Plastic mold basic information

The SprueThe sprue is a round, tapered hole which leads the plastics material from the nozzle of the heating cylinder of the injection molding machine to the distributing runners in the mold. The heater nozzle makes contact with the sprue bushing at the small end of the taper, against some sort of accurately fitting seat which in this diagram is shown to be spherical. The diameter of the small end of the sprue should be .015″ to .025″ larger than the orifice at the end of the heater nozzle.This provides sufficient margin for possible variation in nozzle and mold alignment, so the portion of the sprue which breaks off inside the nozzle when the mold opens will not overhang the hole in the bushing and prevent free passage of the sprue through it.The size of the nozzle and sprue employed for a specific molding application should be in proportion to the size of the shot or charge of material required to fill the mold. Large sprues generally provide better flowing conditions than small sprues, and do no particular harm except to increase the amount of sprue scrap which must be reprocessed and used again.A taper of 2°-30′ on a side is need. This is a practical amount which will insure easy release of the sprue but which will not increase the diameter of the large end unduly for a long sprue. The taper should be reamed smoothly, without tool marks, and it should be polished. Rough sprues may cause losses of as much as 10 seconds in the molding cycle because of the extra time the molded material requires to cool and harden sufficiently to permit it to be pulled out of the rough hole.The use of a standard taper angle for all of the sprue bushings manufactured in a single shop makes it possible to use a single reamer for reaming a wide range of diameters and lengths. The shoulder on the sprue bushing should be rather long, because there is possibility of encountering large thrusting forces which tend to push the shank through the shoulder.A generous radius where the diameter changes avoids stress concentration and hardening cracks. A radius at the large end of the sprue, where it meets the runner, improves the flowing conditions for the material. Mold steel should be used in making the sprue bushing, because it should be hardened to 40-45 Rockwell C. This makes the bushing resistant to crushing and brinelling, and thus it helps in maintaining good seating of the nozzle, which prevents the molding material from leaking out at this junction. Also, lodged or stuck sprues may be hammered out with a rod of brass or other soft metal without damaging the seat or taper.

Some mould makers prefer to perform certain rough machining operations on the mould block before the mould undergoes normalizing heating, while others prefer to carry out the latter process immediately after receipt of the steel. Where the former method is adopted, some little care must be taken to insure that adequate amounts of material are left on all important portions so as to allow sufficient machining depth after normalizing, when some change of shape usually takes place.well polished surfacesAfter the mould steel has thus been normalized and machined up in readiness for the hardening operation, it is essential to make certain that all surfaces have been well polished, especially the walls of the cavity，which, of course, should be entirely free from scratches, burrs, turning tool or milling cutter marks, engraving lines, chatter effects, and any markings, however slight and apparently unimportant they may appear to be.Marks and disfigurations of such a character may prove too deep for easy removal by the usual polishing or buffing operations after hardening, and in addition to their being permanent faults in the mould surface, will also become the source of unsightly markings on the exterior of the finished moulding.Furthermore, it will often be found that such fine scratches, etc.” become in the course of time the source of hair like cracking of the mould surfaces, or the cause of other developing flaws in the polish or smoothness of the mould cavity.sharp cornersAll sharp corners or knife edges, even when situated on non-essential exterior surfaces，should be smoothed off, and if permissible slightly rounded or beveled. Recesses, undercuts, or counter-boring,as for screw heads, should be smoothly finished and polished, because a torn surface in the material may prove doubly harmful and trouble¬some to remove after hardening.Where portions of a mould are thin due to heavy undercutting for cavity formations or to receive other mould mechanisms, special care will be necessary lest hardening produces excessive distortion at such points. It is customary to equip such a mould with supporting pads, these being located temporarily under the weakened portions and so fitted as to allow them readily to be removed after the harden¬ing operation. In this manner, accuracy can be maintained.

Injection moulding is used to create many things such as wire spools, packaging, bottle caps, automotive parts and components, toys, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today. Injection moulding is the most common modern method of manufacturing plastic parts; it is ideal for producing high volumes of the same object

Moulding tolerance is a specified allowance on the deviation in parameters such as dimensions, weights, shapes, or angles, etc. To maximise control in setting tolerances there is usually a minimum and maximum limit on thickness, based on the process used. Injection moulding typically is capable of tolerances equivalent to an IT Grade of about 9–14. The possible tolerance of a thermoplastic or a thermoset is ±0.008 to ±0.002 inches. In specialised applications tolerances as low as ±5 µm on both diameters and linear features are achieved in mass production. Surface finishes of 0.0500 to 0.1000 µm or better can be obtained. Rough or pebbled surfaces are also possible. 

Routine maintenance operations personnel plastic injection mold, the main content of wiping, lubrication and inspection.During production maintenance:1. Production in the corresponding part of the mold on a regular basis were oiled. Such as: drawing die ring binder, rounded; trimming knife mold parts; knife block flange portion and the like;2. Regularly trimming hole punching die to clean up waste scrap Road.After production  maintenance:1. After production should conduct a comprehensive inspection of the custom plastic mold;2. Comprehensive wiping die to ensure the cleanliness of the mold;3. Will scrap the mold clean up the waste box to ensure no waste.

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YUDO, our hot runner supplier-fast-reliable-worldwide

Design Engineer is very critical in the whole mold developing process. They assess the part design and make modifications and recommendations based on key product requirements including product usage and function. The engineer will need to know:1. How will the part be used? Is it a standalone product or a component of a larger assembly?2.What are the dimensional and tensile requirements?3. Does the part need to withstand elements, pressure, chemicals?A plastic injection mold design is built with these criteria in mind. Mold cavities, vents and gate placement will vary based not only on the part design but the type of resin as well. Taking all of these manufacturing factors into account is a challenging task and one that requires a strong knowledge base, not only of mold design but the injection molding process as well.

Design Engineer is very critical in the whole mold developing process. They assess the part design and make modifications and recommendations based on key product requirements including product usage and function. The engineer will need to know:1. How will the part be used? Is it a standalone product or a component of a larger assembly?2.What are the dimensional and tensile requirements?3. Does the part need to withstand elements, pressure, chemicals?A plastic injection mold design is built with these criteria in mind. Mold cavities, vents and gate placement will vary based not only on the part design but the type of resin as well. Taking all of these manufacturing factors into account is a challenging task and one that requires a strong knowledge base, not only of mold design but the injection molding process as well.

1.Mechanical polishing : reach to a surface roughness of Ra0.008um2.Chemical polishing : usually a couple of Ra10um3.Electrolytic polishing : compared to the chemical one, electrolytic polishing could eliminate the negative effect of cathodic reaction;4.Ultrasonic polishing : the cavitation effect of ultrasonic wave in liquid can inhibit the corrosion process, which is beneficial o surface lighting.5.Float polishing6.Megnetic abrasive polishing : high efficiency, good quality, the processing conditions are easy to control. With proper material, the surface roughness could be reached to Ra0.1um.

1.Mechanical polishing : reach to a surface roughness of Ra0.008um2.Chemical polishing : usually a couple of Ra10um3.Electrolytic polishing : compared to the chemical one, electrolytic polishing could eliminate the negative effect of cathodic reaction;4.Ultrasonic polishing : the cavitation effect of ultrasonic wave in liquid can inhibit the corrosion process, which is beneficial o surface lighting.5.Float polishing6.Megnetic abrasive polishing : high efficiency, good quality, the processing conditions are easy to control. With proper material, the surface roughness could be reached to Ra0.1um.

What's the biggest mold Longxiang made? The biggest mold Longxiang made is 35 Ton, the product net weight is 20kgs.

CMM (coordinate measuring machine) is part of the automobile manufacturing process. The accuracy of the touch probe system is 1/1000mm, and reliable information can be obtained by measuring the data generated in the cycle.Each production unit has a separate computer controlled cycle of measurement. Composite components are loaded onto separate design fixtures to ensure that parts are easy to approach the probe.Once installed on the fixture, the position is verified by CMM before the start of the big cycle. Once the CMM program is completed,.CSV files and PDF reports will be generated for visual explanation and diagnosis.It can then identify whether the component has met the specifications required by the customer, so as to determine the quality. CMM also has the capability of laser / surface scanning components, which will be used for future projects.

In general, we select the steel according to the functional of parts :1.For mold base part : 45#、S45C、S50C etc.2.For mold cavity / core: P20、2311、738、738H、718、718H、NAK80、2316、2316H、2083、2083H、S136、S136H etc3. For harden treatment material: 2344、8407、SKD11、SKD61H13、etc.3.For Shaped parts : perhardened steel would be good choice. Such as P20、P5、NAK55、NAK80、738、718、420.4.For cooling parts , choices including aluminum alloy steel, brass, red bronze, BeCu and pure copper.