When you need large plastic components for equipment housings, vehicle panels, or industrial enclosures, heavy gauge thermoforming offers a practical path from concept to production. At Plastic Components, Inc., we've spent over 50 years refining this process to deliver thermoformed plastic parts that meet the demands of engineers and buyers who need size, durability, and reasonable lead times without the capital investment of injection molding.
This guide covers how heavy gauge thermoforming works, when it makes sense over other processes, and what you should know before starting a project.
What Is Heavy Gauge Thermoforming?
Heavy gauge thermoforming shapes thick plastic sheets—typically 0.060 inches to 0.500 inches—into three-dimensional parts using heat and vacuum or pressure. The process starts with flat thermoplastic sheet stock that gets heated until pliable, formed against a mold, cooled to retain its shape, and trimmed to final specifications.
The "heavy gauge" distinction matters because it determines what the finished part can do. Thicker material produces structural components that handle impact, vibration, and environmental exposure. Thin gauge thermoforming, by contrast, makes disposable packaging and blister packs. Different applications entirely.
Heavy gauge thermoforming handles parts ranging from 6x6 inches up to 6 feet by 10 feet. That size range covers most equipment housings, vehicle body panels, and industrial enclosures that would otherwise require stamped metal or fiberglass layup.
How Does the Heavy Gauge Thermoforming Process Work?
The thermoforming process breaks down into four stages, each affecting the quality and cost of your finished part.
Heating the Sheet
Plastic sheet stock enters an oven where radiant heaters bring it to forming temperature. This step requires precision. Heat the material too little and it won't form completely into tight radii. Heat it too much and you risk degradation or excessive thinning. Different polymers have different optimal forming temperatures—ABS behaves differently than polycarbonate or HDPE.
Forming Against the Mold
Once heated, the pliable sheet moves to the forming station where it contacts a male or female mold. Vacuum pulls air from between the sheet and mold surface, forcing the plastic to conform to every contour. For parts requiring sharper detail and tighter tolerances, pressure forming adds positive air pressure (up to 60 psi) to the back of the sheet, pushing it more aggressively into the mold surface.
This forming approach uses single-sided tooling—one mold surface rather than the matched male/female dies that injection molding requires. That tooling difference drives much of the cost advantage.
Cooling the Part
The formed part must cool completely before removal to maintain dimensional accuracy. Cooling time depends on material thickness, polymer type, and mold design. Aluminum molds with internal cooling channels can cycle up to 10 times faster than composite or wood tooling, which matters for production volumes above a few thousand parts annually.
Trimming to Specification
Every thermoformed part comes off the mold with excess material around the edges. CNC routers or 5-axis trimming machines cut the part to final dimensions, add mounting holes, and create any required cutouts. At PCI, our three 5-axis CNC trimmers handle complex trim paths that would be difficult or impossible with hand routing.
When Should You Choose Thermoforming Over Injection Molding?
The thermoforming vs injection molding decision usually comes down to part size, production volume, and tooling budget.
Injection molding excels at small, complex parts in high volumes—millions of units per year. The process requires matched steel molds that can cost $150,000 or more and take 12-16 weeks to produce. Once you've made that investment, per-part costs drop significantly at scale.
Heavy gauge thermoforming makes more sense when your parts are large (over two feet square), your annual volumes are under 3,000-5,000 units, or your timeline won't accommodate months of tooling development. Thermoforming tools typically cost $10,000-$50,000 and can be ready in 1-8 weeks depending on complexity.
A real example: One heavy equipment manufacturer needed to replace a 718-pound steel belt guard with a lighter alternative. The thermoformed ABS replacement weighed 38 pounds—a 95% weight reduction—and the first article prototypes arrived in three weeks. That timeline would be impossible with injection molding tooling.
What Materials Work for Heavy Gauge Thermoforming?
Material selection depends on what your part needs to survive. Common heavy gauge thermoforming materials include:
ABS offers good impact resistance and machinability at a reasonable cost. It's the workhorse material for housings, guards, and covers that need to take a beating.
HDPE and HMWPE provide chemical resistance and work well in cold temperatures. Battery enclosures and chemical-resistant containers often use these materials.
Polycarbonate delivers optical clarity with high impact strength—useful for machine guards and windows that need to remain transparent.
Fire-rated PVC and low-smoke materials meet the FST (flame, smoke, toxicity) requirements for mass transit and rail applications.
Co-extruded sheets combine materials—like a UV-stable cap over an ABS substrate—to get properties that no single material provides. Your thermoformer should help you match material properties to your application requirements rather than defaulting to whatever's cheapest.
What Design Factors Affect Thermoformed Part Quality?
Three design parameters matter most for heavy gauge thermoformed parts:
Draw ratio describes how tall a part is relative to its surface area. A 2:1 ratio (height to width) is generally achievable, though geometry affects this. Deeper draws thin the material more, which may require starting with thicker sheet stock.
Draft angles allow the part to release from the mold. Three degrees minimum keeps tooling costs down; less draft is possible but increases startup costs and can cause release problems.
Wall thickness determines structural performance. Heavy gauge parts start at 0.060 inches and go up from there based on stiffness and impact requirements.
Getting these parameters right during design prevents expensive tooling revisions later. That's why most thermoformed part projects start with a design review before any metal gets cut.
Ready to Evaluate Thermoforming for Your Large Parts?
Heavy gauge thermoforming fills a specific niche: large parts, moderate volumes, shorter timelines, and lower tooling investment than injection molding or metal stamping. If your project fits that profile, it's worth a conversation about what's possible.
At Plastic Components, Inc., we handle tooling, engineering, and manufacturing under one roof. Send us your CAD files or existing parts and we'll provide a quote covering prototype costs, production pricing, materials, and timing.
For more information or to start your custom thermoforming project, contact us today.
