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Efficient and flexible integration of processes

Efficient and flexible integration of processes

Сase studies

ESS TEC in Holland, Michigan, USA, has made a name for itself in the automobile industry with the manufacture of interior and exterior mirrors and functional components for the vehicle interior. Other industrial branches, such as healthcare, have been added over the years. A common trend among all the target industries is an increase in the degree of process integration in production.


21 injection moulding machines make up the ESS TEC machine park in Michigan. Every one of them is tie-bar-less.

"As a subcontractor, we have to be able to predict the future," says Elliot Essenburg, Engineering Coordinator of ESS TEC. It is this foresight that, in combination with decades of injection moulding experience and a strong passion for polymeric materials, secures a decisive competitive advantage for the privately owned company. In order to be prepared when the first enquiries come in, investments in new technologies are made at an early stage. "When our customers have a new product idea, they get the mould in six to eight weeks. We can't plan and procure a new production cell within that time," says Essenburg.
Therefore, the company's newest injection moulding machine, a two-shot ENGEL victory 85 US, is equipped with a rotary table and an integrated ENGEL easix multi-axis robot even though, at this time, there are no applications that require the rotary table. One of the parts the new manufacturing cell is being used to produce is back-lit control panel buttons. Using a 6+6 cavity mould, the first step is the processing of white polycarbonate, which is then partially overmoulded with black PC-ABS in the second set of cavities. Upon mould opening, the multi-axis robot removes the six finished parts, while transferring the pre-moulded parts to the second set of cavities. "The transfer technique is still dominant in multi-component injection moulding," explains Josh Fredenburg, automation expert at ESS TEC. "But I am convinced that we will need the rotary table very soon."


More than 20 years of successful collaboration: Elliot Essenburg, James Davis and Larry Essenburg of ESS TEC, Steve Belrose of ENGEL distribution partner A.L. Belrose in Grand Rapids, MI, Larry Alvey of ENGEL Machinery in York, PA, and Franz Pressl of ENGEL AUSTRIA (from left to right).

Small machines for low unit costs
An instinct for emerging trends and lucrative niches is a recurring theme throughout the history of ESS TEC. When ENGEL was the first injection moulding machine manufacturer worldwide to present a machine with a tie-bar-less clamping unit more than 25 years ago, they were the first customer in the USA to support the completely new design principle. "We quickly realised, back then, that we could secure a competitive edge for our company with the tie-bar-less machines," says Larry Essenburg, Elliot's father and founder of the company. "Small moulds on large machines – that was the standard, and suddenly we were doing just the opposite. Our customers were quickly convinced of the benefits, as that is precisely where the key lies to lower unit costs."

A second piece to keeping unit costs low is avoiding rejects, which can be accomplished through use of a highly precise clamping unit. With the tie-bar-less machine, the flexible central element is the design component that is responsible for this. It makes it possible for the moving platen to follow the mould precisely while building up clamp force. To achieve this, the platen lifts itself from the linear bearing and automatically aligns itself to the stationary platen. In addition, the patented force divider ensures that the clamping force is distributed evenly across the entire cross-section of the mould.


This ENGEL victory 85 US was delivered including a rotary table and an ENGEL easix multi-axis robot, ensuring it is optimally equip- ped for future multi-component applications.

"When the mould is mounted correctly, there is an absolutely constant compression," says Larry Alvey, Business Unit Manager Automotive at ENGEL Machinery in York, PA. "That way we ensure a very consistent part quality and a very high level of mould protection." For the two-component control panel buttons, a clean parting plane is particularly important. Some of the numbers and symbols that are to be back-lit measure only a few millimetres. "Sometimes we produce a better quality part than our customer does using the same mould on a machine with tie bars," says Larry Essenburg. "Last month we had a reject rate of 74 ppm for the whole company. That is practically nothing."

Precise movements in a very small space
Currently, the machine park in Holland includes 21 tiebar-less injection moulding machines, with clamping forces that range from 35 to 240 tons. ESS TEC has specialised in small components. The maximum shot weight processed is 16 ounces, about 450 g. ESS TEC also profits from the barrier-free access to the mould area during machine set-ups, which are changed up to nine times a day. “The moulds can be mounted and dismounted significantly faster than if we had to heave them over tie bars," says James Davis, Vice President of ESS TEC. "We don't need to worry about whether the moulds will fit between the tie bars, and instead, with consideration for achieving maximum overall efficiency, we can select the machine according to the required clamping force.”

Likewise, the robot can access the cavities directly from the side and therefore operate safely within a small space. The ENGEL easix is the first multi-axis robot at ESS TEC. "With it, we can work with extreme precision," emphasises Josh Fredenburg. "Small parts will not tolerate even the smallest inaccuracy." In addition, the multi-axis robot provides a lot of flexibility for the future as the number of multi-component processes continues to grow.

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