It’s a discussion and debate that has been going on since the beginning of modern plastics fabrication—metal versus plastic? It’s a discussion many end-users and plastic part manufacturers still have with suppliers and customers, although today there is a greater level of knowledge and technical sophistication brought to it.
Advances in materials and processes, together with changes in customer and industry needs, have closed many of the physical property, application, and performance gaps between metal and plastic.
Today, with rising commodity prices and supply chain challenges, it is more imperative for companies to investigate new ways to remove cost and add value for their customers. With PCI’s years of experience as a guide, it is easier than ever to capitalize on the inherent advantages of thermoforming and convert your metal parts to plastic in a short period of time.
For an increasing number of applications, plastic thermoformed parts can effectively compete with metal parts made from a variety of forming processes, including manual sheet metal fabrication, metal stamping, and die pressing.
The most common sheet metal material is steel, although aluminum, tin, and other materials are also used. Most sheet metal raw material is supplied in a sheet thickness or gauge between 0.006 in. and 0.250 in.
Sheet metal forming is a relatively low-cost process for parts with simple designs such as single-directional bends. As part complexity increases, however, the fabrication process requires additional steps, such as cutting, bending, and stretching to meet the design specifications.
Some designs may require multi-part assembly accomplished by welding, bonding, riveting, fastening, or a crimped seam. As multiple steps begin to accumulate in metal fabrication, thermoplastics thermoforming becomes an effective alternative enabling a reduction in parts, labor, cycle time, and costs.
When compared to stamped metal parts, thermoforming also offers the advantage of significantly shorter lead times to production, as well as lower tooling costs. A thermoforming tool used in vacuum or pressure forming processes comprises a single male tool.
Depending on the application, required tolerances, and expected production run, the tool can be made from steel, aluminum, or a variety of polymer-based tooling materials, usually in six weeks or less. Cost savings for a thermoforming tool compared to a metal two-cavity press or die tool can exceed 50 percent.
The most common type of thermoplastics forming process used in metal replacement applications is referred to as “heavy gauge” forming, a process with which PCI has years of expertise designing and manufacturing parts for clients in automotive, electronics, and other industries. Heavy gauge forming refers to a broad class of thermoplastic sheet ranging in thicknesses from 0.060 in. to 0.50 in.
PCI has the capability to use both vacuum forming and pressure forming processes for metal to thermoplastic part conversion. In vacuum forming, a thermoplastic sheet is secured over the mold. The sheet is heated to its forming temperature and the air is evacuated from the mold pulling the sheet onto the mold surface. The mold is cooled, and the formed part is removed from the mold and CNC trimmed to part specifications.
In the pressure forming process, as before, the plastic sheet is secured above the mold and heated to its forming temperature. Air pressure is applied above the mold and vented below pushing the “A” surface, or visible side of the plastic sheet against the mold surface. The applied pressure provides tighter radii, similar to an injection molded part.
The pressure also delivers consistent surface finish from part to part, while allowing the flexibility to introduce paint film, surface texturing, and other decorative elements into the part. For this reason, pressure forming is usually the choice for parts and components with surface aesthetic requirements.
PCI can assist customers by converting a metal part to the thermoplastic process that will meet their engineering and performance specifications for their specific part.
For clients looking to capitalize on the benefits of metal to plastic conversion, PCI can guide them through the best options for design, tooling and fixture configurations, material selection, and decorative and aesthetic features, in a single turnkey process.