Injection Molding Workshop: Work Procedures and Precautions
Release date:
2025-11-07
Injection Molding Workshop: Work Procedures and Safety Precautions I. Preparations Before Starting the Machine 1. **Objective:** Ensure the machine operates smoothly after startup and prevent any unexpected accidents. 2. **Steps and Methods:** 1) Operators should first inspect the machine, making sure the area around it is clean and free of foreign objects that could obstruct the equipment or workstations. 2) Verify that electrical components are clean and check for any signs of electrical leakage in insulation systems. If issues are detected, they must be addressed immediately. 3) Confirm that both the lubrication and cooling systems are functioning properly and free from leaks. 4) Check whether mechanical safety devices are working correctly, ensuring all safety screws are securely tightened. Also, verify that mold fastening nuts are not loose. Finally, review the display screen to ensure it’s operating normally.
(6) If no abnormalities are detected, the product can be submitted to QC for confirmation. Only after it is confirmed as "qualified" can the packaging process proceed.
I. Preparations Before Turning On the Equipment
1. Purpose:
Ensure the machine operates smoothly after startup to prevent unexpected accidents.
2. Steps, Methods
1〉Operators first perform a machine inspection to ensure the area around the equipment is clean and free of foreign objects that could block the machinery or workstation.
2〉Are the electrical devices clean, and are there any insulation issues causing leakage? If so, these problems must be addressed first.
3〉Check whether the lubrication and cooling systems are functioning smoothly and if there are any leaks.
4〉Check whether the machine's safety devices are malfunctioning, verify that the securing screws of the safety mechanisms are tight and not loose, ensure the mold fastening nuts are properly tightened, confirm that the parameter settings for ejecting the mold on the display screen are normal, and verify that the selected automatic and semi-automatic modes are functioning correctly.
5〉If all of the above are normal, you may start the motor, open the front and rear safety doors individually, manually operate the machine, and check whether the clamping action occurs. If any abnormalities are detected, troubleshooting must be performed first to eliminate the issue.
2. Power on and test operation
1. Purpose:
Check whether the machine is functioning properly.
2. Steps, Methods
1〉Turn on the power and start the motor.
2〉During formal operation, operators should also listen carefully to ensure the oil pump motor is running smoothly without any unusual noises. Additionally, they should check whether the moving parts of the machine (such as the crank handle, rocker arm, crosshead, etc.) and the mold—during both opening and locking processes—are producing any other abnormal sounds.
3〉The machine and molds may only be officially started if they are both operating normally.
3. Important Notes
1〉If operators detect a machine malfunction or electrical issue, they should immediately stop the oil pump motor, cut off the power supply, and promptly report the problem to workshop management.
3. Start up and begin production
1. Purpose:
Ensure the production of qualified products that meet the required standards.
2. Steps, Methods
1〉Preparations for Formal Production
○1 Before production begins, operators must first prepare the packaging materials (such as cardboard boxes, pearl cotton, blister trays, etc.) and processing tools (like sprue cutters, blades, etc.) according to the product being manufactured.
○2 Prepare the workbench and the processing area.
2〉 Power on
○1 After receiving the start-up instruction, the operator should immediately take their position. The machine operator should use their left hand to hold the safety gate; as the mold opens, simultaneously open the safety gate with the left hand while preparing the right hand to pick up the product. (If removing sprues is necessary, first remove the sprues.) Once the product is ejected, use the right hand to carefully take it out. Some products require being picked up in a specific direction—always follow the guidance of technical staff to ensure proper handling and prevent damage to the product. (When picking up the product, avoid touching the mold with your hands to prevent injury or burns.)
○ After taking out the product, immediately close the front safety door with your left hand, and the machine will proceed to the next cycle.
3〉Inspect the product
○1 After closing the safety door, the operator should perform a self-inspection of the product and compare it with the sample provided by the customer or the Quality Control Department.
(1) Check whether there are any noticeable differences in color;
(2) Check for flash (incomplete filling), shrinkage, and visible weld lines;
(3) Check for cracks, protrusions, white spots, broken columns, and blind holes;
(4) Whether there are noticeable flash marks, flow marks, watermarks, or air bubbles;
(5) Are there any noticeable color streaks or spots?
(6) If no abnormalities are detected, the product can be submitted to QC for confirmation. Only if confirmed as合格 (qualified), can the packaging process proceed.
(7) If operators find that a product does not match the sample, they must immediately report it to technical staff or management for handling until the product meets quality standards.
4〉Processed Products
○ For products with sprues, use sprue-cutting pliers for processing. During the process, proceed carefully and precisely—trimming the sprue cleanly while ensuring the product remains unscathed.
○2 Processes products with flash (excess material along product edges, in empty cavities, or around ejector pins).
(1) If the appearance requirements for the location of the flash are not strict, you can gently smooth it out using a utility knife—just be careful not to scratch the product.
(2) If the location of the flash requires a high level of surface appearance and is situated at the product’s edge, only a smooth-surfaced metal rod—such as a push pin or copper rod—can be used to gently press it down. After pressing, the product must retain a smooth, even edge without any jagged or serrated features.
(3) If the product has oil stains, use nylon gloves to gently wipe it with rubbing alcohol, making sure to rub in one consistent direction until clean.
5〉 Packaging
○1 Understand the specific requirements for products that need packaging as outlined in the "Packaging Work Instruction Manual."
○2 Prepare the corresponding packaging materials (such as cardboard boxes, cartons, blister packs, packing cords, etc.).
○3 When packaging, secure items firmly using packing rope in a cross-shaped tie according to the specific packaging requirements for each product.
○4 Once the products are packed into boxes, operators affix label sheets that include details such as product name, model number, quantity, color, production date, operator’s name, and planned order number. The label sheets must be uniformly placed in the upper-right corner of each cartoon box.
○5 Packaged and labeled product boxes must be neatly arranged in the workshop's designated "Inspection-Ready Area."
6〉Handling of sprues, runners, and scrap materials
○1 Water gate material, glue heads, and scrap must be packed separately for reuse.
○2 Ensure that sprue material and scrap products remain uncontaminated and free from any other foreign debris.
7〉 Important Notes
○1 If operators detect any machine or electrical malfunction, they should immediately stop the oil pump motor, cut off the power supply, and promptly report the issue to workshop management.
○ During the injection molding process, operators must retrieve products from the front safety door and should never touch high-temperature components like heating cylinders directly with their hands to prevent burns.
○3 Operators are not allowed to privately modify any injection molding process parameters.
○4 During operation, operators must not leave their posts without permission and are prohibited from discussing topics unrelated to their job with others.
○ Within the first ten minutes of starting up (or taking over), operators must carefully monitor whether the mold’s lubrication blocks and ejector pins are functioning properly and check for any signs of insufficient oil. If any abnormalities are detected, immediately report the issue to workshop management.
○6 Operators must follow the quality inspector's guidance on quality matters during their work. Any defective products identified through self-inspection must be finally approved by the workshop quality inspector before being placed in the scrap bin.
○ During shift handover, operators should clearly inform the incoming staff about any significant events that occurred during their shift.
4. Drying the plastic
1〉Objective: To ensure that the plastic is thoroughly dried as required, enabling the production of qualified products.
2〉Scope of Application: Applicable to the drying operations of ABS, PC+ABS, and PC raw materials in injection molding workshops.
3〉Steps and Methods
○1 Before adding materials, check the hopper for any remaining residue. If present, verify that the residual material matches the required raw material in terms of model and color. If any discrepancies are found, first remove dust from the outside of the hopper, then open the hopper and carefully wipe it down with a clean cloth.
(1) Use an air blower to remove dust from the outside of the hopper, then open the hopper and wipe it clean with a rag.
(2) If there are stubborn stains inside the container that are difficult to clean, use an appropriate stain remover and wash until thoroughly cleaned.
○2 Clean the glue cylinder
(1) While cleaning the hopper, turn on the heating power supply for the glue cylinder to bring its temperature to 260°C–290°C for (PC+ABS) and 290°C–350°C for PC material.
(2) When cleaning the glue cylinder, you can use runner material of the same color as the product being produced—or even a lighter-colored material. Acrylic runner material is preferred for cleaning.
(3) Repeatedly perform slow, manual injection and resin feeding until thoroughly cleaned—ensure the resin ejected from the barrel matches the color of the material intended for production.
(4) For glue cylinders that are difficult to clean thoroughly, you can add 1% of screw cleaner to the runner material for cleaning.
(5) After thoroughly cleaning the hopper and the melt cylinder, add the plastic material to be dried into the hopper—but avoid overfilling. Leave a space of 5–10 cm (or set a visible fill line for easy monitoring), ensuring adequate room for steam to escape during the drying process. Next, turn on the power and adjust the temperature controller to approximately 95°C for (PC+ABS) materials, then bake for at least 3.5 hours before starting production—but never exceed 6 hours. For PC materials, you can increase the temperature to around 110°C and bake for more than 4 hours before proceeding with production, again making sure not to surpass 6 hours.
4〉 Important Notes
○1 When starting production, operators must completely empty the overheated material from the melt cylinder—continuing until the extruded fluid no longer shows any signs of foaming and appears smooth and glossy—before officially proceeding with plastic molding. Overheated residual material can degrade and even char, potentially causing cracks in the final product.
○2 During production, if there are color deviations or mixed colors, repeat steps 4.3.2.2 and 4.3.2.3.
5. Mold Installation
1〉Objective: Ensure the mold operates smoothly and that no material leaks from the nozzle area.
2〉Installation Steps
○1 The operator locates the corresponding mold according to the arrangement in the "Injection Molding Production Schedule," then uses the mold cart to move the mold to the designated injection molding machine.
○2 Inspect the mold.
(1) Does the mold number match the one specified in the Injection Molding Production Schedule?
(2) Check whether the thimble and spring are broken; if so, repairs should be made.
(3) Ensure that the ejector pins, guide posts, and slider mechanisms are adequately lubricated. If lubrication is insufficient, add ejector pin oil to the ejector pin areas and grease to the guide posts and sliders.
(4) Check whether the water channels are blocked by any debris. If so, use an air gun to thoroughly clean them until the channels are clear and unobstructed before proceeding with mold installation.
(5) Check whether the lifting eye screw holes are centered. If they are eccentric, both the front and rear molds must be fitted with lifting eyes simultaneously, and then secured together using an iron chain before lifting the mold assembly.
○3 Play the part
(1) Raise the mold to approximately 1.1–1.3 meters, then have operators install the copper water pipe beneath the mold according to the actual situation.
*Note: The thread specifications of the copper water pipe must match those of the mold; otherwise, the threads on the copper pipe could be damaged.*
(2) During the mold's lifting and lowering process, operators should avoid standing directly beneath the mold to ensure personal safety.
(3) Lift the mold into position between the injection machine’s moving platen, fixed platen, and the left and right tie bars, then carefully lower it until the mold nozzle is nearly aligned with the injection machine’s sprue. Once properly positioned, slowly start the injection machine’s oil pump motor while simultaneously reducing the speed at which the machine opens and closes the mold—this careful approach is essential before attempting to lock the mold.
(4) If the mold thickness does not match the distance between the injection machine’s moving platen and fixed platen, the operator must activate the mold-adjusting motor on the injection machine. Select the mold-adjustment forward/reverse button to adjust the gap between the moving and fixed platens so that it closely matches the mold thickness. At the same time, carefully monitor the total pressure gauge on the injection machine—ensure it reaches 50 kgf/cm².
(5) The operator selects manual operation, moves the carriage, and checks whether the mold nozzle aligns properly with the injection machine nozzle.
(6) If the alignment is perfect, tighten the mold-fixing screws on both the front and rear molds.
(7) Connect the cooling water circuits for the front and rear molds, and check for any leaks.
3〉Important Notes
○1 Currently, both the front and rear molds of the company must be equipped with mold temperature controllers set to heat at temperatures ranging from 70°C to 180°C.
○ When disassembling or reassembling the mold temperature machine's water pipes, be sure to proceed with caution to avoid burns.
Injection Molding Machine Operation Procedures and Precautions
1. Select either the semi-automatic or fully automatic function based on job requirements (first familiarize yourself with the injection molding machine’s functional symbols).
2. When selecting the semi-automatic function, the operator is responsible for picking up the product and performing a self-inspection, paying particular attention to key areas.
1〉Is there any noticeable color difference?
2〉Check for flash, shrinkage, or weld lines.
3〉Check for cracks, bulging, whitening, broken columns, and blind holes.
4〉Check for flash, burrs, and air traps.
5〉Are there any noticeable color streaks or mixed-color spots?
3. Pay special attention to the following points during the production process:
1〉First, take the water spout. Keep the water spout inside the cardboard box—do not handle the product directly.
2〉When retrieving the product, pay attention to how tightly it fits within the mold.
3〉Close the safety door. After the safety door is shut, pay close attention to ensure the ejector pin has fully retracted into place. If the ejector pin fails to return to its original position, immediately reopen the safety door and notify your team leader’s assistant or workshop supervisors.
4〉The speed at which water nozzles and products are handled, as well as the closing of safety doors, directly impacts the day’s production output—so ensure all movements are smooth and seamless.
5〉Excessive issues with mold collisions, sprue sticking, and production waste are negatively impacting both your own interests and the company’s profitability. Specifically, the original sprue isn’t falling off, products aren’t fully removed, and the ejector pin hasn’t returned to its original position. **Do not close the safety gate under any circumstances.** Additionally, always perform a self-inspection of the product every 10 minutes.
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