Machining of Poly Methyl Methacrylate (PMMA) and Other Olymeric Materials

2022 ◽  
pp. 363-379
Author(s):  
Fredrick M. Mwema ◽  
Job Maveke Wambua

Polymers have been adopted industrially in the manufacture of lenses for optical applications due to their attractive properties such as high hardness, high strength, high ductility, high fracture toughness, and also their low thermal and electrical conductivities. However, they have limited machinability and are therefore classified as hard-to-machine materials. This study conducts a critical review on the machining of various polymers and polymeric materials, with particular focus on poly (methyl methacrylate) (PMMA). From the review it was concluded that various machining parameters affect the output qualities of polymers and which include the spindle speed, the feed rate, vibrations, the depth of cut, and the machining environment. These parameters tend to affect the surface roughness, the cutting forces, delamination, cutting temperatures, tool wear, precision, vibrations, material removal rate, and the mechanical properties such as hardness, among others. A multi-objective optimization of these machining parameters is therefore required, especially in the machining of PMMA.

2018 ◽  
Vol 49 (2) ◽  
pp. 62-81 ◽  
Author(s):  
Shailendra Kumar ◽  
Bhagat Singh

Tool chatter is an unavoidable phenomenon encountered in machining processes. Acquired raw chatter signals are contaminated with various types of ambient noises. Signal processing is an efficient technique to explore chatter as it eliminates unwanted background noise present in the raw signal. In this study, experimentally recorded raw chatter signals have been denoised using wavelet transform in order to eliminate the unwanted noise inclusions. Moreover, effect of machining parameters such as depth of cut ( d), feed rate ( f) and spindle speed ( N) on chatter severity and metal removal rate has been ascertained experimentally. Furthermore, in order to quantify the chatter severity, a new parameter called chatter index has been evaluated considering aforesaid denoised signals. A set of 15 experimental runs have been performed using Box–Behnken design of experiment. These experimental observations have been used to develop mathematical models for chatter index and metal removal rate considering response surface methodology. In order to check the statistical significance of control parameters, analysis of variance has been performed. Furthermore, more experiments are conducted and these results are compared with the theoretical ones in order to validate the developed response surface methodology model.


Author(s):  
Rajesh Kumar Bhushan

Optimization in turning means determination of the optimal set of the machining parameters to satisfy the objectives within the operational constraints. These objectives may be the minimum tool wear, the maximum metal removal rate (MRR), or any weighted combination of both. The main machining parameters which are considered as variables of the optimization are the cutting speed, feed rate, depth of cut, and nose radius. The optimum set of these four input parameters is determined for a particular job-tool combination of 7075Al alloy-15 wt. % SiC (20–40 μm) composite and tungsten carbide tool during a single-pass turning which minimizes the tool wear and maximizes the metal removal rate. The regression models, developed for the minimum tool wear and the maximum MRR were used for finding the multiresponse optimization solutions. To obtain a trade-off between the tool wear and MRR the, a method for simultaneous optimization of the multiple responses based on an overall desirability function was used. The research deals with the optimization of multiple surface roughness parameters along with MRR in search of an optimal parametric combination (favorable process environment) capable of producing desired surface quality of the turned product in a relatively lesser time (enhancement in productivity). The multi-objective optimization resulted in a cutting speed of 210 m/min, a feed of 0.16 mm/rev, a depth of cut of 0.42 mm, and a nose radius of 0.40 mm. These machining conditions are expected to respond with the minimum tool wear and maximum the MRR, which correspond to a satisfactory overall desirability.


2014 ◽  
Vol 590 ◽  
pp. 294-298
Author(s):  
Pichai Janmanee ◽  
Somchai Wonthaisong ◽  
Dollathum Araganont

In this study, effect of machining parameters and wear mechanism in milling process of mold steel AISI-P20 and AISI-1050, using 10 mm twin flute type end mill diameter. The experimental results found that characteristics of milling surfaces and wear of the mill end were directly influenced by changes of parameters for all test conditions. As a result, the quality of milling surfaces also changed. However, mould steels which had the good quality surface is AISI-1050, with roughnesses of 2.120 μm. Quality milling surfaces were milled by using the most suitable parameter feed rate of 45 mm/min, a spindle speed of 637 rpm and a cut depth level of 3 mm, for both grades. Moreover, material removal rate and duration of the milling process, the milling end mills affect wear of the edge in every bite when the feed rate is low, high speed and level depth of cut at least. It was found that limited wear less will affect the surface roughness (Ra) represents the good quality surface.


2018 ◽  
Vol 7 (3.1) ◽  
pp. 162 ◽  
Author(s):  
Ramanan. G ◽  
Rajesh Prabha.N ◽  
Diju Samuel.G ◽  
Jai Aultrin. K. S ◽  
M Ramachandran

This manuscript presents the influencing parameters of CNC turning conditions to get high removal rate and minimal response of surface roughness in turning of AA7075-TiC-MoS2 composite by response surface method. These composites are particularly suited for applications that require higher strength, dimensional stability and enhanced structural rigidity. Composite materials are engineered materials made from at least two or more constituent materials having different physical or chemical properties. In this work seventeen turning experiments were conducted using response surface methodology. The machining parameters cutting speed, feed rate, and depth of cut are varied with respect to different machining conditions for each run. The optimal parameters were predicted by RSM technique. Turning process is studied by response surface methodology design of experiment. The optimal parameters were predicted by RSM technique. The most influencing process parameter predicted from RSM techniques in cutting speed and depth of cut.   


2014 ◽  
Vol 602-603 ◽  
pp. 536-539
Author(s):  
Hai Bin Sun ◽  
Yu Jun Zhang ◽  
Qi Song Li

High hardness, high strength, high fracture toughness and low density are required for novel bulletproof materials. B4C/SiC composite ceramic is one of the most potential candidates. In this study, B4C/SiC composite ceramic was prepared by reaction sintering. The influence of B4C content, species and content of carbon, sintering temperature on the mechanical properties of B4C/SiC composite ceramic were studied. A high performance B4C/SiC composite ceramic was sintered at 1750°C for 30 min. Phenolic resin and carbon black were both chosen as carbon sources, whose favorable contents were 10wt%, 5wt%, respectively. The density of sintered bodies reduces with B4C content increases. To some extent, fracture toughness, bending strength improve initially and then deteriorate with the increase of B4C content whose optimal amount is 30wt%. The optimal fracture toughness and bending strength of the B4C/SiC composite ceramic are 5.07MPa·m1/2 and 487MPa, respectively. Meanwhile, the Viker-hardness of the sintered body is 30.2GPa, the density is as low as 2.82g/cm3.


2005 ◽  
Vol 38 (17) ◽  
pp. 7274-7285 ◽  
Author(s):  
Géraldine Rohman ◽  
Daniel Grande ◽  
Françoise Lauprêtre ◽  
Sylvie Boileau ◽  
Philippe Guérin

Author(s):  
B.S. Raju ◽  
U. Chandrasekhar ◽  
L.H. Manjunath

Accompanying the development of mechanical industry, the demand for alloy materials having high hardness, toughness and impact resistance are increasing. Nevertheless, such materials are difficult to be machined by traditional machining method. Hence CNC machines are used to machine such materials, which are capable of producing fine, precise, corrosion and wear resistance surfaces. The problem of arriving at optimal levels of operating parameters has attracted the attention of the researchers and practicing engineers, for a very long time. Thus, this paper demonstrates the optimization of the process parameter of machining Inconel 718 super alloy material via., the Taguchi methodbased grey analysis. The modified algorithm adopted here was successfully used for both detraining the optimum settings of machine parameters and for combining multiple quality characteristics into one integrated numerical value called grey relational grade. An attempt has been made to identify the influence of various cutting parameters i.e., speed, feed rate and depth of cut on physical part characteristics i.e., metal removal rate and surface roughness. The predictions of optimal process parameter with respect to the response are the end results of the paper.


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