Acceptance Standards for Plastic Injection Molds

Medical Double-Color Plastic Injection Molding Companies has established standards for mold approval from three aspects: mold structure, plastic part quality, and injection molding process requirements. Based on this, the mold quality is evaluated and scored, hoping to continuously improve the mold quality; ensure that the mold can be put into production normally and produce plastic parts of qualified quality to meet the requirements of product design. 1. Mold structure (1) Mold material ① The steel used for each plate of the mold base shall not be less than 1050 steel. (Equivalent to Japan’s ace steel) ② The surface hardness of the materials used for the base, side pins, back pins, middle brackets, and middle brackets shall not be less than HRC60. ③ For ABS and HIPS material front molds and front mold inserts, use super P20 steel (such as 718, M238, etc.). For rear molds, use general P20 steel (such as MUP, M202, etc.), and for rear mold inserts, use 1050-1055 steel or better steel. ④ For beer made of corrosive materials such as PC, POM, PE, etc., the front and rear molds and their inserts must be made of 420 steel (such as S136, M300, M310, etc.). ⑤ The steel used for beer mirror molds is 420 steel (such as S136, M300, M310, etc.). ⑥ The surface hardness of the inclined top and rocker arm shall not be less than HRC35, and the surface hardness of the push plate shall not be less than HRC28. ⑦ If the customer specifies that mold steel should be used, the mold factory shall meet the customer’s requirements.

(2) The mold should have a structure ① Mold identification: The outside of the mold base should be marked with text according to customer requirements. The P/N number and plastic part brand should be marked in the mold base at the position specified by the customer. The mold with multiple cavities should be marked with the mold cavity number, and the multiple inserts should be marked with the insert number according to the design requirements. ② The mold should be installed with a suitable flange ring and a standard code mold pit should be opened. ③ The three-plate mold should be installed with a buckle lock and a locking pin, and the pull hook and the nozzle plate should be installed, and the elastic ring should be opened first. ④ The mold bottom plate should have qualified ejector holes, and the hole position should meet the ejection balance requirements. ⑤ The mold ejector plate should be equipped with a reset spring. When closing the mold, the front template should first contact the return pin, otherwise the mold should first install the reset mechanism (separate requirements for the slide structure). ⑥ Slide structure, the slide movement should be smooth, and the contact surface should have an oil groove. The slide should be installed with a spring that makes the slide pop up, and a limit device should be installed. The total ejection height of the half block moving in the height direction cannot exceed 2/5 of the length of the guide slide. ⑦ Ejector mechanism. ; The ejector setting should ensure that the plastic part does not produce permanent deformation, whitening, or affect the appearance of the plastic part when demolding. The ejector mechanism should ensure flexibility, reliability, and no erroneous action. When the top surface of the ejector and the sleeve is not flat, the ejector and the sleeve should be positioned. ⑧ Trash pins should be evenly set on the bottom plate, and the height of the trash pins should be consistent. ⑨ 4545 or above large molds should be equipped with a middle support edge. If the number of cylinders in a set of molds reaches or exceeds 16, a middle support edge should be added. ⑩ The diameter and length of the runner should be processed reasonably. Under the premise of ensuring the quality of forming, the process should be shortened as much as possible, the cross-sectional area should be reduced to shorten the filling and cooling time, and the plastic loss of the pouring system should be minimized. The runner should generally be equipped with a cold material well. 11 The cavity distribution should be reasonable and should comply with the principle of filling each cavity at the same time. The gate setting should not affect the appearance of the plastic part and meet the assembly of the plastic part. The gate residue should be minimized as much as possible under the conditions allowed by the brewing. 12 Cooling system. The water flow channel should be divided into sections so that the temperature difference of each part of the mold surface is within 10℃. The position of the water flow channel inlet and outlet does not affect the installation, and the size of the throat is 13mm. Inserts and runners on the surface of the cavity should generally be connected to the water flow channel. Inserts such as battery pockets, handles, and speakers must be connected to the water flow channel. The mold water flow channel should be watertight, and the words “OUT” and “IN” should be marked at the flow channel inlet and outlet. If there are multiple groups of water flow channels, the group number should be added. 13 The battery pocket and other parts that exert a large clamping force on the front mold should be evenly equipped with hooks and other parts at the corresponding rear mold parts. 14 The mold structure ensures smooth exhaust. 15 If the column height exceeds 20mm, a sleeve should be used. If the bone position exceeds 25mm, glue guides should be evenly added according to the design requirements. 16 The mold should be evenly distributed with support heads according to the strength requirements to prevent mold deformation. 17 The mold cavity stress center should be consistent with the mold center as much as possible, and the cavity center should not exceed 25% of the mold center at most. 18 If there are any shrinkage-causing surfaces on the corresponding rear mold columns, a volcanic crater should be added. 19 For molds with one-way inclined surfaces and large deep cavities, the parting surface should be equipped with a reliable self-locking device.

(3) Unacceptable structures of molds ① The mold is not allowed to have sharp steel or thin steel with a height greater than 2mm and a thickness less than 1mm. ② Except for the BOSS column, the ejector pin is not allowed to contact the front mold. ③ There is no abnormal sound when the mold is opened and closed. ④ The red lead test is not allowed to be missed within 5mm of the cavity edge, and the red lead test of the parting surface is not allowed to be less than 80%. ⑤ All fastening screws are not allowed to be loose. ⑥ All hooks are not allowed to have different directions. ⑦ The plastic parts are not allowed to stick to the mold. ⑧ The mold is not allowed to have an unbalanced ejection. ⑨ The front and rear templates in the mold height direction are not allowed to lack the lacing hole. ⑩ The mold assembly is not allowed to miss or install the wrong parts. 2. Plastic parts quality part (1) Basic dimensions ① The geometric shape and size accuracy of the plastic parts should meet the requirements of the formal and valid mold opening drawings (or 3D files). ② General structural dimension standards. Plastic parts are generally required to have an average plastic thickness, and non-average plastic thickness should meet the requirements of the drawings. The diameter of the stud root: M3 screw is φ6.0+0.2mm, the diameter of the crater is φ10.0mm; M2.6 screw is φ5.0+0.2mm, the diameter of the crater is φ9.0mm. The thickness of the root of the fork bone and the perimeter bone: 1.2+0.2mm. The top thickness of the RUBBER cross bone of the button: 0.9+0.1mm. The top wall thickness of the cylinder column: 1.2±0.1mm. The glue thickness of the hook needle position of the battery box rear mold is less than 2.0mm. The misalignment of the front and rear molds of the plastic parts at the same PL surface is less than 0.05 mm. The bottom shell matches. A. The second or third level stopper match requires the PL surface misalignment to be less than 0.1 mm, and there is no scratching phenomenon; B. The single-side clearance of the stopper is 0.1~0.3 mm, and the larger value is taken for complex shapes. The horizontal single-side clearance between the battery door and the battery box is 0.2~0.3 mm. Button and hole match. The single-side clearance between general geometric buttons and holes is 0.15-0.25 mm. The single-side clearance between special-shaped buttons and holes is 0.3-0.4 mm, and the clearance between injection buttons should take the larger value. When the button and the flower are matched, their matching can meet the safety test standard. Card insertion position matching. The single-side clearance between the card insertion door and the bottom shell is 0.2-0.3 mm. The single-side clearance between the socket and the plug box is 0.5 mm. The minimum single-side axial clearance of the four major parts is 0.1-0.2 mm. The single-side clearance between the LOCK and the matching pillow hole is 0.2 mm. The single-side clearance between the bracket and the matching hole is 0.1-0.2 mm, and the larger value is taken for the length greater than 150 mm. The single-side clearance between the COVER and the matching hole is 0.1 mm. The single-side clearance between the ROLLER and the matching hole is 0.5-1.0 mm. (2) Surface defects (when the process conditions cannot be met) ① Defects are not allowed on the surface of the rubber part. A. Uneven glue flow (or lack of material, stagnant water) B. Burnt C. White top D. White line E. Peaking F. Bubbling G. White pull (or cracking, breaking) H. Baking I. Wrinkles ③ Surface restricted defects and acceptance level. No. Defect Name Acceptance Level 1 Watermark A. Watermark strength can pass the functional safety test. B. The length of the watermark of the general perforation hole is not more than 15mm, and the watermark of the round trumpet hole is not more than 5 mm. C. The length of the watermark at the fusion of multiple water outlets is not more than 20 mm. D. The watermark at the wrist is not in the middle of the wrist or the stress position. E. There is no watermark on the outer surface of the rubber part corresponding to the column position. F. There is no watermark on the button bracket with spark pattern on the surface. G. The watermark of the internal parts is not restricted in the position where the strength is allowed. 2 Shrinkage A. Slight shrinkage is allowed in the inconspicuous position of the rubber part surface (no dents can be felt). B. The internal parts can have slight shrinkage if the size allows. C. The shrinkage under the non-appearance surface of the plastic part does not affect the size and strength. No. Defect Name Acceptability 3 Whitening A. Slight whitening is allowed on the side of the plastic part with sparkle or sunburn, and it can be eliminated by grinding paste. B. There is no whitening on the first side of the appearance of the plastic part. 4 Deformation A. The unevenness of the supporting feet of the larger bottom shell is less than 0.3mm. B. The unevenness of the KEY bracket is less than 0.5mm. C. The deformation of the plastic part should be controlled by adjusting the rack after beer molding. D. Except for the above items, the plastic part has no deformation. 5 Air marks A. For plastic parts made of PE, PA, PVC, PC and other plastic materials, slight air marks are allowed at the sprue. The air marks do not protrude 3.0mm from the sprue. B. For plastic parts with thick and uneven wall thickness such as dolls, slight air marks are allowed at the sprue and carved protruding positions. C. Except for the above two items, there are no air marks on the surface of the plastic part. 6 Yellowing A. Larger bottom shell with water entering in the middle; slight yellowing is allowed near the sprue. The degree of yellowing should not affect the original color of the plastic part, but only slightly change the color depth. B. Except for the above cases, the plastic part has no yellowing. 7 Sprue residue A. There is no interference between the sprue position and residue of the plastic part during assembly. B. There is no plastic waste at the sprue position, and no plastic film is immersed in water at the ejector position. C. There is no sprue mark on the appearance of the plastic part after assembly. 8 Snake pattern A. There is no snake pattern on the appearance of the plastic part after assembly. B. Snake pattern is allowed on the internal parts or non-appearance surfaces after assembly if it cannot be improved. 9 Sharp and thin plastic parts, except for plastic parts such as piano keys, which are allowed to have specially designed sharp and thin plastic positions, other plastic parts have no sharp and thin plastic positions. (3) Surface modification requirements ① Surface gloss. The glossy surface should be flat and have a mirror effect; the non-appearance surface of the front mold surface and the internal parts are allowed to have slight processing marks on the surface. The glossy surface is not allowed to have defects such as scratches, rust, spots, etc. ② Surface decoration (EDM or sunburn). The texture meets the design requirements, the texture should be uniform and the side and surface should be consistent. Mutual accessories require the texture to be consistent. (Except for matching with old parts) ③ Surface font. The height of the surface font meets the design requirements and must be uniform and consistent. The font width, size, density, number of words, and position meet the film requirements. ④ CORE surface decoration. Generally, the CORE surface should be light-saving, without obvious sparks and processing marks, except for special requirements. The appearance of transparent plastic parts or assembled surfaces meets the design requirements.

4. Injection molding process (1) The mold should have the stability of brewing and the repeatability of process parameter adjustment within a certain range of injection molding process conditions. (2) The injection pressure during mold brewing should generally not exceed 85% of the rated maximum injection pressure of the injection molding machine. (3) The injection speed during mold brewing should not be less than 10% of the rated maximum injection speed or exceed 90% of the rated maximum injection speed. (4) The holding pressure during mold making should generally not exceed 85% of the actual maximum injection pressure. (5) The clamping force during mold making should not exceed 90% of the rated clamping force of the applicable model. (6) During the making process, the removal of the product and the sprue material should be easy and safe (the time should generally not exceed 2 seconds each). Injection Mold Scoring Table 1. Mold Structure Full Score: 50 Actual Score: 1. Mold Material (Full Score 8 points) Full Score Full Score Mold Base Material 1 Front Cavity Material 3 Rear Cavity Material 3 Side Pins, Back Pins, Middle Support, Middle Support Edge, Base Material 1 2. Mold Should Have Structure (26 points) Full Score Full Score Lifting Eye Hole, Code Mold Pit, Flange Ring 1 Buckle Machine, Locating Pin 1 Ejector Stroke 1 Ejector Reset 1 Curved Ejector Sleeve Needle Positioning 1 Hook Pin Same Phase 1 Strength and Quantity of Three-plate Mold Tie Rods and Limit Rods 2 Gate Size Meets Post-Injection Processing Requirements 1 Cavity Pressure Medium The center of the three-plate mold should not be offset. The distance between the A plate and the sprue plate is reasonable. 1. The runner runs smoothly. 2. The mold support head is sufficient. 1. The runner is lubricated. 1. The runner structure is reasonable. 2. The deep rib position is added with glue. The cavity exhaust is smooth. 2. The weight ratio of the runner to the finished product is reasonable. 1. The cross-sectional area of ​​the runner is reasonable. The gate position setting meets the filling requirements. 1. The layout of multiple cavities is reasonable. 1. The gate size meets the filling requirements. The gate type is reasonable. 13. The mold does not allow structure (8 points). Full score. Full score. The parting surface is not allowed to have red lead. Less than 2 sticky Mold 2 No abnormal noise is allowed when the mold is opened and closed 1 The mold is not allowed to have sharp steel, thin steel, unbalanced ejection, mold cooling (or heating) system (8 points) Insert position water transport 2 The mold temperature in the rear mold cavity is uniform 3 The mold temperature in the front mold cavity is uniform 3 2. Rubber part quality Full score: 30 points Score: The geometric shape, size and structural size of the rubber part are accurate, no deformation or acceptable. The surface of the rubber part has no allowable defects. No yellow gas or acceptable. Water-entrapment strength is OK. No snake pattern or acceptable. Water-entrapment position is OK. No gas pattern or acceptable. Water-entrapment length is OK. No sharp and thin rubber parts or acceptable. No shrinkage or acceptable. No whitening of residual rubber material at the sprue or acceptable. Surface modification of the rubber part is OK
5. Injection molding process Full score: 20 points Score: Stable injection molding parameters 4 Suitable injection molding speed 1 High repeatability of injection molding parameters 4 Suitable injection molding pressure 1 Suitable clamping force 2 Easy demoulding and picking up Suitable holding pressure 2 Cycle time meets requirements IV. Description of mold defects Evaluator: Department: Signature: Date: Department: Signature: Date: Remarks: 1. This table only provides the items for injection mold scoring. The pass and fail judgment criteria of the items are the “Injection Mold Approval Standard Book” 2. Scoring method: A. For each item in the table, the “score” in the “full score” column is given in the “score” column for qualified items, and “0” is given for unqualified items. B. For an item in the table that contains multiple contents, only some of which are unqualified, this item cannot get full marks and points must be deducted. The deduction form is “0.5” per level. C. If the evaluated mold does not have the structure of some items in the “scoring table”, please make an “×” mark in the “score” column of the column. D. The full score of this table design is 100 points, but considering that some molds do not fully have the contents to be judged in this table, but these contents account for a certain score. In order to let the scores truly reflect the mold status, a scoring column is set up. Score = actual score Actual full score × 100% = score Actual full score = 100 – score of no corresponding assessment item E. For unqualified items and deducted items, please use text to briefly explain them in the “Mold Defect” column.