Search L3I's Blog

Tuesday, June 22, 2010

Problem Solving

Sometimes the most complex problems have the simplest solutions. Due to complex geometry and the lack of a CAD model our customer’s recent impeller rotational balance problem seemed pretty complex. Level 3 Inspection found a simple solution to this problem that did not require a CAD model and saved the customer time and money, all while improving product quality and time to market.
The key component for Level 3 Inspection White Light Scanning (WLS) combined with Computer Aided Inspection (CAI) software that enables them to perform a complete inspection of every type of shape and feature that characterizes an object, saving time and increasing inspection accuracy.
During the project to improve impeller balance, Level 3 deviated from standard practice that combines WLS and CAI with a CAD model for quality assurance. All processes currently start or end with a CAD model. Level 3 only used the WLS data – there are no CAD models used or created anywhere in the process.
Precision balance of impellers affects the operation and lifespan of every pump. The challenge for Level 3 was to reduce the time to balance impellers and increase material flow.
The standard process called for Level 3 to White Light Scan the impeller, align it to the CAD model and measure the dimensional deviations relative to the CAD model; A process that is time consuming and requires a CAD model. The time required to construct a CAD model was deemed too long by Level 3 Inspection’s customer
The alternate inspection process developed by Level 3 Inspection takes a relatively short amount of time and eliminates the need for a CAD model. Scans of the same impeller are imported into the CAI software twice, so that two copies of the scan exist in the same 3D space.
Within the CAI software, one object is rotated then a procedure called “fine adjustment best fit” is performed on the two copies, making a 3D comparison. Differences that affect balance are visible immediately.
At the time of this project, Level 3 was analyzing around four impellers a day, so the accumulative time savings over the course of a month using the new process amounted to several days. Those savings multiplied over the life of the project, which lasted about 18 months.
It’s a very simple process that reflects the essence of what needs to be measured: rotational symmetry. The underlying message is that WLS and CAI can have significant value for companies and industries even if they don’t rely on CAD models.
The greater volume of analysis in less time leads to faster learning curves, trends are more observable as are many units in succession as opposed to one at a time.
Besides speed, the new process delivered the ability to differentiate between casting-induced unbalance and machining-induced unbalance. Level 3 learned that machining-induced unbalance is relatively uncommon, but there is a big advantage in seeing and demonstrating it when it does happen. We are now able to use CAI visualizations to improve our suppliers’ machining processes and optimize part balance.”
The ability to identify wall thickness variance is another big breakthrough for Goulds Pumps. Variations in wall thickness are caused by differences in the shapes of the casting, mold and pattern tool.
Comparing scans of these three related objects within enables Level 3 to pinpoint the magnitude and source of variations. The process is so accurate that it can measure small differences in wall thickness due to molten metal flowing into and filling sand molds.
Level 3 can clearly show that sand castings are not necessarily perfect replicates of the molds from which they are produced; variation and its source can now be measured down to a level at which it is not economically viable to reduce any further. There is a huge value in knowing that we can control all important factors and be aware of other factors that we might not want to control for cost/benefit reasons.
The ability to quickly and accurately make direct measurements and comparisons of wall thickness has extended to other projects at Level 3. It’s helping to uncover potential production issues with older pattern tools that do not have associated CAD models.
Level 3 can scan the tooling pieces, assemble them electronically in CAI to create a scan model of the casting, and then compare the scan model to a scan of an actual production casting. Using several analysis processes along the way, Level 3 can identify all possible tooling issues and differentiate them from process-induced issues.
Although the benefits of WLS and CAI are sometimes difficult to quantify by numbers, they are nonetheless concrete. WLS and CAI has allowed Level 3 to see foundry process variation that could not be seen previously because of the complex geometries required for hydraulic designs. Level 3 can also ‘see through’ the complexity of the pattern tooling, and the sheer number of factors that influence foundry operations. With WLS and CAI, our customers can focus efforts on the factors that directly influence the quality of their castings.

No comments:

Post a Comment