Research On NC Protrusion Extruder And Its CNC System For Brake Pad

Friction braking is the main way of vehicle deceleration and stop, which takes the friction between the brake pads and the brake disk as the braking force to transform the driving energy of the vehicle to the heat energy of the brake pads and the brake disk (drum). The performances of the brake pads, especially the shear performance, influence the behavior of the braking system directly and furthermore the security of the vehicle. Designers continue to find ways of enhancing the shear performance of brake pads, but the results were not satisfactory. In order to improve the shear performance of the brake pads, a new method which presented by abroad is to process a mass of nibs on the backing plate to enlarge the contact area between the brake linings and the backing plate. These nibs can improve the shear performance of the brake pads dramatically and protect the brake linings from falling off from the backing plate effectively. Machines have been developed abroad completed the new method,however, the production type of these machines belong to the scope of high-volume production, can not match the needs of domestic enterprises. It's imperative to design a new machine which can process nibs on the face of brake pad, and production type of the new machine is multi item-small lot.Based on the in-depth study of the new method, in order to Resolve the contradictions between abroad machines and the special requirement of domestic enterprises, developed a new type of production equipment - Protrusion Extruder. This paper did research on Protrusion Extruder and its CNC system: designed the overall layout and key motion mechanism of the NC protrusion extruder; combined with the study of Open CNC system, planned the hardware and software of the NC system; developed the CNC software for the NC protrusion extruder; tested on the NC protrusion extruder prototype. The main work of this paper is shown below:1. Introduction of the research background of the subject. Introduced a new method to improve the shear performance of the brake pads by processing nibs on the backing plate. The following contents are also included: development course, status and tendency of the NC technology and open CNC system, development status of the NC protrusion extruder and significance of the subject.2. Design of key motion mechanism and the overall layout of the NC protrusion extruderA conclusion that technique is the decisive factor of the overall layout is made by analyzing the principle and the influencing factors of the overall layout which is designed according to the machining principle of the NC protrusion extruder. The motion requirements and the detail design process of the tool motion mechanism (the key motion mechanism) are also presented. Modulation and simulation of the tool motion mechanism are conducted with the ADAMS software, emphasis of which is laid on the motion of the tool nose. The simulation result shows that the tool motion mechanism is reasonable in design and can implement the machining process as required. This mechanism has quick-return characteristics which can improve production efficiency in a large scale.3. Plan of the hardware and software of the NC systemIn the aspect of hardware,'PC + Motion Control Card'mode is selected by analyzing three structure forms of the open CNC system; Windows XP is chosen as the operation system of the NC protrusion extruder by comparing four mainstream operation systems on the real-time performance; MPC07 is determined to be the motion control card and its working principle and technical index is also presented.When it comes to the software, the functional characteristics of the system software of the NC protrusion extruder are introduced. Foreground and background software structure is employed in the system software. Both the function of the foreground program and the background program are discussed. C#.NET of Visual Studio is finally selected as the development language.4. Programming of the NC protrusion extruder system softwareGeneral conception and function modules of the NC protrusion extruder system software are analyzed according to the modularization principle in the software engineering. Foreground and background program are presented with an emphasis on the NC code explanation module and the machining track simulation module. A virtual keyboard for the touch screen is developed independently for the convenience of the operator since an additional keyboard would be necessary if the operator intents to write the NC code. The final system software of the NC protrusion extruder is turned out to be a powerful one, with functions of editing machining program, manual operation, jogging, automatic operation, machining track simulation, etc.5. Performance test on the NC protrusion extruder prototype With the completion of the hardware and software design, a prototype of the NC protrusion extruder is manufactured, appearance of which is shown in Fig.1. A trial machining is conducted on the prototype to test its machining capability. The processing object is a 225mm×110mm backing plate. The machining result, as is shown in Fig.2, proves that the nibs are well conforming to the requirement of the NC code. The simulation function of the machining track is tested in the end.The NC protrusion extruder for the backing plate of brake pads has achieved great success in XinYi Group. The customers speak very high of the compact structure and the convenient operation. It also received comprehensive recognition when exhibited in the 10th International Friction & Sealing Material Technology Exchange and Product Exhibition. As an original product, the NC protrusion extruder inevitably has some deficiencies such as poor adaptability to the backing plate for trucks and coaches. The corresponding solutions of these problems are provided. The application of the NC protrusion extruder is prospected as well.