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Challenge and Solution
Plas-Pak makes disposable syringes, dual syringes, cartridge dispensing systems, adhesive dispensers, static mixers and spray systems. The company operates 24 hours a day, five days a week, but even with all that production time, every second counts.

Plas-Pak was looking for a way to meet the increasing demand for one of its large cylindrical parts for the industrial epoxy market. The company set a goal to decrease cycle time and minimize part warping by changing the gating system and cooling channels for the mold. To make sure it got these precise changes right upfront, Plas-Pak and its moldmaker, B&D Machine of Tolland, CT, turned to D-M-E Company to run a mold flow analysis.

An example of mold cool analysis like that used by Plas-Pak which takes into account number, location, depth and pitch of cooling channels, steel types, cooling circuit layouts, coolant temperatures and flow rates and cycle times.

Based on projections, a new mold using mold flow analysis could reduce cycle times by 17 percent while also eliminating part bowing. Through mold flow analysis, Plas-Pak identified the need to switch to a valve gate system, change gate position and modify the cooling channels. In the end, cycle time exceeded expectations and was reduced another 18 percent on top of the projections.

“Without this analysis, there are adjustments and location changes we never would have done,” says Brent Giansanti, product development manager and engineering manager at Plas-Pak. “It was really exciting to be able to get the cycle time for this challenging part reduced by 35 percent.”

Computer Simulation of Injection Molding
Moldflow Plastic Insight (MPI) is a computer simulation of injection molding that “helps us begin to understand what is going on inside the mold,” according to Rick Millette, D-M-E field service representative.

Part of Moldflow’s mold fill analysis is validating temperature distribution within a mold as shown in this cutlery example. Images courtesy of D-M-E Company and Plas-Pak.

Simulating the way a material will actually flow through a mold before it’s ever built ends up saving time and money in the long run. It’s particularly valuable for any product with varying wall thicknesses, surfaces or challenging part geometry.

“Any time I have a product that has some difficult geometry, I always want to make sure I pick the right place for the gate, core and flow,” notes Giansanti.

This accuracy becomes even more important when competing with low-cost overseas moldmakers. Plas-Pak doesn’t find itself in that position at the moment, but it’s an increasing concern for moldmakers across North America. Even though a complete mold flow analysis costs between $1,000 and $2,000 and takes a few extra days, the practice can pay off quickly, in both time and money.

MPI provides in-depth part/mold design and process parameter optimization. Specific analysis include mold fill analysis, mold pack analysis, mold cool analysis, warp analysis and MPI 3-D.

Without mold flow analysis, the whole process is more about trial and error. Moldmakers have to start with small gates to fill their mold and keep increasing the size little by little until the mold gate is the correct size. Besides wasting time and money, that also creates more backpressure in the mold, which creates core shift. It’s an expensive, inefficient way to determine the appropriate gate size: you have to take the mold out of the machine each time, modify the gate and put it back in. In the process, you also create more scrap and bad parts.

The Expertise to Get the Job Done Right
Plas-Pak now uses mold flow analysis for about 50 percent of its molds. “It’s come to a point in our industry where it’s necessary to perform mold flow analysis on many tools to make sure its right the first time,” explains Giansanti. “We’ve had occasions when a tool was built and it wasn’t a good design, and we can’t afford that anymore.”

But that wasn’t always the case. Up until a year ago, Plas-Pak was skeptical of the process. Then the company purchased the mold flow analysis from D-M-E in combination with a hot runner system for the large cylindrical part, and Plas-Pak’s perspective changed.

D-M-E employs the industry’s most advanced mold flow analysis engineer, Sandy Huang. Huang, an applications engineer with 14 years of experience in mold design and is certified at mold flow’s highest level. She even advises software developer Moldflow Corporation on improvements for the program.

“Mold flow is a complex and careful process,” Huang says. “You can’t just push the buttons and run the software. You really have to analyze and judge the results. It’s about extracting the right information to help the customer.”

The mold for this large cylindrical part for the industrial epoxy market was reconfigured using mold flow analysis resulting in a cycle time reduction of 35 percent and elimination of part bowing. .

For Plas-Pak, Huang says the challenge was to figure out whether one gate could fill the part while completely minimizing warpage, and if one gate could do the trick to identify the exact location needed for the gate.

Summary
In the past year, the 50 percent of the new molds at Plas-Pak built after running a mold flow analysis have required no adjustments after the initial build. That’s quite an accomplishment, one that could save a great deal of money and headaches for moldmakers, molders and OEMs.