Continuous Improvement at Caterpillar includes Six Sigma, Lean, and the Caterpillar Production System (CPS). We will cover all three using various sources.

Six Sigma: 

They initiated their Six Sigma Program in 2001.

Caterpillar had a long road in front of it, but the initial rollout of 6 Sigma used more than 300,000 hours of training in its first year. Dan Campion, Caterpillar Master Black Belt, points out that when Allied Signal sent its people through Black Belt training, the average number of years of company experience was five to seven. At Caterpillar, the average number of years of company experience was more than 20.

According to the company, there were approximately 2,000 active Black Belts at CAT in 2010. As of that same year, they had introduced 850 suppliers worldwide to 6 Sigma, which created more than1,000 supplier Black Belts to help run projects. Source

Lean: 

Beginning in 2012, Group President Gerard Vittecoq established a strategic initiative to establish an enterprise vision to deliver world-class lean results, based upon process capability. 

"The Caterpillar Enterprise System Group builds upon the strong foundation of our Caterpillar Production System and 6 Sigma.” Source

In a short video: Chief Financial Officer Andrew Bonfield highlights lean manufacturing at CAT’s Large Engine Center in Lafayette, Indiana. Source

Caterpillar Production System (CPS):

This new system was launched in 2005.

The purpose was to implement a common enterprise-wide order-to-delivery process with the aim of improving quality, safety, cost management, and velocity while adding capacity. 

Source

The CPS focuses on three types of processes:

Core includes the fundamental factory floor operational processes that encompass all activities from demand planning to delivery of finished products.

Governing is related to governance activities associated with tracking and measuring safety, quality, and 6 Sigma benefits.

Enabling processes are related to information management, people, culture, and value stream transformations. Source