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Acceptance standards for plastic injection molds

Update:06-05-2020
Summary:

Purpose: To ensure that the mold can produce qualified […]

Purpose: To ensure that the mold can produce qualified products, put into normal production, ensure the service life of the mold, and meet the production and use requirements of product design. The standard recognizes the standards for molds in terms of product quality, mold structure, injection molding process requirements, etc., and evaluates mold quality based on this.
1. Appearance, size and fit of the molded product
1. Defects are not allowed on the surface of the product: lack of material, burnt, top white, white line, peak, blistering, whitening (or cracking, breaking), baking, wrinkles.
2. Welding marks: Generally, the length of circular perforated welding marks is not more than 5mm, and the length of special-shaped perforated welding marks is less than 15mm. The strength of the welding marks can pass the functional safety test.
3. Shrinkage: Shrinkage is not allowed on the obvious surface, and slight shrinkage is not allowed on the unobvious surface (no dent).
4. Variation: Generally, the flatness of small products is less than 0.3mm. If there are assembly requirements, the assembly requirements must be guaranteed.
5. There should be no air lines or flowers in the obvious appearance, and the product should generally not have bubbles.
6. The geometric shape and dimensional accuracy of the product should conform to the formal and valid drawings (or 3D files). The product tolerance should be based on the tolerance principle. The shaft size tolerance is negative tolerance, and the hole size tolerance is positive tolerance. As required.
7. Product wall thickness: product wall thickness generally requires an average wall thickness, non-average wall thickness should meet the requirements of the drawings, and the tolerance should be -0.1mm according to the characteristics of the mold.
8. Product coordination: surface shell bottom shell coordination: the surface misalignment is less than 0.1mm, there must be no scratching, and holes, shafts, and surfaces with matching requirements must ensure the matching interval and use requirements.
Second, the appearance of the mold
1. The mold nameplate is complete with clear characters and neatly arranged.
2. The nameplate should be fixed on the mold feet near the template and the reference angle. The nameplate is reliable and not easy to peel off.
3. Cooling water nozzles should use plastic blocks to insert the water nozzles, as required by customers.
4. The cooling water nozzle should not protrude from the surface of the formwork.
5. The cooling water nozzle needs to be processed with counterbores. The counterbore diameters are 25mm, 30mm, and 35mm, and the chamfering of the opening should be consistent.
6. The cooling water nozzle should be marked with entry and exit.
7. The English characters and numbers of the mark should be greater than 5/6, and the position should be 10mm directly under the water nozzle.
8. Mold accessories should not affect the lifting and storage of the mold. During installation, there are exposed oil cylinders, water nozzles, pre-reset mechanisms, etc., which should be protected by supporting legs.
9. The installation of the support legs should be screwed through the support legs and fixed on the mold frame. The over-length support legs can be fastened on the mold frame with a machined externally threaded post.
10. The size of the ejection hole of the mold should meet the requirements of the specified injection molding machine. Except for small molds, it cannot be ejected with only one center.
11. The positioning ring should be fixed and reliable. The diameter of the ring is 100mm and 250mm. The positioning ring is 10 ~ 20mm higher than the bottom plate. Unless otherwise requested by the customer.
12. The external dimensions of the mold should meet the requirements of the specified injection molding machine.
13. The direction of the installation of the mold should be marked with an arrow on the front template or rear template to indicate the installation direction, there should be "UP" next to the arrow, the arrow and the text are yellow, the word height is 50 mm.
14. There should be no pits, rust marks, extra rings, water vapor, oil holes, etc. on the surface of the mold frame, as well as defects that affect the appearance.
15. The mold should be easy to lift and transport. During lifting, the mold parts must not be disassembled, and the lifting ring must not interfere with the water nozzle, oil cylinder, and pre-reset rod.
3. Mold material and hardness
1. The mold formwork should use standard formwork that conforms to the standard.
2. The materials used for mold forming parts and pouring system (core, moving and fixed mold insert, movable insert, diverter cone, push rod, gate sleeve) are made of materials with a performance higher than 40Cr.
3. When molding plastics that are easily corroded by the mold, the molded parts should be made of corrosion-resistant materials, or the molding surface should be protected against corrosion.
4. The hardness of moulded parts should not be less than 50HRC, or the hardness of surface hardening treatment should be higher than 600HV.
4. Ejecting, resetting, inserting core, and picking
1. The ejection should be smooth, without jamming, and without abnormal noise.
2. The inclined top surface should be polished, and the inclined top surface is lower than the core surface.
3. Oil grooves should be set for sliding parts, and the surface needs to be nitridized, and the surface hardness after treatment should be above HV700.
4. All jacks should have anti-rotation positioning, and each jack should be numbered.
5. The limit distance should be limited by the limit block.
6. Standard parts should be used for the return spring. Both ends of the spring must not be polished or cut off.
7. The slider and the core pulling should have a stroke limit, and the small slider is limited by a spring. When the spring is inconvenient to install, the wave screw can be used; the cylinder pulling core must have a stroke switch.
8. The slider core pulling generally adopts the inclined guide column, the angle of the inclined guide column should be 2 ° ~ 3 ° smaller than the angle of the locking surface of the slider. If the stroke of the slider is too long, the cylinder should be used for extraction.
9. When the end face of the core part of the oil cylinder is covered, the oil cylinder should be equipped with a self-locking mechanism.
10. There should be wear-resistant plates under the large slider with a slider width of more than 150 mm. The material of the wear-resistant plate should be T8A. After heat treatment, the hardness is HRC50 ~ 55. The wear-resistant plate is 0.05 ~ 0.1 mm higher than the large surface. Open the oil tank.
11. The top rod should not move up and down in series.
12. Add a barb on the top pole, the direction of the barb should be consistent, the barb can be easily removed from the product.
13. The matching clearance between the jack hole and the jack, the length of the sealing section, and the surface roughness of the jack hole should be in accordance with the requirements of relevant enterprise standards.
14. Products should be removed by the operator.
15. When the product is ejected, it is easy to follow the inclined top, and the top rod should be grooved or etched.
16. The top block fixed on the top rod should be firm and reliable, the non-molded parts around should be processed with a slope of 3 ° ~ 5 °, and the periphery of the lower part should be chamfered.
17. There should be no iron filings in the oil passage holes on the mold base.
18. The end face of the return rod is flat, without spot welding. There is no gasket at the bottom of the embryo head, spot welding.
19. The three-plate mold gate plate slides smoothly and the gate plate can be easily pulled apart.
20. The limit rods of the three-plate mold should be arranged on both sides of the mold installation direction, or a pull plate should be added outside the mold frame to prevent the limit rods from interfering with the operator.
21. The airway of the oil road should be smooth, and the hydraulic ejection reset should be in place.
22. The bottom of the guide bush should be vented.
23. There must be no gaps in the installation of the positioning pins.
5. Cooling and heating system
1. The cooling or heating system should be fully unblocked.
2. The sealing should be reliable, and the system must not leak under 0.5MPa pressure, which is easy to repair.
3. The size and shape of the sealing groove opened on the mold frame should meet the requirements of relevant standards.
4. Butter should be spread when the sealing ring is placed, and it will be higher than the mold surface after being placed.
5. Water and oil channel separators should be made of materials that are not easily corroded.
6. The front and rear molds should adopt centralized water delivery and methods.
6. Pouring system
1. The gate setting should not affect the appearance of the product and satisfy the product assembly.
2. The section and length of the runner should be designed reasonably, and the process should be shortened as much as possible on the premise of ensuring the forming quality, and the cross-sectional area should be reduced to shorten the filling and cooling time. At the same time, the plastic loss of the pouring system should be minimal.
3. The partial section of the three-plate mold runner at the back of the front formwork should be trapezoidal or semicircular.
4. The three-plate mold has a material cutting handle on the gate plate, the diameter of the gate entrance should be less than 3 mm, and a 3 mm deep step recessed into the gate plate at the ball head.
5. The ball-end pulling rod should be reliably fixed, which can be pressed under the positioning ring, can be fixed with headless screws, or can be pressed with a pressure plate.
6. The gates and runners should be machined according to the size requirements of the drawings, and manual grinding and grinding machines are not allowed.
7. The point gate should be in accordance with the specifications.
8. There should be an extended part at the front of the diverter channel as a cold cavity.
9. There should be a smooth transition for the Z-shaped reverse button of the pulling rod.
10. The shunt on the parting surface should be round, and the front and rear molds cannot be misaligned.
11. There should be no surface shrinkage of the latent gate on the top bar.
12. The diameter and depth of the cold cavity of transparent products should meet the design standards.
13. The material handle is easy to remove, there is no gate mark on the appearance of the product, and there is no residual material handle at the product assembly.
14. The curved latent gate, the two parts of the insert should be nitrided, and the surface hardness should reach HV700.
7. Hot runner system
1. The layout of the hot runner wiring should be reasonable for easy maintenance, and the wiring numbers should correspond to each other.
2. The hot runner should be tested for safety, and the insulation resistance to ground is greater than 2MW.
3. Standard parts shall be used for the temperature control cabinet, hot nozzles and hot runners.
4. The main port is threaded and connected to the hot runner, and the bottom surface is in contact with and sealed.
5. The hot runner is in good contact with the heating plate or heating rod, the heating plate is fixed with screws or studs, and the surface is well adhered.
6. J-type thermocouple should be used and matched with the temperature control table.
7. Each group of heating elements should be controlled by thermocouple, and the position of thermocouple should be arranged reasonably.
8. The nozzle should meet the design requirements.
9. The hot runner should be reliably positioned, at least two positioning pins, or fixed with screws.
10. There should be a thermal pad between the hot runner and the template.
11. The temperature control meter set temperature and the actual display temperature error should be less than ± 5 ° C, and the temperature control is sensitive.
12. The cavity between the cavity and the nozzle should be penetrated.
13. The hot runner wiring should be bundled and covered with a pressure plate.
14. There are two sockets of the same specification, which should be clearly marked.
15. The control wire should be sheathed and not damaged.
16. The structure of the temperature control cabinet is reliable, and the screws are not loose.
17. The socket is installed on the bakelite board, and cannot exceed the maximum size of the template.
18. The wires must not be exposed outside the mold.
19. The hot runner or formwork should have rounded corners where all contact with the wire.
20. Before the formwork is assembled, all lines are free from short circuit.
21. All wiring should be properly connected and the insulation performance is good.
22. After the template is installed and clamped, all lines should be checked again with a multimeter.
8. Forming part, parting surface, exhaust groove
1. There should be no irregularities, pits, rust and other defects affecting the appearance of the front and back mold surfaces.
2. The inlay block is matched with the mold frame, and the rounded corners should have a gap of less than 1 mm.
3. Keep the parting surface clean and tidy, no hand wheel grinding and avoiding the air, and the sealing part is not depressed.
4. The depth of the exhaust slot should be less than the plastic overflow value.
5. The research and distribution of inserts should be in place, smooth placement and reliable positioning.
6. The inserts, inserts, etc. should be reliably positioned and fixed, the round pieces have a rotation stop, and no copper or iron pieces are placed under the inserts.
7. The end face of the jack is consistent with the core.
8. There are no defects such as undercuts and chamfers in the molded parts of the front and rear molds.
9. The ejection of tendons should be smooth.
10. For multi-cavity mold products, the left and right parts are symmetrical, and L or R should be noted. If the customer has requirements on the location and size, it should meet the customer's requirements. Generally, it is added where the appearance and assembly are not affected. .
11. The mold frame locking surface should be in place, and more than 75% of the area should be touched.
12. The top rod should be arranged near the side wall and beside the ribs and bosses, and a larger top rod should be used.
13. For the same piece, the number 1, 2, 3, etc. should be indicated.
14. Each contact surface, insertion surface and parting surface should be researched and matched in place.
15. The sealing part of the parting surface should meet the design standards. The middle and lower molds are 10 ~ 20 mm, the large molds are 30 ~ 50 mm, and the rest are machined to avoid air.
16. Dermatoglyph and sand blasting should evenly meet customer requirements.
17. For products with required appearance, the screws on the products should have anti-shrinkage measures.
18. For screw columns with a depth of more than 20 mm, a jacking tube should be used.
19. The wall thickness of the product should be uniform, and the deviation should be controlled within ± 0.15 mm.
20. The width of the ribs should be less than 60% of the wall thickness of the exterior surface
21. The inserts on the slanted top and the slider should have a reliable fixing method.
22. Insert the front mold into the rear mold or the rear mold into the front mold. There should be a bevel lock around and machined to avoid air.
Nine, injection molding production process
1. The mold should have the stability of injection molding production and the repeatability of process parameter adjustment within the range of normal injection molding conditions.
2. The injection pressure during mold injection production should generally be less than 85% of the rated maximum injection pressure of the injection molding machine.
3. The injection speed during the mold injection production, the injection speed of the three-quarter stroke is not less than 10% of the rated maximum injection speed or more than 90% of the rated maximum injection speed.
4. The holding pressure during mold injection production should generally be less than 85% of the actual maximum injection pressure.
5. The clamping force during mold injection production should be less than 90% of the rated clamping force of the applicable model.
6. In the injection molding production process, the products and nozzle materials should be taken out easily and safely (the time generally does not exceed 2 seconds each).
7. For the molds with insert products, the installation of the inserts is convenient and the fixing of the inserts is reliable during production.
10. Packaging and Transportation
1. Mold cavity should be cleaned and sprayed with anti-rust oil.
2. The sliding parts should be coated with lubricant.
3. The inlet of the sprue bushing should be blocked with grease.
4. The mold should be installed with locking plates, and the specifications should meet the design requirements.
5. Spare parts, spare parts and consumables should be complete, with a detailed list and supplier name.
6. Mould water, liquid, gas, electricity import and export should take sealing measures to prevent foreign matter from entering;
7. Paint is sprayed on the outer surface of the mold, as required by the customer.
8. The mold should be packed with moisture-proof, waterproof and bump-proof packaging, as required by the customer.
9. Mold product drawings, structural drawings, cooling and heating system drawings, hot runner drawings, spare parts and mold material supplier details, instruction manuals, mold test reports, factory inspection certificates, and electronic documents should be complete.
Acceptance judgment
1. The mold should be checked and accepted according to the requirements of this standard, and the acceptance records should be made.
2. The acceptance judgment is divided into qualified items, acceptable items and unacceptable items. If all items are qualified or acceptable items, the mold is qualified.
3. Unacceptable number of items: 1 item of product; 1 item of mold material; 4 items of mold appearance; 2 items of ejector core insertion; 1 item of cooling system; 2 items of pouring system; 3 items of hot runner system; 3 items of molding part ; 1 item of production process; 3 items of packaging and transportation; it is determined that the mold needs rectification.
4. Unacceptable items: more than 1 product; more than 1 mold material; more than 4 mold appearance; more than 2 ejector cores; more than 1 cooling system; more than 2 pouring systems; more than hot runner system 3 items; more than 3 molding parts; more than 1 production process; more than 3 items for packaging and transportation; then it is judged as unqualified mold.