface;

Maintenance stage: develop standardized maintenance manuals (such as weekly lubrication of guide rail/screw, daily drainage of pneumatic system and monthly inspection of wearing parts), replace aging and damaged parts in time, and calibrate positioning accuracy regularly;

Training stage: provide professional training for operators, standardize operation procedures, and prevent non-professionals from modifying parameters and disassembling equipment.

To put it simply, the service life of the three-axis injection molding manipulator is the comprehensive result of "innate hardware selection" and "acquired use, maintenance and protection". The former determines the durability foundation of the equipment, while the latter determines whether the equipment can reach the designed service life or even run beyond the time limit.