Virginia Industrial Plastics (VIP) produces plastic parts and products (parts) of various shapes, sizes and colors for a wide variety of markets and uses. VIP utilizes a process known as thermoforming or vacuum forming to make parts, but there are other methods as well. Some satisfy certain aspects of a project better than others. All have their benefits and drawbacks. On this page, we have provided some insight on the most popular processes to aid you in your decision for the best process to use for your particular project. Of course, if you have any questions or concerns, we are always available to discuss your project and suggest the best alternative.
Things to consider when choosing the manufacturing process to make a plastic part?
Shape: Is the part you are looking to have produced designed with complex internal features and/or does it have tight tolerance requirements? Depending on the answer to this question, your manufacturing options may be limited, or they may require significant design for manufacturing (DFM) optimization to fit a specific process. VIP can help you with the DFM process if we are selected as the manufacturer of the part.
Volume/Cost: Consider the volume of how many units of your part you need to make today and in the future. You must balance between high upfront cost/low production cost and low upfront cost/higher production cost. What’s the total or the annual volume of parts you’re planning to manufacture? This is an important aspect of the decision process.
Lead time: What is the time frame requirement for you to get prototype parts? When does production need to ramp-up by to meet your annual volume needs? Some processes create first parts within 24 hours, while tooling and setup for certain high-volume production processes take hours, days or weeks. Tooling production can range from hours to months.
Material: What is the application for the part and what sort of stresses and strains will your product need to stand up to? The optimal material for a given application is determined by a number of factors. Cost must be balanced against functional and aesthetic requirements. Consider the ideal characteristics for your specific application and contrast them with the available choices in a given manufacturing processes (we can help with this evaluation).
The following is a brief description of some popular plastic part manufacturing processes and how each of the factors above fit in with each process:
Thermoforming or Vacuum Forming
Thermoforming uses a plastic sheet, which is formed with a mold by applying air pressure or vacuum through mechanical assistance. The air pressure used can be very small (almost zero psi), or several hundred psi. At 14 psi, which is equivalent to atmospheric pressure, the pressure is created by evacuating the space between the mold and the sheet. This is known as vacuum forming. Thin gauge thermoforming starts with material thicknesses less than .060” and thick gauge starts with material thicker than .060”. VIP is primarily a thick gauge operation.
The following are the specific processing steps used in the thermoforming process:
Clamping: A plastic sheet is clamped in a frame.
Heating: The sheet and the frame are moved into an oven to heat the material to the correct temperature, making the plastic soft and pliable.
Vacuum: The frame comes out of the oven and the mold is either lowered or raised into the soft plastic which is then stretched over the mold, while vacuum is activated to suck all the air out from between the plastic and the mold, thus forming the part. Some parts require a mold that is known as a negative mold, in this case the material is “pulled” into the mold with the vacuum. Based on the specific application for your part, VIP will help you select the correct mold configuration for your particular part.
Cooling and Release: Once the part has been formed over or into the mold, it must be given time to cool before removal. Cooling system like fans and sprayed mist are sometimes used to reduce cycle times. Molds are also made with water lines that are placed near the surface of the mold which allows for the surface to maintain consistent temperatures and produce more consistent parts.
Trimming: Once the part is released, excess material is cut off either by hand or with a CNC machine.
Thermoforming has a wide range of capable shapes and tolerances. The DFM process must still be done on all parts to make sure that all aspects of the part can successfully be producted.
Thermoforming has a big advantage in that the up-front costs for tooling can range from very low to medium level cost, while volume can vary from 1 or 2 pieces to annual volumes in the tens of thousands. Cost of parts decreases as the volume increases due to material volume discounts and the potential for multi-part tooling.
Lead Time for parts is generally 2 weeks to several months for first time runs due to the length of time required for the tooling. Once parts are approved, manufacturing lead time can range from a few days to 5 weeks.
Materials Most Frequently Used For Thermoforming:
- ABS (Acrylonitrile Butadiene Styrene) – Comes in a wide variety of resin combinations used across a number of applications and can be formulated to meet a number of different standards from UL ratings to FDA. Also serves as a cost-effective carrier for various decorative coverings to further enhance the look of your parts.
- PC/ABS (Polycarbonate/ABS) – This alloy delivers UL approval in addition to high impact performance.
- HDPE (High-Density Polyethylene)– This is a cost-effective material for industrial applications requiring high impact strength. HDPE is resistant to most chemicals and stands up to weather.
- LDPE (Low-Density Polyethylene) – Cost effective material utilized to produce that are chemical resistant, require long life and are pliable
- TPO (Thermoplastic Olefin) – This high impact material delivers performance in cold and high heat applications with minimal CTE values.
- HIPS (High Impact Polystyrene) – This low-cost material that is used in many applications requiring excellent forming characteristics.
- PVC/Acrylic (Polyvinyl Chloride Acrylic) – This resin meets most stringent UL standards for flammability.
- PC (Polycarbonate) –also referred to as the brand Pexiglass, has a very dense structure and often is perfectly clear. Known for high impact resistance.
- PETG – Clear but tinted material most frequently used in thin gauge applications.
- Polypropylene – Soft and pliable plastic commonly used for cutting boards and skid plates.
- Acrylic – Also sometimes referred to as the brand Plexiglass, similar in appearance to polycarbonate, but more abrasion resistant and less impact resistant.
This is just a partial list of materials. Contact VIP to discuss the details for your project and we can help you select the best material to fit your application. All materials can be produced with different surface finishes as well.