Technical Papers

CNC Machining of Propellers to Better than Class S Tolerances

Producing class S propellers and water jet impellers presents serious challenges for propeller manufacturers. To overcome these challenges and consistently manufacture propellers with superior quality, an integrated approach was adopted when developing and implementing a process for Computer Numerically Controlled (CNC) machining of propeller surfaces. Highlights of this process are: (1) CNC machining of all blade surfaces; extreme surface blending, (2) CNC machining to final form & finish without hand grinding and (3) high precision, better than class S. This paper will describe various challenges encountered in the production of CP propeller blades and how these challenges were overcome in order to produce accurate CP propeller blades which exceed class S tolerances.

CNC Machining of Monoblock Propellers to Final Form and Finish

This paper describes the innovative way developed by Dominis Engineering Ltd. for CNC machining of monoblock propellers to final form and finish. The foundation of the system is the concept that, in order to preserve accuracy of machined surfaces and eliminate repositioning, monoblock propellers have to be CNC machined in one set-up on a 5-axis milling machine. Using this approach, Dominis has successfully machined to final form and finish a set of high skew 6 bladed monoblock propellers.

Integrated Propeller Manufacturing System

The paper describes Integrated Propeller Manufacturing System which was developed by Dominis Engineering Ltd. for the purpose of Computer Numerically Controlled (CNC) milling of propellers to final form. The foundation of the system is a propeller geometry data base which contains detailed definition of propeller geometry and all propeller surfaces. Propeller surfaces are defined with high resolution so that the data can be used throughout the entire design/manufacturing cycle of the propeller. Integrated Propeller Manufacturing System allows CNC milling of all propeller surfaces to final form which eliminates need for hand grinding of propellers. The system has been used for CNC milling of propeller models, CNC milling of propeller blade patterns, CNC milling of marine propellers and hydraulic turbine blades, and CNC measurement of propellers and turbines.

CNC Milling of Monoblock Propeller Models

Computer numerically controlled (CNC) milling of monoblock propeller models presents several stimulating challenges for propeller manufacturers. This paper describes the technology for 5-axis CNC milling of monoblock propeller models developed and implemented at Dominis Engineering. The paper concentrates on a description of several key problems associated with 5-axis milling of monoblock propellers and describes procedures, techniques and special tools developed to allow 5-axis milling of monoblock propellers

CNC Machining of Ship Model Propellers

Shaping of sculptured surfaces such as propellers has traditionally been the domain of pattern makers and craftsmen. These highly skilled and experienced professionals translate designer's drawings into three dimensional shapes using templates and very frequently interpret designer's wishes on the basis of their own experience and skill. This traditional method of rendering propellers is very labour intensive, very time consuming and the results are very dependent on the individual pattern maker's skills and experience.

This paper describes traditional ship model propeller making, examines the advantages of model propellers milled under computer control and describes technology for Computer Numerically Controlled (CNC) milling of model propellers developed by Dominis Engineering.

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