Important acceptance standards for plastic injection molds

Table of Contents

To make a good mold, not only must have a good mold design level and precision machining injection molding production process but also cannot be separated from the “standard”, which does not allow the existence of the concept of “almost”. This article lists several acceptance criteria for a good set of molds, hope it will help you.

Mold appearance

1. The nameplate of the mold is complete, with clear characters and neatly arranged.

2. The nameplate should be fixed on the injection molded foot near the template and the reference corner. The nameplate should be fixed reliably and not easy to peel off.

3. The cooling water nozzle should use a plastic block insert nozzle, if the customer requires otherwise, according to the requirements.

4. The cooling water nozzle should not stick out from the surface of the mold frame.

5. The cooling water nozzle should be processed with a sink hole with a diameter of 25mm, 30mm, and 35mm, and the hole should be chamfered and the chamfer should be consistent.

6. Cooling water nozzle should be marked in and out.

7. Mark English characters and numbers should be greater than 5/6, positioned at 10mm directly below the spout, and the handwriting should be clear, beautiful, neat, and evenly spaced.

8. Mold fittings should not affect the lifting and storage of the mold. There are exposed cylinders, water nozzles, pre-set mechanism, etc. below the installation, there should be supported legs to protect.

9. The installation of the support leg should be fixed on the mold frame with screws through the support leg, and the support leg which is too long can be fastened on the injection mold frame by turning the external thread column.

10. The size of the ejector hole of the mold should meet the requirements of the specified injection molding machine, except for small molds, which cannot be ejected with only one center.

11. The positioning ring should be fixed reliably, the diameter of the ring is 100mm or 250mm, and the positioning ring is 10~20mm higher than the base plate, except if the customer requires otherwise.

12. The mold dimensions should meet the requirements of the specified plastic injection molding machine.

13. The installation direction of the mold should be marked with arrows on the front or rear template, and the word “UP” should be written next to the arrow, the arrow and the text are yellow, and the height of the word is 50 mm.

14. The surface of the mold frame should not have pits, rust, extra rings, inlet and outlet vapor, oil holes, and other defects that affect the appearance.

15. The mold should be easy to lift and transport the injection mold parts should not be disassembled when lifting, and the lifting ring should not interfere with the water nozzle, oil cylinder, pre-reset lever, etc.

Mould material and hardness

1. The mold frame should be chosen to meet the standard mold frame.

2. Mould forming parts and pouring system (core, movable and fixed mold insert, movable insert, diverter cone, push rod, gate sleeve) should be made of materials with higher performance than 40Cr.

3. When molding the mold easy corrosion of plastic, injection molding parts should be made of corrosion-resistant materials, or its molding surface should take anti-corrosion measures.

4. Mold molding parts’ hardness should not be less than 50HRC, or surface hardening treatment hardness should be higher than 600HV.

Ejecting, resetting, extracting core, and taking out parts

1. The ejection should be smooth, with no stalling, and no abnormal sound.

2. The surface of the slanting top should be polished and the slanting top surface should be lower than the core surface.

3. Sliding parts should be opened oil grooves, the surface should be nitride treatment, and the surface hardness after treatment is HV700 or more.

4. All the ejector bars should have stop-rotation positioning, each ejector bar should be numbered.

5. The ejecting distance should be limited by a limit block.

6. The reset spring should be selected from standard parts, the ends of the spring should not be polished and cut off.

7. Slider, the core should have a travel limit, a small slider with a spring limit, and spring inconvenience installation can be used when the bob screw; the cylinder core must have a travel switch.

8. Slider core generally uses an oblique guide column, the angle of the oblique guide column should be smaller than the slider locking surface angle of 2 ° ~ 3 °. The slider stroke is too long and should be used for cylinder extraction.

9. Cylinder extraction core forming part of the end face is wrapped, the cylinder should add a self-locking mechanism.

10. Slider width of more than 150 mm below the large slider should be a wear-resistant plate, wear-resistant plate material should be selected T8A, after heat treatment hardness of HRC50 ~ 55, wear-resistant plate than the large surface higher than 0.05 ~ 0.1 mm, and open the oil groove.

11. The top bar should not be strung up and down.

12. The barb should be added on the top bar, the direction of the barb should be consistent, and the barb is easy to remove from the product.

13. The clearance between the top bar hole and the top bar, the length of the sealing section, and the surface roughness of the top bar hole should be by the relevant enterprise standards.

14. The product should be convenient for the operator to take off.

15. The product is easy to follow the slanting top when ejected, the top bar should be added groove or etching.

16. The top block fixed on the top bar should be firm and reliable, and the non-forming part around should be processed with a slope of 3°~5°, and the lower periphery should be chamfered.

17. The oil hole on the mold frame should be free of iron filings and debris.

18. The end face of the return rod is flat and free from spot welding. The bottom of the embryo head should be free of shims and spot welds.

19. The three-plate mold gate plate guide slides smoothly and the gate plate is easy to be pulled apart.

20. The three-plate mold limit tie bar should be arranged on both sides of the injection mold installation direction, or add a tie plate to the mold frame to prevent the limit tie bar from interfering with the operator.

21. The oil and gas channel should be smooth, hydraulic ejector reset should be in place.

22. The bottom of the guide sleeve should be opened to make the exhaust port.

23. There should be no gap in the installation of positioning pins.

Cooling, heating system

1. The cooling or heating system should be fully open.

2. The seal should be reliable, the system should not have leakage under 0.5MPa pressure, and easy to repair.

3. The size and shape of the sealing groove opened on the mold frame shall conform to the requirements of the relevant standards.

4. The seal should be greased when it is placed, and it should be higher than the surface of the mold frame after it is placed.

5. The water and oil runner spacer should be made of materials that are not easy to be corroded.

6. The front and rear molds should adopt a centralized water supply and method.

Pouring system

1. The gate setting should not affect the product appearance and meet the product assembly.

2. The cross-section and length of the runner should be designed reasonably to shorten the flow as much as possible and reduce the cross-sectional area to shorten the filling and cooling time under the premise of guaranteeing the forming quality, and the plastic lost in the pouring system should be the least.

3. The cross-section of the three-plate mold sprue at the back of the front template should be trapezoidal or semi-circular.

4. The three-panel injection mold should have a break in the sprue plate, the sprue inlet diameter should be less than 3 mm, and a 3 mm deep step recessed into the sprue plate at the ball end.

5. The ball pulling rod should be fixed reliably, it can be pressed under the positioning ring, fixed by a headless screw, or pressed by a pressure plate.

6. The sprue and runner should be processed by machine according to the size of the drawing, not allowed to be processed by hand.

7. The point sprue gate should be by the specification.

8. The front of the manifold should be extended as a cold material cavity.

9. The Z-shaped buckle of the pulling rod should have a smooth transition.

10. The manifold on the parting surface should be round, and the front and rear mold should not be misaligned.

11. The submerged gate on the top bar should have no surface shrinkage.

12. The diameter and depth of the cold cavity of transparent products should be by the design standard.

13. The material handle is easy to remove, the appearance of the product is free of gate marks, and there is no residual mold material handle at the product assembly.

14. The two parts of the submerged gates should be nitride treated and the surface hardness should reach HV700.

Hot runner system

1. The layout of the hot runner wiring should be reasonable, and easy for maintenance, wiring numbers should correspond one by one.

2. The hot runner should be tested for safety, and the insulation resistance to the ground should be more than 2MW.

3. Temperature control cabinet and hot nozzle, hot runner should use standard parts.

4. The main flow port sleeve is connected to the hot runner with threads, and the bottom surface plane contact is sealed.

5. The hot runner is in good contact with the heating plate or heating rod, and the heating plate is fixed with screws or studs, and the surface is well laminated.

6. J-type thermocouple should be used and matched with the temperature control table.

7. Each group of heating elements should have thermocouple control, thermocouple position is reasonably arranged.

8. The nozzle should meet the design requirements.

9. The hot runner should have reliable positioning, at least two positioning pins, or add screws to fix.

10. There should be a heat insulation pad between the hot runner and the template.

11. Temperature control table set temperature and the actual display temperature error should be less than ± 5 ° C, and temperature control sensor.

12. The cavity and nozzle installation holes should be penetrated.

13. Hot runner wiring should be bundled and covered with the pressure plate.

14. There are two sockets of the same size, and there should be marked.

15. The control line should be sheathed and undamaged.

16. The temperature control cabinet structure is reliable, with no loose screws.

17. The socket is installed on the bakelite board and cannot exceed the maximum size of the template.

18. The electric wire is not allowed to be exposed outside the injection mold.

19. Hot runner or template all contact with the wire should be rounded corner transition.

20. Before the template assembly, all lines are free of the broken short-circuit phenomenon.

21. All wiring should be properly connected and well insulated.

22. After the template is mounted and clamped, all wiring should be checked again with a multimeter.

Forming part, parting surface, exhaust slot

1. There should be no unevenness, pits, rust stains, and other defects affecting the appearance of the front and rear mold surfaces.

2. The insert and the mold frame should have a clearance of less than 1 mm around the rounded corners.

3. The fractal surface is kept clean, neat, and tidy, with no hand-held grinding wheel to avoid hollowness and no depression in the sealing part.

4. The depth of the venting groove should be less than the value of the overflow edge of the plastic.

5. The insert should be in place, with smooth placement, and reliable positioning.

6. Inserts, cores, etc. should be reliably positioned and fixed, round pieces have a stop turn, and no copper or iron pads under the insert.

7. The top bar end face and core are consistent.

8. Before and after the mold forming part without inverted buckle, chamfering, and other defects.

9. The ejection of the bar should be smooth.

10. In the products of multi-cavity mold, the left, and right pieces are symmetrical, L or R should be indicated, if the customer has requirements on the position and size, it should meet the customer’s requirements, and generally add in the place that does not affect the appearance and assembly, the word number is 1/8.

11. Mold frame locking surface research and matching should be in place, in more than 75% of the area encountered.

12. The top bar should be arranged closer to the side wall and next to the tendons, and tabs, and use a larger top bar.

13. For the same piece should indicate the numbers 1, 2, 3, et.

14. Each touching surface, inserting surface and parting surface should be researched and matched in place.

15. The sealing part of the parting surface should conform to the design standard. 10~20mm for medium-sized molds and 30~50mm for large molds and the rest of the part should be machined to avoid hollowing.

16. The skin pattern and sandblasting should evenly meet customer requirements.

17. For products with the required appearance, the screws on the products should have anti-shrinkage measures.

18. The depth of the screw column of more than 20 mm should be selected to use the top tube.

19. The wall thickness of the product should be uniform, and the deviation should be controlled below ±0.15 mm.

20. The width of the bar should be in the appearance of the wall thickness of less than sixty percent.

21. Slanting top, the core on the slider should be a reliable way to fix it.

22. The front mold inserted into the back mold or the back mold inserted into the front mold, there should be a bevel locking around and machined to avoid hollow.

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