Creating a good mold requires not only good mold design and precise processing technology, but also "standards," and the concept of "almost" is not allowed. This article lists several acceptance standards for a good mold. Can you meet them?

01

Mold Appearance

1. The mold nameplate content is complete, the characters are clear, and the arrangement is neat.
2. The nameplate should be fixed on the mold base near the template and the datum corner. The nameplate should be firmly fixed and not easily peeled off.
3. Plastic block water nozzles should be used for cooling water nozzles, and customer requirements should be followed if there are any.
4. The cooling water nozzle should not extend beyond the surface of the mold frame.
5. The cooling water nozzle needs to be countersunk. The countersunk diameter is 25mm, 30mm, and 35mm. The hole mouth should be chamfered, and the chamfer should be consistent.
6. The cooling water nozzle should have inlet and outlet markings.
7. English characters and numbers should be larger than 5/6, located 10mm below the water nozzle, and the font should be clear, beautiful, neat, and evenly spaced.
8. Mold accessories should not affect the hoisting and storage of the mold. When installing, if there are exposed oil cylinders, water nozzles, pre-resetting mechanisms, etc., at the bottom, there should be support legs for protection.

9. The installation of the support legs should use screws to fix the support legs to the mold frame. For support legs that are too long, external threaded columns can be machined and fastened to the mold frame.

10. The mold ejection hole size should meet the specified requirements of the injection molding machine. Except for small molds, a single center ejection cannot be used.

11. The positioning ring should be firmly fixed. The ring diameter is 100mm and 250mm. The positioning ring is 10~20mm higher than the bottom plate. Exceptions apply if the customer has other requirements.
12. The mold dimensions should meet the requirements of the specified injection molding machine.
13. For molds with directional requirements, the installation direction should be indicated by an arrow on the front or rear template. There should be "UP" next to the arrow. The arrow and text are yellow, and the font height is 50 mm.
14. The surface of the mold frame should not have pits, rust, extra lifting rings, inlet and outlet steam, oil holes, or other defects that affect the appearance.
15. The mold should be easy to hoist and transport. The mold components should not be disassembled during hoisting, and the lifting rings should not interfere with the water nozzles, oil cylinders, pre-resetting rods, etc.

02

Mold Material and Hardness

1. The mold frame should use standard mold frames that meet the standards.

2. The materials used for the mold forming parts and the injection system (core, moving and fixed mold inserts, movable inserts, distributor cone, push rod, sprue bushing) should have performance higher than 40Cr.
3. When forming plastics that are easily corroded by the mold, the forming parts should be made of corrosion-resistant materials, or the forming surface should be treated to prevent corrosion.
4. The hardness of the mold forming parts should not be less than 50HRC, or the surface hardening treatment hardness should be higher than 600HV.

03

Ejection, Resetting, Core Pulling, and Part Removal

1. Ejection should be smooth, without jamming or abnormal sounds.
2. The surface of the inclined top should be polished, and the inclined top surface should be lower than the core surface.
3. Sliding parts should have oil grooves, and the surface should be nitrided. The surface hardness after treatment should be HV700 or higher.
4. All push rods should have anti-rotation positioning, and each push rod should be numbered.
5. The ejection distance should be limited by limit blocks.
6. Standard parts should be used for return springs. The ends of the springs should not be ground or cut.
7. Slides and cores should have stroke limiters. Small slides use spring limiters, and if the spring is inconvenient to install, ball screws can be used; oil cylinder cores must have limit switches.
8. Slides and cores generally use inclined guide posts. The angle of the inclined guide posts should be 2°~3° smaller than the angle of the slide locking surface. If the slide stroke is too long, an oil cylinder should be used for pulling.
9. When the end face of the forming part of the oil cylinder core is covered, the oil cylinder should have a self-locking mechanism.
10. Large slides with a width exceeding 150 mm should have wear-resistant plates underneath. The wear-resistant plate material should be T8A, with a hardness of HRC50~55 after heat treatment. The wear-resistant plate should be 0.05~0.1 mm higher than the large surface and have oil grooves.

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

12. Add a hook to the push rod. The direction of the hook should be consistent, and the hook should be easy to remove from the product.
13. The clearance between the push rod hole and the push rod, the length of the sealing section, and the surface roughness of the push rod hole should meet the requirements of relevant enterprise standards.
14. The product should be easy for operators to remove.
15. If the product is easy to follow the inclined top during ejection, grooves or textures should be added to the push rod.
16. The top block fixed on the push rod should be firm and reliable. The non-forming parts around it should be machined with a 3°~5° slope, and the lower periphery should be chamfered.
17. There should be no iron filings or debris in the oil passage holes on the mold frame.
18. The end face of the return rod is flat and without spot welding. There are no shims or spot welding at the bottom of the embryo head.
19. The guide sliding of the sprue plate in the three-plate mold is smooth, and the sprue plate is easy to pull open.
20. The limit pull rods of the three-plate mold should be arranged on both sides of the mold installation direction, or pull plates should be added to the outside of the mold frame to prevent interference between the limit pull rods and the operators.
21. The oil and gas passages should be smooth, and the hydraulic ejection and reset should be in place.
22. The bottom of the guide bushing should have a vent hole.
23. The locating pin installation should not have any gaps.

04

Cooling and heating system

1. The cooling or heating system should be fully unobstructed.
2. The sealing should be reliable, and there should be no leakage in the system under 0.5MPa pressure; it should be easy to maintain.
3. The size and shape of the sealing grooves on the mold frame should meet the relevant standard requirements.
4. Grease should be applied when installing the sealing ring, and it should protrude above the mold frame surface after installation.
5. The water and oil flow dividers should be made of corrosion-resistant materials.
6. The front and rear molds should use a centralized water supply method.

05

Casting system

1. The gate location should not affect the product appearance and should meet the product assembly requirements.
2. The runner cross-section and length should be reasonably designed. While ensuring molding quality, the process should be shortened as much as possible, and the cross-sectional area should be reduced to shorten the filling and cooling time. At the same time, the plastic consumed by the gating system should be minimized.
3. The cross-section of the runner on the back of the front template in a three-plate mold should be trapezoidal or semi-circular.
4. In a three-plate mold, there is a sprue bushing on the sprue plate. The diameter of the runner inlet should be less than 3 mm, and there is a 3 mm deep step at the ball head that recesses into the sprue plate.
5. The ball head sprue puller should be reliably fixed, it can be pressed under the locating ring, fixed with headless screws, or clamped with a pressure plate.
6. The gates and runners should be machined according to the drawing dimensions and should not be manually ground.
7. The point gate should meet the standard requirements.
8. The front end of the runner should have an extended section as a cold slug well.
9. The Z-shaped inverted buckle of the sprue puller should have a smooth transition.
10. The runner on the parting surface should be circular, and the front and rear molds should not be misaligned.
11. The hidden gate on the sprue puller should have no surface shrinkage.
12. The diameter and depth of the cold slug well for transparent products should meet the design standards.
13. The sprue should be easy to remove, the product appearance should have no gate marks, and there should be no residual sprue at the product assembly location.
14. For a hooked hidden gate, the two parts of the inserts should be nitrided, and the surface hardness should reach HV700.

06

Hot runner system

1. The hot runner wiring layout should be reasonable, easy to maintain, and the wiring numbers should correspond one-to-one.

2. The hot runner should undergo safety testing, and the ground insulation resistance should be greater than 2MW.
3. Standard parts should be used for the temperature control cabinet, hot nozzle, and hot runner.
4. The main flow port uses threads to connect to the hot runner, and the bottom surface is in plane contact for sealing.
5. The hot runner should have good contact with the heating plate or heating rod. The heating plate is fixed with screws or studs, and the surface fits well.
6. A J-type thermocouple should be used, and it should match the temperature controller.
7. Each group of heating elements should have thermocouple control, and the thermocouple positions should be reasonably arranged.
8. The nozzle should meet the design requirements.
9. The hot runner should have reliable positioning, with at least two locating pins or screw fixation.
10. There should be a heat insulation pad between the hot runner and the template.
11. The error between the set temperature and the actual display temperature of the temperature controller should be less than ±5°C, and the temperature control should be sensitive.
12. The cavity and nozzle mounting holes should be through holes.
13. The hot runner wiring should be bundled and covered with a pressure plate.
14. There should be two sockets of the same specification, with clear markings.
15. The control wires should have sheaths and be undamaged.
16. The temperature control cabinet structure should be reliable, and the screws should not be loose.
17. The sockets should be installed on the bakelite board and should not exceed the maximum dimensions of the template.
18. Wires should not be exposed outside the mold.
19. All places where the hot runner or template contacts the wires should have rounded transitions.
20. Before the template is assembled, all circuits should be free of open circuits and short circuits.
21. All wiring should be correctly connected, and the insulation performance should be good.
22. After the template is clamped, all circuits should be checked again with a multimeter.

07

Molding part, parting surface, vent groove

1. The surfaces of the front and rear molds should not have unevenness, pits, rust, or other defects that affect the appearance.
2. The inserts should fit well with the mold frame, and the rounded corners should have a gap of less than 1 mm.
3. The parting surface should be kept clean and tidy, without any hand-held grinding wheel marks, and the sealed part should be free of depressions.
4. The depth of the vent groove should be less than the overflow value of the plastic.
5. The inserts should be properly matched, and the installation should be smooth and reliable.
6. Inserts and cores should be reliably located and fixed. Circular parts should have anti-rotation features, and copper or iron sheets should not be placed under the inserts.
7. The end face of the ejector pin is consistent with the core.
8. The molding parts of the front and rear molds are free of defects such as undercuts and chamfers.
9. Ejection at the rib position should be smooth.
10. For multi-cavity mold products, the left and right parts are symmetrical, and L or R should be marked. If the customer has requirements for position and size, they should meet the customer's requirements. Generally, they are added where the appearance and assembly are not affected, with a size of 1/8.
11. The clamping surface of the mold base should be properly matched, with more than 75% of the area in contact.
12. Ejector pins should be placed closer to the side walls and next to ribs and bosses, and larger ejector pins should be used.
13. The same parts should be numbered 1, 2, 3, etc.
14. Each contact surface, insertion surface, and parting surface should be properly matched.
15. The sealing part of the parting surface should meet the design standards. For molds of medium size or smaller, 10-20mm; for large molds, 30-50mm; other parts should be machined to avoid air gaps.
16. The texture and sandblasting should be uniform and meet customer requirements.
17. For products with appearance requirements, screws on the product should have anti-shrinkage measures.
18. For screw pillars exceeding 20 mm in depth, ejector tubes should be used.
19. The wall thickness of the product should be uniform, with a deviation of ±0.15 mm or less.
20. The width of the rib should be less than 60% of the wall thickness on the appearance surface.
21. The inserts on the inclined ejector pins and sliders should have a reliable fixing method.
22. When the front mold is inserted into the rear mold or the rear mold is inserted into the front mold, there should be inclined surfaces for locking and machining to avoid air gaps.

08

Injection Molding Process

1. Under normal injection molding process conditions, the mold should have stable injection molding production and repeatable process parameter adjustment.
2. During injection molding production, the injection pressure should generally be less than 85% of the rated maximum injection pressure of the injection molding machine.
3. During injection molding production, the injection speed in three-quarters of the stroke should be no less than 10% of the rated maximum injection speed or more than 90% of the rated maximum injection speed.
4. During injection molding production, the holding pressure should generally be less than 85% of the actual maximum injection pressure.
5. During injection molding production, the clamping force should be less than 90% of the rated clamping force of the applicable machine model.
6. During injection molding production, the removal of products and runners should be easy and safe (generally no more than 2 seconds each).
7. For molds with inserts, the installation of inserts should be convenient and the fixing of inserts should be reliable during production.

09

Packaging and Transportation

1. The mold cavity should be cleaned and sprayed with rust preventive oil.
2. Lubricating oil should be applied to the sliding parts.
3. The sprue bushing and the feed port should be sealed with lubricating grease.
4. The mold should be installed with clamping plates, and the specifications should meet the design requirements.
5. Spare parts and wearing parts should be complete, and a detailed list and supplier names should be attached.
6. The water, liquid, gas, and electricity inlets and outlets of the mold should be sealed to prevent foreign objects from entering.
7. The outer surface of the mold should be sprayed with paint, according to customer requirements if any.
8. The mold should be packaged to prevent moisture, water, and collisions, according to customer requirements if any.
9. Mold product drawings, structural drawings, cooling and heating system drawings, hot runner drawings, details of parts and mold material suppliers, instruction manuals, mold trial reports, factory inspection certificates, and electronic documents should all be complete.