Wipotec is a leading global supplier of intelligent weighing and inspection technology. At its headquarters in Kaiserslautern, the company develops and produces a broad portfolio of checkweighers, X-ray machines, track & trace products and innovative systems for the mail & logistics industry. Precision naturally plays a major role in the field of weighing technology. Wipotec scales must always display the exact correct weight, even under varying conditions.

This applies in particular to temperature fluctuations: No matter whether it is hot in summer or frosty, the measured value must always be the same. To ensure this, Wipotec goes to great lengths: each load cell - which is the technical core of the scales - has to enter a climate chamber at the end of assembly, where it is subjected to a cycle with different temperatures between 0 and 40 degrees. If there are deviations from the target weight, appropriate correction factors are stored until everything fits.

Heavy-duty scales on course for growth

A particularly fast-growing product line at Wipotec is that of heavy-duty scales. These can be loaded with up to 150 kg and are used in particular in the logistics industry for shipping parcels. However, cement plants, for example, where heavy bags are filled, are also among the customers. In order to meet the increasing demand and at the same time optimize internal processes, the testing of these products was to be relocated to the same hall where their assembly also takes place. For this purpose, Wipotec planned a new testing facility consisting of a generously dimensioned climatic chamber and a feeding and handling system for conveying the load cells in and out.

Achieving the goal in partnership

In order to master the complex challenges, close cooperation with a clear division of tasks between the project partners was necessary. Tobias Stellwagen, Research & Development at Wipotec, recalls: "The whole thing was set up as a large project. The building blocks of the entire plant, i.e. the climatic chamber as well as the feeding and handling system, were designed jointly. We defined the climatic chamber we needed - in other words, the size and the resulting space requirements.

We also took care of the workpiece carriers and the weight chains. MiniTec provided the conveyor technology as well as the linear axis, which moves the weight chain to the appropriate position within the climatic chamber." In order to be more flexible in the future when conveying in and out, a shuttle concept was developed. This allows each load cell to be handled individually, independently of the others. In the first approaches, the load cells could only have been placed on one side. This would have made the climate chamber much longer. For this reason, the company followed the suggestion of MiniTec project manager Peter Müller. He suggested a shuttle solution with a fork arm, where the workpieces can be deposited on the right and left. The advantage for Wipotec was a much more compact climatic chamber.

Flexible workpiece carriers

There are twelve measuring stations for workpiece carriers in the climatic chamber. And just as many are always outside on the RMS. So whenever a WST comes out, a new one can be moved back in. Different numbers of load cells can be placed on the WST, says Stellwagen: "We have three different sizes. We can either put four of our smallest units on the WST, two medium ones or one large one. And also all combinations in between. So we can also run a mixed configuration, so we're very flexible there." To make this possible, the WSTs have been given some intelligence. There is a contact in the middle. Once the carrier is set down, all units are energized via it.

Each has a specific position on the WST and, accordingly, an address. The number of the WST and the address clearly indicate which load cell is which. This is also visually displayed to the worker when the WST comes out later, says Stellwagen: "Either they are all green, and he can remove them and make them ready for shipment, or one is red, which then makes an extra round and is fed in again."

Variable load via weight chains

In the climatic chamber, test weights are automatically applied to weight chains, varying between 10 and 110 kg - depending on the measuring range of the load cells. Depending on how far down the weight chain travels, 10, 20 or more kg are then applied.

Safety first

In order to ensure work safety, a light grid was installed, which automatically shuts down the system when crossed. It was discovered that this would have required a safety distance of over 2.5 m. The reason for this was that the heavy workpieces took up to a second to come to a stop. The reason was that the heavy workpieces took up to a second to come to a stop. Therefore, a second light curtain was installed, reducing the safety distance to 1.2 meters. "This suits us for space reasons. But so that we know that no one is standing inside this light grid, we also additionally monitor the floor with a floor scanner. Only when the scanner says that the floor is clear does the system start up again automatically," explains Positioner trolley.

Advantages already noticeable during the introduction

The new system already showed noticeable advantages during the test and introduction phase, according to Positioner trolley: "The background to this was also the goal of increasing capacity. With the new climatic chamber, we can push through 30 percent more load cells per week. And handling is also much better. As mentioned, with the existing system we loaded and also unloaded our climatic chamber three times a week.

Today, we are much more flexible, because we can load and unload each load cell or each workpiece carrier separately." Positioner trolley also rates the course of the project very positively: "The cooperation was very cooperative and satisfactory.