Geometric dimensioning and tolerancing (GD&T) is a symbolic language that is used on engineering drawings and computer-generated models. It communicates geometric dimensions and allowable tolerances for various parts. Not only is this a useful exercise for product design, it’s also helpful on the manufacturing floor because engineers and operators can quickly see the degree of tolerance that is required for each part.
Polymer science has made tremendous strides over the years, rapidly advancing the ability to compound a variety of resins with fillers and reinforcements that provide a vast amount of structural and chemical integrity.
Shrink rates for injection molded plastic parts vary depending on the materials used andwall thickness. Designing uniform wall thickness offers substantial shrink rate control; on the other hand, non-uniform walls can lead to large pressure drops during filling, significant differences in shrink rates, and internal stresses within the injection molded part that could cause warpage or similar defects.
Surface finish on plastic composites can vary a great deal, depending on the physical and chemical properties of the polymer blend as well as the parameters of the injection molding process.
The first objective for a custom injection molder is working with the customer to determine how important the surface finish is for the appearance and/or performance of the final product. For example, does the product need to be eye-catching or simply functional? Depending on the answer, the material selected and the desired finish will determine the settings for the injection molding process, and any required secondary finishing operations.
It’s generally accepted that roughly 80% of a part’s total cost is determined during the design/development phase, and cannot be reduced – or is extremely difficult and expensive to change – once the design is finalized. However, by utilizing a Design for Manufacturability (DfM) approach and the specialized expertise of a plastics engineer, deliberate design decisions can be made to help manage/reduce total part and production costs.
Total delivered cost (TDC) is the amount of money it takes for a company to manufacture and deliver a product. The definition sounds simple enough, yet all that TDC entails — sourcing raw materials, manufacturing bulk and intermediate products, finished goods packaging, inventory holding, transportation, distribution, and final delivery — reveals its complexity and considerable impact on the bottom line.
The Kaysun Blog is a valuable year-round resource for advice and information about complex injection molding. We have our subscribers to thank for its continued popularity, and look forward to providing you with even more helpful insights throughout 2019.
For now, let’s take a look back at the four most popular blog posts of 2018:
There is little room for error when designing plastic parts for critical-use applications. Anything that could stand in the way of uncompromised performance or end-user safety is unacceptable; there’s too much at risk given the potential for significant issues surrounding recalls, warranty claims, property damage and personal injury. And, no company can afford to lose customer trust.
It can occur in just about any injection-molded part or product — yet the experienced injection molder knows how to eliminate warpage from the production cycle and maintain a steady throughput of high-quality product that meets all customer specifications, including dimensional accuracy and tight tolerances.