Imagine being asked to supply customers with accurate drawings of their parts. This may sound ironic, but many companies do not have up-to-date drawings of their parts and some have never had part drawings of any kind.
Precision manufacturers can offer part drawings to their customers using a process called reverse engineering. Reverse engineering is defined by the Military Handbook MIL-HDBK-115 (ME) as the process of duplicating an item functionally and dimensionally by physically examining and measuring existing parts to develop the technical data (physical and material characteristics) required for competitive procurement. Put more simply, reverse engineering is the process of creating a part drawing by measuring the part to determine dimensions and attainable tolerances, when no formal specifications exist.
Tolerance development, often the most difficult aspect of the reverse engineering process, can be achieved only from a thorough understanding of the part and how it is used.
Reverse engineering is an ideal process to use in the following situations:
- A physical model of a product has been produced, but no drawings exist.
- Drawings have been created, but working prototypes have been modified.
- Worn or broken parts, for which there are no drawings, must be replaced and there is no source of supply.
- A CAD system is introduced to a company, and all existing products must be loaded into the system.
- A disaster destroys parts records.
Reverse engineering also can be useful in the redesign process, as well as in the introduction of new products. In some cases, it may be easier to develop drawings of an existing product and modify them in a CAD system than create drawings from scratch. This is especially true for complex shapes that can be difficult to conceptualize.
Reverse engineering can be accomplished using a variety of tools and technologies. Generally, the complexity of the part being reverse-engineered will dictate the type of equipment and software used.
The simplest reverse engineering process is manual measurement and data collection of a physical model's dimensions. In this process, hand tools such as micrometers, vernier calipers and gages are used to capture the critical dimensions needed to generate a part drawing. A more sophisticated approach is to use a hard probe and a manual coordinate measuring machine (CMM). The CMM operator maintains contact between the hard probe and the surface being measured to record as many dimensions as possible. The most effective reverse engineering techniques minimize measurement errors by gathering and processing data electronically. In such a process, a physical model is measured and the dimensions immediately digitized and collected in a database. Next, this digitized data is transferred to a CAD system, where surfaces are developed and drawings are finalized. Besides reducing the risk of measurement errors, processing data electronically significantly reduces the time required for the overall reverse engineering effort.
Digitizers can range in complexity and accuracy from hand-held units to rigid laser-based systems. Even traditional CMM machines have software accessories to take measurements and translate them into various CAD formats. Manual digitizers are generally the least expensive and let the users work in a free form manner. Users simply touch the model with the sensing tip, and data is recorded. Laser and light digitizers are usually more costly, but bring increased automation to the process and provide more precise control of measurements. Laser and light digitizers scan the profile of a model and automatically generate a large amount of data points, or a series of cross sections. As the need for reverse engineering has grown, there has been an increase in the number and types of commercial packages available. These packages can be divided into two groups, stand-alone systems and CAD integrated systems.
If you have the ability to measure a part and create an accurate CAD drawing, you can offer reverse engineering service to your customers. Many companies have discovered the business growth potential. Next month, I will feature some of these companies and discuss a number of successful reverse engineering projects.