Aumat (Solingen, Germany) has been a wide-ranging authority in building special purpose machines for customers primarily in the automotive and lock industries since 1970. Despite their individuality, cylinder locks are also mass produced articles that above all require one thing for their assembly – high positioning precision with the shortest possible workpiece cycle times. These were the vital key objectives in drafting an advanced linear assembly system design for Aumat’s new cylinder lock assembly plant system.
Industry leading specialist for rotary tables and automation, WEISS (Buchen, Germany), and its’ subsidiary, WEISS North America, Inc. (Willoughby, OH), provided Aumat with a fully automated cylinder lock assembly machine based on their LS280 palletized linear assembly system.
The WEISS LS280 linear assembly system not only provided enough space for the many process steps required, but also features a technology related to indexing tables that indexes pallets considerably faster than conventional transfer systems.
ORIGIN/CHALLENGE
At first glance, the cylinder locks all look alike, yet locks are nothing of the sort as each is unique, inside and out. Installation may require over a hundred different components in the cylinder core and case including core pins, mounting plates, springs, and sealing plugs.
According to Stefan Trommlitz, Managing Director of Aumat in Solingen,
“The very large number of different pins and wafers that are assembled on the basis of data records that give rise to countless combinations.”
Trommlitz added,
“In the lock industry, we mostly have to deal with the exception of the exception.”
Aumat’s previous system was “no exception”.
With the diverse range and precision needed for assembly, cylinder locks are nevertheless mass produced articles. In a fully automated process, the system assembles the complete inner workings of a cylinder lock and then seals the housing on an electronically regulated press.
Aumat designers attached very special importance to “positioning precision” and “short cycle time” in the new system’s draft – both of which are the classical virtues of an indexing table. However, due to the large number of processing stations (15 units), indexing tables were initially ruled out as a potential candidate.
Conversely, even though traditional transfer systems provide enough space and allow for expansion, positioning and indexing the pallets needs a lot of time and several operations to change the workpiece. According to Trommlitz,
“Even 1.5 seconds would still be a full quarter of our cycle time of six seconds.”
Aumat’s Head of Engineering, Achim Ihlefeld, had known WEISS for decades for their comprehensive indexing table expertise and contacted them to seek out a solution for this “space vs. time” dilemma. When first introduced to the WEISS LS280 linear system, it didn’t look at all part of the familiar WEISS product offering. However, an initial inspection revealed a unique and robust design for transporting and interlocking workpiece carriers (pallets) on a cylindrical cam (similar to an indexing table) that combines high positioning precision with stable interlocks, and pallet indexing times of typically 0.5 seconds.
LS280 “SPACE/TIME” SOLUTION
The WEISS LS280 linear assembly system is proven in a myriad of market applications including pharmaceutical packaging, medical device, automotive parts and assemblies, electrical connectors, pad printing/decorating, battery assembly, light bulb/LED assembly and many others – making it a versatile option for Aumat’s lock assembly dilemma.
Paired pallet “trains” on four rollers run free of backlash on a hardened and ground V shaped guideway. The pallet engages in a friction grip, and a guide shoe runs on a toothed belt in the conveyor sections and on a rotating disc at the corners.
Essential to the performance of the LS 280 linear assembly system are the locking stations. Actuated by a cam drive, they are tried and tested thousands of times on WEISS indexing tables. The smooth approach to the conveyor section was regulated by a frequency inverter. The workpiece carriers wait for the next timed stroke at the infeed on the transport cam, whose modified sinusoidal contour safeguards a very gentle and smooth movement of the pallet.
The workpiece is then transported and interlocked in a single movement with no lengthy stopping, raising, and positioning as found in conventional transfer systems. After just one rotation of the transport cam, the pallet assumes the next position quickly, securely, and precisely.
By essentially “cutting up” an indexing table, the end result is a transport system that combines the advantages of an indexing table (short cycle times, high positioning precision, gentle ramp up) with the flexibility and the space of a linear transfer system.
LS280 KEY SPECIFICATIONS & PROCESSES
- 12 m long, straight system with two corners
- 15 processing stations, and 42 circulating pallets
- A paternoster feeds pallets each with ten key/lock pairs
- Cylinder locks run through the plant at a rate of 360 units an hour
At a manual workstation, the locks are fitted in the receiver on the workpiece carrier/pallet. The large number of variants makes automating this operation difficult. While the locks are being assembled, the keys remain in the pallets. An RFID system, monitoring data media on each workpiece carrier, retains the overview and informs the robot at the end of assembly which lock belongs to which key.
The circulating pre-assembled cylinder locks are then measured with a laser, fitted with their pins and springs, examined with optical equipment, and pressed with plugs. Stationary cam followers fitted to the bottom of the system support the product devices on the workpiece carrier plates to absorb the vertical process forces.
For Aumat, this “long” indexing table was ultimately the key to its “space vs. time” problem with the workpiece changing time of just about half a second providing optimal efficiency. Work could now begin on finalizing Aumat’s cylinder lock assembly plant.
LS280 RESULTS/CONCLUSION
Aumat’s Ihlefeld noted the advantage of the system’s overall stable design stating,
“The linear system’s modules are delivered complete with a solid machine base, so we don’t have to build a frame first. Even without the process attachments, the basic LS280 machine looks ‘complete’, and we can show the customer something without having done much.”
Additionally, the substructure is made of steel and when necessary, can be reinforced if desired.
The footprint design also provides enough space for the assembly cell control cabinets. As a rule, the linear system’s controller is also installed here in the form of a master PLC. It’s slaves then take over the function of actuating the locking stations to which the upstream conveyor sections are also assigned.
The additional space in the substructure on the cylinder lock assembly plant was badly needed. This posed no problem for WEISS North America. After full function tests and official acceptance at the plant, the LS280 linear assembly system control components were delivered separately for installation in the switch cabinet on the side of the plant.
Notably, a special version of the WEISS Application Software (WAS), a highly intuitive and uniform graphic user interface, was implemented to control the linear assembly system and communicate with the higher level plant controller.
The WAS.LS provides preset parameter values that allow the operator to configure and monitor the LS assembly system without any programming knowledge. Trommlitz noted the system’s simplicity stating,
“To integrate the LS280, the operator needs solely to enter the control bits for the defined interface signals.”
Ultimately, the WEISS LS280 linear assembly system allowed Aumat to better control the “exception of the exception” problem on the sector and the value was shared equally by an Aumat customer; as a second similar machine has already been sold. Trommlitz concluded,
“The system’s modular layout and ease of access lends itself to a high level of flexibility, and when we can link each station skillfully, we could perhaps even create a standard.”
The process of the initial collaborative first meeting to the delivery of the LS280 took approximately eight months. According to WEISS North America’s Vice President, Bill Eppich,
“The key was educating Aumat on the unique advantages of the system’s ability to deliver multiple processing times on one chassis.”