Projectstory
Seven years of security and control
For many industrial companies, the question arises: Is a servo-electrically driven drive unit worth it? Even Festo SE & Co. KG, a leading company in pneumatic and electric automation technology, faced this question in 2016. Seven years later, the benefits of their decision for Servomold are still paying off - it's time to recap the positive collaboration and draw a conclusion for the future from the past.
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In 2016, the Krallmann Group, at that time one of the leading providers of innovative complete solutions in the field of plastic processing and toolmaking, approached us with a project that required the expertise of our engineers. Festo Polymer GmbH, based in Sankt Ingbert, needed five unscrewing units for a tool that produces complexly designed housings for the pneumatic maintenance device DB Mini of the parent company Festo.
Festo Polymer manufactures the cuboid housing with a side length of around 40 mm from a high-strength and high-stiffness glass fiber reinforced polyamide (PA66-GF50). Its five internal threads have diameters of 1/8", 1/4", and 36 mm with lengths ranging from 12 to 22 mm. Corresponding to the positions of these threads, four of the associated unscrewing spindles are arranged on the ejector side of the single-cavity tool, each offset by 90° to each other, parallel to the parting plane. A fifth spindle moves parallel to the ejector package in the machine's central axis.
:quality(85) "Festo")
The five internal threads and several undercuts made demolding the housing a challenge.
Project manager Hendrik Sanio identified several reasons for preferring servo-electric over the usual hydraulically operated screwing units: "We can thus precisely control the individual movements of each core. The respective torques can be monitored and regulated individually, and the threads of different depths can be demolded at the optimal speed. The servo-electric drive requires less space and enables shorter cycle times compared to hydraulic solutions. Furthermore, the risk of contamination from leaking oil is eliminated."
:quality(85) "Festo")
Servomold selected and dimensioned the five tapping units based on the torque values (MD) ranging from 6 to 33 Nm determined in their own tests. To this day, the tool is equipped with four units of the smallest available standard type SAEW040-050-12-0055 (MD up to 23 Nm) for 1/8" and 1/4" threads, as well as a servo angular drive "gear" type SWZ070-16-0207 (MD up to 75 Nm) for the large metric thread.
The control is taken over by a mobile servo rack controller of type SRS-8.6, which can control up to six servo motors. It adjusts the speeds individually so that all five liquid-cooled threaded cores reach their respective end positions simultaneously when retracting. The SRS also takes over the continuous torque monitoring on each servo unit and outputs corresponding signals when predefined limit values are reached.
Project Overview
:quality(85) "Festo Skizze")
Customer
Festo Polymer GmbH
Application
5-fold spindle housing (PA 6.6 - GF50)
Unscrewing units
Threaded core systems
Temperature control systems
Torques
Thread sideways: 8 Nm per thread core
Threaded core sleeve below: 33 Nm
Drilling time
1.9 seconds
Servo control
Servo rack control (SRS-8.5-20rn)
Even back then, an integral part of the system: Our servo controls including the control panel. Thanks to the innovative control concept, employees can monitor and control all important parameters and functions during operation. All data is quickly accessible on the digital display, making continuous optimization of the injection molding process simple and clear - over the years, this saves time and resources for extensive maintenance or unnecessary wear and tear.
:quality(85) "Festo")
The servo motors are also equipped with resolver position encoders, whose zero point is individually referenced on the clamped and preheated tool. Thomas Meister, Managing Director of Servomold, explains: "We like to use resolvers because they need to be referenced consciously before the tool is put into operation, so that even after a mechanical change such as maintenance, a release is not given lightly. However, the type of application and ultimately the customer often determine the type of position encoder system."
Another safety aspect mentioned by Meister is the continuous force monitoring possible with servo-electric systems, which makes the need for tool maintenance detectable at a very early stage, thus avoiding damage from the outset.
Space-saving, energy-efficient, trouble-free, and easy to maintain. Even back then, Dr. Jan Oliver Hauch, Head of the New Polymer Innovation Transfer Project Division at Festo Polymer, emphasized the future viability of the system. "Due to the small space requirements of these systems, the dimensions of the tool have also remained relatively small. This allows us to use it on the very energy-efficient Arburg Allrounder 570 S e2 2000-400 with a 570x570 mm tie bar spacing. And because this manufacturer mainly uses standardized parts, we can expect a secure supply of spare parts for the future."
Uwe Hemmerling, Head of Toolmaking, adds the following: "The project 'DB Mini' was the first of many projects that we implemented with the company Servomold. We were particularly convinced by the high tool safety and the precise controllability of the process sequences. Servomotor movements are indispensable in modern toolmaking."