Volume manufacturers depend upon the quality and repeatability of their incoming raw material. All subsequent machining processes are designed with the assumption that suppliers will supply parts that have the proper specifications. Unfortunately, that does not always happen. Unplanned variations in raw material can cause disruption in production schedules and additional costs.

Detecting Missing Casting Features

The example to the left shows an incident where castings were supplied that lacked a specified hole. So instead of enlarging an existing hole, the tool used to create this part feature was drilling in solid material. On some castings, the tool was able to drill the feature. On other castings, the tool broke.

Fortunately, this tool was monitored by a WattPilote. WattPilote’s power data was used to diagnose and document the source of the problem. 24 out-of-spec castings were discovered on the production line. As a result of this discovery, a search of the inventory uncovered another 98 out-of-spec castings. These castings were returned to the supplier. In addition, $5,000 in broken tool costs were charged to the supplier.

Good documentation is critical when resolving quality disputes with a supplier.

WattPilote Provides A Window Into Manufacturing Process Quality

The Resulting Power Curves

In the plot below, the blue lines are the upper and lower process limits. The red curve shows the power consumed when the holes are present in the casting. The magenta curves show the power consumed when the holes are not present in the casting. The excessive power consumption generates an alarm immediately.

Castings Specified vs. Castings Delivered

The casting on the left is what was expected. The casting on the right is what was delivered. A quick visual inspection of the castings indicates that the hole is present. It’s only when a cross-section is made that the problem becomes visible.