Blow Molding

Blow molding is a popular plastic molding process that produces hollow, thin-walled containers and offers high-cost efficiency, long run capacity and application versatility. Blow molders manufacture many different products, including toys, blow molded cases, sports equipment, garbage cans, planters, and most commonly, blow molded containers like plastic bottles that hold many beverages including water, milk, juices, carbonated soda, liquor, beer and other foods like peanut butter and cooking oil.

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blow molding
R & D Molders, Inc.
Georgetown, TX
512-763-3600
For over 36 years, R&D Molders has been providing blow molding, tooling and associated secondary services to a variety of customers for a variety of applications. We have successfully produced solutions for the Medical, Industrial, Consumer Goods, Sporting Goods, Electronics, GSA/DOD, Home & Garden and Energy industries. Let us be a one stop turn-key source for your molding requirements.
Agri-Industrial Plastics Company
Fairfield, IA
641-472-4188
Custom, large-part blow molded solutions. Expertise in design & production of structural panels, specialty products, & EPA compliant multi-layer fuel tanks up to 50 gallons. With 30+ years of experience & state-of-the-art machines, Agri-Industrial Plastics is committed to creating the highest quality products & exceeding your expectations at every phase of the process from design to delivery.
Custom-Pak, Inc.
Clinton, IA
563-242-1801
With locations in Clinton & Dewitt, IA, Walnut Ridge, AR & Mexicali, Mexico, Custom-Pak leads the way in advanced blow molding technology, even designing & building energy efficient machines & sophisticated molds for faster, more cost efficient & better quality results. We serve all markets with a wide array of products. Contact us today for more information.
Penguin, LLC
Sturgis, MI
269-651-9488
With blow molding presses from 1 to 80 lbs., Penguin has the ability & resources for every step of your blow molding requirements - from a competitive part quote to part & product development support start to finish. Penguin has an established infrastructure like no other. We can simply mold parts for you or completely assemble & ship your finished products anywhere in the world.
STM Plastics
Augusta, KS
888-269-3385
Since 1965, STM Plastics in Augusta, KS has provided quality products at competitive prices; becoming a leading supplier of custom plastic products. We combine years of experience with knowledge of new techniques and procedures in the ever changing field of blow molding to consistently meet and exceed our customer`s expectations.
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plastic bottles
Cado Company
Fitchburg, MA
978-343-2989
For over 50 years, Cado Company has been a full service blow molding company for the plastics industry. We can take your plastic idea from concept to finished product. We provide solutions for short term blow molding runs as well as high volume production in either commodity or engineering grade resins. At Cado, Let us be your blow molding source.
Scandia Plastics, Inc.
Sheboygan, WI
920-452-2071
Since 1979, Scandia Plastics has been experienced in blow molding. We offer the best in plastic blow molding engineering services and quality blow molded plastic products. We have built a reputation as a technical blow molder with 100 years of combined experience. Scandia Plastics strives to be your high-quality, turn-key solution to all you molding needs.
Blow Molded Products
Riverside, CA
951-360-6055
One Stop Shop for quality blow molding products at prices you can afford. Blow Molded Products has long been the industry leader in blow molding products that require high attention to detail from start to finish. For stock or specially designed products, everything is done in-house--product & mold design & tooling for short or long runs! Call our company today!
Pinnacle Plastic Products, Inc.
Bowling Green, OH
419-352-8688
From design to finish, trust Pinnacle Plastic Products with your blow molding needs. This company has over a century of accumulated knowledge that is brought into every single project. We take pride in our hallmarks of extensive design engineering and molding expertise for custom products. If your job can be done, we can find a way to do it! Call us today to get started.

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Industry Information
View A Video on Blow Molding - A Quick Introduction

Blowmolding products include CD cases, tanks and any consumer item that is hollow and three dimensional in shape. Blow molded products can be used to hold automotive oil, cosmetics, pesticides and herbicides. Blow molded plastics are all thermoplastic resins, and include high and low density polycarbonate, polypropylene, polyvinyl chloride, Barex, butadiene styrene, polystyrene, polyamide, polysulfone and acetal. There are 3 main types of plastic blow molding-injection blow molding, extrusion blow molding and stretch blow molding. These processes are 2 steps and vary mostly during the preform stages. Blow molded products take their shape depending on the shape of their mold cavity. They come in standard sizes and shapes, while some custom blow molding products are specifically made for unusual and unique processes.

The blow molding process begins with melting down the plastic and forming it into a parison, or preform by injection molding. The parison is a tube-like piece of plastic with a hole in one end in which compressed air can pass through. A metal ram pushes the softened and malleable preform, expanding it to the desirable height of the product. Using a blow pin, air pressure is introduced through the inside of the parison, forcing it to balloon out and assume the shape of the mold cavity. The end product is cooled by conduction, cold water running through the mold cavity, or the evaporation of volatile fluids in the container. The purpose of blow molding services is to form a uniform finished product that is smooth, airtight and does not need to be joined together in any way. The whole process takes a few seconds, and blow molding machines can produce up to 20 thousand containers in an hour. Blow molding services use three basic methods for producing blow molded plastic: extrusion, injection and stretch blow molding.

Extrusion blow molding is the simplest type that allows for a wide variety of container shapes, sizes and neck openings, along with handleware of many kinds. It is based on the glass blowing process, and uses 2 mirror molds to create the containers, which causes a thin seam down the middle. Injection blow molding is a hybrid of the injection molding and blow molding services and is suitable for smaller containers but not for handleware of any kind. This process injection molds the plastic preform right before it is blown into a mold. There are two different  types of stretch blow molding-injection stretch blow molding (ISBM) and reheat and blow (RHB) molding, both of which are typically used to manufacture P.E.T bottles for juice, water, etc. In the ISBM process, a preform is injection molded and then transferred to another station on the machine, where it is blown. Because ISBM is so costly, it requires long runs for products such as peanut butter jars, water bottles and liquor bottles. In RHB, a preform is purchased from a vendor that has already put it through an injection molding process. It is then reheated in a relatively simple machine in order to prepare it for blowing. RHB is advantageous because the purchaser does not have to invest in expensive injection molding machinery but still has access to a large catalog of existing preforms.

Distinct advantages exist for choosing the blow molding process over other plastic manufacturing processes. It is the most well-suited method for forming hollow plastic parts. It has much lower mold costs than injection molding. Blow molding has a faster cycle time than that of rotational molding. In many cases, one blow molded plastic piece can take the place of many individual parts. However, the scattering of mold thickness is a potential problem, and quality control is important to make sure none of the blow molded products have holes, leaks or unevenly thin walls. Strong, precisely even walls are better created by rotational molding or plastic extruding, but for the thousands of applications which require high volume production over precision, plastic blow molding is an ideal choice.


  • Blow molded cases are formed by blow molding processes.
  • Blow molded plastics are plastic parts formed by blow molding.
  • Blow molders create hollow plastic parts.
  • Extrusion blow molding is the process in which a hot parison or preform is placed into a two-part mold. In the mold, the parison or preform is inflated with compressed air, which presses it against the walls, and then is cooled and removed by separating the mold halves.
  • Injection blow molding blends the two methods of blow molding and injection molding and is typically used in the manufacturing of soda bottles. A preform, which is similar to the parison, is either injection plastic molded and then transferred to a blow molding machine, or the injection and blow molders are combined.
  • Injection stretch blow molding (ISBM) is a two-stage, stretch blow molding process in which a preform is injection molded and then transferred to another station where it is blown and ejected from the machine.
  • Plastic blow molding is a process that uses inflated thermoplastics in molds.
  • Plastic bottles are hollow containers made of plastic.
  • Reheat and blow (RHB) is a stretch blow molding process in which a preform is injection molded by a vendor and then purchased and reheated by another company.
     

Blow Molded Plastics Terms

Clarity - The lack of haze or cloudiness in a plastic material.
 
Elastomer - A material that at room temperature has the ability to return to its original shape after being stretched up to twice its length.
 
Ethylene Vinyl Alcohol Copolymer (EVOH) - A high-barrier plastic resin packaging material.
 
Finish - Also known as the "E" dimension, it is the material enclosing the neck opening of containers that accommodate particular closures.
 
Flash - Extra plastic attached to a molding along the parting line. Flash must be removed (i.e. deflashed) before the part can be considered finished.
 
Flame Treating - A technique of making inert thermoplastic items responsive to adhesives, inks and paints. The submersion of the item in an open flame induces surface oxidation.
 
Fluorination - A procedure that diminishes permeability and increases the chemical resistance of different plastics and elastomers. The exposure of polymers to fluorine gas causes molecular structural surface changes.
 
Minimum Wall
- The thinnest part of the wall of a bottle.
 
Mold Cavity - The hollow part of a group of molds that forms a container on bottle machines.
 
Mold Seam - A vertical line formed at the point where the mold halves meet, the prominence of which depends on the accuracy with which the halves are matched.
 
Multi-layer Bottles - Bottles comprised of layers of special plastic materials that are co-extruded to preserve and use the unique characteristics of each material to improve the barrier qualities of the container and increase the product shelf life.
 
Natural Color - Refers to the natural translucent appearance of the plastic material of containers and closures.
 
Neck Ring - The component of the molding apparatus that produces the bottle finish.
 
Paneling - The collapse of a portion of a container structure, due to a loss of interior pressure, which occurs during aging and storage.
 
Parison - The empty cylinder of plastic melt that emerges from the extruder die head and expands in the mold space from air pressure, producing the molded part.
 
Parting Line - The mark on a plastic bottle where the two halves of the mold meet at the point of closure.
 
Preform - A heat-softened polymer shaped like a thick test tube with neck threads that is inflated while inside a blow mold.
 
Programming - A procedure for mechanically altering the weight, size or wall thickness of the parison as it forms.
 
Shrinkage
- A decrease in dimension of an article after the molding process, which is caused by the contraction of the plastic material upon cooling.
 
Side Seam - The seam that joins both edges of a blank forming a body.
 
Surface Treating - Any treatment technique, including chemical, electronic and flame treatments, that makes plastic receptive to inks, lacquers and adhesives.