High Precision Machine Based on a Differential Mechanism

2014 ◽  
Author(s):  
Alberto Borboni ◽  
Elisabetta Ceretti ◽  
Alessandro Copeta ◽  
Davide Moscatelli ◽  
Rodolfo Faglia ◽  
...  
Keyword(s):  
High Precision ◽  
Degrees Of Freedom ◽  
Static Friction ◽  
Micro Machining ◽  
Concept Design ◽  
Machining Processes ◽  
Precision Machine ◽  
Macro Scale ◽  
Differential Mechanism ◽  
Servo Drives

Micromachining processes deal with the production of parts characterized by features in the micro range (i.e., with dimension lower than 1 mm). Several works are present in literature analyzing the tool behaviors, the material influence on the process, and the machine design. In fact, the downsize of the process up to the microscale needs a full review of all the knowledge coming from the meso and macro scale. As a consequence, machines suitable for micromachining processes were recently introduced in the market. Usually, these machines are classified by the classical gantry layout structure supported by a granite frame and, in order to guarantee the needed requirements of precision and accuracy in the micro scale, they are based on fluid-supported axes and active and/or passive vibration control systems. This paper proposes a new concept design: a high precision machine (HPM) based on an innovative layout exploiting a differential mechanism with three motors for two degrees of freedom using pulleys and metal belts. This new layout exhibits relevant advantages. The most significant is that all the worktable servo drives, that moves along x and y axes, are ground-fixed. This allows to isolate the working area of the machine from the servo drives. The system of pulleys and belts holding the working table slides on air bearings in order to minimize the micro vibrations induced by all the drives. A further peculiarity of the machine consists of the double z-axis each of them is motorized by a micrometer slide with linear absolute encoder. The first z-axis is equipped with a spindle for performing micro machining processes (drilling and milling). The second z-axis is equipped with a laser head for micro ablation. The servo drives of the two z-axes are controlled by the same control system of the worktable. Another important feature of the proposed layout is that the differential configuration of the xy mechanism admits the use of a constant speed signal to each control reference with no output displacements. This allows to guarantee non-inversion of motion of the servo-drives and so the avoidance of problems due to backlash and/or static friction. Drives are controlled by position and speed control loops with PID architecture, anti-windup and feed forward strategies. Controllers have been tuned by the use of a genetic algorithm applied to a dynamic model of the system. As a general consideration, the quality of the investigated micro machining processes can be improved with the designed machine structure.

On the Modeling of Friction in Micromachining Processes

2007 ◽  
Author(s):  
M. R. Lovell ◽  
P. H. Cohen ◽  
R. Shankar
Keyword(s):  
Friction Mechanisms ◽  
Machining Process ◽  
Micro Machining ◽  
Machining Processes ◽  
Macroscopic Theory ◽  
Contact Conditions ◽  
Macro Scale ◽  
Scale Models ◽  
Basic Understanding ◽  
Physical Phenomena

When machining miniaturized components, the contact conditions between the tool and workpiece exhibit very small contact areas that are on the order of 10−5 mm2. Under these conditions, extremely high contact stresses are generated and it is not clear whether macroscopic theories for the chip formation, cutting forces, and the friction mechanisms are applicable. For this reason, the present investigation has focused on creating a basic understanding of the frictional behavior in micro machining processes so that evaluations of standard macro-scale models could be performed. Specialized machining experiments were conducted on 70/30 brass materials using steel tools over a range of speeds, feeds, depths of cut and tool rake angles. At each operating condition studied, the friction coefficient and the shear factor, τk, were obtained. Based on the experimental results, it was determined that standard macroscopic theory for analyzing detailed friction mechanisms was insufficient in micro machining processes. An approach that utilized the shear factor, in contrast, was found to be better for decoupling the physical phenomena involved. Utilizing the shear factor as an analysis parameter, the parameters that significantly influence the friction in microscale machining process were ascertained and discussed.

scholarly journals FEM and Analytical Modeling of the Incipient Chip Formation for the Generation of Micro-Features

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3789
Author(s):  
Michele Lanzetta ◽  
Marco Picchi Picchi Scardaoni ◽  
Armin Gharibi ◽  
Claudia Vivaldi
Keyword(s):  
Material Properties ◽  
Analytical Modeling ◽  
Cutting Tool ◽  
Sustainable Manufacturing ◽  
Cutting Parameters ◽  
Micro Machining ◽  
Machining Processes ◽  
Steel Alloys ◽  
Diamond Blade ◽  
Micro Features

This paper explores the modeling of incipient cutting by Abaqus, LS-Dyna, and Ansys Finite Element Methods (FEMs), by comparing also experimentally the results on different material classes, including common aluminum and steel alloys and an acetal polymer. The target application is the sustainable manufacturing of gecko adhesives by micromachining a durable mold for injection molding. The challenges posed by the mold shape include undercuts and sharp tips, which can be machined by a special diamond blade, which enters the material, forms a chip, and exits. An analytical model to predict the shape of the incipient chip and of the formed grove as a function of the material properties and of the cutting parameters is provided. The main scientific merit of the current work is to approach theoretically, numerically, and experimentally the very early phase of the cutting tool penetration for new sustainable machining and micro-machining processes.

Systematic Synthesis and Applications of Novel Multi-Degree-of-Freedom Differential Systems

1992 ◽  
Author(s):  
Sridhar Kota ◽  
Srinivas Bidare
Keyword(s):  
Degrees Of Freedom ◽  
Building Blocks ◽  
Degree Of Freedom ◽  
Differential Systems ◽  
Practical Applications ◽  
Epicyclic Gear ◽  
Differential Mechanism ◽  
Long Time ◽  
Gear Trains ◽  
Drive Systems

Abstract A two-degree-of-freedom differential system has been known for a long time and is widely used in automotive drive systems. Although higher degree-of-freedom differential systems have been developed in the past based on the well-known standard differential, the number of degrees-of-freedom has been severely restricted to 2n. Using a standard differential mechanism and simple epicyclic gear trains as differential building blocks, we have developed novel whiffletree-like differential systems that can provide n-degrees of freedom, where n is any integer greater than two. Symbolic notation for representing these novel differentials is also presented. This paper presents a systematic method of deriving multi-degree-of-freedom differential systems, a three and four output differential systems and some of their practical applications.

Numerical Investigation of the Influence of Friction Coefficient on Brake Groan

2010 ◽  
Vol 44-47 ◽  
pp. 1923-1927 ◽  
Author(s):  
Xian Jie Meng
Keyword(s):  
Nonlinear Dynamics ◽  
Friction Coefficient ◽  
Degrees Of Freedom ◽  
Equilibrium Points ◽  
Static Friction ◽  
Kinetic Friction ◽  
Dynamics Model ◽  
Excited Vibration ◽  
Nonlinear Dynamics Model ◽  
The Stability

A two degrees of freedom nonlinear dynamics model of self-excited vibration induced by dry-friction of brake disk and pads is built firstly, the stability of vibration system at the equilibrium points is analyzed using the nonlinear dynamics theory. Finally the numerical method is taken to study the impacts of friction coefficient on brake groan. The calculation result shows that with the increase of kinetic friction coefficient /or the decrease of difference value between static friction coefficient and kinetic friction coefficient can prevent or restrain self-excited vibration from happening.

scholarly journals A Concept Design of an Adaptive Tendon Driven Mechanism for Active Soft Hand Orthosis

Proceedings ◽  
2020 ◽  
Vol 64 (1) ◽  
pp. 21
Author(s):  
Bruno Lourenço ◽  
Vitorino Neto ◽  
Rafhael de Andrade
Keyword(s):  
Degrees Of Freedom ◽  
Low Cost ◽  
Vital Role ◽  
Dorsal Side ◽  
Concept Design ◽  
Cord Injury ◽  
3D Printed ◽  
Biomechanical Constraints ◽  
Active Orthosis

The Hands exert a vital role in the simplest to most complex daily tasks. Losing the ability to make hand movements, which is usually caused by spinal cord injury or stroke, dramatically impacts the quality of life. In order to counteract this problem, several assisting devices have been proposed, but they still present several usage limitations. The marketable orthoses are generally either the static type or over-expensive active orthosis that cannot perform the same degrees of freedom (DoF) that a hand can do. This paper presents a conceptual design of a tendon-driven mechanism for hand’s active orthosis. This study is a part of an effort to develop an effective and low-cost hand’s orthosis for people with hand paralysis. The tendon design proposed was thought to comply with some requisitions such as lightness and low volume, as well as fit with the biomechanical constraints of the hand joints to enable a comfortable use. The mechanism employs small cursors on the phalanges to allow the tendons to run on the dorsal side and by both sides of the fingers, allowing 2 DoF for each finger, and one extra tendon enlarges the hands’ adduction nuances. With this configuration, it is simple enough to execute the flexion and extension movements, which are the most used movements in daily actives, using one single DC actuator for one DoF to reduce manufacturing costs, or with more DC actuators to enable more natural hand coordination. This system of actuation is suitable to create soft exoskeletons for hands easily embedded into 3D printed parts, which could be merged over statics thermoplastic orthosis. The final orthosis design allows dexterous finger movements and force to grasp objects and perform tasks comfortably.

Experimental Investigation Into Sequential Micro Machining (SMM) for Micro Hole Drilling on SS–304

2019 ◽  
Vol 9 (4) ◽  
pp. 1-16
Author(s):  
Raju Mahadeorao Tayade ◽  
Biswanath Doloi ◽  
Biplab Ranjan Sarkar ◽  
Bijoy Bhattacharyya
Keyword(s):  
Xrd Analysis ◽  
304 Stainless Steel ◽  
Hole Drilling ◽  
Machining Parameters ◽  
Micro Machining ◽  
Machining Processes ◽  
Taper Angle ◽  
Micro Holes ◽  
Micro Hole ◽  
Ss 304

Sequential micro machining (SMM) is a strategy of machining applied for micro-part manufacturing. Due to the finding of new sequential machining combinations, the authors have presented a novel combination of micro-ECDM (µECDM) drilling and micro-ECM (µECM) finishing for producing micro-holes in SS-304 stainless steel. An experimental setup was developed indigenously to conduct both machining processes at one station. The sequential processes were employed with desirable machining parameters, during their individual execution. The most desirable parameter like machining voltage, for hole drilling by µECDM was decided by studying hole taper angle, radial overcut, etc. The µECDM generates a recast layer, to overcome the adverse effects of µECDM, with the µECM finishing applied subsequently. The experimental results of SMM indicate a reduction in hole taper angle, improved circularity, and better surface quality. The change of phase of material due to sequencing of µECDM and µECM processes was analyzed by an XRD analysis of SS-304.

scholarly journals Single-Element Dual-Interferometer for Precision Inertial Sensing

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4986
Author(s):  
Yichao Yang ◽  
Kohei Yamamoto ◽  
Victor Huarcaya ◽  
Christoph Vorndamme ◽  
Daniel Penkert ◽  
...  
Keyword(s):  
High Precision ◽  
Degrees Of Freedom ◽  
Dynamic Range ◽  
Inertial Sensor ◽  
Single Element ◽  
Inertial Sensing ◽  
Optical Readout ◽  
One Step ◽  
Isolation Systems ◽  
Laser Interferometers

Tracking moving masses in several degrees of freedom with high precision and large dynamic range is a central aspect in many current and future gravitational physics experiments. Laser interferometers have been established as one of the tools of choice for such measurement schemes. Using sinusoidal phase modulation homodyne interferometry allows a drastic reduction of the complexity of the optical setup, a key limitation of multi-channel interferometry. By shifting the complexity of the setup to the signal processing stage, these methods enable devices with a size and weight not feasible using conventional techniques. In this paper we present the design of a novel sensor topology based on deep frequency modulation interferometry: the self-referenced single-element dual-interferometer (SEDI) inertial sensor, which takes simplification one step further by accommodating two interferometers in one optic. Using a combination of computer models and analytical methods we show that an inertial sensor with sub-picometer precision for frequencies above 10 mHz, in a package of a few cubic inches, seems feasible with our approach. Moreover we show that by combining two of these devices it is possible to reach sub-picometer precision down to 2 mHz. In combination with the given compactness, this makes the SEDI sensor a promising approach for applications in high precision inertial sensing for both next-generation space-based gravity missions employing drag-free control, and ground-based experiments employing inertial isolation systems with optical readout.

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