Feature Articles - Structural Analysis

Why Structural Analysis for Plastic Parts and Components is Important in the Design Process

Expert engineers and finite element analysts using advanced software can now very accurately find and correct costly design defects in plastic parts and assemblies early in the design process using no more than software prototypes in the form of solid models. The entire process can be performed in a tine frame of one to two weeks and can cost as little as a few thousand dollars. The skill and experience needed to properly apply finite element technology to plastic part design shouldn’t be underestimated-skill and experience both in software usage, as well as general engineering.

Furthermore, all finite element software programs aren’t equal in capabilities and accuracy. As in most areas of commerce, you get what you pay for. If design flaws are found and corrected early, significant product-to-market cost savings can be realized.

The elements of structural analysis

Structural analysis of plastic parts usually involves on or more of:

• Stress and deformation in a plastic part. Under service loading, will the plastic part break and or deform to such an extent that it won’t function properly?
• Fatigue life of plastic part. Under repeated service loading, will the plastic part develop cracks later in service life?
• Vibration behavior of part. When the plastic part is mounted on the larger assembly, will it resonate, creating noise and eventually crack?

Keeping costs down

Generally, a solid model (software prototype) from any of the industry standard solid modeling programs provides the basis for the finite element model. This solid model may be used directly or modified to get a sufficiently dense mesh of the appropriate type of finite elements, which with loads and constraints comprise the finite element model.

Studies have demonstrated an exponential cost increase by a plastic part design flaw as it flows with the design from the initial concept engineering stage (the most cost-effective time to perform structural analysis) to final mass distribution in the marketplace (the least cost-effective time to perform structural analysis). In short, the benefits of structural analysis are readily attainable at anytime along the way from concept engineering to mass-market distribution, but these benefits are most cost-effective when applied early in the design process.

Can your company afford this?

Every manufacturer of plastic parts regardless of the industry needs to address the compelling question: WHAT’S THE COST OF PART FAILURE TO MY BUSINESS? The answer to this question will vary across different industries and market sectors, but in many cases, this list applies:

• Expensive tooling modifications, which oftentimes compromise the tool.
• Delays in getting the part to market, giving competitors an edge in time.
• Customer perception of inferior quality in the marketplace.
• Diminished distributor confidence due to questionable quality.
• Reduced morale in the ranks of the engineering department, with feelings that adequate resources aren’t provided to really do the job right the first time.
• Expensive product recalls, including the associated “marketing fallout.”
• Expensive product liability lawsuits not easily defendable due to the failure on the part of the manufacturer to use existing engineering technology (existing at the time of the design activity) to correct design flaws before market distribution.