5 Tips For Designing A Functional Prototype

In today’s highly competitive, global market, product manufacturers are presented with both time and cost challenges associated with production mold development. To avoid delays and reduce risk for costly design changes, it is becoming more common for the development and manufacturing of parts to be treated as parallel steps. The sharp line that was once drawn between development and production is now, oftentimes, blurred with manufacturers leaning on input from market representatives, focus groups or conducting market tests. This process, along with the following design recommendations, can eliminate post-development issues and delays, while bringing your product to market faster.

1. Add draft to your CAD model.
   Draft refers to the angles incorporated into your part design that aids in the ejection process from the mold. The amount of draft required for your part will vary depending on material thickness and texture. Consider the shrink properties of the material as it hardens. By tapering the sides of a mold to a recommended draft angle, the part will be easier to remove. Here are a few general draft guidelines to follow when designing your next part:

2. Add draft to your CAD model.
   Draft refers to the angles incorporated into your part design to help eject the part from the mold. The amount of draft required will vary depending on material thickness and texture. Consider the shrink properties of the material as it hardens. By tapering the sides of a mold to a recommended draft angle, the part will be easier to remove. 
3. Always use as much draft as possible:
   1. 1-5 deg on your part
   2. Draft your part in the direction of pull
   3. Consider more draft with texture: 2-3 deg (or 3-5 deg with deep texture)
4. Eliminate undercuts as much as possible.
   An undercut is any back drafted area that prohibits the ejection of a part from a mold and adds complexity to the build. Reducing the number of undercuts or eliminating them altogether, will simplify the tooling process. Experienced design engineers can assist with providing modification solutions to decrease or eliminate undercuts from a part design – which will likely result in a better design, a more efficient molding process and reduced costs.
5. When possible, avoid sharp corners.
   Sharp corners are an important feature to avoid during the prototype design process because they can greatly increase the stress concentration and lead to part failure. It is imperative to avoid part stress because it can cause warpage, sink marks, cracking, premature failure and more. While some stress in a part is expected, designers should always keep the stress factor in mind to ensure the integrity of the part.
6. Try to reduce thick areas.
   Material thickness is one of the most critical factors in part design. Thickness plays a role in a number of factors including performance, appearance, moldability, cost and more. Thinner material walls will reduce the amount of material, and cycle time. While minimalizing material use should be on the mind of a designer, achieving an ideal wall thickness can be a balance between the strength of the material and weight which are important factors to the part’s overall durability and cost. Here are some general material thickness guidelines to consider:
   
   

   ABS	0.045 - 0.140
   Acetal	0.030 - 0.120
   Acrylic	0.025 - 0.500
   Liquid crystal polymer	0.030 - 0.120
   Long-fiber reinforced plastics	0.075 - 1.000
   Nylon	0.030 - 0.115
   Polycarbonate	0.040 - 0.150
   Polyester	0.025 - 0.125
   Polyethylene	0.030 - 0.200
   Polyhenylene sulfide	0.020 - 0.180
   Polypropylene	0.025 - 0.150
   Polystyrene	0.035 - 0.150
   Polyurethane	0.080 - 0.750
   Rigid PVC	0.090-0.250
   Soft PVC	0.025-0.150

   
   
   
7. If ribs are necessary, keep them 50% of the adjoining wall thickness.
   In part design, ribs provide strength, stiffless and minimalize warp without having to increase the material thickness. Ribs should be approximately 50% of the joining wall thickness to avoid sink marks. If strength is critical to the functionality of the part, using cross-hatched rip patterns can increase strength and avoid sink. Thin ribs may be hard to fill, making it important for designers to consider the material in the design phase.

There are many resources available to help alleviate the complexity of part design and challenges faced with speed to market. It is essential to align with trusted and knowledgeable experts who understand and use the latest technology and resources to guide you through the design and production process. By following a few basic recommendations and guidelines in regard to design and material selection, manufacturers can produce the highest quality part while saving time and reducing costs.