01/01/2011 - 02/01/2011 - Mechanical engineering
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Friday, January 7, 2011

The changing face of part inspection

The changing face of part inspection

 October 21, 2010

* Authored by: Ron Branch, Verisurf Application Engineer, Verisurf Software Inc., Anaheim, Calif. Resources: Verisurf Software Inc., verisurf.com
* Inspection software helps 3D CAD, 3D GD&T, and measuring devices work together to ensure design intent.

A necessary component of the model-based definition (MBD) approach to product design is 3D geometric dimensioning and tolerancing (GD&T), a universal symbolic and tolerancing language. In the MBD approach, the 3D CAD model is the authority, providing all the detailed product information for the entire product life cycle. The method moves the 3D CAD model from design to a manufacturing orientation, and lets software automate and validate steps in simulation, manufacturing, and inspection, thereby reducing human error.

Verisurf X illustrates high and low tolerance deviations on associated model-based GD&T specs.

Last updated in 2009, GD&T has been rigorously studied and applied by thousands of manufacturers around the world. It is often considered essential for communicating design intent — that is, that parts from technical drawings have the needed form, fit, function, and interchangeability. The recent update includes changes in feature design, datum references and degrees of freedom, surface boundaries and axis methods of interpretation, profile tolerances, and symbology and modifiers tools.

In manufacturing, the direction of CAD is to 3D, however not all CAD programs provide intelligent 3D GD&T data. Here, “intelligent” means computer readable, thereby capable of feeding downstream applications. There are two 3D GD&T definition-data formats. Potentially confusing, both are labeled “3D annotation,” but one format is purely for display, while the other provides intelligence back to the CAD model.

The distinction is that in the display format, tolerancing associated to the model is in the form of text. In other words, humans must interpret the GD&T information, opening the door to potential errors. The display or presentation format is similar to typing a math equation in Microsoft Word. It conveys information, but the computer cannot use it in calculations. In conversation, this approach is commonly referred to as “decorating the model.”
Verisurf X inspection software uses ASME Y14.5-2009 GD&T symbols as part of its MBD interface. Model-based GD&T annotations can be imported as part of the 3D CAD file if supported by the program, or added to the 3D model with Verisurf X.


What makes the effort of applying GD&T to 3D models worthwhile? As part of the MBD approach, it helps users leverage data throughout product development, cutting time from processes and improving them. It can even be said that 3D GD&T data provides a form of “artificial intelligence” for manufacturing and inspection.

How to compare a 3D CAD file to a measured part

Here are the steps to using an MBD package that includes 3D GD&T, such as Verisurf X:

1. Open the part’s 3D CAD file of the part using the inspection software. All intelligent and presentation GD&T data may be included.

2. If necessary, manually add presentation specifications to the model.

3. Develop a manual or automated inspection plan.

4. Run the inspection process. Verisurf X works with all digital metrology devices, including laser scanners for high-density point clouds, and portable CMMs (PCMMs), such as laser trackers and articulated arms with touch probes for capturing discrete points.

5. When using a PCMM, the software prompts operators to pick points that will align the physical object to the CAD model. For GD&T definitions, these alignment features are datum references. Once aligned, the software prompts operators to pick points on the part in the sequence determined by the inspection plan.

6. As measurements are taken, the software displays results graphically. Immediate feedback shows the value and deviation from the embedded GD&T tolerance. Thus, operators know immediately if a feature passes or fails inspection. This information is also documented in the pre-formatted inspection report, which eliminates data entry and manual calculations.

Model-based GD&T for inspection

GD&T defines quality requirements, and inspection then confirms these requirements are being met. A MBD implementation requires there is a GD&T representation and that inspection software can import its data from the native CAD software. Or, when intelligent GD&T data is not available, users can add it to the 3D model in the inspection software.

In the MBD approach, 3D GD&T for inspection involves inspecting physical part measurements against a CAD model. This process can be dependent or independent of how or where tolerancing is defined on the CAD model. Consider, for example, inspection software such as Verisurf X from Verisurf Software Inc., Anaheim, Calif. It connects to and controls measuring devices such as scanners and laser trackers as well as stationary and portable coordinate-measuring machines (CMMs). It also accommodates both presentation and intelligent GD&T specs from 3D CAD models. Intelligent GD&T data is imported directly from supported software with the native 3D model and provides nominal dimensions. For presentation annotations, the quality or manufacturing engineer uses Verisurf to add GD&T specifications to the 3D model.
Importing information from a native CAD package as a 3D GD&T representation is a good example of MBD at work. The accuracy of the dataset is preserved. The same applies when GD&T display data (presentation) is imported directly (or via STEP translation) and entered into the inspection application. In both scenarios, there is no need to invest in creating or maintaining 2D drawings. Of course, 3D GD&T provides the most automated method.
Verisurf X uses a 3D CAD model as the nominal definition to generate custom reports in industry-standard formats, including GD&T constraints and color-deviation maps. A Database Write feature in the program formats and sends inspection information to SPC applications and PLM databases used by major manufacturers. The feature also supports Microsoft Access and SQL Server database formats for combining Verisurf inspection data with numerous enterprise databases.
Closing the loop
MBD with 3D GD&T closes the product-development loop by eliminating ambiguity. In addition, it provides GD&T inspection feedback to manufacturing engineers, who can use the data to determine root cause and either put processes under control or revise dimensioning and tolerance specifications.

A closer look at 3D GD&T


GD&T is used on engineering drawings and computer-generated 3D models to explicitly describe nominal geometry and allowable variations. Dimensioning specs (for example, a basic dimension) define nominal geometry. Tolerancing specs (for example, linear dimensions) define allowable variations for individual features and allowable variations in orientation and location between features.
3D GD&T is defined in ASME Y14.41-2003 and ISO 16792:2006. 3D GD&T symbols include those for form, profile, orientation, location, and runout. Here are a few examples:
Measure difficult parts

Measure difficult parts

 Making it easy to measure difficult parts

An engineer might design the components, but someone on the production floor eventually has to measure them precisely.
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And until now, few handheld tools could accurately measure distances to theoretical sharp corners, apexes, mold lines, and intersection points.



CornerCalipers from SPS Industries, Farmington, Conn., (www.spsind.com), solves this problem by letting one (single-pivot model) or both jaws ( doublepivot model) conform to slanted walls. The pivot point is precisely located on the bottom edge of the device's caliper beam. So as the pivot jaw rotates, it stays at the zero reading of the caliper. The device can be used on sheet metal, plastics, casting, and extrusions, and on any parts with slanted or drafted walls.

It comes in 6, 8, and 12-in. sizes with resolution and repeatability to 0.0005 in. An LCD powered by a 1.55-V silver-oxide button battery shows results. The singlepivot model measures angles from 35 to 160°, while the doublepivot version handles 20 to 160°.

Monday, January 3, 2011

Do Inventors Need a Product Engineer?

Do Inventors Need a Product Engineer?

By Fred Heys

A product engineer is a person that can design, develop, and manage new product ideas for corporations or individual inventors. Being an engineer is not always required, but the person must be familiar with all phases of the Product Development Cycle, and keep up with the latest technologies. Also, the designer has to combine technical knowledge, human factors, and creativity in order to make a product successful in the marketplace.

The responsibility of a Product Design Engineer is to take an idea and develop it so that it can be produced and sold. He or she must select the materials, type of prototyping, tooling, and manufacturing methods that are cost effective and meet the Product Definition. This person should also be able to generate drawings and 3D models that will be used for tooling, Prototyping, patents, marketing, and manufacturing. Some engineers even help with branding, packaging and testing as needed.

A unique set of conditions comes with each Product Idea. These include, but are not limited to finances, time lines, and goals. Product Designers consider these to be normal, and deal with them routinely. A design engineer is often a person who is curious about how things are made, and how they function. By nature, they are creative, artistic, and have vivid imaginations. These attributes, as well as others, provide them an advantage in designing products that appeal to consumers.

If you're reading this because you are an inventor, you are basically a product engineer. You have a new idea, or believe that you can make an improvement to an existing product, right?

Now you can be the product engineer by taking control of your invention and going through The Product Development Cycle. You may choose to skip phases when possible, spending time and money on areas that are practical for your invention. If you have already paid for a Patent and you believe people are wasting your money on marketing, regain control of your idea. You can develop it yourself, or hire someone else to do it.

Saturday, January 1, 2011

What Is The Production Engineering?

What Is The Production Engineering?

A branch of engineering that involves the design, control, and continuous improvement of integrated systems in order to provide customers with high-quality goods and services in a timely, cost-effective manner. It is an interdisciplinary area requiring the collaboration of individuals trained in industrial engineering, manufacturing engineering, product design, marketing, finance, and corporate planning. In many organizations, production engineering activities are carried out by teams of individuals with different skills rather than by a formal production engineering department.

In product design, the production engineering team works with the designers, helping them to develop a product that can be manufactured economically while preserving its functionality. Features of the product that will significantly increase its cost are identified, and alternative, cheaper means of obtaining the desired functionality are investigated and suggested to the designers. The process of concurrently developing the product design and the production process is referred to by several names such as design for manufacturability, design for assembly, and concurrent engineering. See also Design standards; Process engineering; Product design; Production planning.

The specification of the production process should proceed concurrently with the development of the product design. This involves selecting the manufacturing processes and technology required to achieve the most economical and effective production. The technologies chosen will depend on many factors, such as the required production volume, the skills of the available work force, market trends, and economic considerations. In manufacturing industries, this requires activities such as the design of tools, dies, and fixtures; the specification of speeds and feeds for machine tools; and the specification of process recipes for chemical processes.

Actual production of physical products usually begins with a few prototype units being manufactured in research and development or design laboratories for evaluation by designers, the production engineering team, and sales and marketing personnel. The goal of this pilot phase is to give the production engineering team hands-on experience making the product, allowing problems to be identified and remedied before investing in additional production equipment or shipping defective products to the customer. The pilot production process involves changes to the product design and fine-tuning of unit manufacturing processes, work methods, production equipment, and materials to achieve an optimal trade-off between cost, functionality, and product quality and reliability. See also Pilot production; Prototype.

The production facility itself can be designed around the sequence of operations required by the product, referred to as a product layout. General-purpose production machinery is used, and often must be set up for each individual burrito, incurring significant changeover times while this takes place. This type of production facility is usually organized in a process layout, where equipment with similar functions is grouped together. See also Human-machine systems; Production methods.

The production engineering process does not stop once the product has been put into production. A major function of production engineering is continuous improvement�continually striving to eliminate inefficiencies in the system and to incorporate and advance the frontier of the best existing practice. The task of production engineering is to identify potential areas for improving the performance of the production system as a whole, and to develop the necessary solutions in these areas.

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