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Injection Mold Acceptance Standards Guide

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In our article “Injection Molding Quality Standards,” we specifically focus on recommended acceptance criteria for injection molded parts. As these parts pertain to both the appearance and functionality of the product, the standards set by each buyer can vary significantly. FirstMold provides services related to mold manufacturing and injection molding production, both involving the creation of molds.

Many buyers, particularly startups, tend to have their injection molding production carried out at the facilities of mold manufacturers, and as a result, they might not be as concerned about the injection mold acceptance standards. However, FirstMold still hopes that you take the time to gain a basic understanding of the acceptance standards for molds.

We have established very detailed guidelines for the acceptance of injection molds for your reference. The specific guidelines for mold acceptance are as follows:

I. Mold Appearance:

Texts On Mold Surface

1. Check whether the nameplate content includes the mold number, mold weight (KG), and mold dimensions (mm), with all characters printed in 1/8 inch size, ensuring clear, neatly arranged characters.

2. Verify if the nameplate is fixed on the mold feet near the rear template and the datum corner (15mm away from each side) using four rivets, ensuring a reliable fixation that is not prone to peeling off.

3. Confirm if English letters and numbers are uppercase (5/6″), positioned directly 10mm below the water nozzle, ensuring clear, aesthetic, neat, and evenly spaced characters.

4. Ensure all mold plates on the mold base have the datum symbol, uppercase English DATUM, character height 5/16″, positioned 10mm from the edge, ensuring clear, aesthetic, neat, and evenly spaced characters.

5. Check if each plate has a component number, positioned directly 10mm above the base surface below the reference corner symbol, requirements as in item 4.

6. For molds with directional installation requirements, check if the top or rear clamp plate indicates the installation direction with an arrow, with “UP” next to the arrow, both arrow and text spray-painted yellow, character height 50mm.

Cooling Water Nozzle

1. Check if the cooling water nozzles are using plastic blocks to insert nozzles, with a 10mm pipe, specifications can be G1/8″, G1/4″, G3/8″. If the contract has special requirements, follow the contract.

2. Ensure cooling water nozzles protrude from the mold base surface, with the nozzle tip recessed no more than 3mm from the outer surface.

3. Verify if the cooling water nozzle’s relief hole diameters are either ¢25, ¢30, or ¢35mm, with a chamfer around the hole, greater than 1.5×45, ensuring consistent chamfer.

4. Check for inlet and outlet markings on cooling water nozzles, with ‘IN’ for inlet and ‘OUT’ for outlet, followed by a sequence number, e.g., IN1, OUT1.

5. Confirm if the inlet and outlet oil nozzles, and air nozzles are like the cooling water nozzles, with a space before IN, OUT followed by a G (for gas), O (for oil).

6. For water nozzles on the top and bottom sides of the mold installation direction, check if they are internal and have flow channels or supporting pillars for protection.

7. Verify if non-internal oil or water nozzles have supporting pillars for protection underneath.


1. Verify if mold components affect the lifting and storage of the mold; if there are external leaks such as oil cylinders, water nozzles, pre-reset mechanisms during installation, supporting legs should protect them.

2. Check if mold feet are installed using screws passing through the mold feet fixed on the mold base, or if long mold feet are machined with external threads secured on the mold base.


1. Ensure the mold ejection hole matches the specified injection molding machine. Except for small molds, in principle, a single center ejection is not in use (when one dimension of mold length or width exceeds 500mm), the ejection hole diameter should be 5-10mm larger than the ejection rod.

2. Confirm if the mold dimensions fit the specified injection molding machine.

3. For molds weighing over 8000KG installed on an injection molding machine, check if screws are used with a press-through method, and not just a press plate alone. If using hydraulic locking molds, we must use screws to prevent hydraulic mechanism failure.

4. Verify if the mold is easy to lift and transport, with lifting not requiring the disassembly of mold components (except oil cylinders, which need separate packaging). If lifting rings interfere with water nozzles, oil cylinders, pre-reset rods, etc., change the lifting ring hole position.

5. Check if every mold component weighing over 10KG has an appropriate lifting ring hole. If not, ensure taking measures to facilitate part disassembly and installation. Design the size and position of lifting rings according to relevant corporate standards.

6. Confirm if lifting rings can rotate fully, ensuring balanced lifting.

Mold Base

1. Inspect the mold frame surface for any pits, rust, unused lifting rings, inlet and outlet water, air, oil holes, and other defects affecting the appearance.

2. Ensure all plates of the mold base have a chamfer greater than 1.5mm.

Locating Ring

1. Verify if the locating ring is securely fixed (typically using three M6 or M8 Allen screws), generally with a diameter of ¢100 or ¢150mm, protruding 10mm above the top plate. Follow the contract if there are special requirements.

2. The locating ring installation hole must be countersunk, not directly on the mold base top surface.

Sprue Bushing

1. Check if the sprue bushing radius R is greater than the injection machine nozzle radius R.

2. Verify if the entrance diameter of the sprue bushing is larger than the nozzle injection diameter.

Slides And Lifters

1. For ejection mechanisms like ejection rods and blocks, if there is interference with components like sliders, check if there is a mandatory pre-reset mechanism, and the top plate has a reset travel switch.

2. Verify if oil cylinder core pulling and ejection have travel switch control, ensuring reliable installation.

3. Confirm if all lifters can be disassembled through a hole through the rear clamp plate and ejector retainer plate, with the angle matching the angle of the lifters.


1. Confirm if the mold oil distributor is securely fixed.

2. Check if the oil tube connecting the oil distributor and the oil cylinder uses rubber tubing, with fittings using standard parts.

3. Verify if the ejector pin plate has a stop pin.

4. Check if the mold support pillar area is 25% – 30% of the area between spacer blocks on the rear clamp plate surface.

5. Confirm if the support pillar is 0.05 – 0.15mm higher than the mold legs and does not interfere with the knock-out hole.

6. Ensure the die locker device is reliably installed, with locating pins, symmetrically installed, no fewer than 4 (small molds may have 2).

7. For three-plate molds, check if there are springs between the top clamp plate and the runner stripper plate to assist in mold opening.

8. For large molds, after all components are installed, check for any interference during mold clamping.

9. For injection molding machines using extended nozzles, check if there is sufficient space inside the locating ring to ensure standard extended nozzles with heating rings can extend into it.

10. Verify if the bottom surfaces of screw installation holes are flat.

11. Check if screws M12 (including M12) and above are imported screws (grade 12.9).

II. Ejection Return, Core Pulling, And Demolding

1. Part One

1. Is ejection smooth without any sticking or strange noises?

2. Are lifters surface polished, 0.1–0.15 mm lower than the core surface?

3. Do lifters have guide grooves, made of tin bronze, embedded in the mold base and fixed with screws, located by dowel pins?

4. Is the end face of the ejector rod 0–0.1 mm below the core surface?

5. Do sliding components (except for ejector rods) have oil grooves, surface nitrided, hardness HV700 (large sliders as per customer requirements)?

6. Do all ejector rods have anti-rotation positioning, according to the three standard positioning methods of the enterprise, and are they numbered?

7. Does the ejector pin plate return completely?

8. Is the ejection distance limited by a stop block, material 45# steel, not replaceable by screws, with a flat bottom surface?

2. Part Two

9. Are return springs standard parts, unground, uncut at both ends?

10. Is the bottom surface of the reset spring installation hole flat, with a hole diameter 5 mm larger than the spring?

11. For springs over ¢20 mm in diameter, is there a guide rod inside, which is 10–15 mm longer than the spring?

12. Generally, are short-section blue mold springs used for light loads, red for heavy loads, and yellow for lighter loads?

13. Do springs have a pre-compression amount, 10%–15% of the total spring length?

14. Are the materials for the pressure plates of angled lifters and sliders 638, nitrided hardness HV700 or T8A, quenched to HRC50–55?

15. Do sliders and cores have travel limits, small sliders limited by springs, wave screws used when springs are inconvenient, oil cylinder cores controlled by travel switches?

16. Slider cores pulls generally use angle pins, is the angle pin 2–3 degrees less than the angle of the slider locking block? If the travel is too large, use an oil cylinder.

17. If the oil cylinder core pull part has wall thickness, is a self-locking mechanism added to the oil cylinder?

3. Part Three

18. Large sliders should not be positioned above the mold installation direction; if unavoidable, are the springs enlarged or increased in number, and the core pulling distance increased?

19. Is the maximum ratio of slider height to length 1, the length dimension 1.5 times the width dimension, height 2/3 of the width?

20. Is the sliding fit length of the slider more than 1.5 times the directional length of the slider, and after completing the core pulling action, is the retained length in the slot less than 2/3 of the slot length?

21. For large sliders (over 30KG), are T-slots guided by removable pressure plates?

22. Are sliders limited by springs? If the spring is inside, do spring holes appear entirely on the mold core or slider; if outside, are spring fixing screws double-ended to simplify slider disassembly?

23. Is the sliding distance of the slider 2-3 mm greater than the core pulling distance, similar for lifters?

III. Standard System (Cold-Runner)

1. Is the surface of the sprue inside the sprue bushing polished to ▽1.6?

2. Are the runners polished to ▽3.2 or 320# oilstone?

3. In three-plate molds, is the part of the runner that exits at the back of the top clamp plate trapezoidal or circular?

4. Is there a gap of about 10-12mm between the top clamp plate and the runner stripper plate?

5. Are the gate and runners machined with machine tools (CNC, milling machine, EDM) according to the dimensions on the drawings, manual grinder machining not allowed?

6. Is the point gate processed according to gate specifications?

7. At the point gate, is there a small protrusion on the mold cavity, with a corresponding recess in the mold core?

8. Is there an extended section at the front end of the sprue to act as a cold slug well

9. On the parting surface, is the surface of the runner circular, with no misalignment between the cavity and core?

10. For transparent products, do the diameter and depth of the cold slug well meet the design standards?

IV. Hot Runner System

1. Part One

1. Is the wiring layout of the hot runner system reasonable, and easy to maintain, with wire numbers corresponding one-to-one?

2. Has a safety test been conducted to prevent electrical leakage and other safety accidents?

3. Do the temperature control cabinet, hot sprue, and stripper plate meet customer requirements?

4. Is the main sprue bushing connected to the stripper plate with threads, sealed by flat surface contact at the bottom, and welded around the perimeter?

5. Does the stripper plate have good contact with the heating plate or heating rods, fixed with screws or studs, the surface fits well without gaps, and the heating rods have a fit-gap of no more than 0.05-0.1mm (h7/g6) with the stripper plate for easy replacement and maintenance?

6. Are J-type thermocouples used and correspond to the temperature control meter?

7. Do the stripper plate end plugs have dead corners that could prevent material degradation, with screws tightened and welded, sealed?

8. After installing the heating plate on the manifold, is the air insulation layer gap between the heating plate and the mold plate within the range of 25-40mm?

9. Does each group of heating elements have thermocouple control, with thermocouples positioned logically for precise temperature control?

10. Do the hot runner nozzles and heating rings make tight contact, with minimal exposure at both ends, and the cold material section length and nozzle are processed according to the drawings, with the dimensions of the clearance sections, sealing sections, and positioning sections meeting design requirements?

11. Is the outlet size of the nozzle smaller than ¢5mm to prevent surface sink marks of the product due to large sprues?

2. Part Two

12. Is the nozzle tip sealed with a copper or aluminum ring, with the sealing ring height 0.5mm above the major surface? The inlet diameter of the nozzle head is larger than the outlet size of the stripper plate to prevent overflow due to stripper plate thermal expansion and misalignment with the nozzle.

13. Due to thermal expansion, does the stripper plate have reliable positioning, with at least two dowel pins, or fixed with screws?

14. Is there thermal insulation between the stripper plate and the mold plate, using asbestos mesh, stainless steel, etc.?

15. Is there a pad under the main sprue bushing and above each hot nozzle to ensure sealing, made of stainless steel with poor heat transfer or using insulating ceramic washers?

16. If the pad above the hot nozzle protrudes from the top plate surface, besides being 0.3mm higher than the top plate, are these pads within the locating ring of the injection machine?

17. Is the temperature set on the temperature control meter within ±2℃ of the actual displayed temperature, and is temperature control sensitive?

18. Does the cavity communicate with the hot nozzle installation hole?

19. Are the hot runner wires bundled and covered with a press plate to prevent the wires from being crushed during assembly?

20. If there are two sockets of the same specification, are they clearly marked to avoid incorrect insertion?

21. Are control wires sheathed, undamaged, generally cable wires?

22. Is the structure of the temperature control cabinet reliable, with no loose screws?

3. Part Three

23. Are sockets installed on the phenolic board, exceeding the maximum size of the mold plate?

24. Does the pinpoint of the hot nozzle needle protrude from the cavity surface?

25. Are wires exposed outside the mold?

26. Are all places where wires contact the manifold or mold plate rounded to prevent wire damage?

27. Are all stripper plates and nozzles made of P20 material?

28. Before assembling the mold plate, are all circuits free of short circuits?

29. Are all wires correctly connected and insulated?

30. After the mold plates are clamped, are all circuits checked again with a multimeter?

VI. Packaging

1. Is the mold cavity sprayed with anti-rust oil?

2. Are sliding parts greased with butter?

3. Is the sprue bushing inlet blocked with grease?

4. Is the mold equipped with lock plates, and do their specifications meet the design requirements (at least two plates for three-plate molds to fix the stripper plate to the mold core)?

5. Are the mold product drawings, structural drawings, waterway diagrams, spare parts and mold material supplier details, instruction manuals, packing lists, and electronic documents complete?

6. Is the exterior of the mold sprayed with blue paint (if the customer has special requirements, follow the contract and technical specifications)?

7. Does the product have an assembly conclusion?

8. Does the product have any surface defects or issues with refinement?

9. Are spare parts and consumables complete with a detailed list, including supplier names?

10. Is there a release order from the marketing department?

11. Is the mold packaged with a thin film?

12. If packed in a wooden crate, is the mold name and orientation direction painted on it?

13. Is the wooden crate securely fixed?

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