Design consideration for plastic parts and its applications

Plastic Design

Even today plastic finds extensive use in product development. The higher usage pattern of plastic can be easily attributed to its strength, light weight and low cost for re-production. The other advantages of plastic is that it gives a clean finish to the product, absorbs less water, is odorless, is chemical inerrant, corrosion resistant and can be recycled.

Use of plastics in the automotive industry

Plastics are generally used in automotive industry for manufacturing like bumpers and dash boards, in consumer industry to create enclosure for mobiles phone, display panel for television, mouse, and keyboard and in medical, packaging industries and safely equipment’s are the other industrial area where plastics are used extensively.

Design elements associated with plastic product development

When it comes to plastic product development, there are certain design aspects that are to be taken into consideration. Some of them are discussed below in brief:

Many times, product design specialists need to increase the stiffness of a particular component as it needs to withstand substantial load that is applied to its design. To address this matter, the best and easiest way is to add ribs and change the part geometry. Using ribs is not only practical method but it is also an economical way to increase a part’s structural strength. However, it is important to follow certain rules while adding ribs so as not to cause surface blemishes or sink marks on the parts. For instance, the thickness of the rib should always be less than the wall thickness. Additionally, it is always better to add more number of ribs for a particular stiffness instead of the height.

Bosses

Bosses are mainly used for mounting, locating and assembly purposes. One of the most important aspects to consider while placing them is the nominal wall thickness. A lot of times the bosses are made with the thick wall sections which can affect the overall look of a plastic part as well as the final product. Ideally, wall thickness around the boss design feature must be maintained at 60% of nominal part thickness in case that thickness is lower than 1/8th of an inch.

Holes

Holes are usually made in the molded parts. The core pins that are inserted into mold cavity give rise to the holes when that part gets molded. It is easier to create through holes in molded parts than the standard blind holes.

Key points for plastic part design

During plastic part designing, there are many critical parameters that should be maintained, these could be the drafting angle, parting line, maintaining a uniform wall thickness and so on, so that by maintaining these parameters stress in mold, sink marks, warpage, and tolerances during the molding of the part can be avoided. A few good practices are listed below:

  • To maintain uniform thickness across the radius and horizontal & vertical walls
  • To provide ribs to strengthen the boss
  • To create ribs for uniform flow of mold and weight reduction

Keeping the above consideration in mind during the design phase can help greatly to attain the desired benefits of using plastic. These benefits in terms of cost reduction, ease of manufacturing through injection mold for the higher quantity and superior quality and the appearance of the parts contribute to extensive adoption of plastic in the product development by the industry.

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