Zero-defect assembly of tire pressure sensors

Zero-defect assembly of tire pressure sensors

MMS designed and built a compact and fully automated assembly line for tire pressure sensors using Scara robots.

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Every six seconds a highly automated assembly line manufactures tire pressure sensors for a Chinese automobile industry supplier, with an output of 4 million units per year. This innovative line was designed and produced by Austrian assembly line manufacturer MMS Modular Molding Systems. Three SCARA robots and a complex quality assurance process guarantee zero-defect assembly.

Today’s car tires all come with a sensor that measures tire pressure and subsequently sends a radio signal to a receiver unit. This is how a million-dollar market for automobile industry suppliers with sensor know-how as well as an interesting new area for specialists in the automation technology and robotics industries came to be.

MMS Modular Molding Systems GmbH of Berndorf, Austria, is one such specialist. Founded in 2008 by engineer Peter Buxbaum, the company focuses mainly on interlinked and modular lines that manufacture plastic/metal hybrid components. MMS solutions stand out with their high levels of innovation, productivity and efficiency.

 

Goal: Non-stop manufacturing of ready-to-use sensors every six seconds 

MMS designed and built a compact and fully automated assembly line for tire pressure sensors (TPS) able to be directly built into the tire valve for BH Sens, a Chinese supplier and joint venture between Baolong and Hülsbeck & Fürst (Huf).

Alongside the assembly of ten components to form a ready-to-use TPS, BH Sens also required several quality steps to be integrated and needed its fully automated line be able to guarantee high availability and quick production turnaround. Four million ready-to-use sensors per line is the company’s goal, with one sensor being made every six seconds. Flexibility is also key due to three sensor variants being assembled using different printed circuit boards. 

 

Meticulous handling by three SCARA robots

Stefan Babka, BSc, Designer and Project Manager at MMS, describes the construction process from individual components to a completed TPS: “Assembly begins on a rotary table, with three Stäubli robots responsible for handling the individual components. The first SCARA robot takes the circuit board out of a tray on the rotary table and places it into a workpiece carrier. The second robot removes the battery from another tray and places it on top of the circuit board as part of the next step.”  

To guarantee continuous monitoring and documenting of test and measurement data, components are all assigned a data matrix code (DMC) by a marking laser. These codes are scanned and assessed at every station.

 

Non-stop 100% testing

Processes and quality checks such as voltage testing are carried out within six seconds, before they are transported to pressure chambers on the linear transport conveyor. In these chambers, the airtightness of the now sealed components is monitored.  The end-of-line test that simulates communication with vehicle electronics takes place to ensure that each individual sensor is 100% functional.

The whole process comes to an end on the rotary table where the sensor is attached to the valve and the finished product automatically screwed in place. This completed sensor/valve combination is then able to be packaged for use as an original or aftermarket part. 

 

Custom-fit: Three robots in three sizes

All three SCARA robots are from Stäubli’s TS2 range, albeit in three different sizes. Stefan Babka: “A TS2-80 is responsible for handling the circuit boards. The battery is handled by a TS2-60 that is equipped with a longer ball screw. A TS2-40 is camera-assisted and used to place the seal inside the housing.”

Stäubli’s SCARA models were chosen by designers at MMS because of their interaction capability with the camera systems in place to ensure correct component positioning as well as communication with the Anyfeeders. Because the movement of the components had to take place on four axes, a decision was made in favor of SCARAs and not 6-axis robots that would have otherwise been too slow for use in this environment. MMS decided to partner with Stäubli as its robotics provider because of successful previous engagements in other projects as well as the engineering support provided during project planning.

 

Simple integration into the entire production process

Specialists at MMS’ partners, SBA Engineering, were also able to profit from Stäubli robots’ uniVALplc interface throughout programming. The interface enables seamless connection to a superior Siemens S7 control system. MMS designers also appreciated the integration of safety technology.

The fact that the production line undergoes several automated steps (at least fourteen) within a very compact area MMS also considers the demand for flexibility by ensuring that changes can be made to the systems without completely restructuring hardware. Not even the grippers would need to be changed in such an event. Production changeover is also made easier given a small proprietary development: MMS has installed an automatic clearing function into the Asyril feeder system, meaning the operator does not need to manually clear the conveyor. Rather, all parts are automatically cleared from the Anyfeeder and transported further via a conveyor.

High availability and good support

According to MMS, another important factor when selecting robots was the need for extremely high availability: The assembly line works non-stop and in short turnarounds. Due to the small components being handled, long-term precision is an additional criterion baked into the decision-making process. The soft facts are also ideal, according to Peter Buxbaum: “As a systems integrator, we are reliant on the expertise of our core partners. Stäubli offers great customer service in Austria and Bayreuth. We are able to access support during simulations, for example, and they don’t take long to respond to all questions quickly and professionally.

 

From the Vienna Woods to China

All this begs the question: What made a Chinese automobile industry supplier choose an Austrian systems integrator in Berndorf/Vienna Woods to put together a complex assembly line? Well, alongside the expertise and technical know-how, the whole thing was also born of personal initiative: Company owner, Peter Buxbaum, went on an entrepreneur trip to China in 2015, which is when contact was made initially.

MMS were obviously able to convince with their project proposal, which is anything but surprising. Despite the systems integrator still being relatively new as a company, it still has a diverse list of references comprised of global players within the automobile and electronics industries. Peter Buxbaum: “With our ‘one-stop shop’ offer comprised of chain production lines that combine different production, assembly and testing processes, we have been able to successfully establish ourselves as specialists within the field of automation technology.” MMS is able to corroborate this statement with an innovative assembly line for China.