To save time and money during the manufacturing phase of your project, you will want to think about several things while designing plastic components that will be injection molded. Foresight from the start of product design can help you comprehend the restrictions and problems experienced by your product’s producers.
Consider these points when deciding on injection molding mold design, and you will be well on your way to making the proper decision or at least pointing you in the right path.
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Material options and consequences
To avoid misunderstanding, it is best if the parties involved agree on the materials before moving on with the design. You can purchase large amounts of certain resins at significant reductions from time to time. Customers may benefit from these savings. Likewise, it is possible to save many thousands of dollars if a designer chooses an ABS grade that matches the qualities bought in bulk by a molder. Viscosity, high glass content, or crystallinity may make a designer realize that a specific high-performance resin isn’t the best choice for a molder.
You can select resins for their unique physical or chemical resistance, but they may be difficult to mold or maintain required tolerances. Thus, they are not always the best choice. Molders are the ones who will be doing the molding; therefore, they need to be on the same page as far as resin specifications and overall component needs are concerned.
Uniformity
You will achieve the optimum flow by maintaining a constant wall thickness throughout your component. The nominal thickness of the wall should be between 2-3mm. Conventional injection molding procedures call for a minimum wall thickness of 1 mm and a maximum of 4 mm.
Critical tolerances
One of the most challenging aspects of developing an injection molded product is ensuring that the design has adequate room for tolerance variance. Diverse factors influence the variance in tolerance, such as the materials used, process control measures used, and the tool design itself. The acceptable tolerance limits for a design will be vastly different depending on the molder.
Consider the possibility of mold changes if essential tolerance criteria need to be lowered. Some design elements may require additional built-in clearance, which you can tighten by removing steel from the mold later on. No one wants to sell steel into the mix to solve interference issues. Other ideas from molders include post-machining, fixturing, and gate positions for ensuring tight tolerance control.
Add draft
If you want to avoid constant mold contact during the mold opening, you need to angle otherwise vertical walls. All vertical walls parallel to the mold pull direction should have a one-degree draft. Ribs and bosses need to be considered, as well as textured surfaces, which require an additional 1 degree per side for every.001″ of texture depth. As a component of the design process, drawing is vital.
Keeping an eye out for undercuts
Adding undercuts to your component won’t necessarily make molding it more difficult, but it will make demolding it more complex. Once the plastic piece has cooled and solidified, the undercut section will get caught within the mold and will be difficult to remove without further mold movements. Undercuts are often required for a component to work correctly.
The ejection of your piece necessitates the addition of side movements and lifting mechanisms to your tool. If you are hoping to save money on tooling expenses, you may want to consider redesigning your product to reduce the need for expensive tooling.
Secondary operation or molded in?
Inserts may need to be inserted into your component from time to time. They must be considered whether they are molded in, pressed in, or welded in after the molding process has begun. Both solutions are possible, and the operation’s economics will determine which is best for the company. A more expensive tool that can accept inserts to be molded over or press them into the component after the fact is your best option. For a small manufacturing run, a post-molding procedure may be worthwhile. For lengthy manufacturing runs, having the inserts molded in may be preferable. As a result of these factors, it is impossible to provide a definitive answer.
Injection molding is the most challenging plastic production method to design for. It is impossible to overstate the importance of working closely with your molder and tool manufacturer throughout the design and development phase. When all stakeholders agree on key design specifications, it strengthens relationships, fosters confidence, and eliminates unpleasant shocks when production gets underway.
