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Moldflow : PLASEL
PLASEL LTD. was established in 1992 in the Tefen industrial park, on the hills of Western-Galilee in the northern region of Israel. The company employs 100 in three divisions: injection molding, mold making, and alpha precision tools, spindles, and precision metal parts. Today, the company is located at a new industrial site in Lavon, Israel. The company serves the agriculture, irrigation, consumer goods, and electronic industries, with special expertise in volume production multi-cavity tools.
Plaselís manager of engineering, Amicai Vardi, responsible for tool design and production technology, is well aware of the fiercely competitive nature of the mold making business.
"The market is very international. It is very common practice for customers to order tools from suppliers all over the globe. Tool cost and fast delivery are the dominant decision factors. Our competitive advantage is gained through specializing in a specific product line - such as our irrigation dripper expertise - or by adding extra value to customerís product through incorporating our plastics expertise into the early stages of part design. We also pay special attention to the toolís ease of operation and maintenance - which have significant impact on the overall productivity of the tool."
Using Moldflow software
When Vardi obtains a request for a complicated or specialty part, he counts on Moldflow software from Moldflow, Inc. (Lexington, MA) to determine how the part will be produced. He relies on Gal Sherbelis, a flow analysis expert at GS Design. Recently, Vardi and Sherbelis collaborated on an important project.
Plasel currently produces a plastic reels used for storage of electronic chips for an international Israeli-based corporation. The reels must comply with an international standard, within which many versions are possible. Since this type of product is produced and sold by other vendors, the competition began to infringe on Plaselís marketshare. Plasel general manager Yehuda Shilo and marketing manager Shalom Uliel set an ambitious target for a new part design - reduce 30% of the weight of the product and slash 40% of the cycle time.
The first step of the project was for Uliel and Vardi to thoroughly review customer needs. They visited all of the customerís manufacturing sites in Israel, spoke with the engineers and machine operators, and gathered all the data to make sure that the new design will fit each type of machine that the reels will be mounted on. In addition, they met with the heads of engineering, quality assurance, and purchasing in order to confirm the partís compliance to the appropriate standards and target price. Then, Vardi and his designers generated drawings and STL models for final approval by the customer.
"We worked with our customer to assure 100% that the part design was going to suit their needs," says Vardi. "We were confident that, geometrically, it would work on every machine that they operate."
Once the part geometric specifications were approved, Vardi and his team set to optimize the design with regard to tooling and weight considerations. After implementing their plastics know-how into the part features, they sent the model design to Sherbelis for the first flow analysis. "My first intuition was to gate the part at two points, which is unconventional for round parts, which are traditionally gated in the center," says Vardi. "We spoke to some well known hot-runner manufacturers and they also recommended to gate from the center." Sherbelis used Moldflow to evaluate several gating scenarios including a single central gate as well as two and four gate locations.
Sherbelis says, "Vardi was right. The two-point gate solution was the best option." Next, Sherbelis used the technology to determine shrink, warp, and their dependence on cycle time. Using Moldflow software enabled Vardi and Sherbelis to modify the design and evaluate the effect of each change. Their ideas of implementing variable wall thickness over the top flange radius, location of vents and ribs, and corrections to tool geometry in order to compensate for some unavoidable warpage were all assessed and confirmed using the software. Sherbelis was even able to predict cooling line efficiency in the tool sliders, and accordingly the channels layout was changed to two parallel lines.
At the final analysis, Sherbelis calculated a cycle time of 13 seconds, which was longer than the target cycle. Vardi suggested setting the cycle time at 10 seconds as a fixed parameter, and checking the effect on the reel with different mold temperatures. "At 10 seconds," says Sherbelis, "the flanges were coming together out of the tolerance. Then, I suggested that Plasel increase the cavity size to the top side of the tolerance. So, after the part is molded and is warping, the outer side will still be in tolerance."
At this stage, Plasel entered mold production. "The mold features a very simple and robust parting line which is peripherally vented to accommodate for high injection speeds," says Vardi. "We used brazing technology to achieve superior cooling of sliders and inserts, and a short stroke stripper plate that half-ejects the part by the sliders. A special challenge was to drive each slider over its 100 millimeters stroke. The pistons would have been too slow and traditional angle pins would have to be 300 mm long and would accelerate the sliders to shoot out of their guides at the mold opening speeds we needed. We solved this problem by using a ball bearing and ĎSí shaped groove, that smoothly accelerates and decelerates the slider with no limit on the mold opening speed."
Today, the mold successfully completed the first and second injection molding trials. After the first trial, Plaselís team only needed to polish a few ribs and increase a draft angle in one area. At the second test the mold was fully functioning, producing parts at a 50% shorter cycle time and 35% lighter than the older version reels - exceeding the set goal and customer expectations.
According to Plaselís estimations, the new reel - which complies with all international standards - can be readily exported at very competitive prices.
Click here for a Moldflow image in tif format.
Author: Laura Carrabine