By Joe Zink
For the past two years, the Sheet Metal Team at Chrysler’s Advanced Metrology Group has been developing unique tools for automatically capturing and storing inspection data within CATIA V5 models. These tools allow users to generate and use inspection plans that make it possible to generate PC-DMIS inspection programs automatically. The inspection plans are linked directly to the latest version of the CAD models.
As part of their upgrade to CATIA V5, Chrysler developed a software module called eTool. It allows designers to incorporate plans for verifying their part into CAD models. PC-DMIS CMM software then uses these plans to generate optimized inspection programs. This integrated approach ensures that the links between the inspection criteria and resultant measurement programs and the CAD file are never broken.
Another tool, the Change Manager (developed by Hexagon Metrology’s Wilcox Associates), automatically detects changes made to inspection plans, so that the programmers can quickly reconcile any differences between the inspection programs and the master CAD model.
Wilcox Associates has now made a version of these tools available to any manufacturer, regardless of which CAD systems they use.
A Recurring Problem
Part designers must convey to programmers the dimensions and tolerances they should evaluate to create their inspection routines. There are many ways to do this, but each shares the same flaw. In many cases designers print out 2D blueprints of the part model and mark up the critical dimensions, or they might jot down some notes in a text document, or pass on the information via phone calls. In each case, the link between manufacturing and the original design data is broken, and there is no assurance that the parameters used to inspect the parts are current.
Chrysler knew that there had to be a better way. So, as part of its upgrade to Dassault Systèmes CATIA V5, it developed a module inside a software package called “eTool” that allows designers to embed their inspection plans in the CATIA file. This ensures that the link between design data and its inspection requirements is never broken. The plans include datum definitions, feature measurement information, and dimensional evaluation information.
Once PC-DMIS converts an eTool Plan into a measurement program, it provides a computer-
simulated CMM where Chrysler programmers can quickly fine-tune their programs to accommodate fixturing and other physical components that may not be present in the CAD model.
Chrysler’s next objective was to find a software tool that could use its inspection plans to automatically create inspection programs for a range of CMMs used at several of its facilities. This would save a substantial amount of time and money. Hexagon’s software arm, Wilcox Associates, was already at work on this very problem. They were developing a new, stand-alone product, PC-DMIS Planner, which would let designers embed inspection plans inside their CAD data. Not only that, but they were developing tools inside PC-DMIS to convert these plans into part programs.
Work began to meld Chrysler’s eTool inspection plan technology with the new PC-DMIS-based capabilities about two years ago. The tools inside PC-DMIS were a natural fit for converting eTool plans into part programs. They included a plan importer, a path optimization module, an auto clearance move insertion tool, and a change manager, which keeps the plan and the part program in sync.
The plan importer takes a PC-DMIS Planner inspection plan (.ip) file and converts it into a part program. The task required the team to first identify differences in file formats and command structures. Then they developed software to convert from one format to the other. The end result enabled Chrysler to use eTool plans to create PC-DMIS part programs that are 98 percent complete. In most cases, the only tasks remaining to do before sending programs to the end users are for the part programmers to personalize and verify them.
PC-DMIS Planner Software developed by Wilcox Associates is commercial software similar to Chrysler’s eTool. It enables users to automatically generate inspection programs using models from most CAD systems.
The other significant contribution Wilcox engineers made to the project was the change manager. It automatically compares changes made to the inspection plans with the part programs at the plant level so that the programmers can quickly reconcile any differences between the programs and the master CAD model. The part program always maintains a link to the inspection plan.
This module recognizes changes made on the plan by designers. It notifies the part programmer of any modifications, shows what the changes are, and then allows the part programmer to decide whether to accept each change.
New Approach Benefits
In the past, Chrysler’s Sheet-Metal Team spent countless hours comparing the CMM programs used at the plant to the ones used by the Advanced Metrology Group and reconciling the differences. Now, using the most current CATIA model as a reference, team members use Change Manager to review differences between inspection programs and reconcile them quickly by clicking an accept- or a reject-button. Sheet-Metal Team Leader Howard Casey estimates that this procedure reduces labor by as much as 70 percent.
The four members of Chrysler’s Sheet-Metal Team are currently working on CMM programs for evaluating new Chrysler truck and passenger car designs including model launches scheduled for 2010 and 2011. This year, Casey believes his team is already 40 percent more productive than it has been in previous years because of the new software tools. As the team becomes more proficient, the goal is to increase productivity by 60 percent.
The Sheet Metal Team for Chrysler’s Advanced Metrology Group (from left): Dave Roudebush, Norbert Sprunk, Howard Casey (team leader), and Donald Miller.
According to team members, there are a number of reasons why this new approach is so effective.
“Everybody gets the same information,” says Casey. “It is all standardized in accordance with our corporate feature definitions. It’s really important to give anyone who is touching Chrysler parts throughout the world exactly the same information all of the time. That information is stored in the CATIA model. Anytime somebody pulls a model, no matter where they are, no matter if they are third tier or second tier supplier, they get exactly the same information as anyone else.”
“Consistency is a huge deal,” says team member Donald Miller. “One of the best things about eTool is that all of our dimensional engineers are now naming hundreds of features consistently according to corporate standards. Measurement parameters are then applied automatically according to the feature definitions we helped to develop. This removes all sorts of guess work from the task of creating part validation programs and makes the entire process much more efficient.”
According to team member David Roudebush, eTool and Change Manager are the main reason the team’s overall productivity is up 30 to 50 percent. “That’s because there are fewer steps and there are so many checks and balances to ensure that no inappropriate changes have been made to the inspection procedures and data during six stages of product development,” he says.
Team member Norbert Sprunk noted the importance of being failure free. “We have a pretty heavy workload so we are continually bouncing tasks from one team member to another to keep on schedule,” he says. “This is not a problem because everything is so consistent that it’s easy to share work. Even though we are working with a smaller staff, we have not had a single failure, which is defined as not meeting a validation software delivery date for prove-outs at one of our plants. Everything is getting done.”
Commercial Product Release
With the latest version of PC-DMIS CMM software, Wilcox is releasing a planning product similar to eTool for manufacturers looking to close the loop between their CAD models and measurement programs. PC-DMIS Planner is a tool for part designers to record their intentions for validation or verification of a part without getting involved in the technology of the inspection process. With it they define datums, specify the features to measure, and establish the dimensional relations among them. Then PC-DMIS uses this plan, along with the associated CAD model, as the basis for automatically generating a measurement program.
PC-DMIS Planner offers a full range of tools for developing and maintaining inspection plans. It also includes a Change Manager for keeping the inspection plans and the CAD model in sync.
Joe Zink is the global product manager for PC-DMIS Planner at Wilcox Associates, a division of Hexagon Metrology. Please send your comments to DE-Editors@deskeng.com.