What are the acceptance criteria for a good set of molds?

01 Mold appearance

1. The content of the mold nameplate is complete, the characters are clear, and the arrangement is neat.

2. The nameplate should be fixed on the mold foot near the template and the reference angle. The nameplate is reliable and not easy to peel off.

3. The cooling water nozzle should be made of plastic block water nozzle, if the customer requires otherwise, please follow the requirements.

4. The cooling water nozzle should not protrude from the surface of the mold base.

5. The cooling water nozzle needs to be processed with a counterbore. The counterbore diameter is 25mm, 30mm, and 35mm. The orifice is chamfered and the chamfering should be the same.

6. The cooling water nozzle should be marked for entry and exit.

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

8. Mould accessories should not affect the hoisting and storage of the mold. During installation, there are exposed oil cylinders, faucets, pre-reset mechanisms, etc., which should be protected by supporting legs.

9. The mounting of the support leg should be fixed on the mold base with screws passing through the support leg, and the excessively long support leg can be fastened to the mold base with a machined external threaded 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, one center cannot be used for ejection.

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 customers.

12. The overall dimensions of the mold should meet the requirements of the designated injection molding machine.

13. For molds with orientation requirements, an arrow should be used to indicate the installation directly on the front template or the rear template, and there should be “UP” next to the arrow. The arrow and text are both yellow and the height of the font is 50 mm.

14. The surface of the mold base should not have pits, rust marks, redundant rings, water vapor in and out, oil holes, etc., and defects that affect the appearance.

15. Moulds should be easy to hoist and transport. Mould parts must not be disassembled during hoisting. Lifting rings must not interfere with faucets, cylinders, pre-reset rods, etc.

02 Mold material and hardness

1. The mold base should be a standard mold base that meets the standard.

2. The material of mold forming parts and gating system (core, movable and fixed mold insert, movable insert, diversion cone, pushrod, sprue sleeve) shall be made of materials with performance higher than 40Cr.
3. When molding plastics that are corrosive to the mold, the molded parts should be made of corrosion-resistant materials, or the molding surface should take anti-corrosion measures.
4. The hardness of the molded parts should not be lower than 50HRC, or the hardness of the surface hardening treatment should be higher than 600HV.

03 Eject, reset, pull out the core, take out

1. The ejection should be smooth, free of jamming, and no abnormal sound.

2. The inclined top surface should be polished, and the inclined top surface is lower than the core surface.

3. The sliding parts should be provided with an oil groove, and the surface needs to be nitrided, and the surface hardness after treatment is HV700 or higher.

4. All ejector rods should have stop-rotation positioning, and each ejector rod should be numbered.

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

6. Standard parts should be used for the return spring, and both ends of the spring should not be polished or cut off.

7. Slider and core-pulling should have stroke limit, small slide is limited by spring, if spring is inconvenient to install, corrugated screw can be used; cylinder core-pulling must have a stroke switch.

8. Generally, inclined guide posts are used for core pulling of the slider, and the angle of the inclined guide post 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 oil cylinder should be used for drawing.

9. When the end surface of the core-pulling forming part of the cylinder is covered, the cylinder should be equipped with a self-locking mechanism.

10. There should be a wear plate under the large sliding block with a width of more than 150 mm. The material of the wear plate should be T8A. The hardness after heat treatment is HRC50~55. The wear plate is 0.05~0.1 mm higher than the large surface. Open the oil tank.

11. The ejector rod should not move up and down.

12. Add barbs to the top rod, and the direction of the barbs should be consistent, so that the barbs are easy to remove from the product.

13. The clearance between the ejector pin hole and the ejector pin, the length of the sealing section, and the surface roughness of the ejector pin hole should be in accordance with the requirements of the relevant enterprise standards.

14. The product should be convenient for the operator to remove it.

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-formed parts around the circumference should be processed with a 3°~5° slope, and the lower periphery should be chamfered.

17. There should be no iron filings in the oil passage hole on the mold base.

18. The end face of the return rod is flat and there is no spot welding. No gasket at the bottom of the embryo head, spot welding.

19. The gate plate of the three-plate mold slides smoothly, and the gate plate is easy to open.

20. Three-plate mold limit rods should be arranged on both sides of the mold installation direction, or pull plates should be added to the mold base to prevent the limit rods from interfering with the operator.

21. The oil circuit and air passage should be smooth, and the hydraulic ejector reset should be in place.

22. An exhaust port should be opened at the bottom of the guide sleeve.

23. There should be no clearance for the positioning pin installation.

04 Cooling and heating system

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

2. The seal should be reliable, the system should not leak under the pressure of 0.5MPa, and it is easy to check and repair.

3. The size and shape of the sealing groove opened on the mold base should meet the requirements of relevant standards.

4. Grease should be applied to the sealing ring when it is placed, and it should be higher than the surface of the mold base after it is placed.

5. Water and oil flow channel separators should be made of materials that are not easily corroded.

6. The front and back molds should use a centralized water supply.

05 Gating system

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

2. The runner section and length should be designed reasonably, and the process should be shortened as much as possible under 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 the least.

3. The partial cross-section of the three-plate mold runner at the back of the front mold plate should be trapezoidal or semicircular.

4. The three-plate mold has a material breaker on the gate plate, the diameter of the gate entrance should be less than 3 mm, and the ball head has a 3 mm deep step recessed into the gate plate.

5. The ball end pull rod should be reliably fixed, can be pressed under the positioning ring, can be fixed with headless screws, or can be pressed with a pressure plate.

6. Gates and runners should be machined according to the size requirements of the drawings, and manual grinding and polishing machines are not allowed.

7. The pointed gate should be in accordance with the requirements of the specification.

8. There should be an extension at the front end of the runner as a cold slug hole.

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

10. The runner on the parting surface should be round, and the front and rear molds cannot be misaligned.

11. The latent gate on the ejector rod should have no surface shrinkage.

12. The diameter and depth of the cold slug hole for transparent products should meet the design standards.

13. The handle is easy to remove, there is no gate mark on the appearance of the product, and there is no residual handle at the product assembly.

14. For the curved hook latent gate, the two parts of the insert should be nitrided, and the surface hardness can reach HV700.

06 Hot runner system

1. The wiring layout of the hot runner should be reasonable for easy maintenance, and the wiring numbers should be a one-to-one correspondence.

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

3. Standard parts should be adopted for temperature control cabinets, hot nozzle, and hot runner.

4. The main flow port sleeve is connected with the hot runner with threads, and the bottom surface is in contact with the hot runner for sealing.

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 fits well.

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

7. Each group of heating elements should be controlled by thermocouples, and the position of the thermocouples should be reasonably arranged.

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 an insulation pad between the hot runner and the template.

11. The error between the set temperature of the temperature control meter and the actual display temperature should be less than ±5°C, and the temperature control should be sensitive.

12. The cavity and nozzle installation hole should pass through.

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 line 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 and cannot exceed the maximum size of the template.

18. The wires must not be exposed outside the mold.

19. There should be rounded transitions at all the places where the hot runner or template is in contact with the wires.

20. Before the template is assembled, there is no open circuit or short circuit in all circuits.

21. All wiring should be connected correctly, with good insulation performance.

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

08 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 process conditions.

2. The injection pressure during mold injection production should generally be less than 85% of the injection molding machine’s rated maximum injection pressure.

3. The injection speed during the injection molding production of the mold, 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 of the mold during injection molding production should be less than 90% of the rated clamping force of the applicable model.

6. During the injection molding production process, the product and nozzle material should be taken out easily and safely (the time is generally not more than 2 seconds each).

7. For molds with inserts, the inserts are easy to install and the inserts are fixed reliably during production.

09 Packing and shipping

1. The mold cavity should be cleaned and sprayed with anti-rust oil.

2. The sliding parts should be lubricated.

3. The inlet of the sprue bushing should be sealed with grease.

4. The mold should be equipped with a clamping piece, and the specifications meet the design requirements.

5. Spare parts and wearing parts should be complete, with a detailed list and the name of the supplier.

6. Sealing measures should be taken to prevent foreign matter from entering the mold water, liquid, gas, and electrical inlets and outlets.

7. Spray paint on the outer surface of the mold, as required by the customer.

8. Moulds should be packaged in moisture-proof, waterproof, and bump-proof packaging, as required by customers.

9. Mold product drawings, structural drawings, cooling, and heating system drawings, hot runner drawings, spare parts, and mold material supplier details, operating instructions, mold test report, factory inspection certificate, and electronic documents should all be complete.

Learn More:

1. LKK Mold Making Service

2. Mold Assembly Process Video

3. Mold Making Process Video 

4. Mold T0 Sample, T1 Sample Video -Sweeping Robot

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