Lehrstuhl für Technologie der Fertigungsverfahren Laboratorium für Werkzeugmaschinen und Betriebslehre Manufacturing Technology II Exercise 2 Powder Metallurgy Werkzeugmaschinenlabor Lehrstuhl für Technologie der Fertigungsverfahren Prof. Dr. - Ing. F. Klocke RWTH - Aachen Steinbachstraße 53 52065 Aachen
17
Embed
Manufacturing Technology II Exercise 2 Powder Metallurgy€¦ · Manufacturing Technology II Exercise 2 Powder ... purity metals, super ... a typical area of application for powder
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Technologie der FertigungsverfahrenProf. Dr. - Ing. F. Klocke
RWTH - AachenSteinbachstraße 53
52065 Aachen
Inhaltsverzeichnis
Fertigungstechnik II - Übung 2 2
Table of Contents1 Introduction .................................................................................................... 3
2 Technology and design related parameters................................................... 42.1 Potential and limitations of powder metallurgy............................................... 42.2 Sintering-oriented design ............................................................................... 6
• Narrow cross sections and bridges to be at least 2 mm thick
• Pressing tools to be as straightforward as possible; i.e. through-holes only in
the round section, no finely interlocked knurling, no modulus < 0.5 in the case
of gear wheels
UNFAVOURABLE FAVOURABLE
height H of the part to be pressed nothigher than 2,5*D, otherwise breakageof the punch or over-pressing
no small cross sections, otherwiseunequal density distribution
faces instead of sharp edges to reducethe risk of punch breakage
Fig. 2.2.1: Design guidelines for sintered pre-formed parts [1/4] (Source:
Association of Powder Metallurgists (König/Klocke Vol.4, P.56, Fig. 2-52)
Technologische und konstruktive Randbedingungen
Fertigungstechnik II - Übung 2 7
avoiding tangential transitions to reducethe risk of breakage at the punches
avoiding acute angles and rounding-offs,in order to minimise the risk of breakageat the punches
avoiding circular profiles transverse to the compaction direction, otherwisethe punches become to pointed
UNFAVOURABLE FAVOURABLE
punc
h
die
die
punc
h
punc
h
die
die
punc
h
Fig. 2.2.2: Design guidelines for sintered pre-formed parts [2/4] (Source:
Association of Powder Metallurgists (König/Klocke Vol.4, P.56, Fig. 2-52)
dimensioning ofholes and fixed links:diameters resp. widths not smaller thanone third of the component height.s and d > 2 mm.
no fine toothed straight knurlings, due to difficult production of the tool crossed knurlings impossible
at a modul smaller than 0,5 it becomeshard to have a complete compaction of the teeth
UNFAVOURABLE FAVOURABLE
Fig. 2.2.3: Design guidelines for sintered pre-formed parts [3/4] (Source:
Association of Powder Metallurgists (König/Klocke Vol.4, P.56, Fig. 2-52)
Technologische und konstruktive Randbedingungen
Fertigungstechnik II - Übung 2 8
bigger distance between the bottomof the tooth space and the internal bore,risk for punches
breaking througs if possible rounded,otherwise the tools become expensive
diameter tolerances not smaller thanIT 7, height tolerances not smaller thanIT 12.
UNFAVOURABLE FAVOURABLE
Fig. 2.2.4: Design guidelines for sintered pre-formed parts [4/4] (Source:
Association of Powder Metallurgists (König/Klocke Vol.4, P.56, Fig. 2-52)
Wirtschaftliche Randbedingungen
Fertigungstechnik II - Übung 2 9
3 Economic parameters
The outcome of cost comparisons with rival processes, depends largely on the
characteristics of the parts, Fig. 3.1. The cost comparison increasingly favours
sintering, the more exacting the requirements in terms of material characteristics,
the closer the tolerances relating to complex shapes and the larger the quantity
concerned. In principle, however, the investment cost for tools and equipment is
high. Powder metallurgy frequently becomes the most favourable option from an
economic point of view only when substantial quantities are involved. The
automotive industry is therefore a typical area of application for powder
metallurgy.
piece number alloy geometry accuracy machining
after sintering
decr
ease
<<
pro
duct
ion
cost
s >>
in
crea
se
indirect coststool costssinteringcompactingpowder
>7,2
density
<6,8
small
high
MoCoCrNi
Fe
IT 6
IT 9
sump-tuous
little
Fig. 2.2.1: Influence exerted by part characteristics on the manufacturing cost of
sintered parts (König/Klocke Vol.4, P.61, Fig. 2-57)
One of the special characteristics of powder metallurgy is the 100% use of
material. This goes some way towards balancing out the disadvantages in terms
of the higher cost of the powder in comparison with that of molten metal, Fig.
2.2.2.
Wirtschaftliche Randbedingungen
Fertigungstechnik II - Übung 2 10
step 3:2nd rough-machining
step 2:1st rough-machining
step 4:internal toothing
step 5:fine turning of planefaces
step 6:broaching the outsideprofileweight: 286 g
detent„forging and cutting“
step 1:forged blankweight: 590 g
detent„powder metallurgical manufacturing“
final partweight: 191 g
several turningoperations
sintered blank
powderweight: 327 g
compactingsinteringsizing
Fig. 2.2.2: Comparison of processes used to manufacture synchronous parts -
conventional forging and cutting versus sintering (Source: Krebsöge) König/Klocke
Vol.4, P.59, Fig. 2-56“
The shorter manufacturing sequence can be a decisive advantage of powder
metallurgy, as the exemplar application “Manufacture of a synchronous part”
shows, Fig. 2.2.2 and Fig. 2.2.3. The powder metallurgical process eliminates the
need for numerous operations required when forged compacts are used. There is
additional potential for rationalisation when it is possible to take account of certain
Wirtschaftliche Randbedingungen
Fertigungstechnik II - Übung 2 11
geometrical elements of the part during the pressing operation, since this
eliminates the need to produce these elements in a finish cutting operation.
source: Metallwerk Unterfranken, ZF
1 - forging and cutting• cutting to length• forging and punching• burr removing• annealing• turning the front side• turning the back side• broaching the internal toothing• plain turning• broaching the external toothing• milling the grooves• milling the oil pockets
alternative manufacturing sequences
2 - sintering and cutting• compacting the green compact• sintering• sizing• turning the front side• turning the back side