Manufacturing Engineering II lecture two (3).pdf

At this ppt students will be able to internalize kinematics and mechanics of machine operation. and systematize machine tool for machining.

1. Lecture Two
Kinematics of Machine tools
By;-Belete A. ( Msc.)

2. Presentation out line
At the end of the session, the students will be able to;-
Internalize kinematics from the perspectives of Engineering
mechanics and machining operation.
Systematize the drives machine tool for machining.
List types of motions involved while machining.
Categorize and examine the effects of direct and auxiliary
motions in a machine tools.

3. kinematics
Engineeringmechanics;-isthestudyofforcesthatactonbodiesandthe
resultantmotionthatthosebodiesexperience.
Engineeringmechanicssubjectinvolvestheapplicationoftheprinciplesof
mechanicstosolvereal-timeengineeringproblems.
Kinematicsis;-thestudyofmotionofasystemofbodieswithoutdirectly
consideringtheforcesorpotentialfieldsaffectingthemotion.
kinematicsexamineshowthemomentumandenergyaresharedamong
interactingbodies.
Engineering
mechanics
Statics
Dynamics
studyof
objectsatrest.
studyofobjectsin
motionandtheforces
causingsuchmotion.
Kinetics:dealswiththe
studyofthemotionofbodies
byconsideringthecauseof
motion.
Kinematics:(studyofthe
motionofbodieswithout
considerationofthecauseof
themotion)

4. Drives in machine tool
Machinetoolsarepreciseandcomplexmachinewhichareusedtoproduce
varioustypeofcomponentsbymetalcuttings(byremovingmetalintheformof
chips).
Theworkpieceisheldinamachinetoolwiththehelpofvarioustypesofwork-
holdingdevicessuchas;
chucks,
collets,
faceplates,
mandrel,etc,
orheldbetweencenters(centerlathe,grindersetc.)orclampedona
machinetable(planers,shapers,slotters,millingmachine,surface
grindingmachineetc.).

5. Cont.
Themetalcuttingtoolisheldinvarioustypesoftoolholders,for
example;
•atoolpostofacenterlathe,
•anarborsofamillingmachine,
•spindleofadrillingmachineandsoon.
tool post of a center lathe spindle of a drilling machine
Arbors of a milling machine,

6. Motion in Machine Tool.
Motion in Machine tools;-For removing the metal from a work piece,
a relative motion is necessary between tool and job.
The various motion characteristics of machine tools are;-
Working motion.
Auxiliary motions.
Working motion;-Affect the process of clip removal. These are transmitted
either to the cutting tool, or to the work or to both simultaneously.
It includes;-
Primary cutting motion
Feed motion

7. Cont.
Primary cutting motion;-provide for cutting the chip from the job at the cutting
speed which determine the rate at which the chips are formed.
•Theprimarycuttingmotionof
acertainmachinetoolsmaybe
quitecomplexbutbitcanbe
describedasacombinationof
rotaryandreciprocating
motions.
•Primarycuttingmotionmostcommonlyusedare;rotationandstraightlinereciprocation.

8. Cont.
Rotarymotionmaybetransmittedtothe;
•job(turning),or
•tool(millingcutters,drillsetc.)
•ortobothsimultaneously(cylindricalgrinding).

9. Cont.
Straightlinereciprocatingprimarymotionisemployedinplaners,
sharpers,slotters,broachingmachine,powerhacksawmachineetc.
Thismotioncaneitherbetransmittedtothetoolsortothework(
planers).

10. Cont.
Thefeedmotionsarethemovementeitherofthetoolorofthework
inreferencetoeachother.
Thismotionenablesthecuttingoperationtobeextendedtothe
wholesurfaceoftheworkpiecetobemachined.
Thismotioncanbe
rectilinear
curvilinear
Crossdirection
Longitudinal

11. Cont.
Itmaybeinalongitudinaldirectionorinacrossdirection.
Example;-Turningacylindricaljobthecuttingmotionisobtained
bytherotationofjobbetweencentersandfeedmotionis
obtainedbythemovementoftoolparalleltotheaxisofjoband
normaltocuttingmotion.
Turning operation

12. Cont.
Inadditiontoworkingmotion(primarycuttingandfeedmotions)thereare
alsoauxiliarymotionswhilemachining,leastatlistthreeauxiliarymotionsof
machiningprocess.
Motion in Machine tools.
The various motion characteristics of machine tools
are;-
Working motion.
Primary cutting motion
Feed motion
Auxiliary motions

13. Cont.
TherearealsoAdditionalAuxiliaryMotion
examplepreparethemachine,workpieceandtoolforcarryingout
thecuttingProcess.
Thismotioninclude:
loadingclampingthejob,
removingthefinishedwork,
clampingand
swivelingunitsonwhichtheworkortoolsaremounted,
rapidapproachandwithdrawalofunitscarryingthecuttingtool,
measuringworkpieceandotheroperation.

14. Cont.
Note;-Sinceallthesemotionarenoncuttingmotion,these
shouldbeperformedasfastaspassibletoreducethetotaltimeto
produceonecomponentandtherebyincreasetherateof
productionofmachine.

15. Drives in machine tools
Both the primary cutting motion of machine tools and feed motionare power
driven, except on small machine (may be performed manually).
Theoperatingcycleofmachinetools,includingbothworkingandauxiliary
motion,isobtainedbymeansofadriveanddefiniteunitsandmechanism.
Thedriveofmachinetoolconsistof;-
1.Asourceofenergy,and
2.Devicesfortransmittingpowerfromthesourceofenergytotheoperating
elementsforproducingthecuttingmotionandfeedmotion.
Machinetoolsaredrivenalmostuniversallybyelectricmotors.Eachmachine
maybedrivenindividuallybyitsownmotorordrivenbybeltformalineshaft
furnishingpowertoothermachinetoolsaswell,thisbeingcalled“Group
Drive”

16. Cont.
(a)GroupDrive;-Groupdrivemotorareoftenmountedoverheadandmachine
toolsaredriveningroupsthroughlineshaftsandbelts.Thislimitsthesizeof
motortoabout75.Groupdriveisusuallymoreeconomicalinfixedcharges,
powerconsumptionandmaintenance.
(b) Individual Drive;-Such a drive should be used in following situation
(1) in areas requiring over head crane services
(2) on machine which would require countershaft if grouped and are likely to be
moved frequently as activity in department varies
(3) on machine that require considerable power say about 17.5 kw or more
(4) on a few machine scattered over a large area
(5) machine requiring wide speed variation also are best driven by individual drive
in complex machine, Various movement are better synchronized electrically than
mechanically.
Machinetooldriven

17. Cont.
GroupVsIndividualMachineToolDrive.Thechoicebetweentwodependon
1.Comparativefirstcost.
2.totalannualoperatingexpenses.
3.Suchminoradvantagesanddisadvantagesfromtheproductionpointas
canbeforeseenfromexperienceinsimilarinstallation.

18. Quiz 5%
1.List at least three additional Auxiliary Motion while machining. (1%)
2.Define kinematics and kinematics of machine tool. (1%)
3.Define working motion and give clear example that can elaborate working
motions (1.5%)
4.What are group and individual machine drive (1.5%)