• How to calculate mould shrinkage

    Thermoplastics shrink as they cool and solidify during the plastic injection molding process and after part ejection.   The plastic injection mold cavity is machined larger than the final desired molded plastic part size in order to compensate for part shrinkage as the part cools.   Mold shrinkage data for the specific plastic material can be used to calculate the amount of mold expansion needed.     Shrinkage in mould units are expressed as length-per unit-length, or as a percentage, and is calculated using the following mould shrinkage calculation formula :     (mold dimension – part size) / mold dimension  = Mold Making Shrink Factor   We could alse use a simplied formula as below.   S={(D-M)/D}×100%(1)   Shrinkage; D-Mold Size; M-Molded part size   However, since the actual shrinkage is influenced by many factors, only the approximate value can be used,When building the mould, the cavity should be machined according to the lower deviation while the core be machined according to the upper deviation to leave…

    Injection molding process February 29, 2020
  • What is Mould Shrinkage?

    Shrinkage is a characteristic of resin which occurs during plastic injection molding process. Different resins have different mold shrinkages. Crystalline and semi-crystalline materials exhibit higher shrinkage than amorphous materials. Unreinforced plastics have higher shrinkage than reinforced grades. It is important that the grade of material be selected before the injection mold tooling is constructed and that the proper mold shrinkage be specified.   Mold shrinkage rate can vary with part and tool design: thick walls will have higher shrinkage rates than thin, variation in section thickness can cause differential shrinkage and warpage;flow direction will effect shrinkage,particularly with glass fiber-reinforced grades       Shrinkage in mould is also influenced by process conditions. As cavity pressure increases,shrinkage typically will decrease. The plastic injection mold and melt temperature will also influence shrinkage. Cooler molds will reduce shrinkage while hotter melt temperatures will increase shrinkage especially with semi-crystalline materials.   Contact HS Mold Company for shrinkage recommendations on any of plastic injection molded products. We…

    Mold making February 27, 2020
  • Injection Molding Defects Delamination

    What is delamination/Peeling? Delamination is thed detached, slate-like surface layering of the polymer as it fills and packs the plastic injection mould tools. With this defect, different unconnected layers of plastic develop and form within the plastic injection molded parts. , e.g. due to cross cutting. usually not easy to identify since the surface is flawless; a “skin” can often be pulled off when the surface is scratched with a blade. The molded plastic product exhibits bubbling after warm storage. The cause of delamination High shear stresses result in the formation of layerseven in compatible multiphase systems during injection molding process. Contamination with an incompatible thermoplastic or master batch Sharp Corner around the injection gate and runner in the plastic injection mold Correction Increase the melt temperature and reduce the injection speed. Avoid contamination due to extraneous material or due to an unsuitable master batch (specifically the carrier) Channge all shapr corners to be round corner….

    Injection molding process February 23, 2020
  • What causes weld lines in injection molding

    What is weld lines in injection molding  During the manufacturing of injection molding process , the Weld lines , also calles as Knit lines or Meld lines are present on the surface of plastic molded parts where two flow fronts meet and when they are not able to to “knit” together, or “weld” together .These harilines or dark lines usually occur around holes or obstructions and cause locally weak areas in the molded resin part. Appearance of weld lines in injection moulding  Notches, hairlines Change in apparent color; especially when inorganic decorative effect pigments are used the weld line appears as a dark line; conspicuous in dark, brilliant or transparent moldings having smooth surfaces polished to a high gloss. Cause of weld lines injection molding Appear in multiphase systems such as ABS or ASA. Flow fronts having an already cooled peripheral layer encounter one another and no longer allow fusion without marks. Decorative effect pigments and, e.g., glass fibers tend to straighten up in the…

    Injection molding process February 20, 2020
  • Injection Mold tryout guideline

    As known, the manufacturing of plastic injection mold determines the quality of plastic molded parts, production effieciency and cost of finished products.Mold trial is run to solve any problems with the design, resin, tooling,machine. Thus procedures of mold trial is very important for a injection molder. Be sure to follow this nine-step process to make sure you’ll be making good parts through a successful trial.   Firstly, Keep the  injection mold run on the press without any resin to verify the function of  the mold    A. Check mold opening and closing condition at low pressure:   Mold should beopened and closed by 3 times at fast, medium and slow speed. During the process, there should be no abnormal sound nor block phenomenon;   Mold opening and closingshould go smooth  without any interference.   B.Checkejection system of the injection mold (at low pressure)   1.Check the ejection action at  fast, medium and slow speed.   2.Check whether ejector pins  or sleeves on the…

    Injection molding process February 17, 2020
  • High Performance of Molded Fiberglass Products

    Glass fiber reinforced plastic are composite materials made of polyester, usually thermoset resin,glass fiber and filler in custom fiberglass molding  process. Generally speaking, most of the glass fiber reinforced materials can be used to create large, complex structures in any number of geometric shapes, including contoured and rounded FRP Molded Products.  Thermoset polymers used as resins in the manufacture of reinforced plastic includes PP, ABS, PA66, PA6, PC, POM, PPO, PET, PBT, PPS, etc.. Fiber reinforced plastics are overall a highly advantageous material providing a number of benefits in a wide variety of areas from physical properties to resistances to aesthetics.   Advantage of glass fiber reinforced plastic 1.Glass fiber reinforced plastic is a high-temperature resistant material, therefore, the heat-resistant temperature of reinforced plastics is much higher than that non-reinforced polymers, especially nylon plastics.  FRP is a durable material which can last years in extreme hot weathers and temperatures with minimal wear. With theaddition of glass fiber,the reinforced plastic restricts the plastic movement between the…

    Mold making February 14, 2020
  • Coolant Expansion Tank

    This is the bottom of Coolant Expansion Tank for a branded automotive company. The material is PP. The part features with two screws. We could use either automated unscrewing system or hand load inserts to release the screws. Since this part is supplied to the after sales 4s car companies, the quantity is not that big.  We use hand load inserts to save manufacturing cost for clients.  For the water tank, the key technology is the part must be flat without any deform and assembly holes must be aligned perfectly. If there is any warp, the two parts could not be vibrated-welding together and water leaks. In order to solve the issue, firstly we have to run mold flow to do a pre-warp analysis so that the warp degree could be calculated and gate position decided. Mold flow is only an assistant tool in theory. Sometimes, mold flow result differs…

    plastic products, Uncategorized February 10, 2020
  • Gate Design-HS Plastic Mold Shop

    What proper gate design is important? The gate serves as the entrance to the mould cavity and should be designed to permit the injection mold to fill easily. It is very important to follow below gate considerations while picking gate location at the early stage of plastic mould design. Gates should not be placed where part-bonding or impact will take place in use. The gate area will usually have higher residual stresses than the rest of the part due to the packing that takes place. Therefore, it will be weaker than the rest of the part. Position the gate to minimize trimming problems. Scissor-type gate cutters, kept sharp, will work smoothly and leave no “blemish” marks. If possible, gate into the thickest section to avoid incomplete fill or sink marks. This will also minimize flow marks and distortion associated with setting into a thick section from a thin one. Position the gate so that venting…

    Mold design February 8, 2020
  • How can you make mold slide comes out of lifter?

    It is rare to see the structure of slide coming out of lifter in plastic injection molds. We are not experts, but we just design a typical mechanism that works quite well based on our experience.  Hope that it helps you. Mold Design Concept If we use common mold slide, the steel circled in red get stuck. And the undercut could not be released with this. How to design lifter head?   Green block is lifter with a prominent tail while the purple block is slide which is to release undercut and drive lifter to release undercut downwards. Further explanation on slide out of lifter in plastic injection mold Mold lifter needs a limit screw to limit the stroke of lifter travelling down while the spring is to prevent lifter from moving right with slide The science of structure of slide from lifter   Angel lifter drive slide to move right And…

    Mold design February 6, 2020
  • Top 10 Tooling engineer interview questions 

    Below is a list of general questions to ask during the interview of tooling engineer job in China.  What kind of questions you may meet in your area? What kind of answers do you have for below questions?Welcome for discussion! Answers to be followed!   What steel you use most frequently? What is the difference between NAK80 and S136? If cavity steel is H13, what material shall be used for lifter, why? What is the machining process of plastic injection mold? What causes flash in plastic injection molded parts? What causes void in molding plastic parts? How to solve part sticking to slide issue? What is the function of cooling? What are your biggest strengths? Why we hire you?

    Industry news February 3, 2020
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