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10/02/2006
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When it comes to engineering calculations, engineers need to be careful. Dean Palmer canvassed the views from a specialist in this area at Rolls Royce
 When it comes to engineering calculations, engineers need to be careful. Dean Palmer canvassed the views from a specialist in this area at Rolls Royce
While Microsoft Excel spreadsheets are normally adequate for most people's day-to-day calculations, when it comes to mathematical analysis for engineering companies, only the best will do. So said Alan Stevens, mathematical modelling and simulation specialist at engineering giant Rolls Royce.
Stevens, who works for Rolls Royce's submarine division, said that while engineers at the company tend to use specialist software codes for certain engineering calculations (eg. Ansys, Abaqus, Fluent, Minitab, etc.) or special in-house developed tools. But he added that all engineers at some stage also have a need to perform general purpose calculations (eg. ancillary or support calculations for pre- and post-processing) and for this, he explained, most engineers use Excel. Why? "Because the engineers know that Excel is on every PC in the company, it's readily available and easy to use," said Stevens.
Stevens, who recently persuaded his company to invest in 25 software licenses for Mathsoft's specialist mathematical modelling tool, MathCad, wants the whole company to do away with spreadsheets for engineering calculations and move towards using MathCad instead.
Stevens believes Excel is simply not a reliable enough tool for engineering calculations. He cited three main areas where Excel was inferior to MathCad: lack of clarity; standards; and accuracy.
"As far as clarity is concerned, Excel is not well controlled and calculations tend to be written ad hoc," he explained. "Most become uncontrolled as they grow in size and are poorly documented. And, if that engineer then leaves the company, somebody else has to understand that spreadsheet, which can look cumbersome and over-complicated. It can be a real problem for companies."
On 'standards', he said that there are certain peculiarities within Excel that engineers need to be aware of. "Calculations and results can be ambiguous. He gave a simple example of calculating -x2, which can be ambiguous when written down. For example, it might mean (-x)2 or -(x2). Similarly, -x2 + 1 is not the same as -1 + x2. Stevens explained that, depending on which way the software reads the calculation, you get different results with MathCad and Excel. With Excel, you always get a positive answer; with FEA and CFD packages, you always get a negative answer.
Accuracy is the third area where Stevens believes Excel is inferior to MathCad and other specialist tools. Ata recent seminar at Rolls Royce, Stevens said he devised a workshop in which engineers had to calculate how many times a simple pendulum hit a target pin. The exercise was set up specifically to highlight the inaccuracies of Excel versus MathCad.
Using Excel, the delegates calculated three hits. Using specialist mathematical software, the answer was four hits. Even reducing the time step to well below the MathCad value still produced three hits using Excel.
But his real concern is the lack of clarity in Excel. "Unclear spreadsheets can hide errors," warned Stevens. "This is why engineers should turn to tools like MathCad, where formulae and equations are laid out clearly. This means that when an engineer looks back on his or her own work, or indeed someone else's, in 12 months' time, results can be traced and verified easily and quickly."
In the last two years, engineers within Stevens' submarine division have been using MathCad for all their engineering calculations. There were 25 MathCad licenses with another 25 floating licenses for the rest of the company, which admittedly isn't many for a company of Rolls Royce's size, but Stevens said that he is working on changing the mindset of other divisions who use Excel. The number of MathCad seats is now 80, although Stevens admitted that not all engineers with the software on their PC were actually using it in the way he envisioned.
Other mathematical modelling tools are used at the company, including Matlab (from MathWorks) and Simulink, but Stevens advised that MathCad is the easiest to use as "the others tend to look like complex software languages".
Stevens concluded: "I firmly believe that, for engineers, turning to MathCad rather than Excel as their first tool of choice when their specialist [FEA, CFD] codes are not needed, will significantly improve the quality of their work and can make a useful contribution to reducing costs."
Chris Randles, CEO at Mathsoft, the developer of MathCad software, told Eureka: "MathCad is a mathematical modelling and documentation tool that performs numerical calculations, algebraic calculations and manages geometric information from CAD systems. In engineering, our software is used as documentary evidence alongside text and drawings, to support engineering information such as FEA, CFD and risk analysis calculations."
The other key area of use for MathCad is knowledge management. Randles said that aerospace companies such as BAE Systems' Wharton site is using MathCad along with IBM Catia and MSC Software for stress analysis and structural analysis of assemblies. "MathCad is a key component here," said Randles. "At the time of type certification, when BAE hands over the aircraft to its customer, all engineering documentation that supports the design and manufacturing of the assembly is passed over on an optical disk. Our software works with the company's PLM (product lifecycle management) software to manage all this."
Engineers that use our software can print out the analysis information, use it as supporting evidence in a report, email it as a PDF file to a customer, or upload it to a website for a customer.
Automotive manufacturers such as Delphi Automotive also uses MathCad, as do civil engineering companies. Randles told Eureka that civil engineering contractors were becoming more cautious with their spreadsheet calculations because several had been sued by customers that had spotted errors in their spreadsheets. With MathCad, unit conversion and mathematical formulae are automatic and are not prone to human error.
According to Randles, all engineering disciplines can benefit from using MathCad: mechanical, electrical and electronics engineers. Mathsoft is also currently working closely with National Instruments to define and share open standards for numerical methods. Randles said he hoped that calculations performed using NI's LabVIEW 8 virtual instrumentation software could then be passed to MathCad for easy understanding and clear layout of engineering analysis, test and documentation records.
While MathCad has a strong following in the aerospace and defence industry, oil and gas, civil engineering and to a lesser extent, the automotive industry, other engineering and manufacturing sectors could benefit too. R&D is a key target market for Randles.
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Author
Tom Shelley
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