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Delcam’s CADCAM software cuts the cost of custom propellers

Owners of luxury yachts need the custom propellers supplied by Teignbridge Propellers to minimise noise and vibration

Using Delcam’s CADCAM software has enabled Teignbridge Propellers to reduce the cost and to speed the delivery of its custom propellers.  The improvements enabled by adding the company’s PowerSHAPE CAD software and the PowerMILL CAM system have made them more competitive with the standard propeller ranges offered by most other manufacturers.

Since its formation over 30 years ago, Teignbridge Propellers has grown from its base in Newton Abbot, Devon, to become a major supplier of propellers and propulsion systems to many of the world’s major motor yacht and boat builders, as well as many navies and commercial boat operators.  The company, which recently became part of the Mercury Marine group, specialises in custom propellers.  They are designed individually for each specific vessel and engine combination, and so enable the craft to achieve its optimum performance.

The definition of "optimum performance” depends on the particular vessel.  For example, the main criteria for an inland cargo vessel might be low noise and vibration as the crew’s cabins are often located above the propeller, whereas an ocean yacht might have high cruising speed and low fuel consumption as the main objectives.

Whatever the requirements, a propeller selected from a standard range will always be a compromise.  However, because they can be mass produced, standard propellers will offer the advantages of lower cost and faster delivery.  The key aim at Teignbridge is to minimise those advantages.  The company’s Delcam software helps achieve this objective throughout design and manufacture.

"We start the development program by calculating the ideal configuration, in terms of the diameter, pitch, number of blades, and the style, from the characteristics of the vessel and the requirements of the customer,” explained Jerry Aplin, Engineering Manager from Teignbridge.  "In general terms, having more blades is slightly less efficient but is smoother and quieter, while the increased complexity means greater cost.”

The overall design is produced using a special set of command files developed by Delcam to automate the process.  "This automation has been achieved without any loss of flexibility as it is easy to change any parameter and optimise the design,” commented Mr. Aplin.

With more boat builders now moving towards 3D design, the propeller models are becoming an increasingly important part of the discussions with the customer.  "Firstly, it is much easier to review the proposed design as a 3D model than it is as a series of 2D drawings,” explained Mr. Aplin.   "Secondly, the designers can incorporate the propeller model into the overall model of the craft.  The combined model can be used to check the position and orientation of the propeller in relation to the hull, rudder and brackets to ensure adequate clearances are maintained.  Simulations can then be run to predict the performance and also to check that there is sufficient clearance for assembly and repair.”

Once the design has been approved, the data is sent to PowerMILL to generate the cutting paths for the patterns.  The toolpaths are sent directly to a five-axis CMS TP 328 router.  "Even though we had used the Delcam software for many years, we have only gained the full benefits in the three years since we added the five-axis router,” said Mr. Aplin.  "Before upgrading to the five-axis version of the Delcam software, we looked at all of the other systems out there.  None of them could do what PowerSHAPE and PowerMILL can do.”

"With the combination of the CMS router and the Delcam software, we have been able to reduce the manufacturing times for a typical pattern by approximately 50 to 75%,” claimed Mr. Aplin.  "We have moved to using synthetic materials instead of wood so we don’t need to coat the finished pattern and wait for the coating to dry; the pattern is also more stable.  Overall, we can now produce a pattern from the approved design in days instead of weeks.”

"The introduction of five-axis machining with PowerMILL has also improved the quality of the patterns.  We work to very tight tolerances and a more accurate pattern produces a casting that needs much less machining, grinding and finishing.”

The market for custom propellers has increased as customers have become more demanding over the past ten years.  "Boat builders want to be able to offer the best performance to their customers,” said Mr. Aplin.  "With our Delcam software, we can keep the extra cost of a custom propeller down to a very small percentage of the total cost of the vessel.  Similarly, any extra time that is needed to produce a custom propeller is now a small part of the overall project.”

Mr. Aplin is optimistic that this healthy situation will continue.  "Customers specifying the finest yachts are much more particular about excess noise and vibration,” he claimed.  "At the same time, with rising fuel prices, commercial operators are becoming more concerned about fuel efficiency.  Both these trends will prompt an increased use of custom propellers.”

27 February 2007