The importance of mold maintenance

Plastic Injection mold plays one of the most important roles in plastic molding process, its quality is directly related to the quality of products. Moreover, since plastic mold building occupies a large cost proportion of the production for a plastic mold company, and its life directly affect injection products cost. Therefore, improving the quality of injection molds, having good maintenance and extending its life cycle, are important issues for any injection molding companies
Due to product variety, frequent exchange of the mold, after the completion of a production cycle, the mold is generally stored for a long time until the next production cycle begins. However, some plastic molding companies don’t pay much attention to mold maintenance, which invite corrosion on the mold, poor surface finish, resulting in lower-quality product and high rejection rate. Statistics show that the usage and maintenance accounted for 15% to 20% in the mold life, the injection mold life in general can be up to 80 million times, good maintenance mold maybe own a longer life extension of 2 to 3 times. However, as for some other plastic molding companies, due to the poor maintenance, injection mold life is relatively short,, only about 1/5 to 1/3 times of good maintenance mold. Therefore, the plastic injection mold maintenance is very important. The following words would discuss some mold maintenance methods:
The maintenance of mold in production
Maintenance technician should check the following items and make a complete record before mold installment;
l Check whether the molds get rusted, if any, it should be cleaned;
l Check whether there is oil or stains on mold, if any, it should be cleaned;
l Check whether the locks get damaged, if any, it should be changed;
l Check whether the water channel and/or oil channel is thru;
l Check whether the mold P/L locker missing or damaged;
l Check whether the hydraulic cylinder works;
l Check whether the spring is broken;
l Check whether mold surface get damage, if any, fix that and clean;
l Check whether the slider runs smoothly and lubricate it;
l Check whether the ejector pins get scratched or missed;
l Check whether the guide pins and guide bushing get lubricated

Checked daily whether all the align guide pins, guide bushing get damaged, including mold guide pins, sliders, lifters and other components, regularly lubricate them twice on 2 shifts
Check whether there is plastic remained, foreign material and oil stains on the P/L and vent slot; check the ejector pins and lubricate that regularly. Clean the P/L and runner twice a day. Lubricate the EGP, EGB and dowel pin twice a day.
Regularly check whether the water channel is thru, and tighten all the screws.
Regularly check whether the limits switch, lifters, cam pins work well. Click for more mold maintenance tips

Mold downtime maintenance
Before shutoff the machine, stop the cooling system and blow the water channel dry, then check whether there is foreign material on mold surface, if any ,remove them ,spray the anti-rust agent and finally record.
Key points for plastic mold maintenance
l cleaning the mold surface, cavity, core and other parts of the mold
l cleaning and lubrication of moving part of mold, and screw fastening
l Checking anti-rust for cooling water holes and short circuit of electrical components.
l Having a regular maintenance in a continuous production. As to intermittent production, at the completion of a batch, the mold should be in an optimum maintenance state when unscrewed from the injection machine. The mold should conduct daily maintenance and regular maintenance. All should be in accordance with mold maintenance regulation and all maintenance should be performed and documented

Regulation of mold usage.
1.1, select appropriate molding machine equipment, determine reasonable technology conditions to ensure that no damage to the mold and poor efficiency due to improper clamping force. When selecting injection machine, the considerations would be the maximum amount of shot volume, effective distance of pulling rod, mold mounting dimensions on the plates of the injection machine, maximum and minimum mold thickness, mold plate stroke, ejection ways and stoke, injection pressure, clamping force and the etc.
1.2, after mold installed on plastic injection machines, the first operation carried should be no plastic shooting to observe the flexibility of various mold parts movement and the operation phenomenon. Check ejector stroke, opening stroke in place, to check the mold P/L surface is tight and clamping screw is tightened and so on.
1.3, the mold under operation should maintain a stable normal temperature; prevent a quick hot and quick cold change. Mold working under normal temperature would extend its life.
1.4, moving parts on the mold, such as guide pins, return pins, ejector pins and moving core insert, etc., should always be observed, regularly checked, timely wipe and properly lubricated,. Especially in the summer when the temperature is high, at least on each shift they could be lubricated 2 times, in order to ensure these moving parts to be in flexible movement and prevent the scratching.
1.5, before mold closing, it should be noted that the cavity is clean, absolutely free of residual products, or any other foreign material. Prohibit the usage of hard ware when cleaning tool cavity surface to prevent any scratches.
1.6, the very specific demand for the surface of the mold cavity. If the surface roughness Ra is less than or equal to the special requirements of 0.2μm, definitely the hand, silk or cotton rub is forbidden, use compressed air to blow, or very good cotton napkin and absorbent cotton dipped in alcohol to wipe gently.
1.7, the cavity surface of plastic mold should be cleaned regularly. During the molding process the plastic material tends to be decomposed into low molecular compound which would erode the mold cavity, so after a period of time the bright cavity surface gradually lost its luster and then lower product quality. Therefore the regular scrub should be operated with alcohols or ketones material, and after scrubbing, the surface should be timely dried.
1.8, if a temporarily shut down need, the mold should be closed, do not let the cavity and core expose in the air to prevent accidental damage. If downtime is expected to exceed 24 hours, the cavity and core should be sprayed with the anti-rust oil or mold release agents on the surface, especially during the rainy season, a short time downtime also need corrosion resistant treatment. Moisture in the air will reduce the surface quality of the mold cavity and the article surface quality. When the mold operated again, the oil on the mold should be removed before use. Especially for the mirror demand surface, the compressed air should be used to clean the surface, and then blown dry with hot air. Otherwise they will bleed leaving defect in the molding products.
1.9, after a temporary shutdown, when operate the mold again, sliders movement stoppers should be checked. Keep it in mind, you couldn’t’ be too careful
1.10, to extend the life of cooling channels ,when mold is under maintenance, compressed air should be used to clear the water in the cooling channel ,and then spay a little engine oil into the channel to coat the channel for corrosion resistant
1.11, during operation, work carefully to check the working status of the control unit to prevent abnormal auxiliary systems. Heating and control systems maintenance is particularly important for hot runner mold. At the end of each production cycle, all stick heaters, band heaters and thermocouples should be measured and compared with the technical demand of the data of the mold to ensure the integrity of its functions. At the same time, the control circuit may be tested by the meter. Emptying the oil inside the hydraulic cylinder, and seal the opening to prevent the leakage of hydraulic oil during transportation to prevent the possible pollution of the surrounding environment.
1.12, during the mold working, if abnormal sound is heard or other abnormal situation occurs, operation should immediately be stopped for inspection. Mold maintenance technician for the normal operation of the plant should conduct inspection tours; any found abnormal phenomenon should be promptly treated and documented.
1.13, When the number of products is completed, the mold cavity should be coated with anti-rust agent before unfastening from the injection machine or fastening a new mold to injection machine, mold and its annex should be sent to mold maintenance technician, along with the last piece of the production of qualified products as a sample. Furthermore, a new sheet should list the injection machine specification, operation date, a total number of products and the current mold situation. If the mold has problems, the sheet should list the problems, propose to modify and improve specific requirements, and also deliver an untreated sample for fixing technician reference.
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