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Process parameters that require attention in injection molding process generally include these. These process parameters are not divided into major and minor factors. Each factor is crucial for the quality of injection molding products. It requires injection molding engineers to make reasonable reference of process parameters according to the product information of different products and different plastic types to ensure the quality of plastic parts.
Steel is the decisive factor affecting injection mold quality, so selecting reasonable steel is very important. The criteria for selecting steel are followings:
(1) Plastic parts requirements
Different plastic parts should use different steels, such as plastic part requiring high polishing and corrosion resistance, etc. 
(2) Price
Not the more expensive, the better. Considering the cost factor of injection mold, select the mold steel corresponding to the mold service life to prevent unnecessary waste. The service life of general P20 mold steel is about 300,000 times, 2738 mold steel can be 500,000 times, H13/2344 mold steel is usually more than 80-100 million times. So the mold steel can be selected according to specific situation.
(3) Surface processing
Surface of injection mold is also very important. Nit riding can enhance the surface hardness of mold steel, and it can also increase injection mold service life. Electroplating can modify the performance of mold steel. For some plastic parts requiring high brightness and corrosion resistant, electroplating can be used to enhance and improve the performance of mold steel.
How to choose plastic injection mold steel?
Plastic injection mold is a tool for producing plastic products and a tool for giving the plastic products complete structure and precise dimensions. Plastic injection molding is a processing method used in mass production of some parts and components with complex shapes. It specifically refer to the material that is heated and melted is injected into the cavity by high pressure, after cooling and solidification, and then the injection molded part is obtained. So, what gate methods does the plastic injection mold have?
In the process of injection mold production, it is unavoidable that there are residual raw materials, water and other substances, which may react with the injection mold steel to oxidize and rust. This is harmful to the injection mold. Therefore, after the injection mold is used, it should be cleaned and maintained. If necessary, apply anti-rust liquid (e.g. before long-distance transport or long-term preservation).
After the injection mold is used, there will be plastic residue on the injection mold surface. With the latest injection mold cleaning machine, any residue on the surface can be removed within ten minutes, including The most difficult gas residue.
After appearance tests such as galvanic wear, track marking, and residue content of the injection mold in the vent and non-vent hole areas, the technician can determine the procedure and frequency of the injection mold cleaning by visual inspection. 
New Rapid Tooling Materials. Rapid mold technology was welcomed by the market , it combines new technologies such as polymer material application, rapid prototyping, rapid turning and CNC processing, and can be used in rapid and low-cost manufacturing of non-metallic molds for rapid manufacturing of 10-000 batch products.
The development of precision injection molds, precision injection molding was first produced in the 1970s. With the development of science and technology has been widely used, many industrial developed countries have reached a high level of research on precision injection molds. In recent years, China plastic injection mold has made certain achievements. Cheng Jun applied Pro/E to the design process of precision plastic molds. Taking the plastic mold of a certain type of mobile phone housing as a specific example, it was concluded that the 3D mold design of Pro/E is more efficient and intuitive than 2D design. Such advantages have important significance for the application of three-dimensional technology in precision plastic molds.
The characteristics of large-scale injection molds, compared with ordinary injection mold manufacturing, large-scale injection molding products have large volume, high weight, high mold temperature accuracy, complicated structure, high cost characteristics, large-scale injection molding have unique requirements in the mold design, mold selection and other aspects.
With the increasingly widespread application of plastic products, the surface quality of plastic molding is required to reach mirror polishing degree. Polishing not only can increase the appearance of the molding, but also can improve the corrosion resistance and wear resistance of the molding surface, what’s more, make the molding easily demolded and reduce the injection molding cycle. Therefore, polishing is an important process in the plastic mold manufacturing process
Rapid Temperature Cycling, (also referred to as Rapid Heat Cycle Molding or Vario-thermal Molding) will enable you to heat the surface of the injection mold to 200C.

The technology uses Saturated Steam to heat the injection mold and Tower Water to cool the injection mold. At the end of the cooling cycle Compressed Air is blown through the injection mold cooling channels to remove the water. Steam at up to 235C is then flowed through the cooling channels to heat the surface of the injection mold PRIOR to plastic injection, the steam is subsequently removed by Compressed Air followed by cooling water to remove the heat from the plastic.
As far as drying goes you could dry the material for 12 hours but you need to make sure that the hose that goes from your dryer to your hopper is not too long. I have seen cases where the mold will run fine for a while and once you get into a cycle the material has a chance to sit in the hose and gather moisture. If the problem is a burning issue you may want to make sure that your nozzle orifice on the injection molding machine matches the orifice on the hot runner. If your injection molding machine orifice is larger than the one on the hot runner you are causing shear heat when the material passes over the edge of the hot runner inlet. Other factors that the hot runner may be causing is degrading of the material in the system.

You need to make sure that you follow the proper start up and shut down procedures recommended by your supplier. You should also make sure that the hot runner supplier sized the flow channels correctly and you are not holding too much material in the system allowing it to either degrade the material or the colorant. This could also be happening if the system is allowed to sit and the material is cooking in the system. If your melt channels are too small you may be creating too much shear heat. You should be able to determine this by the injection pressures that are required to fill the parts.
As a custom injection molder we face a broad range of customer requirements, and a wide variety selection of resins. To give the fuzziest of answers regarding proactivity in testing, the answer is: "It depends."

The level of testing we choose to perform is custom tailored to the resin family, the molded product applications, our internal molding needs, and the customer's expectations, and certainly the presence of customer warranty claims where, this testing can add a bit of insight or forewarning of trouble in the absence of other testing that is far less obscure in nature.

As an example, if faced with a problem that appears to be isolated to a particular component it is probably cheaper and the test results certainly less obscure, to develop a destructive test with built in and appropriate safety margins for the part. Everyone can quickly grasp and accept the concept and result of a broken v. not broken part. Better still is a destructive test that can incrementally describe the force required to fail the part, you test to destruction and record the highest force attained.
Over many years' experience with melt flow index (MFI) testing with many operators we have concluded that for our purposes as a custom injection molder, we do not sweat getting exact numbers compared to the numbers published by the resin supplier. We have built up our own database of acceptable ranges of melt flow index based upon our testing alone.

If there comes a time where a dispute occurs, i.e. we have a reading unacceptable outside of the range of our database of readings and we have revivified by repeated tests. We will use an A2LA registered outside lab service to perform a more sophisticated characterization of the resin. This may be via FTIR, GPC, TGA looking for the presence of contaminants or hybrid molecules of the same resin, and assuming we detect something abnormal, take this to resin maker. This generally ends the dispute. Fortunately this doesn't happen very often with the major resin makers and is more likely to occur with compounders or even bulk distributors who have been known to make packaging/labelling errors when they repackage the material in bags or barrels out of a bulk train car load or similar shipment that they have received.
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