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What problems should be paid attention to when accepting plastic molds?

Update:06-11-2020
Summary:

What problems should be paid attention to when acceptin […]

What problems should be paid attention to when accepting plastic molds?

A. Appearance, dimensions and cooperation of molded products
1. The appearance of the product does not allow for shortcomings: lack of material, burnt, white top, white lines, peaks, blistering, whitening (or cracking, breaking), baking, wrinkles and other defects.

2. Welding mark: Generally, the length of circular perforation weld mark is not more than 5mm, and the length of special-shaped perforation weld mark is less than 15mm. The weld mark strength can pass the functional safety test.

3. Shorten: the appearance is not allowed to be shortened, and the inconspicuous areas are allowed to have slight shrinkage (no dent in the hand).

4. Generally, the flatness of small products is less than 0.3mm. If there are device requirements, the device requirements must be ensured.

5. There should be no air lines or material flowers in the prominent appearance, and the product generally cannot have bubbles.

6. The geometric shape and scale precision of the product should meet the requirements of formal and useful mold drawings (or 3D documents). Product public service shall be based on the principle of public service. Shaft-scale public service is negative public service, and hole-scale public service is For official duties, customers have requirements as required.

7. Product wall thickness: The product wall thickness is generally required to be uniform, non-uniform wall thickness should meet the requirements of the drawing, and the public service should be -0.1mm according to the characteristics of the mold.

8. Product cooperation: face shell and bottom shell cooperation: the appearance misalignment is less than 0.1mm, and there should be no scratching. The holes, shafts, and surfaces that have cooperation requirements must ensure the cooperation interval and application requirements.

B. Mold appearance

1. The content of the mold nameplate is intact, the characters are clear, and the arrangement is regular.

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

3. The cooling water nozzles should be made of plastic block water nozzles, and customers have other requirements as required.

4. The cooling water nozzle should not extend out of the mold base

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

6. The cooling water nozzle should have in and out symbols.

7. The English characters and numbers of the symbol should be greater than 5/6, and the orientation should be 10mm directly below the tap. The handwriting should be clear, beautiful, regular, and evenly spaced.

8. Mould accessories should not affect the hoisting and storage of the mould. There are exposed oil tanks, faucets, and pre-reset tissues under the device, which should be protected by supporting legs.

9. The support leg device is fixed on the mold base with screws through the support leg, and the over-long support leg can be fastened on 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 firmly. The diameter of the ring is generally 100mm and 250mm (different depending on the model). The positioning ring is 10-20mm higher than the bottom plate. Customers have other requirements.

12. The shape and 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 direction of the device on the front or back template, and there should be "UP" next to the arrow. The arrow and text are both yellow and the height of the text is 50 mm.

14. The surface of the mold base should not have pits, rust marks, remaining 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, oil cylinders, and pre-reset rods.

C. Mold information and hardness

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

2. Mold forming parts and pouring system (core, movable and fixed mold inserts, movable inserts, split cones, push rods, sprue sleeves) are selected for materials with performance higher than 40Cr.

3. When molding plastic that is corrosive to the mold, the molded parts should be made of corrosion-resistant materials, or the molding surface should adopt anti-corrosion methods.

4. The hardness of the moulded parts should not be lower than 50HRC, or the surface hardening treatment hardness should be higher than 600HV.

 

D. Ejecting, resetting, pulling out the ferrule, picking up

1. The ejection should be smooth, without jamming, and without abnormal movement.

2. The surface of the inclined top 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 nitridated, 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. Use limit block to limit the ejection interval.

6. Standard parts should be selected for the reset spring. Both ends of the spring cannot be polished or cut off.

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

8. Generally, the inclined guide post is used for core pulling of the slider. The viewpoint of the inclined guide post should be 2°~3° smaller than the viewpoint of the locking surface of the slider. If the slider stroke 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 self-locking.

10. There should be wear-resistant plates under the large sliders with a slider width exceeding 150 mm. The material of the wear-resistant plates should be T8A. After heat treatment, the hardness is HRC50~55. The wear plates are 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 on the top rod, the direction of the barbs should be kept the same, the barbs are easy to remove from the product.

13. The cooperation gap 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 specifications.

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

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 strong and reliable, the non-formed parts around the circumference should be processed with a slope of 3°~5°, 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 without spot welding. There is 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 placed on both sides of the direction of the mold device, 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. The bottom of the guide sleeve should have an exhaust port.

23. The positioning pin device cannot have gaps.

E. Cooling and heating system

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

2. The sealing should be firm, the system should not leak under the pressure of 0.5MPa, easy to repair.

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

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

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

6. The front and back molds should be assembled and fed.

7. The diameter of the cooling water channel is between 8~12mm.

F. Pouring system

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

2. The runner cross 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. The plastic loss of the pouring system should be the least.

3. The partial cross section of the three-plate mold runner on the reverse side 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 firmly 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 requirements of the drawings. Hand grinder processing is not allowed.

7. The point gate gate should be in accordance with the specifications.

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

9. The Z-shaped inverted buckle of the pull rod should have a smooth transition. 1

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

11. The ambush gate on the ejector rod should have no appearance shortening.

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

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 device.

14. For curved hook and ambush gate, the two parts of the insert should be nitrided, and the surface hardness reaches HV700.

G. Forming part, parting surface, exhaust groove

1. The front and back molds should not have unevenness, pits, rust and other defects that affect the appearance.

2. The inserts cooperate with the mold frame, and the rounded corners should have a gap of less than 1mm.

3. The parting surface is kept clean and tidy. There is no portable grinding wheel to avoid the air, and the sealing part has no depression.

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

5. The inserts should be researched and matched in place, placed smoothly and positioned firmly.

6. The inserts, inserts, etc. should be firmly positioned and fixed, the round pieces have a stop, and there is no copper or iron pad under the inserts.

7. The end face of the ejector pin is the same as the core.

8. The forming part of the front and rear molds has no shortcomings such as undercut and chamfer.

9. The ribs should be pushed out smoothly.

10. For products of multi-cavity molds, the left and right parts are symmetrical, and L or R should be indicated. If the customer has requirements for location and size, it should meet customer requirements. Generally, it should be added where it does not affect the appearance and installation. .

11. The clamping surface of the mold base should be in place, and more than 75% of the area should be touched.

12. The ejector rod should be placed closer to the side wall and beside the ribs and bosses, and a larger ejector rod should be used.

13. The numbers 1, 2, 3, etc. should be indicated for the same parts.

14. Each contact surface, penetration surface, and parting surface should be researched and matched in place.

15. The parting surface sealing part should meet the design specifications. 10-20mm for medium-sized molds, 30-50mm for large molds, and the remaining parts are machined to avoid voids.

16. The skin texture and sandblasting should reach customer requirements evenly.

17. For products with requirements for appearance, the screws on the products should have anti-shrinkage methods.

18. Jack pipes should be used for screw columns with a depth exceeding 20 mm.

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

20. The width of the ribs should be less than 60% of the wall thickness of the appearance

21. The core inserts on the inclined roof and slider should have a firm fixing method.

22. The front mold pierces the back mold or the back mold pierces the front mold. There should be bevels around it for locking and machining to avoid air.

H. Injection molding production process

1. The mold should have the stability of injection molding and the repeatability of process parameter adjustment within the range of normal injection molding process conditions.

2. The injection pressure when the mold is produced is generally less than 85% of the maximum injection pressure of the injection molding machine.

3. When the injection speed of the mold is produced, the injection speed of the three-quarter stroke is not less than 10% of the extra maximum injection speed or 90% of the extra maximum injection speed.

4. The holding pressure of the mold during injection molding should generally be less than 85% of the actual maximum injection pressure.

5. The clamping force during injection molding should be less than 90% of the additional clamping force of the applicable model.

6. In the process of injection molding, the removal of products and nozzle materials should be simple and safe (generally no more than 2 seconds each time).

7. For molds with inserts, the inserts are convenient and the inserts must be fixed firmly during production.

I. Packaging and shipping

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

2. The sliding parts should be lubricated.

3. Use grease to seal the inlet of the sprue bushing.

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 supplier name

6. The mold water, liquid, gas, and electricity imports and exports should be sealed to prevent foreign objects from entering;

7. Spray paint on the outside of the mold, as required by customers.

8. The mold should be packaged with moisture-proof, water-proof, and bump-proof packaging, and customers have requirements as required.

9. Mold product drawings, structural drawings, cooling and heating system drawings, warm runner drawings, spare parts and mold data supplier details, operating instructions, statement of mold test conditions, factory inspection certificates, and electronic documents should be complete.