Klocke F. Manufacturing Processes 1: Cutting

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10.3 Planing and Shaping 461

Cutting speed v

Lengh of stoke H

Gear shaping wheel

Workpiece

Gear shaping f

Radial feed stroke f

Lifting direction

Out running flank

In running flank

Offset

Fig. 10.16 Terms of workpiece and tool during shaping

The bell design assures that the mounting nut does not collide with the workpiece

clamping or the workpiece itself. Shank gear shaping wheels are used for internal

gears with small circular pitch diameters. Such tools can also be used to pro-

duce workpiece contours of embedded internal external gearings. Alternately, often

internally toothed shaping wheels are used (hollow shaping wheels) [Baus06].

Disk gear shaping wheel

Bell gear shaping wheel

Shaft gear shaping wheel Hollow gear shaping wheel

Fig. 10.17 Types of shaping

wheels

462 10 Processes with Translatory Primary Movement

B-B

A-A

Fig. 10.18 Tooth geometry of a shaping wheel

For gear shaping, HSS with hard material coatings and a tip rake angle between

= 10

◦

and γ

= 0

◦

is preferred.

Figure 10.18 shows the cutting part geometry on a shaping wheel tooth. As ele-

ment C shows, the tool orthogonal clearance is produced by the relief grinding of the

ﬂanks and the tooth tip. The tool orthogonal clearance at the circular pitch (cut A-A)

is selected small, to achieve a high use of the tool height. The tool orthogonal clear-

ance at the tip α

(cut B-B) can on the other hand not be freely selected but is

calculated with the help of the tool orthogonal clearance on the circular pitch and

the tool engagement angle [Bouz76]. In this way, proﬁle deviations during shaping

wheel re-sharpening are avoided.

The rake angle at the tooth tip γ

and on the ﬂanks has no essential effect on the

tool’s service life and can thus be freely selected from the standpoint of wear.

The machining process in the case of gear shaping has some peculiarities. As

opposed to hobbing, in which a hob tooth removes the same chip each time, all

chips are cut by one tooth in shaping, so that one shaping wheel tooth produces one

workpiece gap. The ﬂanks of a gear shaping wheel are involute-shaped. Figure 10.19

shows the cross-sections of undeformed chip in the manufacture of a tooth gap of a

common gear. The cross-section calculated with the help of a digital computer pro-

gram is plotted over the uncoiled cutting edge every single stroke [Sulz73]. The chip

cross-sections remain in the case of spur gears practically constant across the width

of the workpiece. Figure 10.19 shows that one-ﬂank, two-ﬂank and even three-ﬂank

chips are produced during the machining process. The three-ﬂank chips have the

biggest inﬂuence on wear. The smallest cross-sections of undeformed chip arise on

the wear-endangered location.

The chip forms of the tool life-relevant u-shaped chip cross-sections, caused by

various gear geometries, are shown in Fig. 10.20. The cross-sections of undeformed

chip are shown schematically in the upper part of the illustration and the ﬂow

10.3 Planing and Shaping 463

In running

flank E

Out running

flank A

Uncoiled cutting edge

Undeformed chip

thickness h

Risky position

Number of strokes

Fig. 10.19 Cross-sections of undeformed chip during gear shaping of a tooth ﬂank

directions of the chip parts on the top and on the ﬂanks are indicated by the plotted

arrows. The photographs in the lower half show the associated chips. The second

cross-section of undeformed chip in Fig. 10.20 is the most often encountered in

practice. The chip on the outgoing ﬂank is very thin in comparison to the chip of the

top and entry cutting edge. As a result, this chip is pressed onto the rake face by the

top chip and strongly impeded from ﬂowing.

Figure 10.21 shows the typical development of wear on the tooth of an uncoated

shaping wheel. The upper part of the illustration shows the width of ﬂank wear

land along the uncoiled cutting edge for three different tool operating lives. The

wear maximum can clearly be recognized at the transition from the top to the

outgoing ﬂank. As opposed to that, wear on the in-running ﬂank is much smaller

and evenly distributed. The lower part of the illustration shows the measurement

of the crater edge and photographs of the shaping wheel tooth at the end of the

tool life. The depth of the craters is basically the same at the three labelled loca-

tions of the cutting edge. On the other hand, the wear-endangered location at the

transition from the top to the outgoing ﬂank exhibits the smallest crater centre dis-

tance and furthermore a shrinking of the crater edge, which prevents further use of

the shaping wheel because of the subsequent rapid increase of the width of ﬂank

wear land.

Wear protection from a hard material layer reduces the stress on the cutting part

signiﬁcantly, so that it is possible to increase performance compared to uncoated

464 10 Processes with Translatory Primary Movement

Photos

Cross-section of undeformed chip

Gear shape:

Material:

Cutting tool material:

m = 3 mm,

α = 20°, β = 0°, b = 25 mm

16MnCr5N R

= 600 N/mm

HS6−5−2−5,

= 5°

−68

1,1

1,3

138.5

−204

−68

133.5

−204

133.5

131,7

x d

[mm]

[mm] d

[mm]

133.5

137.3

1 2 3 4

1 mm 1 mm 1 mm 1 mm

1: Tool; 2: Workpiece

: External diameter;

x: Profile offset; z: Number of teeth

Fig. 10.20 Inﬂuence of the cross-section of undeformed chip onto the chip ﬂow during gear

shaping

tools in two ways: on the one hand, it is possible to increase the tool operating life

by 1.5–4 times while keeping the same cutting parameters. On the other hand, it is

possible to maintain the same tool operating life while selecting more productive

cutting parameters. Increasing the rolling feed reduces the t ool operating life less

than increasing the cutting speed.

Eighty percent of the materials used for gearbox gear wheels are case-hardened

steels. Otherwise, heat-treated steels (especially in the case of hollow wheels) are

used, and more rarely cast iron materials. In special cases, construction steels are

used as gearwheel materials (e.g. in crane construction). Case-hardened steels are

gear shaped in a technologically sensible way with a cutting speed of v

= 40−

60 m/min using a roughing process. For ﬁnishing, the cutting speed can be increased

to up to v

= 140 m/min if the rolling feeds are reduced. Heat-treated steels with

a tensile strength of R

= 900−1100 N/mm

are ideally machined with a cutting

speed of v

= 30 −40 m /min with a roughing process [Able04]. Cutting speed

selection also depends on the respective workpiece width.

The most practical cutting parameters for industrial applications do not stem from

the largest tool life or maximum setting data but rather from an optimal combination

of tool life and machining time. A possible measure for machining time in the gear

10.3 Planing and Shaping 465

Out running flank In running flank

500 µm

25 µm

Head

uncoiled cutting edge

Width of flank wear land VB / mm

0.2

0.4

0.6

0.8

1.0

m = 3 mm

b = 25 mm

= 42

= –63

16MnCr5G

= 55 m/min

= 0,63 mm/DH

= 0°

K K

Position of

maximum

wear

risky position

30 gaps

500 µm

Fig. 10.21 Flank and rake wear on a cutting tooth

shaping process is t he rolling speed W, which is related to the machining speed

and results from the double stroke number n

and the rolling feed f

as follows

[Kauv87]:

W = n

· f

[

m/min

]

(10.2)

The machining costs result from the tool price, tool life with a given cutting

speed/feed combination as well as the overall auxiliary machine and personal costs

[VDI3333].

The danger of a cutting wheel/workpiece collision i n gear grinding is especially

high when the rolling feeds are high. There is a risk that the cutting wheel can col-

lide with the unmachined workpiece material during the return stroke. Due to the

continuous rolling feed, penetration between the shaping wheel tooth and the work-

piece during the return stroke would occur – as shown in Fig. 10.22 – i f measures are

not taken to prevent the collision. The largest penetration occurs in the upper face

cross section of the workpiece. This is especially problematic when manufacturing

internal gearings.

The collision causes a “cut”, in which case the ﬂank face of the shaping tooth

takes over the role of the rake face. Severe damage to the cutting edge results from

these cutting conditions as well as considerable degradation of the gear quality and

heavy loading of the machine.

466 10 Processes with Translatory Primary Movement

TDC

Length of stroke

BDC

Working stroke

BDC

Return stroke

Next working

stroke

Interpenetration at the

end of return stroke

Workpiece

Direction of rotation

Gear shaping wheel

Fig. 10.22 Cause of collision danger during gear shaping

The main inﬂuencing variables that affect collision during the return stroke are,

besides the rolling feed, the plunge depth, the geometry of the workpiece and shap-

ing wheel, the amount of lift during the return stroke of the shaping wheel and the

axis offset. The real variable to avoid collision is the amount of lift off and the axis

offset. Since the lifting movement of the shaping spindle is not always sufﬁcient,

especially in the case of internal gears, the support of the gear shaping machine is

laterally shifted by a certain amount AV, resulting in a slanted lifting motion.

10.3.3 Gear Planing

The motion sequence in gear planing basically corresponds to the kinematics of the

shaping process. Nonetheless, the term “gear planing” has become established for

this process in industrial practice, and it will also be used in the following. The

principle of gear planing is shown schematically in Fig. 10.23.

The tool used in gear planing, the “planing rack”, consists of a gear rack segment

with a relief-ground ﬂank (Fig. 10.24). The cutting force is received by a support

crest so that the tool can be exploited optimally, i.e. can be re-sharpened to a small

residual thickness. Since the planing rack is derived from a gear rack, the rolling

motion of the workpiece must be superimposed with a translatory motion in the

longitudinal direction of the gear rack when manufacturing involute-shaped gears.

Due to the ﬁnite length of the planing rack, it is necessary that the workpiece be

moved back to the starting position after producing several gaps with a decoupled

feed motion. This is referred to as “partial rolling” as opposed to continuous rolling

methods such as hobbing, gear shaping and hob peeling.

10.3 Planing and Shaping 467

Streight toothed spur gear

Helical gear

Helical rack with

limited space

beside the gears

Feed

motion

Primary

motion

Schematic diagram

Planing rack

back motion

Fig. 10.23 Principle of gear planning

(New) Planing rac

Supporting rack

Fig. 10.24 Planing rack (Source: Maag)

Since for this reason gear planing is less economical than other rolling methods, it

is only used in special cases, e.g. to produce externally toothed cylindrical gears with

large dimensions and high strength. The advantage here is that tool change is easy

and can be done without affecting quality during the manufacture of a workpiece.

References

[Abel93] Abel, R.: Hartbearbeitung mit Schneidkeramik und Bornitrid. VDI-Z Spezial

Werkzeuge 8, 20–26 (1993)

[Able04] Abler, J., et.al.: Verzahntechnik: Informationen für die Praxis. Liebherr

Verzahntechnik, Kempten (2004)

[Abou05] Abouridouane, M.: Bruchverhalten von Leichtmetallen unter Impact-

Beanspruchung. PhD Thesis, RWTH Aachen University (2005)

[Abou76] Abou-Aly, M.: Ein systematischer Überblick über die Oberﬂächenprüf- und

Messverfahren. Metalloberﬂäche 30(12), 569–572 (1976)

[Abra97] Abrão, A.M., Aspinwall, D.K.: Temperature evaluation of cutting tools during

machining of hardened bearing steel polycrystalline cubic boron nitride and ceramic

cutting tools. Mater. Sci. Technol. 13, 445–450 (1997)

[Acke89] Ackerschott, G.: Grundlagen der Zerspanung einsatzgehärteter Stähle mit

geometrisch bestimmter Schneide. PhD Thesis, RWTH Aachen University (1989)

[Adam02] Adams, C.: Trockenbearbeitung in der industriellen Anwendung. In: WZL der

RWTH Aachen University (ed.) Perspektiven der Zerspantechnik – Entwicklung und

Integration der Fertigungsprozesse von morgen (2002)

[Adam98] Adam, P.: Fertigungsverfahren von Turboﬂugtriebwerken. Bikenhäuser, Basel (1998)

[Albr60] Albrecht, P.: New developments in the theory of the metal-cutting process. Part I, the

ploughing-process in metal cutting. Trans. ASME 82 (1960), 348–358 (1960)

[Alta02] Altan, T., et al.: Estimation of tool wear in metal cutting with the ﬁnite ele-

ment method. CIRP International Workshop on Modelling of Machining, Purdue

University, Lafayette, Indiana (2002)

[Alti00] Altintas, Y.: Manufacturing Automation – Metal Cutting Mechanics, Machine Tool

Vibrations and CNC Design. Cambridge University Press, Cambridge (2000)

[Andr59] Andreatch, P., Anderson, O.L.: New device for measuring the adhesion between

metallic rods. In: Kuper, J.B.H. (ed.) The Review of Scientiﬁc Instruments, vol. 30.

American Institute of Physics, New Series (1959)

[Ansc86] Anschütz, E., Tikal, F.: Drehräumen – ein fortschrittliches Fertigungsverfahren.

Werkstatt und Betrieb 119(7) (1986)

[Aust99] Aust, E., Niemann, H.-R.: Fertigungspotenziale für die spanende Bearbeitung von

γ-TiAl. Mat.-wiss. u. Werkstofftech. 30, 43–50 (1999)

[Axer55] Axer, H.: Beitrag zur Erforschung der Verschleißursachen an spanenden

Werkzeugen. Ind.- Anz. 77(45), 610–614 (1955)

[Bail01] Baily, M., et al.: Hochharte Schneid- und Schleifstoffe in der Automobilindustrie.

Ind. Diamanten Rundschau IDR 35(4), 334–345 (2001)

[Barr00] Barry, J.: Machining hardened steels cutting tool wear acoustic emission, chip

formation and surface integrity. PhD Thesis, University College Dublin (2000)

[Barr06] Barry, J., et al.: Application areas of PCBN materials. Ind. Diam. Rev. 66(3), 46–53

(2006)

469

F. Klocke, Manufacturing Processes 1, RWTH edition,

DOI 10.1007/978-3-642-11979-8,



Springer-Verlag Berlin Heidelberg 2011

470 References

[Bath96] Bathe, K.J.: Finite Element Producers. Prentice Hall, Englewood Cliffs, NJ (1996)

[Baus06] Bausch, T. et.al.: Innovative Zahnradfertigung: Verfahren, Maschinen und Werkzeuge

zur kostengünstigsten Herstellung von Stirnrädern mit hoher Qualität. Expert,

Renningen (2006)

[Bech62] Bech, H.G.: Richtwerte für die spanende Bearbeitung einiger Leichtmetall-

Gusslegierungen. Metall 16(5), 385–393 (1962)

[Bech63] Bech, H.G.: Untersuchung der Zerspanbarkeit von Leichtmetall-Gusslegierungen.

PhD Thesis, RWTH Aachen University (1963)

[Beck00] Becker, J.: Weichschaben, die wirtschaftliche Zahnﬂankenbearbeitung – Heutiger

Stand und Entwicklungstendenzen. In: TAE-Seminar “Praxis der Zahnradfertigung“.

Esslingen, 28–30 June 2000

[Beck69] Beckhaus, H.: Einﬂuß der Kontaktbedingungen auf das Standverhalten von

Fräswerkzeugen beim Stirnfräsen. PhD Thesis, RWTH Aachen University (1969)

[Beck95] Beck, H.W.: Formgenauere Zylinderbohrungen in Aluminium-Motorblöcken.

Werkstatt und Betrieb 128(3), 137–138 (1995)

[Beis82] Beiss, P.: Pulvermetallurgisch hergestellter Schnellarbeitsstahl. Vortrag DGM

Symposium Schneidstoffe, Bad Nauheim (1982)

[Berg03] Berg van den, H., et al.: Moderne Fertigungstechnologien in der Hartmetallindustrie.

In: Kolaska, H. (ed.) Pulvermetallurgie in Wissenschaft und Praxis. vol. 19:

“Material – Prozeß – Anwendung”, pp 27–48. ISL, Hagen (2003)

[Berg05] Berg van den, H., et al.: Eigenschaften und Anwendung von modernen

Hartstoffbeschichtungen. In: Kolaska, H. (ed.) Pulvermetallurgie in Wissenschaft

und Praxis. vol. 21: “Hochleistungsprodukte der Pulvermetallurgie”, pp 245–254.

Heimdall, Witten (2005)

[Berg90] Bergmann, E., et al.: Ion-plated titanium carbonitride ﬁlms. Surf. Coatings Technol.

42(3), 237–251 (1990)

[Berg97] Berg van den, H., et al.: Die Bedeutung von modiﬁzierten Randzonen für die

Hartmetallbeschichtung. In: Ruthardt, R. (ed.) Pulvermetallurgie in Wissenschaft

und Praxis. vol. 13: „Hartstoffe, Hartstoffschichten, Werkzeuge, Verschleißschutz“,

Hamburg: Werkstoff-Informationsges., pp 77–87 (1997)

[Berk01] Berky, E.: Aerostructures made in Augsburg. International ARO Seminar

Aluminium - HSC Machining, Reutte (A) (2001)

[Berk92] Berktold, A.: Drehräumen gehärteter Stahlwerkstoffe. PhD Thesis, RWTH Aachen

University (1992)

[Bett03] Betten, J.: Finite Elemente für Ingenieure. vol. 1 Grundlagen, Matrixmethoden,

elastisches Kontinuum Berlin: Springer (2003)

[Beye72] Beyer, H.: Fernseh-Thermographie. Ein Beitrag zur Erfassung der

Temperaturverteilung am Drehmeißel. PhD Thesis, Technische University Berlin

(1972)

[Bobz00] Bobzin, K.: Benetzungs- und Korrosionsverhalten von PVD-beschichteten

Werkstoffen für den Einsatz in umweltverträglichen Tribosystemen. PhD Thesis,

RWTH Aachen University (2000)

[Bobz05] Bobzin, K.: Script of Lecture Oberﬂächentechnik SS 2005. Institut für

Oberﬂächentechnik, RWTH Aachen University (ed.) (2005)

[Böke14] Böker, R.: Die Mechanik der bleibenden Formänderung in kristallinisch aufgebauten

Körpern. PhD Thesis, TH Aachen (1914)

[Bömc85] Bömcke, A., Erinski D.: Bohren von Kupfergußlegierungen. Ind.-Anz. 107(12)

(1985)

[Bömc87] Bömcke, A: Kernlochherstellung für Innengewinde in Al-Druckguß: Bohren ins

Volle oder Aufbohren. HGF Report 87. Ind.-Anz. 109(13), 38–39, 1987

[Bömc89] Bömcke, A.: Ein Beitrag zur Ermittlung der Verschleißmechanismen beim Zerspanen

mit hochharten polykristallinen Schneidstoffen. PhD Thesis, RWTH Aachen

University (1989)