Overcoming the issues associated with migrating CAD data

Overcoming the issue of migrating CAD data
Globalisation, higher product complexity, more demanding customers and brutal competition are all driving the need for ever-more effective collaboration. This, in turn, depends on a core competence in sharing product data. Although there has been much progress in recent years, poor product data interoperability remains as an enormous technical barrier to effective collaboration and is believed in some quarters to be the single largest source of cost and waste in engineering.

Interoperability problems appear in many places and the most visible of these issues occur when trying to read data from one CAD system into another. However, even different versions of the same CAD system are often unable to share models. According to Longview Advisors' 2011 Collaboration and Interoperability Survey "there are countless other sources of wasted time and energy — which could be spent innovating — caused by poor CAD interoperability".

According to David Prawel of Longview Advisors: "Companies involved in lean initiatives often consider the cost of waste in manufacturing, but fail to understand these impacts in their CAD departments. They see 3D models rotating on computer screens and assume productive design is ongoing. The vast majority of these managers have no idea that their CAD users are often wasting a huge amount of their time fixing errors or recreating lost or corrupt data in their models, instead of creating new products or adding value in product development processes."

Quite how many man hours are spent on this process is genuinely shocking. According to the Longview survey, 41% of respondents report that more than 50% of their product design and engineering employees are involved with CAD interoperability or data exchange activities, and 9% have all of their product development and engineering resource involved. Additionally, 22% of design or engineering professionals at companies self-described as OEMs spend more than one day of a typical work week reworking and/or recreating CAD data.
This situation is worse for suppliers, which report that 29% of their design or engineering professionals spend more than one day of a typical work week reworking and/or re-creating CAD data.

Perhaps the single most time-consuming and risk-laden aspect of this process is that of data validation and checking. Stuart Thurlby, managing director of data exchange specialist Theorem Solutions says of this process: "Everyone assumes that the validation and checking have been done properly and that everything is wholesome and perfect. That's the theory, but it's never actually done! If you ask most big companies they'll say they do it, but they don't and they never have because they just don't have the time or manpower to do it. The vulnerability that gives you is that you may send out something that is not of the right quality or that doesn't contain everything. Or, similarly, you may receive something that is not appropriate and the danger is that you might start to do something that is based around bad data."

This problem has become particularly acute as key manufacturing data is increasingly incorporated within 3D CAD models. Says Thurlby: "What used to happen was that a 3D model was sent along with a 2D drawing, which was used for manufacturing. The problem, of course, is that as more and more people are just sending the 3D data, the need for validation and checking is even more important because, were there's a separate drawing and model, you might have a better chance of picking up discrepancies, if there is just one neat package, it becomes imperative that proper validation takes place."

However, the technical requirements of CAD data validation and checking are fairly daunting. CAD systems are different, even if they use the same internal kernel for holding data. The different ways in which they work and the different tolerances that they apply, can result in a perfectly valid translation producing a model that is not quite the same as the pre-translated source model. Where the CAD systems have entirely different kernels, the possibility that there may be differences is even greater.

These differences are important to engineers because they need to measure, make comparisons and to ensure that design measurements are carried through to the manufactured part. Sometimes the differences that can be identified between pre translated source models and post translation destination models is so small that it really is insignificant, but it is equally possible that even after a successful translation the differences are mathematically significant and sometimes large enough to be significant in engineering terms.

For example, even assuming that no errors were reported during the process of a translation, a comparison of the mass properties of the source and destination models may show differences. Moreover, it is possible that the mass properties are shown to be so similar as to be considered the same and yet the shapes could be different. Comparison for the purpose of CAD model validation and checking is not simple and it should include procedures to compare both mass properties and shape.

The complexity of the comparisons required to establish that the data is within acceptable engineering tolerances and the volumes of data likely to be involved indicate that it is not practical to carry out manual verification and checking processes. Such an approach would be costly in terms of equipment and software licences, would require many dedicated man hours and would be error prone.

According to Thurlby, the process of data validation is fraught with difficulty. He says: "One of the most difficult aspects of CAD translation is verifying that the resulting translated model or drawing is the same as the original source data. Where transitions are done interactively, unless a designer has access to both CAD systems, he may have no idea at all what the pre-translated data looks like and his only view is the one he gets once the translation has actually taken place. At this stage, the most likely actions a designer will take are to visually inspect the model and drawings for obvious flaws and to run a system check to see if the CAD system believes the model to be wholesome. It takes time and expertise to be sure that everything is as it should be."

The challenge facing most engineering companies is that their engineers are fully employed adding value to the company through their core competence. There are not normally free man hours that can be applied to devising and implementing a validation and checking process. Moreover even within a pool of experienced CAD and IT specialists, not many companies would have the experience and skills to undertake such a project. This, of course, opens the door to specialist companies such as Theorem Solutions. Says Thurlby: "I could introduce you to a senior engineer who spends 40% of his time on data translation. It's an unwarranted, unwelcome cost and it's not what he signed up for. That's basically where we come in. We also offer validation and checking for Theorem and non-Theorem applications. We'll do validation and checking for third party applications as well."

Given the size and complexity of the task – and the risks involved in it going wrong – it is understandable that many choose this option.

Paul Fanning

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