QMT Features: January 2009
Designed for speed
Engine redesign is speeded up by using 3D laser scanning systems to reverse engineer/digitise the internal geometry of cylinders.

A manufacturer of performance engine components needed to redesign one of their cylinders, featuring a water jacket, through a reverse engineering process. The assembled jacket contained “hidden” areas that were not accessible to common measuring technologies, neither contact or non-contact.  Oftentimes, CT scanning is used to document these types of parts, but it is time consuming and much more expensive.

To obtain a highly accurate CAD model of the entire as-built part quickly and at a reasonable cost, the company’s QA manager decided to use the 3D laser scanning services from GKS Inspection Services.  The manager had worked with GKS Inspection Services before to develop a very successful and time-efficient method for scanning these cavities even though, as with any part containing a deep cavity, measuring the exact dimensions of the internal geometry was problematic.

Larry Carlberg, GKS Service Bureau Manager, explained, “The company was introducing a new product based on the old one.  They wanted to utilize the good parts of the existing part to redesign the new part. Using this digital reverse engineering technique allowed them to implement new features using the legacy product’s geometry as a building block. This significantly sped up their product design process.” 

 Carlberg continued, “The internal geometry of cylinders is difficult to see and measure.  This particular cylinder also had a water jacket with deep and hidden areas between the inside and outside walls of the jacket, which meant a very complex scanning process for us.”

The solution 
For this project the entire cylinder was scanned including the internal features of the water jacket. GKS engineers began by 3D laser scanning the entire part on the Laser Design Surveyor WS-2030 (20” X 30” X 20” work volume), a dual-purpose Wenzel CMM with Laser Design 3D laser scanning technology.  With the precise SLP-400 laser line scanning probe, the system obtained accuracies of +/-0.001”. (Higher accuracies to +/- 0.0005” are available from other Laser Design 3D Scanning Systems.) They scanned all of the external geometry and as much of the internal area as possible using Laser Design’s Surveyor WS-2030  3D laser scanning system featuring 6-axis scanning capability incorporating the Renishaw PH-10 indexing head and rotary 4th axis stage.

Then, with the company’s permission, GKS engineers cut the cylinder assembly into five sections based on criteria that would produce the best cut placement for laser scanning. The goal was to obtain complete and accurate data by exposing all the internal surfaces.

The five sections of the cylinder were then set up individually on the WS-2030 system, mounted to the LDI universal scanning fixture and automatically scanned from a variety of different orientations that were easily and quickly programmed by the operator in only a few minutes. Surveyor Scan Control (SSC), the system’s native scanning software, allows six axes of articulation of the part and laser probe to scan unattended, keeping the operator involvement during scanning to less than one hour. The part was scanned as a whole, then cut into a series of cross sections with reference targets for each, and then scanned separately for inclusion into a single coordinate system. 

The whole part’s inside and outside geometry was combined into a single coordinate system within +/- 0.001” for use in reverse engineering the complex investment casting / assembly of the engine cylinder  

After the scanning process was complete, Geomagic and Rapidform software products were  used to process the scan data into a nonparametric solid CAD model. The GKS engineers edited the curves of the fillets inside the water jacket to create sharp-cornered edges, which are easier to make changes to in the redesign process and to round out afterwards. Unique attributes of each software product were advantageous to completing this project quickly and accurately. 

Modelling time, including merging the voluminous amount of data, editing, double-checking, and correcting the features, took approximately 25 hours.  The total turnaround time for this very complex project was less than five days, or one work-week. GKS saved weeks of design time, bringing the product to market at least one month sooner. 

GKS sent the customer a nonparametric solid model which he requested because it is easiest for their designers to work with in the reverse engineering process.  GKS’s Carlberg stated, “Our 3D laser scan data gave this company the tools to leap ahead and do new product design with valuable information that would have taken a long time to acquire without laser scanning and this technique. It solved the problem of digitizing hidden, inaccessible surfaces and exactly replicated the shape of the casting so they could make the new mold for aluminum casting the water jacket cylinder.”  In addition GKS sent the cut sections of the cylinder back to the customer so they could also perform more measurements on the inaccessible parts, if needed, for the design process.

email: measure@gks.com

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