Reverse Engineering in the Aerospace Industry

REVERSE ENGINEERING IN THE AEROSPACE INDUSTRY

Submitted to

Mr. David A. McMurrey

Technical Communication Partners, inc.

Austin, Texas

December 6, 2015

Kelli Pickett

This report examines the use of reverse engineering in the aerospace industry. The process as well as various technologies used are discussed and analyzed. The report concludes with the benefits and drawbacks to different methods of measurement for reverse engineering and why reverse engineering is beneficial to the industry.

TABLE OF CONTENTS

[TOC would go here, but you can send just the TOC file.]

LIST OF TABLES AND FIGURES

Figure Page

1. Method in which the ATOS captures images………………………………………

2. Results of the ATOS scan compared to the calibrated object……………………….

3. Results of the ATOS scan compared to the CMM…………………………….....…..

4. Results of the ATOS scan compared to the PME…………………………………….

5. Results of the two ATOS measuring volumes……………………………………….

ABSTRACT

Reverse engineering is continuing to grow in importance in the aerospace industry as technology is ever changing. Reverse engineering is used to gather information, support maintenance of older technology, and to incorporate old technology with new technology. It allows for competition between companies for the advancement of technology by different companies. The most important step in reverse engineering is to capture accurate measurements from the object that is being reverse engineered. The methods of measurement are: (1) coordinate measuring machine (CMM), (2) 3D digital scanner, or (3) precision measurement equipment (PME). The coordinate measuring machine is a contact 3D measurement device that can produce measurements within one hundred thousandth of an inch. This method of measurement is widely accepted for reverse engineering purposes. The 3D digital scanner, also known as a noncontact 3D measurement device, is not widely accepted as a measurement device, so measurements using an ATOS were taken and compared to calibrated objects with known measurements. Both angular and linear measurements were compared. The largest difference between the ATOS scan and a calibrated value for a linear measurement was 121 hundred thousandths of an inch. The acceptable tolerance for reverse engineering is two to three thousandths of an inch. For the angular measurements, the largest difference between an ATOS scan and the known, calibrated dimension was 11 thousandths of a degree. The acceptable tolerance for angular measurements is typically one degree. This proved that the ATOS is an acceptable method of measurement for reverse engineering. The large volume ATOS scan data and the small volume ATOS scan data were compared, concluding that for the tolerances that are used for reverse engineering, the measuring volume does not cause one measuring volume to be inaccurate compared to the other. The ATOS scans were also compared to the CMM data and the PME data. This showed that all methods of measurements fell within the acceptable tolerance for reverse engineering. Each method has its benefits and drawbacks, so these must be considered when choosing what method to use. The ATOS provides an image of the object after scanning occurs when the other methods do not. PME tends to be the quickest method followed by CMM and ATOS, but PME tends to have a larger possibility for error compared to the other methods. Reverse engineering continues to grow in importance and play a major role in the aerospace industry.

REVERSE ENGINEERING IN THE AEROSPACE INDUSTRY

I. INTRODUCTION

Reverse engineering is the process of obtaining knowledge, data, and design information about a product that is currently in service for the purpose of recreating or enhancing that product or a portion of it. As technology continues to grow at a rapid rate, reverse engineering has become more and more important to businesses in various industries, especially the aerospace industry. Reverse engineering is used for a multitude of reasons, especially acquisition of information about new technology produced by competitors. Reverse engineering can also be used on old technology. For example, it can be utilized to incorporate outdated technology with new technology, to support maintenance and supply of products for continuous operation that are no longer supported by the original equipment manufacturer (OEM), and documentation of the design. Reverse engineering can be used for purely educational reasons as well. It provides the opportunity to understand key features of a design, the function, shortcomings, and how it can be improved [1; 3].

The aerospace industry mainly uses reverse engineering to keep up with the ever-changing technology and to compete with competitors that sell similar products. Many companies have developed their own research and development (R&D) departments to further the company’s capabilities through processes such as reverse engineering. This process has become imperative for the continued success and business of third-party repair shops that compete directly with the OEM. In a world where profit is the bottom line, OEMs have started developing programs such as Power By the Hour where airlines will lease the engine for a specified amount of time and the OEM will repair the engine for the airline or replace it with a new one [4]. The airlines are no longer buying engines like they used to, so this greatly reduces the amount of commercial business jet engine repair shops will receive. This is causing the businesses to develop new repairs through reverse engineering for older engines that are already part of business. Reverse engineering is also allowing these businesses to develop their own replacement parts for the engine so that they don’t have to be bought from the OEM. This is increasing the profit of repair shops and decreasing the profit for the OEM. In addition, the OEMs are becoming more strict about who they will sale the engine repair information to. The OEM receives a greater profit if they are the source of the repair as opposed to selling the repair information to a repair shop and the repair shop performing the repair. The combination of these events has caused reverse engineering to drastically grow in importance for business such as jet engine repair shops.

Reverse engineering has many different critical steps required in order to capture the data needed without infringing on OEM proprietary information. The process begins by capturing dimensional and geometric data using precision measurement equipment (PME) such as calipers, a coordinate measurement machine (CMM), and 3D laser scanners such as an ATOS Triple Scan by GOM. These methods all provide the user with information about the design and dimensions of the object being reverse engineered. After the data is collected, it is then analyzed using inspection software such as GOM Inspect [2]. Once analyzed, a computer-aided design (CAD) can be constructed. This step concludes the data collection portion of reverse engineering. After this step, repairs can be developed, parts can be produced, and improvements can be made.

II. REVERSE ENGINEERING TECHNOLOGY

Reverse engineering relies on coordinated measuring and 3D technologies

Coordinate Measuring Machines

A coordinate measuring machine (CMM) is a mechanical system that uses a probe to determine coordinates and geometry of a surface of a component. A CMM is an example of a contact 3D measuring device. A CMM is comprised of three parts, the machine, the measuring probe, and the control or computing software. A CMM can either be operated manually with an operator or through computer numerical control (CNC). The product that is being reverse engineered is placed on the machine table. The probe then comes in and touches the part recording dimensions and mapping X, Y, and Z coordinates [5; 6; 7]. The measurements obtained from a CMM machine are acceptable to use for inspection and reverse engineering purposes. The CMM is a widely accepted form of measurement and therefore the data is considered accurate if the machine is within calibration.

The selection of the machine for is key to applicability of a CMM for a company. When selecting the machine, it is ideal to spend a minimal amount of money while still acquiring the needed features. Before picking the needed features, it is essential to have a well-defined idea of what the CMM will be used for. The measuring length, capacity, resolution, measurement speed, and weight capacity are important features to pick from [6]. These describe the limits in which the machine will be able to operate. In addition, the capabilities of measurement, control mechanism, style of measuring, and mounting style will need to be defined. The types of measurements the CMM will be required to record will determine the dimensional measurements, profile measurements, angularity, depth mapping, and imaging format [6]. After these selections are made, the selection of the machine itself will be complete. The selection of the measuring probe will follow.

The measuring probe is the part of the CMM that detects and records position. There are various types of probes and each probe uses a different method to record measurements. The most common type of probe used, as well as the cheapest, is the touch probe [6]. This probe records the measurements by coming down and physically touching the object. Once the object is touched, the probe sends a single back to the CMM with the coordinate measurements. The probe is then moved away from the object and to the next measurement location. This process is repeated until the needed measurements are gathered. Although the touch probe is the most common type of probe used, laser triangulation probes, line lasers, camera probes, and video camera probes can also be used [6]. The laser triangulation probe acts as a scanner where the probe passes over the object at a specified distance. Scanning the object as the probe travels around and collects the measurements. Line lasers are a popular probe type to use in reverse engineering because it can capture nonlinear objects and contours with a high degree of accuracy [6]. These features are typically hard to capture with a great degree of accuracy. The camera probe is a probe that has a camera located at the tip. It operates by taking pictures to capture measurements. The video camera probe operates in a similar way. The tip of the probe has a video camera on it and data is collected through video imaging. This type of measurement is typically suited for objects without a complex geometry [6]. The type of probe is important because it will determine the ease of measurement as well as the accuracy.

The software packages that can be utilized with a CMM have many different functions. To operate a CMM using CNC, the CMM will need a software package that supports CNC programming. To account for temperature change in the environment, there are program packages that are compatible with a CMM. This software can eliminate the effect of the thermal expansion coefficient [6]. Lastly, the software that allows the data captured by the CMM to be utilized to create a computer-aided design (CAD) is important for reverse engineering. This software is essential for companies wanting to use a CMM to capture measurements and geometry of objects for the purpose of reverse engineering. Once the software package, probe type, and the machine are chosen, a CMM can then be installed and utilized for the desired purposes.

3D Digital Scanners

Recently, the use of 3D scanners has become more and more popular for use with reverse engineering projects. A popular 3D scanner used by companies such as Chromalloy Component Services is the Advanced Topographic Optical Sensor (ATOS) III Triple Scan. A 3D scanner automatically captures the coordinates of an object by systematically collecting thousands of points per second [8]. A laser emits a light and measures the amount of time the reflected light takes to return to the sensor. The 3D coordinates are then determined using the time and the speed of light. The ATOS uses targets on the object to triangulate the points. As each scan is captured, the targets are assigned a number and become a known position on the part. Once the entire object is scanned, a 3D point cloud is created. From the 3D point cloud, a mesh is created that allows for analysis of the object using inspection software.

The method in which the ATOS captures images is depicted in Figure 1. This image shows the fringe pattern and triangulation of the ATOS. The ATOS utilizes different measuring volumes depending Figure 1: Fringe projection and triangulation of ATOS Triple Scan. Source: Drvar, N., M. Gomerčić, and M. Horvat. "Application of the Optical 3D Measurement Methods in Sheet Metal Processing."Proceedings of the 8th International Conference on Industrial Tools and Material Processing Technologies ICIT&MPT. Vol. 2011. 2011, 1.

on the amount of detailed associated with the object that is being scanned. The small volume is denoted as MV170 (170 x 130 x 130) mm and the large volume is denoted as MV560 (560 x 420 x 420) mm. Both measuring volumes capture data using the same method though. The different measuring volumes were tested and compared to validate the ATOS as an acceptable method of measurement for reverse engineering.

3D Software

Machines such as an ATOS require software to operate and analyze the data. Without 3D software, the measurements collected are of little use for reverse engineering. To operate the ATOS and then examine the data, three different software programs are required. These programs include ATOS Professional, GOM Inspect, and Geomagic Control. The interface of these programs can be seen in the Appendix. The ATOS Professional program allows the ATOS to be operated either manually or automatically. Through the program, script files can be run to systematically scan the object in a repeatable fashion. ATOS Professional will also allow hardware such as a rotation table or a multi-axis control system (MCXL) to be operated through the program. The program captures the points, performs the triangulation of the points, and produces a 3D point cloud. Once the 3D point cloud is created, the points can be polygonized and a polygon mesh is created.