In some plastic-based belt pulleys used in electric drive systems, material had broken off in isolated instances. If the fragments become loose inside the housing, the drive may seize up. Microvista inspected 5,960 systems individually using industrial CT scanning, each one traceable via its component ID: 3.3 per cent had to be rejected, whilst the majority could be reused.
Initial situation
In the case of electric drive systems, isolated instances were identified where material had broken away from a plastic-based pulley.
The loss of material itself did not pose the main risk. The critical issue was the possibility that fragments might become dislodged within the housing and become trapped between the belt and the drive components. In the worst-case scenario, this could lead to a blockage of the drive system.
There was a lack of reliable information regarding the affected systems. Without reliable data on the condition of each individual component, there was a risk that large quantities of fully functional products would be discarded as a precautionary measure.
Objective
The aim was not merely to identify instances of flaking. The key was to provide a reliable basis of information so that well-informed decisions could be made:
- Which systems can still be used?
- Which systems need to be phased out?
- How can the risk to the end customer be reliably managed?
- How can as much of the value already created as possible be retained?
- Is there a pattern to the way faults occur (e.g. always in the same place, of the same magnitude)?
- What needs to be changed about the process?
Solution
A total of 5,960 drive systems were inspected using industrial computed tomography. Two drive systems were scanned at a time. The scanning time was around 6 minutes per system.
Even before each CT scan began, the component ID and component position were clearly matched. This ensured the traceability of each individual system throughout the entire test campaign.
After the scan, the components were automatically separated and the belt pulley was aligned for analysis. The alignment was a crucial step in this process. The relevant spalling was located on the upper edge of the belt pulley. In order to detect this reliably, the entire circumference of the pulley had to be precisely registered in each data set.
Based on this registration, an image stack was generated that extended along the axis of rotation of the belt pulley. This made it possible to systematically assess the entire circumference of the component. Spalling could be identified quickly and reproducibly.
From component ID to sorting decision
- 1Assign ID
part ID and position recorded before every scan
- 2CT scan
two systems at once, about 6 min per system
- 3Separate and align
automatic, full pulley circumference registered precisely
- 4Image stack
along the axis of rotation, entire circumference assessable
- 5Assess and sort
by the operator, deliberately without software automation
- 6InspectHub
result and CT images available to the customer immediately
Deliberately no automatic rating
Automatic defect detection could have been implemented without any technical difficulties. In this particular case, however, it would not have generated any additional throughput. Whilst the scan was running, the operator had sufficient time to assess and sort the components that had been scanned previously, as well as to prepare the next batch of components.
Additional software costs would have been incurred without delivering any time savings in the process. For this reason, the most economically viable solution was chosen.
What changes need to be made to the process?
Data provision via InspectHub
Once the assessment had been completed, the inspection results and the underlying CT image data were made available immediately on the InspectHub portal. This meant that all the relevant information was directly available to the customer:
- Traceability via the component ID
- Centralised access to all test results
- Immediate availability of image data
- Seamless collaboration between Quality, Production and Development
- A documented basis for decision-making for future evidence
Result
The CT scan revealed that the actual reject rate was just 3.3 per cent.
Before the investigation began, it was unclear how many components were affected by critical spalling. It was only the CT-based assessment that provided the necessary basis for decision-making to specifically sort out the affected components and continue to use the vast majority of those already produced. In this way, both product safety and value creation were safeguarded. Overall, the following added value was achieved in this case:
- 100% inspection of the relevant characteristic Enquire now with no obligation
- Traceability via component ID
- Reliable assessment of the total wheel circumference
- Quick sorting decision after scanning
- Avoiding unnecessary stoppages and scrap costs
- Preserving value already created
- Underpinning technical decisions with reliable data
- Real-time insight into the progress of inspections and a documented basis for decision-making to support future evidence via the InspectHub portal