Process Reliability

in the screwdriving technology

To avoid the failure of devices, machines, vehicles, etc., the highest process reliability has to be used during assembly.

1. Designing the screw-connection and selecting a tool

Basis for a request appropriate design layout of the screw-connection. Performing a suitable screw-joint analysis can help with the determination of the needed connector-parts (screws), the influence of the materials and friction having on the parts to be assembled and will also help with the selection of the most-suitable screwdriver.

2. Qualifying Screwdrivers

To qualify screwdrivers, we can perform a Machine Capability Study (MFU) or English Cmk.

According to the hazard condition, the testing and monitoring of the screwdriving process is an important criteria. For the automotive sector, the VDI guideline 2862 with 2 safety categories and their safeguarding measures are clearly stated.

3. Testing and monitoring the assembly process

For the adherence of the process reliability, the screwdrivers have to be tested on regular basis or after operating for a predetermined number of cycles. Their functionality has to be tested and verified, prior to them going back out on the line. If a maintenance or repair was performed, then a new Machine Capability Study (Cmk) has to be performed.

For the evaluation of the screwdriving process, in regards to capability and stability, a Process Capability Study (Cpk) applies. For such a study, the torque – during the screwdriving process – using an external rotary, non-contact transducer, is acquired and analyzed (Cpk-value).