8526Compression load cell

• Long-term observation of expansion during charging and discharging cycles
• Measurement of forces that occur, with monitoring of temperatures
• Optimization of pressure distribution and service life

Description

Due to the charging and discharging cycles, the age and the resulting temperature fluctuations, disturbing gases are produced in the battery cell, which expands as a result. This places a high load on the housing and cell surroundings. Stresses vary depending on the design and on the formulation of the chemical compounds.

Specific requirements

• Precise measurement of the forces – i.e. expansion with temperature – during cell charging and discharging
• Accurate assessment of long-term behavior and the aging process

A critical look at the details is necessary for exact reproducible recording. Precisely defined pretensioning forces can be applied by the fine pitch of the mounting screws. Uniformly applied tightening torques, if possible, generate an even distribution of forces (preload).

The gases produced during use and the resulting expansion of the flexible pouch cell generate a force on the receptacle surface. The resulting force depends on the chemistry, cell structure, shape, temperature and number of charging and discharging cycles.

Solution

A precise investigation of the temperature/force curve during various charging and discharging cycles provides key insights into the relationship between the chemical constituents and structural variants. This question is becoming more urgent with ever-increasing packing densities, which are usually achieved by cascading many cells.

With the precise investigation of the expansion, the composition of the battery and the design of the housing can be optimally adapted. This knowledge of the maximum thermal and mechanical load under extreme conditions thus helps to define a precisely specified requirement for the environment in order to guarantee protection and safety time.

Video Application

• High accuracy
• Rapid measuring value collection
• Configuration via PROFIBUS 

TASK

On a completely automated test bed motor vehicle seats should be checked for their encumbrance. The following features should be tested and recorded:

• Adjusting angle of the back
• Torque required for turning handle
• Total weight of the seat (with and without dummy)
• End position determination

In order to be able to make a well defined statement about the categorization of the motor vehicle seat, the measurement data must be recorded and networked and deposited together as test result on the PROFIBUS level.

SPECIFIC REQUIREMENT

All test data should be transferred at the same time for storage, in order to obtain relevant samples of information for comparative logging of this test. A tare function is a consideration for mounted sensors addressing the issue concerning initial load (dummy load).

SOLUTION

For the recording of all mechanical values following sensors are used:

• Adjusting angle of the back → angular displacement sensor model 8820
• Torque of the turning handle → torque sensor model 8661
• Total weight of the seat → 2 load cells model 8526
• End position determination → displacement sensor model 8719

All sensor signals are recorded by 4 individual Sensor Profibus Modules 9221. Concomitantly the modules display the sensors with voltage and evaluate their signals. The transferring of measurement data takes place in parallel via PROFIBUS. The tare activation concerning a possible initial load, which can be modelled as a dummy, takes place directly via simple PLC unit communication, over PROFIBUS.

• Versatile
• Connecting cable suitable for drag chains
• Multipurpose compression load cell
• Protection class IP64

Task

The task is to test a lever mechanism once installed in a motor vehicle body. This is done by fitting the load cell to a robot arm. Any lateral force resulting from the horizontal working position and the intrinsic weight of the tool can be absorbed using four linear guides immediately surrounding the load cell.

DIGIFORCE® 9311

• High sampling rate ensures high-speed recording of force signal
• 25 ms evaluation time
• Graphical evaluation elements used for monitoring

Compression load cell model 8526

• Compact design
• Stainless-steel construction
• Protection class IP64

TASK

A process that uses crimping and rolling machines to join (crimp) rotationally symmetric components and assemblies in a form-fit needs to be monitored. Depending on the machine design, 4 to 16 jaw segments compress the components symmetrically to produce a form-fit. In addition to 100% monitoring of the form-fit, the system must also identify a possible failure of one or more crimping jaw segments during the crimping process.

SPECIFIC REQUIREMENT

It is essential to ensure strain relief between sleeve and cable and/or that the joints are both liquid-tight and gas-tight. Since safety-critical components are often involved, these production processes must be fully documented with 100% process monitoring.

SOLUTION

To monitor the crimping process, the force applied by the jaw segments to the material deformation is analysed as a force/time curve. The 8526 compression load cell is located in the lever and measures the pressing force. The DIGIFORCE^® 9311 analyzes the force/time curve synchronously with the crimping process. Recording the force signal at this rapid speed is possible thanks to the instrument's high sampling rate. The servo-drive delivers constant and reproducible movement (displacement) and therefore the force signal is recorded as a pure force/time curve. The measured X/Y curve is monitored using the envelope evaluation element.

Any failure, breakage or wear of a jaw segment produces a significant change in the force/time curve characteristic. The synchronous recording by the DIGIFORCE^® 9311 can help to guarantee zero-fault monitoring thanks to immediate evaluation of the crimping process and the output of an OK/NOK signal.

• Compact design
• Easy to integrate
• Inexpensive load cell
• Standardized nominal sensitivity for easy replacement

Task

In an automated manufacturing process, small helical springs are pressed onto a component and pre-loaded to a defined force. The 8526 load cell with 0 ... 10 kN measuring range is very compact so can be fitted directly into the tool. Thanks to the tool’s construction, the sensor is easy to access and can be replaced quickly in the event of damage. The tool is designed to absorb inadmissible lateral forces, so that the load cell is loaded solely along the primary axis.