Three specialized molding processes under one roof — the right method for your material, geometry, and production volume, selected by an engineering team that knows the difference.
The three molding processes we offer address fundamentally different production requirements. Here’s how they compare at a glance:
| Injection Molding | Compression Molding | Rotational Molding | |
|---|---|---|---|
| Material Type | Thermoplastics & elastomers | Thermosets & thermoplastics | Thermoplastics (PE, Nylon, PVC) |
| Part Geometry | Complex, thin-wall, multi-feature | Solid, thick-section | Large, hollow, seamless |
| Tooling Cost | Medium to high | Low to medium | Low |
| Cycle Time | Fast | Moderate | Slow |
| Best Volume | Medium to high | Low to medium | Low to medium |
| Part Size | Small to medium | Small to large | Medium to very large |
| Key Advantage | Precision, repeatability, speed | Thermoset compatibility, thick sections | Large hollow forms, low tooling cost |
Not sure which process applies to your part? Read on — each process is explained in detail below — or send us your drawing and our engineering team will recommend the right approach.
What Is Injection Molding?
Injection molding is a high-precision manufacturing process in which molten plastic is injected under controlled pressure into a custom-designed mold cavity. Once the material cools and solidifies, the mold opens and the finished part is ejected — ready for use or post-processing.
The process is exceptionally well-suited for producing parts with complex geometries, tight dimensional tolerances, and consistent repeatability across medium to high production volumes. Because the mold defines the part, every unit produced is virtually identical — making injection molding the go-to process for components that cannot tolerate variation across a run.
Custom Injection Molding & Rapid Prototyping
No two projects are identical, which is why Plastic-Craft approaches every injection molding engagement as a custom solution. Whether you need a single functional prototype to validate your design, a low-volume pilot run, or a full-scale production program, our engineering team works directly with you from the start.
Our injection molding capabilities include custom mold design and development engineered to your exact part geometry and tolerance requirements, functional prototypes for design testing and validation, scalable production support with consistent quality from first article through thousandth unit, broad material capability across thermoplastics and elastomers, and CAD design and DFM support — our team can work from your existing files or collaborate on design for manufacturability from the ground up.
Using current CAD and simulation tools, we identify and resolve potential forming issues before cutting a single tool — saving time, cost, and downstream rework.
Injection Molding Materials
| Material Category | Examples | Best For |
|---|---|---|
| Thermoplastics | ABS, polycarbonate, nylon, polypropylene, PETG | General-purpose to structural applications |
| High-Performance Polymers | PEEK, Ultem (PEI), Torlon (PAI) | Extreme temperature, chemical, or load-bearing environments |
| Elastomers | TPE, TPU | Flexible, soft-touch, and sealing applications |
| Recyclable Plastics | PP, HDPE, rPET | Sustainable manufacturing and eco-conscious product lines |
Injection Molding Applications
Injection molding supports precision part production across a wide range of industries, including automotive interior and structural components, medical device housings and surgical trays, consumer electronics enclosures and connectors, industrial gears, brackets and mechanical components, packaging caps, closures and containers, and aerospace and defense components where lightweight, high-performance plastic parts are required.
What Is Compression Molding?
Compression molding is a process in which a pre-measured charge of plastic material — in powder, granule, or pre-formed blank form — is placed directly into a heated open mold cavity. The mold is then closed under hydraulic pressure, forcing the material to flow and conform to the mold geometry. Heat and pressure are maintained until the material has fully cured or solidified, at which point the mold is opened and the finished part is removed.
Compression molding is the process of choice for thermoset plastics — materials that cure permanently under heat and pressure and cannot be processed by injection molding. It is also well-suited to thick-section thermoplastic parts, filled engineering compounds, and applications where low residual stress and flash-free edges are important.
Compression Molding Materials
Materials commonly compression molded at Plastic-Craft include phenolic (Bakelite), Hydlar Z, filled nylon compounds, UHMW polyethylene, PEEK, and other engineering plastics and thermoset compounds. Contact us to discuss your specific material and part geometry.
Compression Molding Applications
Compression molding is used for phenolic and thermoset electrical components where injection molding is not viable, high-load-bearing wear pads and bushings in filled engineering plastics, thick-section structural components in UHMW and PEEK, and laboratory and industrial components requiring thermoset material properties.
What Is Rotational Molding?
Rotational molding — also called rotomolding — is a process in which a measured charge of plastic powder is loaded into a hollow mold that is then rotated biaxially (on two axes simultaneously) inside a large oven. As the mold rotates and heats, the powder melts and coats the interior mold surfaces evenly. The mold then moves to a cooling station where it continues rotating while the material solidifies, after which the mold is opened and the finished hollow part is removed.
Rotational molding is uniquely suited to producing large, hollow, seamless one-piece parts — tanks, containers, housings, floats, and complex hollow enclosures — that cannot be practically produced by any other molding process. Wall thickness is controlled by the charge weight, and the process naturally produces uniform wall distribution around complex three-dimensional shapes.
Rotational Molding Materials
The most common rotational molding material is polyethylene (PE), particularly HDPE and linear low-density polyethylene (LLDPE), which produce durable, chemical-resistant hollow parts. Nylon and PVC plastisol are also commonly rotationally molded for specialty applications.
Rotational Molding Applications
Rotational molding is used for polyethylene storage tanks and chemical containers, large outdoor equipment housings and covers, marine floats, buoys, and water management products, and custom hollow forms for industrial and commercial applications.
While each of the three molding methods has its own specific process steps, every project at Plastic-Craft follows the same core workflow — starting with engineering and ending with verified, inspection-documented parts.
We begin by reviewing your part design, application requirements, and production volume to recommend the right molding process. Material selection follows — balancing mechanical strength, thermal resistance, chemical compatibility, surface finish requirements, and regulatory considerations. Getting this right before tooling begins prevents costly downstream revisions.
A custom mold is designed and fabricated to your exact part specifications using advanced CAD tooling and precision machining. Mold design accounts for wall thickness, draft angles, gate placement (for injection molding), charge distribution (for rotational molding), and cooling to ensure optimal part quality and cycle efficiency.
Parts are produced using the appropriate process — injection, compression, or rotational — with precise process parameters maintained throughout each run. Our equipment and operators maintain the consistency that ISO 9001:2015 certification requires.
Parts are cooled in a controlled manner to prevent warping, sink marks, and dimensional variation. For rotational molding, controlled cooling while the mold continues to rotate is critical to uniform wall quality.
Every part is inspected against your design specifications before release — dimensional verification, surface quality inspection, and any required functional testing. For customers in regulated industries, full inspection documentation is available.
Finished parts are carefully packaged and shipped to your requirements — with the supply chain reliability and on-time delivery that production programs depend on.
Each process addresses a different set of part geometries, materials, and production requirements. Injection molding forces molten thermoplastic into a closed mold under high pressure — it’s fast, precise, and best for complex thin-walled parts at medium to high volumes. Compression molding places material directly in an open mold and closes it under pressure — it’s the right process for thermoset materials that cannot be injection molded, and for thick-section parts where injection molding would produce sink marks or long cycle times. Rotational molding rotates a plastic powder charge inside a heated mold to produce large, hollow, seamless one-piece structures — tanks, enclosures, and containers — at very low tooling cost. Plastic-Craft offers all three processes and can recommend the right approach for your part.
Injection molding is best suited for producing complex plastic parts with tight tolerances at medium to high volumes. It excels when consistent repeatability, fine surface detail, and production efficiency are priorities. Common applications include automotive components, medical device housings, consumer electronics enclosures, and industrial mechanical parts.
Injection molding forces molten plastic into a closed mold under high pressure, producing parts with detail on all surfaces and very tight tolerances — ideal for complex, high-volume parts. Thermoforming heats a flat plastic sheet and forms it over a single-surface mold — it uses lower-cost tooling and is better suited for large parts and lower-to-mid production volumes. The right process depends on your part geometry, volume, and budget.
Compression molding is used for thermoset materials — such as phenolic — that cannot be processed by injection molding, for thick-section parts where injection molding would produce quality issues, and for low-to-medium volume programs where injection mold tooling investment is not justified. It’s also the appropriate process for filled engineering compounds and parts requiring low residual stress and flash-free edges.
Yes. Phenolic is a thermoset material — it cures permanently under heat and pressure and cannot be processed by injection molding. Compression molding is the standard process for phenolic parts. Plastic-Craft regularly molds phenolic and other thermoset compounds.
Rotational molding is used to produce large, hollow, seamless plastic parts — most commonly polyethylene tanks, containers, equipment enclosures, and marine products. Its primary advantage is the ability to produce large hollow forms at very low tooling cost compared to any alternative process.
Yes. For injection molding, we offer rapid tooling approaches that allow you to get functional prototype parts in hand before committing to full production tooling. Once your design is approved, we scale into full production while maintaining consistent quality throughout. Compression and rotational molding programs are similarly supported from prototype through production.
Yes — our molding processes operate under an ISO 9001:2015-certified quality management system. Every production run is governed by documented procedures, inspection checkpoints, and continuous improvement protocols that ensure consistent, verifiable quality — particularly important for customers in regulated industries including defense, aerospace, pharmaceuticals, and medical device manufacturing.
Most thermoplastics are compatible with injection molding, including ABS, polycarbonate, nylon, polypropylene, PETG, PEEK, Ultem, and Torlon, as well as thermoplastic elastomers for flexible applications. Material selection is guided by the functional, environmental, and regulatory requirements of your part.
Blogs, how-tos, and guides to help you understand plastic molding processes.
A comparison of injection molding and thermoforming to help you select the right process for your plastic parts.
When and why compression molding is the right choice for phenolic, UHMW, and other thermoset and engineering plastics.
How rotomolding produces seamless tanks, enclosures, and containers at low tooling cost.
Tell us about your part geometry, material, and production requirements and our engineering team will recommend the right process — injection, compression, or rotational — and provide a quote. Whether you’re qualifying a prototype or scaling into production, Plastic-Craft has the capability to deliver.
