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Tag Archives: custom plastic molds

Difference Between Injection Molding and Blow Molding

Difference-Between- Injection-Molding-and-Blow-MoldingMost people in the plastics manufacturing industry are familiar with both blow injection molding and blow molding these days. However there is still some confusion by product designers and engineers new to the industry about the difference between injection molding and blow molding . The blow molding process has become a standard for specific applications and understanding the differences between these two plastic molding processes can save design, prototyping and production time. This of course results in money savings and increases the speed of completion and delivery of your plastic part.

There are several significant differences between injection molding and blow molding:

  • manufacturing process itself
  • tolerances and margins of error
  • design considerations
  • role of the process for intended result

Main difference between injection molding and blow molding:

  • Injection molding – produces a part that is solid such as a reusable coffee cup lid
  • Blow molding – produces hollow parts such as water bottles

The blow molding process can produce plastic parts with very complex shapes. However to achieve this the wall thickness may vary from place to place depending on how much the material has to stretch when it is being blown. The thickness of a plastic part created through injection molding is determined by the relationship of the mold and the core.

You will be farther ahead if you are able to determine the best molding process for your plastic product in the product development stage. 

Be prepared to answer a lot of questions from plastic mold engineers:

  • How is your plastic part going to function?
  • Is it a stand alone item?
  • Is it a part that connects to other parts or works in tandem with other parts to achieve a result?
  • Does it need to pivot, move, expand, condense?
  • Is the weight critical to the function?
  • Will the part need to withstand extreme levels of cold or heat?
  • Does the item need to adjust to specific pressure levels or PSI?
  • Will the part hold fluids?
  • Does it need to be food safe?
  • Does it need to be flexible or does it need to be solid and rigid?
  • What length does the part need to be, width, depth?

Answering these questions when designing and manufacturing any item is good a idea. With items requiring plastic molding the large variety of plastics to choose from, the importance of accuracy, and the difference between injection molding and blow molding it’s best to determine these answers as soon as possible. When one millimeter size difference can make the item usable or unusable for its intended purpose, accuracy and creative solutions are required. That’s why we have engineers, right?

Custom Plastic Molding Solutions

Because of the many variable in producing molded plastic parts, nearly every part we produce requires a custom solution. Engineers review all variables based on the end use of the product.

Variables to consider in Molded Part Production:

  • type of plastic used
  • flexibility or strength
  • psi pressure rate required
  • withstand temperatures levels – hot or cold
  • wall thickness
  • product dimensions

Once these variables are considered the whole process will go much smoother and quicker. The use of 3D printers in the prototype stage helps to reduce time too. Designing molds and fine tuning them to perfection can take a few tries but once complete production can begin.

When injection molding is determined to be the best process for your plastic part once you have an approved mold you’re practically golden. The injection molding process begins, the product is produced and there is very little concern of production issues with the injection process.

Therein lies another difference between injection molding and blow molding. In the blow molding process getting the mold perfect is only part of the battle. During the blow molding production process there are many variables manufacturers must pay attention to. The iterative nature of the blow molding process lends itself to production variables.

Periodically checking the production line is important for quality control. If the plastic is stretched too much small pin holes or cracks in seals can result. Checking for wall thickness uniformity to ensure they are within the tolerances needed for the part to behave as it is intended is also critical. As an example, a plastic bellows is made to collapse when pressure is applied and then expand back to it’s original form once pressure is released. Consistent wall thickness helps the bellows to function correctly. If the plastic bellows collapses on one end faster than the other because the wall is thinner your plastic part may wear out quicker and may not function smoothly. Having sold process control systems in place will produce consistent parts with high quality function.

Blow Molding Production Concerns:

  • pinhole leaks
  • leaking seals
  • flexibility or strength
  • velocity or pressure of blown air
  • speed of the mold closing
  • process temperature
  • wall thickness
  • poor function
  • consistent product dimensions

You can learn more about the various plastic molding processes that are applicable to your product or new invention at Plastic news.

Do you have a new plastic product invention and you aren’t sure about which plastic mold process is the best solution for your item? Give SPI a call today, our engineers love a challenge! We will help guide you in the most appropriate and cost efficient plastic molding solution for your unique requirements.

SPI Blow Molding Breaks Ground Expands Fulfillment Services

SPI Blow Molding expansion - fulfillment services department  Coloma, MI, SPI Blow Molding LLC, a custom blow molding company is increasing building capacity to implement fulfillment services.

SPI Blow Molding is the sister company to SPI Injection Molding, a custom injection molder in South Bend, Indiana,

The expansion is taking place in two phases. The first is a smaller 2,400 square foot storage building meant to house fixtures and support equipment to the blow molding and fulfillment functions. Construction of this initial phase began in October of this year and should be completed by mid-December.

The second phase, which will be connected to the northwest corner of the current production plant, will be 6,000 square feet. Its primary uses will be secondary assembly, warehousing of work in process and finished goods as well as providing additional capacity for customer supplied components. All of these functions provide added capacity to perform complete fulfillment services for SPI’s valued customers. SPI hopes to begin construction on the larger structure during the spring of 2015.

When both phases have been completed, SPI Blow Molding will have enhanced its ability to mold, assemble, box and ship products to their customers. Products can be fully assembled and drop shipped to end users. Companies can then choose to have blow molded plastic parts shipped to another of their production facilities, a distribution center or directly to their customers. Multiple loading docks allow for ease in large shipments and receiving. Shipments will be transported throughout the United States and overseas.

SPI Blow Molding Fulfillment Services Capabilities:

  • Manufacture, assemble, inspect, package, and ship final products
  • Drop ship orders to our clients’ customers
  • Ability to warehouse products for our customers
  • Dock to stock shipping
  • Ability to use third party transport, mail and delivery systems

SPI Blow Molding provides fulfillment services for The Best Bins Company, headquartered in Minneapolis. SPI currently produces, assembles, warehouses and distributes their bulk food container product line. The bulk container is used for dispensing coffee beans, candies and a wide variety of bulk food items. Having all these capabilities and fulfillment services under the control of the SPI production plants has improved efficiency and saved Best Bin Company both time and money.

SPI Blow Molding provides custom molds and class-A molded parts in a variety of colors. SPI Blow Molding resin capabilities include: High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polypropylene, K-Resin, Styrolux, Ethyl Vinyl Acetate (EVA), Polyurethane, Nylon, PETG, and Polycarbonate. Nutraceutical and food products are blow molded from an FDA approved resin.

Along with manufacturing custom molds and molding parts, SPI Blow Molding is a complete manufacturing, fulfillment and distribution center. Newly installed equipment and warehousing space will allow SPI to comfortably offer manufacture, assemble, inspect, package and ship final products.

Expanding SPI Blow Molding’s current manufacturing plant footprint to house the new fulfillment services department will also open up several new jobs to the area.

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SPI’s mission is to provide the best custom molding experience for the injection and blow molded requirements of its valued customers. This experience involves flawless support culminating in successful global product delivery. SPI’s core software, mechanical, and human technologies insure future profitability and growth to its employees, community and customers. SPI’s commitment is embodied in its value statement and quality policy.

SPI Blow Molding molds the HDPE Buzz Ball Football game table that was awarded 2nd place at the Annual Society of Plastics Engineers’ (SPE) Awards. The award was granted in the Industrial Blow Molding Division of the 2nd annual blow molded parts competition. The ABC, SPE Blow Molding competition showcases the latest innovations and advancements in the blow molding industry. The competition was held in conjunction with the 30th Annual ABC and SPE Blow Molding Conference in Chicago, October 5-7, 2014.

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Media Contact for SPI Blow Molding
John Doster 269-488-2752
john.doster@moldedparts.com
3930 Bessemer Rd
Coloma, MI 49038