Precautions for maintenance and adjustment of injection molding machine

Time:2021-09-25 10:04:59 / Popularity: / Source:

1. Adjustment of parallelism of guide rail of clamping part

Use a precision level to make a rough longitudinal level adjustment on two quenched guide rails (lift and adjust shim iron, so that bubble of level meter is set in the middle), and use a parallel ruler to span two guide rails. Place level meter on parallel ruler for rough adjustment of horizontal level. For large and medium-sized combined injection molding machines, a level gauge is also used to adjust parallelism of injection rail, a positioning pin connecting clamping device and injection device is installed, connecting bolts and nuts are tightened. .
maintenance and adjustment of injection molding machine 

2. Inspection and adjustment of level of guide column of movable formwork

Use a precision level to adjust horizontal and vertical directions on guide column. Place level first horizontally and then vertically, repeat measurement and adjustment until it meets requirements. A parallel ruler that spans two guide posts is also required for horizontal measurement. Allowable tolerance: horizontal ≤0.16MM/M; longitudinal ≤0.24MM/M.

3. Inspection and adjustment of parallelism between mold plates

Parallelism between movable mold plate and mold plate reference plane has been adjusted at factory, and is generally stable. However, due to transportation and installation reasons, this parameter may change. Therefore, check and adjust after installation. This parameter adjustment should be performed by professionals.

4. Adjustment of coaxiality of nozzle and mold positioning center hole

Adjustment of coaxiality between nozzle and positioning center of mold should be performed after horizontal and vertical horizontal adjustments of mold plate and fuselage are completed.
Adjustment method is as follows:
① Loosen fastening screws connecting front and rear brackets of injection seat guide rod with body; loosen lock nuts on horizontal adjustment bolts on both sides of front bracket of injection seat guide rod.
② Measure L1, L2, L3, L4 in horizontal and vertical directions along diameter with a vernier caliper with an accuracy of 0.05mm or more. When measuring, pay attention to adjusting horizontal adjustment bolts so that L1=L2; adjust upper and lower adjustment screws so that L3= L4.
③ When adjusting coaxiality of nozzle and positioning center hole of mold, due to change of guide rod of injection seat, it may be twisted, causing gap between screw and barrel to shift and wear. Therefore, when adjusting coaxiality of nozzle and positioning center hole of mold, it is also necessary to measure and adjust level of guide rod of injection seat (tolerance value is less than or equal to 0.05/M); use a feeler gauge to measure gap between screw tail and barrel.

Reasons for screw wear of injection molding machine and methods to reduce wear

Screw of injection molding machine works under high temperature, high pressure, high mechanical torque and high friction environment for a long time. The first few factors are required by process conditions, and loss caused by friction is inevitable.
Generally, screws have undergone surface nitriding treatment to increase surface hardness, that is, to improve wear resistance. However, if causes of wear are ignored and wear is not minimized, working life of screw will be greatly reduced.
Every kind of plastic has an ideal processing temperature range for plasticization, and processing temperature of barrel should be controlled to make it close to this temperature range. Granular plastic enters barrel from hopper and first reaches feeding section. Dry friction will inevitably occur in feeding section. When these plastics are not heated enough and melted unevenly, it is easy to increase abrasion of inner wall of barrel and surface of screw.
Similarly, in the compression and homogenization section, if molten state of plastic is disordered and uneven, it will also cause increased wear.
Speed should be adjusted properly. Because some plastics are added with strengthening agents, such as glass fibers, minerals or other fillers. Friction of these substances on metal materials is often much greater than that of molten plastics. When injecting these plastics, if you use a high speed, it will increase shearing force of plastic, and will also make reinforcement correspondingly produce more shredded fibers. Shredded fibers contain sharp ends, which greatly increase wear force.
When inorganic minerals slide at high speed on metal surface, their scraping effect is not small. Therefore, speed should not be adjusted too high.
To remove debris in the plastic. Generally speaking, there is no debris in fresh plastic purchased originally, but after transportation, weighing, drying, color mixing, especially addition of recycled materials, it may be mixed with debris.
It is as small as metal scraps, as large as heating coil nuts, paper clips, and even a bunch of warehouse keys. It has been mixed into barrel. Damage to screw is self-evident (barrel will also be damaged at the same time. ), so it is necessary to install a magnet holder, strictly manage and monitor feeding.
Water content in plastic has a certain effect on wear of screw surface. If plastic is not completely drained of water before injection, when residual water enters screw compression section, it will form "steam particles" with high temperature and pressure that are previously melted and mixed in molten plastic. With advancement of screw during injection process, from homogenization section to screw head, these "steam particles" will relieve pressure and expand during injection process, just like tiny hard particles of impurities, which will cause friction and damage to wall.
In addition, for certain types of plastics, under high temperature and high pressure, moisture may become a catalyst that promotes cracking of plastic, producing harmful impurities that can attack metal surface. Therefore, drying work before plastic injection molding not only directly affects quality of parts, but also affects working life of screw.

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