Professional Design Project PDP ‐ 11 ‐ 103 Designing and development of cnc cylindrical grinder MSME name - City - State - Zone - Atul machine tools Rajkot Gujarat West Zone Designer/Firm- West J itendra p ranlal mehta City - State - PROJECT CODE Rajkot Gujarat Approved cost : Start Date : Completion date : Rs.750000 01-05-2012 20-03-2014
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Professional Design Project
PDP‐11‐103
Designing and development of cnc cylindrical grinder
MSME name -City -State -Zone -
Atul machine toolsRajkotGujaratWestZone
Designer/Firm-
West
Jitendra pranla l mehtagCity -State -PROJECT CODE
J pRajkotGujarat
Approved cost :Start Date :Completion date :
Rs.75000001-05-201220-03-2014
PHASE 1 – RESEARCH
PHASE 1. PRODUCT DEFINATION PHASE
IDENTIFY THE CUSTOMERS: WHO ARE THEY?
The key to this step is collecting information from customers. There are essentially three methods commonly used: observations, surveys, and focus groups.
As we are in business of manufacturing Cylindrical Grinder for long time, we are in contact of users of CNC Cylindrical Grinder.
We already have the customer using our machines and CNC Cylindrical grinder machines.
We have contacted them and studied their requirement in detail.
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COMPETETOR BENCHMARKING
Also study of similar product manufacturer in India and Taiwan for generating the specifications of project machine.
Detail of this study is given in excel sheet
After the study, Detail discussion and brainstorming, we have derived the specifications.
CAPACITIES
Max. Dia. Of swing 250 mm
Max. Distance bet. Centres 600mm
Grinding Length 450 mm
Grinding Diameter (max) 200 mm
Maximum Weight Between Centre 60 kg
Work Head Centre Height 150 mm
WHEEL HEAD
Wheel Surface Speed 30 m/s
Grinding Wheel (OD x ID) 400x127 mm
Grinding Wheel Width (Max) 50 mm
Minimum Wheel Size OD 280 mm
R.P.M of wheel spindle (rpm) 1783 rpm
Linear Velocity 30 m/s
Spindle Type Cartridge Type
Spindle Motor 3.7(5.5) KW/HP
WHEEL SLIDE
Guide way Type V NEEDLE SLIDE
Movement Ball screw dia. 32
Slide Stroke 200
Feed Servo Motor torque 4/6 Nm
Rapid Feed Rate (on dia) 10
(Feed back resolution) Minimum Increment/Pulse 0.0001
Further to this decomposition of major assembly, are further divided in to sub assemblies to simplify the design process. This finer functional detail leads to a better understanding of the design problem. Breaking down the functions of the design may lead to the realization that there are some already existing components that can provide some of the functionality required.
Guideways are machine component used to guide slides (saddle, table, etc) and to
bear the loads applied on them.
They are devised to constrain five degrees of freedom of the slide and allowing only
the linear motion along the machine axis.
To design these guideways for modern machine tools, a set of requirements should
be met as follows: high positioning accuracy, high load capacity and stiffness,
minimum friction and wear, motion without stick-slip, high damping of vibrations,
long service life and low power-consuming.
The types of guideways most used on machine tools are the following: plain, rolling,
hydrostatic, aerostatic and combined guideways (one type in combination with another).
Normally antifriction guide ways are used in recent technology, but for grinding machine
rigidity is very important when we consider the Indian customers. In Indian condition, in
put to the machine is not as per requirement.
We have decided to go with plastics-coated slideways plain slide with V and Flat.
These slideways are constructed with thin-film PTFE (Polytetrafluorethylene) bearings pads The materials used for the construction of plain slideways should have the following properties: a) A low coefficient of friction, preferably even under dry friction conditions; b) A coefficient of friction that does not decrease with increasing velocity and that does not vary markedly with lubrication conditions; c) A low rate of wear and a high resistance to abrasion; d) Good dimensional stability and damping behaviour with adequate stiffness; e) Reasonable cost, simplicity of application and good machining properties; f) Good chemical stability and good compatibility with lubricating oils and cutting fluids.
TYPE OF GUIDE WAYS FOR WHEEL HEAD For guide ways of head, posinitional accuracy is very important, We have decided for antifriction slide. But again to achieve rigidity, we have decided to go with V roller slide Also we have bench marked with other Manufacturer Drive to Slide with Ball Screw and Servo Motor RAPID AND FEED TRAVEL OF BOTH SLIDES We have bench marked from other Manufacturer For Table Slide – 8 mt/Min For Cross Slide – 12 mt/Min WORK HEAD DRIVE To make our machine competitive in the market we have decided to go with A C motor and Frequency variable drive for same. Work Head Drive RPM Varies from 30 to 300 TYPE OF GRINDING WHEEL SPINDLE Spindle manufacturing is very specialised and accurate process. Instead of spending time and money, we have decided to outsource it. Now a day’s good manufacturers are in market. Also recent era is grinding spindle with Antifriction bearing WHEEL DRESSING ARRANGEMENT For wheel dressing, rigid and fixed bracket is to be design TYPE OF BALL SCREWS AND MOUNTING ARRANGEMENT According to accuracy requirement, and length of ball screw, we have decided to go with both end fix for table and One fix and One Floating for Cross Slide TAILSTOCK RAM MOVEMENT Normally tailstock Ram is spring loaded manual but we are planning for Hydraulic movement.
LUBRICATION POSSIBILITIES We will go with Centralised Automatic Lubrication system CNC SYSTEM REQUIREMENTS For CNC System, option available in India is Fanuc and Siemens. Discussion is in process with both.
After creating concept, Design work starts with some standard data and formula used from CMTI Machine tool design data book
Unit Formula
Diameter of Wheel D mm 350
Peripheral Speed of Wheel v m/sec ̟*Dn/1000*60 32mt/Min
Wheel Revolution per Minute n RPM 1740
Diameter of Work piece Dw mm 50
Work piece rev per Minute nw RPM 200
Peripheral work Speed Vw m/min ̟*Dw*nw/1000 3.14
Depth of Grind Traverse grinding t mm/pass 0.025
Table traverse feed rate ft mm/min 2000
Width of cut Plunge Grinding b mm 40
Plunge in feed rate per work revolution S mm/Rev .01
Plunge in feed rate per minute fp mm/min S*nw 2
Metal Removal Rate Q
Traverse Grinding Q1 Cm³/min ̟*Dw*t*ft/1000 7.85
Plunge Grinding Q2 cm³/min ̟*Dw*b*fp/1000 12.56
Unit Power U Kw/.cm³/min From Data Book 0.85
Power at Spindle N Kw U*Q 4.003
Efficiency of Transmission E % 90
Power of Motor Nel Kw N/E 4.447
Tangential Cutting Force Pz Kgf 102*N/v
Torque at Spindle Ts Kgf.m 975N/n 2.22413
DESIGN OF BED Bed is designed with One V and One Flat For each contacting surface, Maximum pressure calculated and compared with maximum permissible value of pressure as obtained from experimental investigation is give in CMTI Machine tool design data book. For cast iron slide ways of grinding machine is .005 to .008 Kgf/mm2 Base on this data Shape and Size of V and flat is decided