Micro/Meso Scale Machine Tool Systems
Contents
TOC o “1-3” h z u Abstract PAGEREF _Toc376411506 h 1Introduction PAGEREF _Toc376411507 h 2Objective and rationale micro machine tools PAGEREF _Toc376411508 h 7Micro Machine Tool Test bed Development PAGEREF _Toc376411509 h 12Positioning system PAGEREF _Toc376411510 h 12Piezoelectric- actuated systems PAGEREF _Toc376411511 h 13
Abstract This paper addresses the Development Of Meso/Micro Scale Tool Systems. The reason for this paper is the need of processes and efficiency achieving high accuracy. The analysis of meso/micro scale tool system is addressed first followed by the examples of the micro/meso scale tool system. Meso/micro manufacturing related technology is the key to maximizing high value manufacturing. Methodology to design reconfigurable meso/micro scale machine tool in the integrated manufacturing, process and product system development context is also addressed in this paper. Two axis first generation test bed micro machine tool developed to assess the new design method also follows. Open architecture and axis movement uses the micro actuator, so as to guarantee the micro machines. Three critical problem areas pertinent to the development of precision high speed spindles for meso/ micro scale machine tool, driven by air turbines make the focus of this work. The principle for machine tool miniaturization is depicted and also the followed by the description of the design of initial experimental testbeds that physically demonstrate the feasibility of the meso/micro machine tools system concept. The testbeds uses high speed miniature spindles that are needed to obtain the required cutting velocities for the effective cutting of metals.
The use of voice coil actuated and piezoelectric feed drive technologies is also talked about. The
Meso/micro machine tool systems are instrumented with load cells that collect gather data for experimentation on micromachining processes. Three dimensional features are machined on one of the testbeds and cutting force data, machined feature profiles, and surface finish data are presented.
Introduction Miniature components are required for a wide range of applications from the biomedical to the aerospace industries. Many of these components contain three-dimensional features and are constructed from materials such as titanium, stainless steel, aluminum and brass. Parts of the size of 500 micro millimeters with holes 125 micro millimeters in diameter and wall thickness of 50-25 millimeters are now common in many places. Such components are recently being manufactured on large, ultra-precision machine tools. Lately, a number of investigations have been reported on the machining of micro-scale components, features and the associated issues of process mechanics at this level. Generally, this work has been done using specially-fitted ultra-precision, conventionally-sized machine tools. Given the cutting forces and the part size present during micro-machining, using large machine tools results in a very inefficient utilization of resources in terms of cost floor space, and energy required. These ultra-precision machines in general require specialized and expensive design features to achieve the satisfactory level of accuracy. Simplification of the design allows one to meet the accuracy requirement and the result is less expensive machine tool. For example, shorter Abbe offsets leads to less amplification of angular errors. These enable one to use components with less stringent geometric tolerances and these results to less expensive components. Smaller moving masses mean less if no inertial effects and less energy necessary to move the machine components. Less input energy also result in smaller heat radiation that result in smaller heat deformation of the machine structure and less expensive machine designs to transport the thermal energy away from vital components. Some part of research is being directed toward developing smaller machine tools. For instance the micro lathe measuring 32 mm in length developed in 1996 (Kim, C. J., Mayor, J. R., & Ni, J, 2004). This paper present the evaluation and design of miniature machine tools that have the ability of achieving significantly higher cutting speeds, producing three-dimensional features in metals, and recording the cutting force signal during machining. Data are presented that measures the performance of these testbeds.
Review Recently, a number of investigations have been reported on the machining of micro/ meso scale component and features and the associated issues of process mechanisms at this level. Precision machining processes have been studied on milling machines (Tansel and Bao, 2000; Schaller et al., 1999; Friendrich et al., 1998; Adams et al., 2001 ) and also diamond turning machines (Lucca et al., 1994; Cheng and Lee, 2001). In almost all cases these works have been done using conventionally sized, special fitted ultra-precision machine tools. Using large tools will result to an inefficient utilization of resources in terms of costs, energy requirement and also the floor space. To achieve satisfactory level of accuracy for ultra-precision machines requires special design feature which generally expensive. There are many sources of errors found in machine scale favorably with miniaturization (Kussul et al., 1996), this result to simplification of the design to meet the accuracy requirement, this leads to a less expensive micro/ meso machine tool. Some research has been directed toward developing smaller micro/ meso machine tools. In 1996 Kitahara developed a micro lathe which measured 32 mm in length. Lu and Yoneyama in 1996 reported that the micro lathe sufferers’ poor accuracy and it is also very limited shape generation capability. As per the Lu and Yoneyama in 1996 the lathe was instrumental with a tool dynamometer and study of cutting forces was done ( for the list of those who contributed to developing micro machine scale tools see the Appedix). The cutting speed was exceptionally low as result of using 15,000-rpm dc motor for the spindle. The cutting speed was about one to three meter per minute for brass.
Examples of micro/ meso scale machine tool systemVoice-Coil-Actuated System
The Specification performance
Since one of the functionality of this test bed is to machine 3D properties in metals, adequate cutting speeds need to be achieved for efficient material withdrawal. To obtain a cutting speed of [200 m / min] with tools of diameter of [250 – 500 µm] spindle velocity of [125,000 – 250,000 rotation per meter are required. Surely, the smaller diameter tooling around will need even higher arbor velocity. In order to effectively and conclusively study the machining procedure at feed values of a few µm/tooth, an arbor desired (Vogler, M. P., Liu, X., Kapoor, S. G., DeVor, R. E., & Ehmann, K. F, 2002).
In order high quality components and have the ability to create composite features, closed-loop positioning resubmit is needed. Ideally, submicron resoluteness is required to make the properties that are desired.
Cutting force measurement is needed to ensure a closer examination of the micro-milling procedures. Anticipated cutting forces are of the order of the magnitude of [100 m N]. This requires that a given force sensor with a brink limit well below 100 m N is used.
Test bed Design.
In this section, all the designs of the illumination machine tool testbed shown in the figure 4 will be exclusively described. Descriptions of the elements used in the machines as well as the procedure sensing equipment used will be delivered (Lai, X., Li, H., Li, C., Lin, Z., & Ni, J, 2008). Finally, the controller abilities will be briefly described
The testbed is comprised of three subsystems categories:
1) A system that provide the absolute rotation of the cutting tool.
2) A system that gives a proportional motion between the work piece and the tool.
3) A system to supervise the cutting procedure. The general size of the test bed, excluding the power supply, is [250 mm (L) x 150 mm (W) x 200 mm (H).]
Spindle.
Prognosticating technologies for the arbors of miniaturized machine tools are the high-speed spindles used in the den try industry. These air-turbine arbors are very small (lees than 20 mm in the diameter and length) and are very inexpensive. However, these spindles will need an improved run out ability. Therefore, while the total accuracy improvement of all these small air-turbines is being researched on, a huge, much accurate air-turbine arbor was chosen for the first test bed.
The spindle is waxed on a micrometer-driven linear glide to facilitate the changing of the tooling. The spindle can be retracted from the work piece, the tooling around changed, and then moved backwards on to the cutting position.
Analyses and discussionMicro-manufacturing is the manufacture of highly important components with characteristic sizes less than 1mm. This is a huge and rapidly rising manufacturing field sector. Meso scale/ Micro-manufacturing devices (machines) constitute both high-volume and extremely high-value products. The first most step in the generation of micro-manufacturing tools is the absolute definition of the particular problem domain. Parts and properties that lie in between what is usually mentioned as the “micro” phase and the traditionalistic “macro” phase. This is what is normally referred to as the “meso” level. Miniature element are needed for a broad range of applications from the aerospace sciences to the biomedical industries. Many of these elements contain 3D features and are created from materials such as aluminum, stainless steel, brass, and titanium. small Parts of the size of 500 µm having holes of size 125 µm in their radius doubled and thickness of 25-50 µm on their walls.
This work of micro-manufacturing has been conducted using established, particularly-fitted hyper-precision machine tools. Recently, a number of researches have been evidently reported on the machining of several micro-scale features and elements and the associated issues of process mechanics at this given level. Precision-machining procedures have been analyzed on milling machines (Bao and Tansel, 2000; Schaller et al., 1999; Friedrich et al., 1998; Adams et al., 2001) and diamond turning machines (Lucca et al., 1994; Cheung and Lee, 2001). Generally, this work has been dealt using ultra-precision, specially-fitted, conventionally-sized, machine tools.
Given the portion size and the cutting forces posing during the micro-machining, using huge machine tools outcomes in a very inefficient and inadequate utilization of the of resources on floor space, costs and energy requirements. These hype-precision machines do generally require the most expensive and highly specialized design properties to achieve the required level of accuracy.
Many genesis of the error available in machine tools scale more favorably with miniaturization, allowing the space simplification of the design to meet the accuracy standards, resulting in a more less expensive machine tool. For instance, the shorter Abbe offsets outputs in less amplification of all angulate errors. This gives a chance to use components with a lesser strict geometric tolerances, and, therefore, output in cheaper components. Lesser moving masses average less inertial outcomes and small energy required in order to move the machine components. The less input energy also greatly results in a smaller heat dissolution that results in a much smaller thermal deformation of the machine components and structure and less expensive machine designs to move the total thermal energy away from crucial component.
Objective and rationale micro machine toolsIn defining a specific problem domain for the micro-Machine Tool development, it is really significant in that size and precision necessities are considered as total separate and different issues but yet in a joint way. Figure 1 consistently represents the precision/size problem field. In the bottom to the far right, the conventional hype-precision problem domain is shown, for which there has been a much considerable study, including several pioneering work led by one Bryan (1979) at Lawrence Livermore Labs at around 1970’s. Likewise, the upper left most part of the graph shows the micro and the nano-scale quantified difficulties that the (MEMS) and material fields continue to address. To the upper right all those applications that do deal with hype-precision at the mini-scale standard are represented. It is the target of this study to consider mechanical manufacturing at the micro-scale through the use of micro-scale machine tool systems. An important properties capability of such systems will be the ability to machine three dimensional properties with no materials restrictions, which further differentiates the micro-machine tool system from the distinctive (MEMS) and LIGA systems.
Two pairs of metrics are gearing the conceptualization and subsequent development of the micro Machine Tools systems (Dornfeld, D., Min, S., & Takeuchi, Y, 2006). The first is proportional accuracy, defined as the ratio of the most maximum achievable tolerance to the work piece size, and the following is a volumetric utilization, explained, as the direct proportion of the machine and Work piece volumes. It is extremely evident that the second metric is also much closely related to the subsequent energy efficiency of this mechanism.
The figure 2 quantitatively shows the region of their letter effort in terms of the proportional accuracy.
The main objective is the development of micro-scale machining potential with proportional accuracy between [10 – 2] and [10 – 4] when the machining objects with dimensions ranging between 50 and 5000 µm, considered “conventional micro-scale machining” [region 5 in Figure 2]. It is believed that later developments can considerably increase this metric. It can also be taken that in inviolable terms this kind of development would yield much tolerances corresponding to the hype-precision machining on the conventional equipment.
Figure 3 spotlights the relation of the projected micro-scale machine tool system to conventional machines. It is evident that this conventional machines do exhibit a very low volumetrically utilization. This is, in particular, the situation when machining small portion on the conventional machines where their volumetric utilization can go beyond [106]. The development of micro Machine Tools attempts, on the micro scale, in order to improve this ratio by ten [10] to hundred [100] times. The bold ellipsoid in figure 3 shows the areas of this effort.
During the development of an micro Machine Tool, there are various functions and abilities of the given machine tool system that need to be put in to consideration are those that are fundamental to the conventional systems: a stationary or a rotating cutting tool, a means to rotate this cutting tool or the given work piece at the needed speeds, a device in order to facilitate proportional motions in between the Work piece and the final cutting tool, including propulsion of axes, portion featuring, a physical component structure within which to integrate the afore mentioned fully functional elements, a power source(s) and motion controller. Lastly, machine tool systems in the given (50 mm) 3 to (250 mm) 3 volume ranges will then be developed, with the given power sources and controller occupying outside of this space. It is very important from the beginning that all these entities are considered as part of the machine tool “functions”, not necessarily be confused with the components and mechanisms that are habitually used to get these functions in universal machine tools. This distinction will enable more innovative and creativity in executing these functions, for instance, machining several parts components from a huge sheet and then usually removing the parts that may be utilized in order to avoid the difficulties of fixing the individual parts
It is desired to put into consideration the machining of all the holes, pockets, slots, etc. of a intensity that can be accomplished with all current tooling, which is fixed to about the [50 – µm] in diameter level. The initial aims are to deal with joyriding that is in the [250 – 500 µm] range. Cutting of the metals (SAE 1045, for example, at universal cutting speeds of approximately [200 m / min] with such tools that will need spindle rotational speeds in the [100,000 to 250,000 r pm] range. Miniature arbors, powered via/through an air turbine mechanism, such as that are used in today’s dentistry, have the capability, with the run-outs that are on the order of 8-µm with the already existing bearing systems. It is much clear that the most successful realization of the high accuracy micro-Machine Tools will need a considerable approaches in high-speed miniature arbor technologies.
In the meso-machine tool system, the total range of motions, all motion increases, and the forces that are required to enable motion are all the orders of magnitude below those that are need of universal machine tool systems. Since habitual macro-actuators with extremely high rotor mass cannot be used because of the demands of accuracy, dynamic and gentleness, new driven-feed intense technologies need to be considered.
Micro Machine Tool Test bed DevelopmentThe aims of developing the micro/meso Machine Tool test beds are dual. The first aim is to develop testbeds in which several technologies could be researched for extensive use in later machine tool miniaturization developments methods. Secondly is to use these same testbeds to study the well renowned micro-milling/drilling procedures (Kim, C. J., Mayor, J. R., & Ni, J, 2004). Several different types of meso-Machine Tool model testbeds have been developed in order to dig into the feasibility of different feed-drive and arbor technologies and to search on the cutting operations in milling and in drilling execution.
Ratings are still in progress. The two primary feed-drive technologies that have been commonly used are voice-coil motors and piezoelectric actuators. A brief description of the testbeds created to study these two technologies follows.
Positioning systemAfter surveying all the present technologies for the positioning subsystem of the
Meso- Machines Tool’s, dual technologies were of immediate stake- piezoelectric rubbing drives and voice-coil drives. Voice-coil positioning systems with several linear encoders for position resubmit and higher containing force were chosen for all the first micro-machine Tool test beds due to the availability of readily packaged point location positioning systems and the hope to further exclusively quantify the [m MT] edging force system. This kind of the given system utilizes direct-drive applied science so that the movement is free and smooth from any rebound. The cutting speed can be easily controlled and adjusted.
Controller
A four-axes controller offered by SMAC corporation is used to explicitly process the encoder signals, to perform the positioning resubmits, and deliver the
Required current to these voice-coil actuators . The controller also has programmable end product and hence allowing the accumulation of the following error, motor current and encoder distortions.
Piezoelectric- actuated systemsTo set the feasibility of further miniaturization, to search and assess the different element technologies, and at the same time accomplish an important reduction in the total cost of the
M MT a test bed that fully utilizes piezo-actuators and dental turbine based arbors is also being generated. Piezoelectric actuators are highly attractive because of their extremely low cost, their small size and the probability of generating unconstrained travel distances.
Static Accuracy Characterization
The 6-DOF geometrical error measuring for m MT . A novel optic 6-DOF geometrical error measurement scheme was created by using a laser module, a beam divider, and position location sensitive detectors.
A series of research experiments to get full pose of the laser module were carried on and their outputs were compared with those from laser interferometer. Measure accuracy was more in effect than ±0.6 um for total translational elements and ±0.6 arc seconds for rotational elements respectively with the linear calibration.
ConclusionMicro/ meso machine scale tool system reduces the time and cost involved in production improving the profitability and productivity. Micro/meso machine scale tool system facilitates the ease in material handling for unloading and loading the work piece, eliminating the risk of losing or damaging the work piece in the process.
ReferencesDornfeld, D., Min, S., & Takeuchi, Y. (2006). Recent advances in mechanical micromachining. CIRP Annals-Manufacturing Technology, 55(2), 745-768.
Kim, C. J., Mayor, J. R., & Ni, J. (2004). A static model of chip formation in microscale milling. Transactions of the ASME-B-Journal of Manufacturing Science and Engineering, 126(4), 710-718.
BibliographyVogler, M. P., Liu, X., Kapoor, S. G., DeVor, R. E., & Ehmann, K. F. (2002). Development of meso-scale machine tool (mMT) systems. TECHNICAL PAPERS-SOCIETY OF MANUFACTURING ENGINEERS-ALL SERIES
Chae, J., Park, S. S., & Freiheit, T. (2006). Investigation of micro-cutting operations. International Journal of Machine Tools and Manufacture, 46(3), 313-332.
Lai, X., Li, H., Li, C., Lin, Z., & Ni, J. (2008). Modelling and analysis of micro scale milling considering size effect, micro cutter edge radius and minimum chip thickness. International Journal of Machine Tools and Manufacture, 48(1), 1-14
AppendiceThe list who contributed to the development of micro/ meso scale machine tool systems:
Kitahara et al. in 1996 developed a micro lathe.
Lu in 1999 contributed in developing a micro lathe.
Yoneyama in 1999 also contributed in developing micro lathe.
Bao and Tansel 2000
Schaller et al., 2001
Friedrich et al., 1998
Adams et al., 2001
Lucca et al., 1994
Cheung and Lee, 2001
