The molten material is injected under high pressure into metal moulds during injection moulding. Once it has sufficiently cooled, the completed portion is immediately removed. The procedure is highly automated and can produce vast quantities of goods, particularly plastic components. To produce these high volumes, injection moulding equipment must undergo routine preventative maintenance. To maintain tools and inspection machines prepared for manufacturing, mould maintenance is essential. Moulds that are not properly maintained may produce parts that do not meet standards, leading to additional downtime, raw material waste, and financial consequences.
This article describes some essential things for an injection mould maintenance checklist.
Make sure you are using the right amount of tonnage for each mould. Injection pressure can surpass the required tonnage requirements and blow open the mould if an operator uses too little tonnage. If a user applies too much force, the injection moulding machine will compress the tool’s separating lines, vent areas, and mould components.
Use the formula below to calculate the correct tonnage for each mould to prevent these scenarios:
Cavity Area = Mould Face Length x Width (in/2)
Cavity Area (Pa) = # of Cavities Parts Area (Pa)
Parts Area *(T) = Tonnage (T) = 3 tons/in2.
2. Low Pressure Close
Install a low-pressure closure (LPC) on the press to safeguard the mould. The high-pressure lock-up setting should be no more than 0.05 above the actual mould touch location. Additionally, cycle the mould to lower LPC pressure till it doesn’t lock up. Slowly increasing pressure gives the mould enough pressure to change from low-pressure to high-pressure lock up. Additionally, set the mould close timer to 0.5 seconds longer than the necessary mould close time. Set the mould close timer to 1.26 seconds, for instance, if the actual mould close duration is 0.76 seconds.
3. Set Up Core
Adapt core pressures and speeds to the demands of the application. Remember for inspection machines, speed does not affect pressure set points, but pressure might limit speed. To avoid crash circumstances, fire cores are based on position rather than time. Cycle speed is impacted by core functioning. Keep a close eye on core functioning to spot any indications that parts are pulling or setting irregularly.
4. Mould Open and Close
Clamp speeds undoubtedly influence cycle time, although more incredible speeds are not always preferable because they risk damaging or wearing out the tools. Look for lunging at close, rapid speeds that could lead to mould drop and possible pin and component misalignment. Ensure that the change from close fast to close slow is seamless and that the close slow condition happens right before the component/pin matches up. Ensure the transition between the mould open fast segment and the mould breakaway phase is seamless. The open fast segment should happen after all components have passed through the pins.
5. Ejection Set Up
By over-stroking or ejecting pieces improperly, which causes them to jam between mould halves, incorrect set points might damage the life of the mould. Determine the necessary separation for properly removing components from the mould before establishing forward positions. Ejector pins and lifters endure too much stress from over-stroking. Never should bottoming out the ejector plate be necessary for part extraction. Ensure pressure set points only employ the necessary amount to reduce stress on ejection components.
6. Hot Runners and Valve Gates
Mould life is affected by start-up and shutdown procedures. Poor start-ups result in over-packed cavities that need mould removal and maintenance. Manually fire valve gates to ensure appropriate setup and functional condition before starting any components. To ensure the hot runner drops are heated and ready for start-up, purge plastic through them. Run the barrel dry during hot runner shutdown, then promptly lower hot runner temperatures to lessen the chance of degradation.
7. Mould Watering
Limit mould temperatures to the bare minimum necessary for acceptable part aesthetics because higher mould temperatures might negatively influence mould life. Additionally, make sure there is no more than a 20 F difference in temperature between the stationary and moving mould portions. Temperatures over this range result in poor tool mating and incorrect heat soak conditions, both of which harm the tool. To avoid installing a mould incorrectly, clearly mark circuits and supply and return requirements.
8. Cleaning and Care
Injection moulding machine should always be inspected, cleaned, and greased at least once each shift in production environments. Look for wear indicators like metal shavings, burrs, galling, and parting line wear. To set preventative maintenance frequencies that will aid in reducing unplanned service events, create a regular preventative maintenance schedule, maintain mould service records, and examine recurring service/repair events.
Check to see that the slides are operating correctly and that the slide slots are lubricated. Keep an eye out for loose gibs and detent failure symptoms. After each cleaning and inspection, ensure the slide locations are accurate before leaving the mould. When a mould won’t be used for more than six hours, use a rust preventative and extensively coat textured and glossy parts to guard against rust damage.
Prolonging the life of your injection moulding machine is a wise investment in efficiency and sustainability, as well as a way to reduce costs. You can ensure that your machine keeps performing at its best for years by putting the concepts covered in this article into practice, such as routine maintenance, appropriate training, and technology upgrades. By extending its lifespan, you may improve productivity while minimising downtime, lessening your impact on the environment, and maintaining the competitiveness of your manufacturing operations in a market that is changing quickly.