Below is a brief description of various thermoplastic forming and molding processes Kren Plastics specializes in...



As there are many different plastic processes available, we hope this information will assist you in determining what plastic process may be the best one to produce the part that you may want. Contact our technical sales personnel to discuss the processes further and which process and which material is best suited for your specific application.

The fabricators at Kren Plastics are among the most skilled and trained in the industry - what the master carpenter does with wood, we do with plastic. We have the tools and equipment to create almost anything you can imagine. Such things aquariums, display cases for art galleries and museums, retail displays, restaurant fixtures, furniture, skylights, as well as a wide variety of components for industrial, electronic, computer and medical equipment.

Our fabricators utilize every possible technique available in the fabrication of plastics, including heat strip bending, cutting, solvent cementing, polymer cementing, sandblasting, flame polishing, buff polishing, hot air welding, thermoforming, drape forming and free blow molding. In addition, we offer die-cutting, screen-printing, hot stamping right through to the final assembly and installation.

Utilizing the best techniques and equipment, we can fabricate and machine any thermoplastic material available including acrylic, polycarbonate, ABS, PVC, polystyrene, polyethylene, polypropylene, UHMW and nylon.

The fabricators work closely with our sales personnel and customers to ensure everything they build looks and works exactly as required.

Having the highest skilled fabricators in the industry, combined with the best materials, techniques, tools and equipment. we will build you a part that will meet and exceed your expectations the first time around. Bring us a sample, a photo, a drawing, a sketch or just an idea and we will discuss with you the best way to proceed. TOP

Pattern Making
Kren Plastics has extensive in-house tool, jig and pattern making capabilities. For the majority of parts we manufacture for our customers we manufacture the tooling right in house. This allows us to have complete control over our quality and production schedule.

We greatly reduce delivery time and costs ensuring our customers receive their products in a timely and economical manner. We utilize a wide variety of methods and materials to build production jigs and tools, depending on the desired quality, quantity and material of the finished product. A plywood and aborite mold will be fabricated for a one-off acrylic display piece or a reinforced fiberglass mold will be hand laid up for vacuum/pressure forming.

We also have the capability to use a customer supplied CAD file to carve complex 3-dimensional shapes from a solid block of wood or MDF (Medite). Using the electronic CAD file, we can either shape a short run production tool or a plug to create a long lasting fiberglass or aluminum mold.

If you have a product you would like manufactured, talk to our technical sales personnel to get suggestions for the best process and material to pursue with. TOP

Free Blow Forming
Free Blow Forming is used to produce dome shaped parts that require extremely high optical clarity. Some examples of this would be aircraft windows, skylights, observation domes and covers for security cameras.TOP

Drape Forming
Drape Forming is used to produce parts with a simple curve. Some examples of this would be cones, cylinders, sneeze guards, motorcycle fairing, automobile windows, boat windshields, and aircraft light lens covers. It involves draping a sheet of hot plastic over a mold of the desired shape and allowing the plastic to cool and harden to take that shape. TOP

Matched Mold Forming
Matched Mold Forming is a similar process to drape forming, however instead of draping a sheet of hot plastic over a one- piece mold; the sheet of plastic is sandwiched between matching halves of a two-part mold. It is used to produce more complex shapes with finer details. TOP

Vacuum Forming
Vacuum Forming is used to produce complex three-dimensional shapes such as dashboards, instrument consoles, door panels, machine guards, paint masks, and retail displays. Vacuum forming is when a sheet of hot plastic is drawn over a three dimensional mold. A seal is created around the edges of the mold, and then a vacuum is used to remove the air from between the mold and plastic. Once the air is removed, atmospheric pressure forces the material to take the exact shape of the mold, the piece of plastic is allowed to cool and then removed to be trimmed to the final size. TOP

Pressure Forming
Pressure Forming is a very similar process to vacuum forming except that while one side of the part has vacuum applied to it the other side is pressurized with high-pressure compressed air. This forces the hot plastic to take on sharper contours and finer details than one can produce with vacuum forming.

This process produces parts that match injection-molding quality on one side (inside or outside) for a fraction of the injection molding tooling cost. We use pressure forming to produce parts for computer, electronic and medical equipment such as protective housing and enclosures, monitor bezels, keyboard casing, etc.

Pressure Forming is an ideal process to produce small to medium quantities anywhere from fifty parts to several thousand parts per year. In addition, it is an ideal process to produce parts for prototyping and test marketing before going to the large mold expense of injection molding.

Pressure forming molds are a lot easier, quicker and more economical to modify if changes have to be made; however, production cycle time of pressure formed parts is relatively longer than injection molded parts. Therefore small to medium volumes, particularly of larger parts, lend themselves to pressure forming, while large volumes, particularly of small parts, tend to favor injection molding. TOP

Injection Molding
Injection Molding is a process suitable for high volume production. It involves injecting molten plastic pellets at high pressure and temperature into a closed mold. It produces complex parts with fine details on both sides of the part, however as the plastic needs to cool uniformly to prevent warpage the wall thickness of the part has to remain relatively constant. Because of the high temperature and pressures involved, molds are typically machined out of blocks of hardened steel complete with injection ports and thermocouplers.

Tooling for injection molding therefore tends to be expensive and typically takes several weeks to produce. Modifications to injection molds, if in fact they can be performed, are very expensive and require time. Majority of the plastic components in high volume consumer products that we see around us today: telephones, televisions, computers, etc. are injection molded. TOP

Rotational Molding
Rotational Molding is a process for producing hollow parts such as tanks, totes, floats, buoys and bins. Plastic powder or pellets are loaded into a closed mold then heated while being rotated about two axes. The melting resin sticks to the hot inner surface of the mold, layer upon layer, until all the resin is consumed and fused into a solid-wall, hollow product. Molds are constructed from fabricated sheet metal for less complex shapes.

For more complex shapes and to produce parts with higher aesthetic value and precision assembly cast aluminum is typically used. Features such as handles, threads, metal inserts, custom colors, graphics, variable and adjustable wall thickness, double-cavity or double-walled foam filled products are all common with this process. TOP