crank camshaft

7/31/2019 Crank Camshaft

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Efficient machining of

Crankshafts and Camshafts


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Contents

Crankshafts2

Turning of crankshafts2

Thrust Bearings3

Milling of crankshafts7

Internal Milling of crankshafts7

Main Bearings4

Turning or Turn- Broaching5

A new approach for a better crankshaft quality10

Milling of camshafts12

Cutting sequence15

Further information16

External Milling of crankshafts8

Flange - Stub end2

Wiper inserts3

Inserts and grades6


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Crankshafts are common machine elements which transferrotational movement into linear. Crankshaft design inmodern internal combustion engines is driven by the de-sire for more power at higher efficiency rates and reduced

weight.

The demands on crankshaft material, therefore, are in-creasing, while the crankshafts themselves become smaller.The many different designs of crankshaft vary consider-ably, and even during mass production there can be subtledifferences from one to another.

To machine such a variety of cranks, Sandvik Coromanthas developed tool systems which are based on well de-signed and production tested components and inserts.

Crankshafts

Flange - Stub end

Turning of crankshafts

Turning of crankshafts in mass production is still a verypopular method of machining. It dominates for the ma-chining of both flange and stub end but can, in manycases, also turn the number one main bearing.

These operations are performed on normal TurningLathes, or increasingly on special Turning- or Turn-Turnbroaching centres, used to machine the ends of the crank-shaft as well as the areas around the main bearing centreline.

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Four cylinder crankshaft - Flange, Stub end and Main bearings

are machined


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Wiper inserts

Thrust Bearings

One of the first operations on a crankshaft is the prepara-tion of flange and stub end, so that they can be used forclamping purposes in further operations.

As the crankshaft is still unbalanced at this stage, the max-imum RPM is limited and so is the cutting speed. Thatmakes the feed rate even more crucial. The use of Sandvik

Wiper inserts guarantees good surface finish even at highfeed per revolution. Next to machining time costs could,for example, be saved by using all 8 cutting edges on aCNMU-Type insert. Wherever possible, we try to use thestrong 100 degree corner, especially in cases of interruptedcuts or more heavy chiploads.

Wiper inserts are innovative high-produc-tivity inserts for turning. Due to a subtlechange to the insert corner-radius thefeed rates can be doubled without chang-ing the surface finish.

If the feed can be doubled, the cuttingtime is halved and almost twice as manycomponents are made in the same time.

Back turning of the thrust bearing is oneof the last chip forming operations during

the production of crankshafts. Best re-sults are obtained with Coro Turn 107Wiper inserts in adjustable tool holders.

Using a feed of fn 0,12 mm, a surface fin-ish value smaller than Ra


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Main Bearings

The machining of main bearings is done on special crank-shaft Turning- or Turn-Turn- Broach centres. These ma-

chines are equipped with two, disk like turrets, each hold-ing 45 insert-carrying cassettes.

The small disks allow a collision free operation betweenthe crankshaft cheeks, giving a short overhang and maxi-mum stability for the mounted cassettes.The Sandvik Coromant disks and cassettes are designed insuch a way that an individual assembly of all tool posi-tions is possible, allowing a short indexing distance duringthe operation, ensuring minimum downtime from an opti-mized cutting sequence.

The 45 cassettes per disk allow an efficient number of sis-ter tools to be mounted, so that, depending on the indi-vidual contact time of each cutting edge, the most eco-nomical arrangement of inserts can be selected.Sandvik cassettes are very stable, simple to exchange andeasy to clean.

45 1

23

4


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Turn- Broaching and

Turning inserts for

Crankshaft Machining

Coromant Grades

MP K

HC

2025

HC HC

4025

4015

3005

3025

HC HC

Engineered solutions

CAPP- solutions

For VBMT + DCMT Standard inserts see our Turning tools catalogue 2002 (C-1000:8)

341.G.540-214

341.G.540-591

341.G.540-450

341006 152N2

341.G.530-294

341.G.530-369

120412-KM

120412-PM

120412-QM

160412-KM

160412-WM

080412-KM

080412-WM

120416-KM

341.G.RNMU-001

120412-MR

1204MO-KH

S-CNMU

S-TNMU

S-WNMU

S-SNMU

S-CNMT

S-RCMX

567SA

1525

6

341.G.DCHT-005

341009150N1

4125

4125

Z 465

Z 465

Z 465

L 465

L 465

L 465

Please inquire for

further grades and

dimensions.

Please inquire for

further grades

and dimensions.

2015


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Internal Milling of

crankshafts

Crankshaft machining with ring-shaped millingcutters, having their inserts positioned internally,is referred to as: "Internal Milling", "Whirling"or "Planetary Milling".Sandvik Coromant has built many of these cut-ters over the years, and most of them have beeninstalled in production lines for truck crank-shafts. They not only mill crank pins andmain journals, but also external webshapes and flange diameters.

Forged steel crankshaft blanks fortruck engines, for example, requiretools which can withstand heavychip loads over a long period oftime. The need for adequate chippockets, and the restricted internaldiameter, limits the number of ef-fective inserts. By positioningthese inserts, with 4 or 8 cuttingedges, tangentially or laterally, amaximum edge security is

achieved. The inserts aremounted in replaceable seg-ments, which are specially hard-ened to give maximum tool lifeto the body and allow machin-ing to close tolerances over along period.

The simple cutter body construc-tion and the stable segment systemin combination with the Sandviktailor made inserts contribute to a

very reliable and economical toolsystem.

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Segment for

split pin

crankshaft

Milling of crankshafts


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External Milling

of crankshafts

100 years of car production also means 100 years ofcrankshaft mass production. The machining technologyinvolved, always determined by the current "state of theart", has undergone multiple changes over those years.

The technique of external milling has seen its ups anddowns during this long period, but has always been suc-cessfully applied. Developments in machine tooling in re-cent years, however, have brought about a renaissance ofexternal crankshaft milling. In particular, the universalpossibilities allowed by modern NC controlled machines,combined with improved cutting tool materials and highprecision milling cutters, have allowed the development ofnew and far more economic production methods.

External crankshaft milling, with two cutters on one ma-chine, allows both the simultaneous machining of pins andmain bearings, and also the milling of cheeks, flanges ortimer ring seats in one set up.

The crankshaft rotates slowly around the main bearingscenterline and so creates the circular cutting feed over therespective radius, while the required cutting speed is pro-duced by the rotation of the milling cutter. To machinethe pins, the milling cutter follows the eccentric move-ment of the pin, while milling its diameter in a linear mo-tion.

The cutting feed and speed can be adjusted for the respec-tive pin position to achieve the correct chip thickness anda well balanced cutting force. Depending on the contactzone, the cutting speed can reach 300 m/min which, incombination with a well-selected feed, leads to extremelyshort machining times.

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Milling inserts


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The insert layout of Sandvik milling cutters correspondsto the crankshaft profile to be milled. Depending on theoperations, we offer roughing cutters with a premillingcontour, and finishing cutters with an end profile contourincluding the radial undercuts.

In most cases the cutter width corresponds to the bearingwidth, and the cutter diameter has to be large enough tomill the pin in the lower position without colliding withother parts of the crankshaft or the clamping chuck. Themost common cutter diameter is 700mm.

Sandvik produces such cutters equipped with exchange-able segments, which are easy to change in case repair isneeded. The close insert pitch gives a smooth cut, goodsurface finish and low chip load, which again results inclose tolerances on the crankshaft. Sandvik has supplied

cutters equipped with up to 270 inserts.

Through the relationship of the large cutter; the smallworkpiece diameter, the high number of inserts, and wellsuited carbide grades, extremely long tool life can beachieved.

External crankshaft milling allows for high quality surfacefinish with close profile and position tolerance to be ob-tained. Green grinding of bearing diameters is not neces-sary and roller burnishing of the undercuts can be done

directly after the milling operation.

Extremely short machining times, high product qualityand a very secure production process make the externalmilling method both an interesting and economical formof machining technology.

Roughing

segment

Finishing

segment

Finishing

profile

Roughing

profile

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Roughing

Finishing


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A new approach for better

crankshaft quality

Engine builders demands' for better surface quality, lowerfriction and improved fuel efficiency are sometimes con-

trary to the needs for reducing part and production costs.

A big push forward to fulfil those wishes brought a com-pletely new approach to external crankshaft milling bySandvik Coromant. Considerable quality improvementsas well as a drastic reduction in production costs were theresult.

Up to now, the milling operations have usually been splitinto a roughing and finishing. The premilled profile, pro-duced by the roughing cutter, left some material for thefinishing operation on the bearing diameter as well as on

the oil collar faces. The finishing cutter, working like theroughing cutter as full side and face mill, had to take awaythe rest of the material.

The cutting forces, created by the tangentially positionedinserts, influenced the surface quality produced by the lat-eral positioned inserts, which are working at the sametime on the oil collar faces. Also the roughing cutter, per-forming on another part of the crankshaft simultaneouslywith the finishing cutter, affects the surface quality of thefinishing operation by way of its cutting forces.

As a result, the topographical condition of the finishedsurfaces are influenced by all those factors and very often,because of their reduced tolerances, often not good

enough to pass statistical quality control. And, as weknow, in engines with crankshaft guided connecting rods,the surface quality of the oil collar faces are extremely im-portant.

Sandvik Coromant investigated the machining process, thecrankshaft behaviour during machining action and also thecutting forces working on both the crankshaft and millingcutter.

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Surface quality


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The findings lead to a new insert and cutter design butmore important to a new cutting sequence.With this new arrangement, the roughing cutter semi-finish mills the bearing diameter before being finishground in a later operation.

That leaves just the finishing cutter to work on the oilcollar faces and the undercuts.We tested these new developments on a pin millingoperation on a 4 cylinder steel crankshaft under real-time, two shift production conditions. This applicationhas now been repeated constantly for the past year.

The improvements we achieved in this operation re-garding component quality and carbide cost reductionwere enormous.

Tool life for the roughing cutter went up to4000 crankshafts = 16 000 pins

Tool life for the finishing cutter went up to8000 crankshafts = 32 000 pins

Improvement of surface quality on oil collar faces= 280 %

Reduction in carbide cost per crankshaft= 57 %

Adjustable

insert design

Fixed pocket

design

Insert layout and cutting sequence

Conventionalversion

Newv

ersion

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Insert and cutter design


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Milling of camshafts

Variable valve timing is a recently developed technologywhich improves fuel economy and exhaust emissions. Italso shows that even after many decades of valve andcamshaft usage there is still room for improvements, aprinciple which is also valid for camshaft production.

Sandvik, therefore, have developed some high perfor-mance milling cutter variations, which show a new ap-proach to camshaft milling. This programme contains tan-dem cutters for the simultaneous milling of two cams aswell as cutters for milling the cam length, including theundercuts.

All cutters can be delivered in solid versions or equipped

with segments. Cast iron camshafts with their smallamount of stock can be milled with cutters having extraclose pitch. That could mean, for example, 70 effectivecutting edges on a 500 mm cutter, giving a smooth cut,low cutting force variation and a long tool life. Insertswith well tuned grades, optimised geometries and up to 8cutting edges result in safe production and low productioncost.

Camshaft for a truck engine - milled from a solid bar


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Milling Cutter Profiles

Cam Profiles

Milling insert with

2 left and 2 right

hand cutting edges

One of the new Sandvik developments, the combined

profile and chamfering insert, allows a drastic increase ofeffective cutting edges in a given cutter diameter. It alsooffers easy access for insert changing, especially importantwhen tandem cutters are used.

Sandvik takes particular care that our cutters are producedwith an exact run out and a good overlapping of the indi-vidual insert rows in order to get perfect cam surfaces andprofiles.

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Cast Iron camshaft for a 4 cylinder 16 valve engine


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Based on our experience, and the long hours we spentwith our customers in their workshops, we know how theideal tool should look like from a customer perspective:

Reliable and secure in production,easy to handle and as few differentparts as possible. These are just

some basic wishes.

The cutter design and the insert layout of the lobe millingcutters shown on these next two pages fit perfectly intothose customer demands.

Only one type of insert, for lobe milling as well as forchamfering, with 4 main and 8 chamfering cutting edges,keeps the inventory and the carbide cost per part low andcreates no confusion when changing the inserts.

The cutters shown have a diameter of 500 mm and areconfigured in the latest modular design. The segments,which carry the inserts, are separated from the cutterbody.

They are identical and can be mounted in all positions.So a customer, having different cam profiles to machine inlow batches, can keep the cutter bodies and exchange onlythe individual segments.This is another point to consider for reducing the capitaltied up.

Cutter

profile

Segment

Cutting

insert

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Cutter design


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Cutting sequence

All segments are produced with extremely close tolerancesand placed precisely against a shoulder and radially on thecircular ground diameter of the cutter body.

The cutting force is transferred by a simple "key and slot"system and the segment position is securely fixed by twostrong screws.

Cutting edge, component and the regular repeating impactforce acting on the camshaft, can lead to vibrations.

To avoid this the milling cutters were built with some ex-tra mass to create a flywheel-effect in order to stabilise thecutting action for longer tool life, better surface qualityand lower noise level.

The intensive discussions we have with our customers andmachine tool builders before we start a project, are alwaysa guarantee to get the expected performance and best re-sults.

Milling of 6 cylinder steel camshaft

lateral

location

radial

orientation

= Steady Rest

15

= Cutter position

cut 1cut 2cut 3cut 4cut 5cut 6


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Printed on recycleable paper

Printed in Sweden

Sandvikens Tryckeri

www.sandvik.com

Your Productivity PartnerC-2940:091 ENG/09

AB Sandvik Coromant 2003.09

Sandvik Coromant

Center of Competence

Heerdter Landstr. 229-243

DE - 40549 Dsseldorf

Tel: 0049 (0) 211 - 5027 - 303

Fax: 0049 (0) 211 - 5027 - 103

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