Solar Plastics - Frequently asked Questions (FAQ’s)
At Solar Plastics Inc., we get a variety of questions related to rotational molding. Here are some of the most important and frequently asked questions regarding our processes, products and capabilities.
How does a rotomolded part compare to a blow molded part?
Although both processes make hollow parts, rotational molding offers design flexibility and molded part characteristics that are difficult to match in blow molding.
- Complex shapes with deep draws can be rotomolded with consistent wall thickness with relative ease. Rotomolded parts actually have their thickest wall sections in outside corners where durability is often critical.
- Rotomolding tooling can be made to provide undercut and cored features that even if possible would be very costly to tool and process in blow molding.
- In-mold decorating and mold-in inserts are also easily accomplished with rotational molding. Rotational molding allows the designer more freedom to design to part function rather than to the constraints of the process or tooling.
How can I complete a design for rotational molding?
Solar offers many design help resources, and can even complete the design to your specifications. Numerous design manuals, technical bulletins, and other references are available.
- A process and design presentation tailored to your needs can be given at your facility. We can even suggest design seminars presented by SPE and the Association of Rotational Molders. These resources will help you determine suitable geometry, features, and material characteristics.
- Solar's experienced design team can then review your design and provide direction to fine-tune it to enhance processing, tooling reliability, and part quality. Our designers can also complete a design to your requirements using ProE CAD tools.
What is a typical production rate?
A single tool may produce approximately 3,000 to 3,500 pieces per year depending on complexity and wall thickness. Peaks in annual usage may require multiple tools.
How can I find out if a product can be contained in a rotomolded part?
Specific chemical resistance information is available upon request. It is important to provide additional information such as temperature, concentrations, density, and how the product is to be used.
What kind of tooling is required?
Thin wall, hollow molds of two or more sections are most common. These molds are typically cast or machined aluminum, or fabricated from steel or aluminum. Individual mold sections are fitted with frames and a clamping system. The mold is provided with a method to mount it to a rotomolding machine.
- Cast tools, which are most common, are built in four stages. 1) Pattern creation: a full size (plus shrink) model of the part is built from design specifications. 2) Foundry: individual mold sections are produced with a sand casting process from the pattern. 3) Finishing: castings are polished, fit, and framed. 4) Final detailing: machined features, texture detail, and coatings are applied. In some instances, tooling can be CNC machined from the part model, eliminating the need to produce a pattern.
- Prototypes can be produced from a mold that is 50 - 80 % complete.
- Solar's development engineers will help you determine the most appropriate and cost effective construction method. We also provide coordination services during tool build to ensure tools are accurate, durable, and meet our production needs.
Learn more about tooling options
How long does it take to go from design to production?
While the actual duration depends on the complexity of the design, and the approval process, the typical development timeline is: 6-12 weeks for tool build, 1-3 weeks for inspected samples, 1-3 weeks for finished part evaluation (total 8-18 weeks).
What kind of tolerances can rotomolding hold?
Typically, production part wall thickness can vary from nominal by +/- 20%, and linear dimensions by a basic +/- .030" plus .005" per linear inch of the dimension in question. Additionally, a tooling tolerance of +/- .030" plus .0025" per linear inch of dimension must be considered when molds are being built.
Tighter production tolerances may be achieved. Our development engineers are available to discuss important features, and how well they can be controlled.
What colors are available? Can I choose my own?
Color can be incorporated by dry blending a customized pigment formulation with ground natural material, or by hot melt compounding prior to grinding. With both methods, a wide range of colors is available. Our design team will evaluate specific requests. Important considerations are: base resin, pigment type restrictions (if any), environment, cost, opacity required, and part surface finish.
My parts are all metal now. Why should I consider rotomolded plastic parts?
Benefits include weight reduction, corrosion resistance, and reduced cost. Rotational molding provides the designer the freedom to address form along with function. Parts can be designed to be more ergonomic, and esthetically pleasing without affecting performance. In many cases rotomolded parts reduce the number of components in an assembly.
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