Designing Injection Mold Tooling Virtually To Reduce Scrap & Rework

Let’s take a deep dive into the injection molding process and some of the common mistakes or pitfalls that we’ve seen customers encounter as they’re designing new mold tooling. Let’s start by breaking down some of the typical costs associated with the injection molding process:

• Material costs: $1-5/kg depending on availability and material properties
• Labor Costs: Varied depending on several factors
• Tooling Costs: $5,000-50,000 depending on complexity of the mold

As we can see, that’s a relatively large upfront investment in the molding process for a part. If you missed my blog on the injection molding pitfalls we’ve seen in the industry, here’s a quick summary of the 5 most common injection molding mistakes:

• Weld Lines
• Sink Marks
• Air Traps
• Warping
• Short Shots

All of these issues have the potential to pop up during the mold cycle, so we need to beware of them and do everything we can to avoid them. But what if we could ensure that none of these issues pop up before we even cut the tooling for the mold? That would protect our investment and minimize downtime for the molding machine, resulting in more output and 100% perfect parts every time. How can we guarantee that these issues are screened for? That’s where a tool like SOLIDWORKS Plastics comes in. This tool is part of the design validation suite of products offered by SOLIDWORKS to screen out potential issues and get your product to market faster. Let’s go issue by issue and see how SOLIDWORKS Plastics can help us weed out the bad designs and settle on the final design faster.

Weld Lines: The Weakest Park Of An Injection Mold

These defects are not always purely cosmetic; weld lines are often the weakest point of an injection molded part because the melt fronts partially solidify when they collide, resulting in much weaker molecular bonding. We can predict where the weld lines are going to occur and minimize the impact, or redesign the mold to eliminate them entirely.

Sink Marks Make An Injection Mold Look Bad

Once the melt front enters the mold cavity, it comes into contact with the mold wall and starts to cool, causing it to contract and pull away from the mold. These blemishes are purely cosmetic but still undesirable. We can predict the amount of sink and adjust the packing pressure accordingly to minimize these defects.

Air Traps

If the air in the mold gets compressed tight enough and hot enough, it can actually explode, damaging both the mold and the finished part. SOLIDWORKS Plastics can help identify locations for air vents to prevent this explosive phenomenon and keep the mold safer.

Warping

Warping of plastic parts is also caused by uneven cooling as the part sits in the mold. This can also cause some precision parts to be out of tolerance, leading to scrap and rework. We can use SOLIDWORKS Plastics to help minimize warping and keep the part cooling uniformly.

Short Shots

The most crippling issue when dealing with injection molding is the short shot or an incomplete fill of the plastic part. These issues can lead to the mold being recut or reworked, expensive project delays, and massive financial and productivity losses. Optimizing injection locations, fill speeds, and more is easy with SOLIDWORKS Plastics to ensure the part fills correctly the first time.

Still not convinced?

If this sounds appealing to you, reach out to our Simulation Services department and let our team of experts guide you step by step through utilizing SOLIDWORKS Plastics to reduce your design cycle time and maximize the uptime of the molding machine. Design your next part with us!

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