Category: injection molding parts

10 Tips for Polypropylene PP Injection MOLDING

Polypropylene continues to gain popularity in the injection mold industry. With a low-density consistency and chemical resistant design, it is often used to produce items such as medical devices and automotive parts. While polypropylene resins offer a number of benefits, it is important to monitor the temperature threshold during the smelting and printing process. Here are the top 10 tips for injection molding polypropylene resins.

Injection Mold
Injection Mold

1) Make sure you have the right molding equipment

The road to successful injection moulding starts with the right molding equipment. Fortunately, polypropylene can be printed accurately using unchanged one-stage thread molding equipment.

2) Consider pre-drying ONLY if you use certain polypropylene resins

“In most plastic processing factories, resin dryers are standard equipment. An important exception to this is facilities that exclusively process polyolefins such as polyethylene and polypropylene. These are some polymer families which do not require drying because this material family is not hygroscopic. “

Unlike most commercial polymers that are highly polar, polypropylene is a non-polar substance, allowing you to pass the pre-drying process. The only resin that may require pre-drying is some filled polypropylene resin. This advantage allows you to save time during the injection moulding process.

3) Use a melting temperature range of 400 ° F to 500 ° F

Using melting temperatures higher than 500 ° F can cause flashing, warpage, shrinking and burning. Temperatures lower than 400 ° F, on the other hand, can produce poor quality flow and surface markings. When you set your melting temperature, try to reach a melting temperature that is 25-50 ° F higher than the minimum filling temperature.

4) Strives for an injection pressure range of 800 to 1,500 psi

Injection pressure is another variable that can help control common injection moulding problems with polypropylene molding. While the injection pressure you set must reflect the construction and size of the item. In general, the pressure should be able to fill about 99% of the parts to prevent problems with flashing and stickiness.

5) Don’t rush the injection process

Be prepared for the injection process to consume the majority of each whole cycle. While injection time does not significantly affect the warpage, patience with the injection process is important because the accurate injection is a major factor in controlling shrinkage.

6) Choose a mold temperature around 50-150 ° F

The mold temperature must be carefully regulated to reduce stress and surface imperfections. A mold temperature of 50-150 ° F helps prevent this trap. In addition, ensure that the mold is uniformly cooled to facilitate the removal of components from the mold.

7) Never rush time

Hold time plays an important role in preventing warpage and shrinkage. Therefore resist the urge to remove parts of the mold before it is cool enough. Allowing the part to cool to around 130 ° F is recommended to produce satisfactory results.

8) Use minimal back pressure to increase your cycle time

The ideal backpressure for polypropylene injection mold is usually between 50 and 100 psi. Backpressure in this range can help increase your cycle time. Exceptions to this rule of thumb are cases that require mixing pigments.

9) Adjust your mold or polypropylene level if sticking occurs

Sticking is not common with polypropylene because it has exceptional release properties. However, if minor adhesions occur, you can easily improve the attachment by making minor changes to the mold or using a grade of polypropylene that has been lubricated internally.

10) Seek support from trained industry professionals

The only best way to ensure your satisfaction with polypropylene resin injection molds is to seek guidance from a leader in the injection mold industry. We invite you to contact us for further injection mold tips. With almost years of industry experience, we have the resources and expertise to help you develop the unlimited injection moulding process. We look forward to hearing from you!

Molds-free Fabrication Technology

White Bear Lake, MN—Design flexibility and shorter lead times are among the reported benefits of a “No Molds Required” (NMR) manufacturing technology that is enabling Envision Plastics & Design to fabricate custom plastic housings without using plastic tooling or molds. One of only a handful of companies that are currently employing NMR technology, Envision claims that its niche capability can save customers “thousands of dollars in tooling,” while shaving weeks or months from development time. The company uses common materials, such as ABS, polycarbonate, and high-impact polystyrene (HIPS), to fabricate custom enclosures and other plastic parts in quantities ranging from prototypes to short runs of up to 5,000 pieces. Other materials used include acrylics, PETG, and Kydex®, a high-performance thermoplastic sheet from Kleerdex Company.

“There comes a time in every part’s life cycle, whether at the beginning or the end, that a decision must be made on what manufacturing process to use,” says Doug Rosenthal, Envision’s vice president. “Sometimes, due to quantity, it makes sense to tool up right away. Other times, it makes more sense to use the NMR technology to set the first stage for the product’s life. This especially is the case for products that have not been thrown into the marketplace yet to test their viability or functionality. The NMR process can be of huge value when determining this important factor of a new product.”

The NMR technology permits design changes, ranging from simple product enhancements to complete makeovers, to be made throughout the entire life of a product. Production of parts requires a series of relatively simple steps, beginning with programming and progressing to CNC milling faceting/deburring, sawing, CNC bending, and solvent bonding. If necessary, parts can be silk screened or coated for EMI shielding. Envision can also incorporate gaskets or provide painting, miscellaneous hardware, and additional secondary assembly.

“NMR is a very unique technology, so the customer must be willing to consider another avenue of design to properly utilize the technology,” says Brian DuFresne, sales and marketing manager for Envision Plastics & Design.

Rosenthal says that the technology is suited to various markets, and has already established a presence in the thriving medical manufacturing community of the Twin Cities area. Orders from medical manufacturers for 25-50 parts per month are common, he says, because these quantities would not support the  injection molding cost. However, orders from customers in other industries sometimes total 400-500 parts per month. Besides the medical industry, Envision Plastics & Design serves manufacturers in the electrical/electronics, telecommunications, and computer peripherals industries. Additional markets include safety and security, traffic control, industrial controls, and point-of-purchase displays, according to the company.

Envision Plastics & Design is a spin-off of DuFresne Manufacturing, an ISO 9001:2000-certified sheet metal fabricator based in St. Paul, Minnesota.