Design Case Study - Diseño De Mecanismos De Precisión

TOPIC: | PAGE |
* IDEX | 1 |
* Initiation of the design process | 2 |
* Definition of machine: function and specifications | 3 |
* Conceptual Designs of the HSMC | 6 |
* Detailed Design | 8 |
* Linear Bearing Selection | 9 |
* Actuators | 10 |
* Axis Drive Motors | 10 |
* Spindle Design | 11 |
* Structural Design | 11 |
* Hydraulic andPneumatic Support Systems | 12 |
* Sensor Systems | 12 |
* Summary | 13 |
INDEX

Design Case Study: A HIGH SPEED MACHINING CENTER
This case study describes the evolution of the design of Cincinnati Milacron’s high-speed three-axis (X, Y, Z) computer-controlled machining center. A discussion of the historical background of the project is followed by a discussion of the initiation of thedesign process for this machine at the company. The conceptual and detailed developments of the High-Speed Machining Center (HSMC) are then discussed.
Initiation of the Design Process
As the demand of the automobile industry of a faster product manufacturing appeared, were the Required Specific Objectives (RSO) for a new machine generated. After the RSO was initially developed, a management teammade a quick review to determine market potential. This review was positive, so the job of performing a design feasibility study was delegated to a conceptual design manager. The conceptual design manager assembled a team of senior design engineers and analyst. In addition to the senior design team, some less experienced design engineers were included to further their training and allow for freshthoughts and ideas.
The conceptual design team concentrated around a very creative design engineer who was capable of handling the infinite several issues associated with the machine’s RSO. The chief design engineer had to be aware of technological limitations of all the machine’s component systems, although usually only considered first-order effects at this point. Using this knowledge, hisresponsibility was to guide the design team for the creation of as many plausible designs as possible. All through the early design stage, whenever in doubt as to the feasibility of a process, manufacturing specialist were consulted. The result was the formulation of an acceptable working conceptual design. Providing input and support were specialist in actuators, sensors, control systems, andmanufacturing. The RSO was updated every time that the design was refined and developed. RSO modifications were also continuously reviewed by upper management and marketing to ensure that the customer’s needs were met.
Once the conceptual design was developed, analyzed, and refined, an estimate of its cost and time to manufacture was made. At this point, management and marketing determined that themachine could be sold in sufficient quantities to justify the R&D investment needed to build a production prototype. The success of the project often depends on engineers with a strong appreciation for manufacturing engineering to make recommendations as to how parts and assemblies can be modified in order to reduce cost and increase quality and performance.

Definition of Machine - Function andSpecifications
High spindle and axis speeds, on the order of 20,000 rpm and 25—50 m/min (1000—2000 ipm), were specified in order to fulfill the precise and demanding sequence that the automobile manufactured asked for. The machine should be compatible with transfer line equipment, be able to quickly remove large amounts of metal, and engine blocks and other components that used a large number ofbolts during assembly. It was first determinate that to move a tool through aluminum at the required speeds and feeds would require a twenty horsepower motor with a special high-speed spindle. Motor and spindle technology was available to meet the 20,000 rpm goal. However, the highest linear axis speed that could be economically attained was judged at the time to be 30m/min.
With respect to the...