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Blow molding is the process of forming a molten tube (referred to as the parison or preform) of thermoplastic material (polymer or resin) and placing the parison or preform within a mold cavity and inflating the tube with compressed air, to take the shape of the cavity and cool the part before removing from the mold.

Any hollow thermoplastic part can be blow molded.

Parts are not just limited to bottles, where there is one opening and it is usually smaller in diameter or size than the overall body dimensions. These are some of the most common shapes used in consumer packaging, however there are other typical types of blow molded parts, including, but not limited to:

• Industrial bulk containers
• Lawn, garden and household items
• Medical supplies and parts, toys
• Building industry products
• Automotive-under the hood parts
• Appliance components

History of Blow Molding

The basic concept of blow molding comes from the glassblowing process. As early as the 1880’s there was a patented method of extruding a Celluloid polymer into a parison and blow molding a part. Early methods and materials to blow plastics into shapes were very crude and not suitable for mass production. It wasn’t until the late 1930’s that the first commercial machines and products were developed for the manufacturing of blow molded bottles. The major event that triggered and fueled the early years of commercial blow molding was the development of low and high density polyethylene suitable for blow molding and consumer packages. From this, there was an explosion of blow molded products and equipment in both Europe and North America.

Blow Molding Manufacturing Processes

There are three main types of blow molding:
• Extrusion blow molding
• Injection blow molding
• Injection stretch blow molding

The main differences among them are the method of forming the parison; either by extrusion or injection molding, the size of the parison and the method of movement between the parison and blow molds; either stationary, shuttling, linear or rotary.

In Extrusion Blow Molding-(EBM) the polymer is melted and the solid extruded melt is extruded through a die to form a hollow tube or parison. Two halves of a cooled mold are then closed around the parison, pressurized air is introduced through a pin or needle, inflating it into the shape of mold, thus producing a hollow part. After the hot plastic has cooled sufficiently, the mold is opened and the part is removed.

In EBM there are two basic methods of extrusion, Continuous and Intermittent. In continuous, the parison is extruded continuously and the mold moves to and away from the parison. In Intermittent, plastic is accumulated by the extruder in a chamber, then forces through the die to form the parison. The molds are typically stationary under or around the extruder.

Examples of the Continuous Process are Continuous Extrusion Shuttle machines and Rotary Wheel machines. Intermittent extrusion machines can be Reciprocating Screw or Accumulator Head. Various factors are considered when selecting between the processes and the size or models available.

Examples of parts made by the EBM process include many hollow products, such as bottles, industrial parts, toys, automotive, appliance components and industrial packaging.

With respect to the Injection Blow Systems – (IBS) process, the polymer is injection molded onto a core within a cavity to form a hollow tube called a preform. The preforms rotate on the core rod to the blow mold or molds at the blowing station to be inflated and cooled. This process is typically used to make small bottles, usually 16oz/500ml or less at very high outputs. The process is divided into three steps: injection, blowing and ejection, all done in an integrated machine. Parts come out with accurate finished dimensions and capable of holding tight tolerances—with no extra material in the formation it is highly efficient.

Examples of IBS parts are pharmaceutical bottles, medical parts, and cosmetic and other consumer product packages.

Injection Stretch Blow Molding- (ISBM) the Injection Stretch Blow Molding- (ISBM) process is similar to the IBS process described above, in that the preform is injection molded. The molded preform is then presented to the blow mold in a conditioned state, but before final blowing of the shape, the preform is stretched in length as well as radially. The typical polymers used are PET and PP, that have physical characteristics that are enhanced by the stretching part of the process. This stretching gives the final part improved strength and barrier properties at much lighter weights and better wall thicknesses than IBS or EBM—but, not without some limits such as handled containers, etc. ISBM can be divided into the One Step and Two Step process.

In the One Step process both preform manufacture and bottle blowing are performed in the same machine. This can be done in 3 or 4 station machines, (Injection, Conditioning, Blowing and Ejection). This process and related equipment can handle small to high volumes of various shape and size bottles.

In the Two Step process the plastic is first molded into the preform using an injection molding machine separate from the blow molder. These are produced with the necks of the bottles, including threads on the open end of the closed end hollow preform. These preforms are cooled, stored, and fed later into a re-heat stretch blow molding machine. In the Two Step Reheat Blow process, the preforms are heated (typically using infrared heaters) above their glass transition temperature, then stretched and blown using high-pressure air in the blow molds.

The Two Step process is more suited to very high volumes of containers, 1 liter and under, with very conservative use of resin providing great strength, gas barrier and other features.

Materials suitable for Blow Molding

Examples of Blow Molding Polymers in single layer or multiple layer structures or combinations include such materials as:
(i) High Density Polyethylene,
(ii) Low density Polyethylene,
(iii) Polypropylene,
(iv) Co-polyester,
(v) PET,
(vi) PVC,
(vii) Nylon,
(viii) EVOH,
(ix) EVA,
(x) TPE,
(xi) COP and COC,
(xii) Polycarbonate,
(xiii) Polystyrene,
(ix) ABS, etc.



ABOUT US

Hi-Rel Plastics & Molding, Inc. offers custom plastic injection molding and blow molding for all major industries. At Hi-Rel Plastics & Molding, Inc. we serve every facet of the molding process from part evaluation, 3D Printing, prototyping, tool design, tool making, sampling and production of quality finished plastic and metal parts. Our commitment to product quality, on-time delivery, and superior customer service has enabled us to forge strong.

Hi-Rel Plastics & Molding, Inc. processes an almost infinite variety of thermoplastic resins, including engineering grade materials such as PEEK, ULTEM, PVDF, LCP, PPS, PES, PC, PBT, ABS, NYLON, Glass Filled Nylon, ACETAL, PP, HIPS, HDPE, LDPE, ELASTOMERICS (TPE), POLYURETHANES, ACRYLIC, PVC and many other specialty filled / unfilled grades too numerous to list. Since we started the business in 1984, we've built partnerships with every customer on the basic business principles of integrity, responsibility and ingenuity.

Whether you’re looking for complex technical parts for medical, aerospace, military or scientific application or luxury item components for your high end customers, the mold designed & build by Hi-Rel Plastics & Molding are always very high precision.

With more than 35+ years of experience, our employees master technical & practical knowledge of design & building of molds for plastic parts. Our team has acquired a level of technical skill & problem-solving experience that guarantees the delivery of high quality products to our clients. Some of the parts we make here we have to meet tolerances of up to ± 0.001 inch in order to maintain a low rejection rate of less than one-half percent.

Our Capabilities Include:

  • PRODUCT DESIGN
  • 3D PRINTING / RAPID PROTOTYPING
  • MOLD/TOOL MAKING
  • INJECTION MOLDING
  • BLOW MOLDING
  • CLEAN ROOM MOLDING
  • MICRO MOLDING
  • LIQUID SILICONE MOLDING
  • INSERT MOLDING
  • OVER MOLDING
  • ROTATIONAL MOLDING
  • EXTRUSION MOLDING
  • RUBBER MOLDING
  • THERMOFORMING
  • METAL STAMPING
  • COIL MANUFACTURING
Value Added Secondary Services:

  • Plastics & Metal CNC Machining
  • In-Mold Decorating
  • Color matching
  • Pad Printing
  • Hot Stamping
  • Label Application
  • Heat Transfer
  • Sterilization
  • Ultrasonic Insertion
  • Ultrasonic Welding
  • Heat Insertion / Heat Staking
  • Adhesive Bonding
  • Metal Plating
  • Product Assembly Services
  • Custom Packaging & Shipping Services

EXPERTISE

We are well-known in our industry, not only for the top quality work we produce, but also for our ability to discover unique and effective solutions to customers' dilemmas. Such difficulties may lie in the areas of design or processing or somewhere in between. Our scope of knowledge is broad and covers many topics. these include, but are not limited to, plastic injection molding and blow molding needs, machinery, auxiliary equipment, molds and their components, resins, colorants and additives, processing parameters as well as the numerous types of interactions among these and other factors.

On many occasions through the years when our competitors have been unable to successfully produce a particular part, Hi-Rel Plastics & Molding, Inc. has triumphed. The depth and breadth of our expertise make us an invaluable resource for our customers. Our customers recognize our capabilities and continue to return to us for their custom injection and blow molding needs.
WHY US?

  • 35+ years of thermoplastic injection and blow molding experience.
  • ISO 9001:2015, AS 9100 Rev D, 13485:2016 Certified
  • ISO 7 (Class 10,000) Type Clean Room Manufacturing Space
  • Consistent high-quality parts at competitive prices.
  • Environmentally clean facility.
  • Engineering Solutions for demanding applications.
  • Encompass all of the offerings of the business. ( Part Design, Mold Making, Thermoplastic Molding, Electronic Assembly, Value Added Secondary Services)
  • We offer JIT ( KANBAN ) orders.
  • We utilize our own fleet of delivery vehicles to ensure accurate just-in-time delivery.
  • We invest in training associates through a full-time trainer and pay-for-knowledge training system to ensure associates continue to learn and maintain industry skill levels.
  • We are a team of dedicated Associates ready to serve your injection and blow molding needs.
  • Our quality is superb, price is competitive, and delivery is the best in the industry.
  • Hi-Rel Plastics Molding, Inc. is serious about providing customer service.


  • Our Capabilities Include:

    • PRODUCT DESIGN
    • 3D PRINTING / RAPID PROTOTYPING
    • MOLD/TOOL MAKING
    • INJECTION MOLDING
    • BLOW MOLDING
    • CLEAN ROOM MOLDING
    • MICRO MOLDING
    • LIQUID SILICONE MOLDING
    • INSERT MOLDING
    • OVER MOLDING
    • ROTATIONAL MOLDING
    • EXTRUSION MOLDING
    • RUBBER MOLDING
    • THERMOFORMING
    • METAL STAMPING
    • COIL MANUFACTURING
    Value Added Secondary Services:

    • Plastics & Metal CNC Machining
    • In-Mold Decorating
    • Color matching
    • Pad Printing
    • Hot Stamping
    • Label Application
    • Heat Transfer
    • Sterilization
    • Ultrasonic Insertion
    • Ultrasonic Welding
    • Heat Insertion / Heat Staking
    • Adhesive Bonding
    • Metal Plating
    • Product Assembly Services
    • Custom Packaging & Shipping Services