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Johannes Schneider and Tobias Hering Efficient machining of GJL and GJS materials Experience new limits when milling with ceramics and PCBN Werkstatt + Betrieb Zeitschrift für spanende Fertigung SPECIAL: Fräsen // Seite 39 März 2014 / 147. Jahrgang www.werkstatt-betrieb.de 3/14 > > LEICHTBAU Bohren von Titanbuchsen: Doppelt so schnell bei halbem Verschleiß // Seite 20 > AEROSPACE Präzisions-Lohnfertigung: Mit Standardmaschinen zu Premiumqualität // Seite 28 > CAM-SYSTEME Virtuelle Maschine: 20 Prozent schneller rüsten bei Neuteilen // Seite 78 www.HaasCNC.com CeramTec GmbH Geschäftsbereich SPK- Werkzeuge Hauptstraße 56 Germany - 73061 Ebersbach/Fils E-Mail: [email protected] www. spk-tools.de www.ceramtec.com Special reprint from WB Werkstatt+Betrieb 3/2014 © Carl Hanser Verlag, München. 2014. All rights including reprinting, photographic reproduction and translation reserved by the publishers.
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Page 1: Johannes Schneider and Tobias Hering Efficient machining ...

Johannes Schneider and Tobias Hering

Efficient machining of GJL and GJS materialsExperience new limits when milling with ceramics and PCBN

Werkstatt + Betrieb

Zeitschrift für spanende Fertigung

SPECIAL: Fräsen // Seite 39

März 2014 / 147. Jahrgang www.werkstatt-betrieb.de

3/14

>

> LEICHTBAUBohren von Titanbuchsen:Doppelt so schnell beihalbem Verschleiß // Seite 20

> AEROSPACEPräzisions-Lohnfertigung:Mit Standardmaschinen zuPremiumqualität // Seite 28

> CAM-SYSTEMEVirtuelle Maschine:20 Prozent schneller rüstenbei Neuteilen // Seite 78

www.HaasCNC.com

CeramTec GmbH Geschäftsbereich SPK- Werkzeuge Hauptstraße 56 Germany - 73061 Ebersbach/Fils E-Mail: [email protected] www. spk-tools.de www.ceramtec.com

Special reprint from WB Werkstatt+Betrieb 3/2014

© Carl Hanser Verlag, München. 2014. All rights including reprinting, photographic reproduction and

translation reserved by the publishers.Internet-PDF-Datei. Diese PDF Datei enthält das Recht zur elektronischen Verbreitung.

Page 2: Johannes Schneider and Tobias Hering Efficient machining ...

> Milling2 S P E C I A L

bination of ceramics and PCBN for fin-ishing now allow optimization strategiesto be adapted for milling of GJS and GJLworkpieces. Rough face milling , finish-ing milling and milling of shoulders andslots may now be performed at high ma-chining speeds, cutting down machiningtime. New milling tool concepts further-more allow special machining methodssuch as high feed, helical milling andplunge milling.

High feed Milling Tool

for high chip removal rate

The high feed BFL milling tool range allowsparticularly high feed and metal removalrates. They have five to seven inserts for di-ameters D = 63 to 100 mm and an axial rakeof +5° to hold positive SPHX130612-T in-

serts. Maximum permissible rotationalspeeds are n = 13,000 rpm for D = 63 mmand n =8,000 rpm for D = 100 mm. Therecommended range for cutting speeds andfeed per insert is vc = 600 to 1,400 m/minand fz = 0.14 to 0.8 mm respectively.When face milling GJS workpieces withSiAlON ceramics, the small effective en-tering angle of 15 ° at moderate depths ofcut up to ap = 2.6 mm maximum will al-low feed speeds up to vf =18 m/min. Thecutting performance is achievable on ma-chining centers with drive power P = 25to 30 kW. A cutting insert with ZZ Geom-etry 88Z150 may be used to achieve par-ticularly high workpiece surface qualities.Apart from high feed face milling, the sys-tem BFL is also the solution to helical andplunge milling (Picture 1).

Efficient machining of GJL and GJS materials

Experience new limits whenmilling with ceramics and PCBNCeramics – specifically SiAlON ceramics – together with powerful milling tool inno-

vations, offer alternatives to machining based on traditional tungsten carbide cutting

materials. Their economy is based on increased cutting speeds and feed rates offer-

ing shorter machining times.

> Innovative tooling systems and high-ly effective cutting materials togetherform the basis for optimal economic ma-chining of GJL and GJS materials. All thecomponents of the machining systemsuch as the cutting insert, tool carrier andtool geometry must be taken into ac-count, along with the machining strate-gy and cutting data, the material and fi-nal shape of the workpiece. This holisticprocedure will guarantee optimal pro-ductivity and cost-effective productionper workpiece.

New milling cutter developments andnew ceramic cutting materials, or a com-

BY JOHANNES SCHNEIDER

AND TOBIAS HERING

High feed milling (left) and helix milling (right) with milling tools series BFL1

pict

ures

: Cer

amte

c

© Carl Hanser Verlag, München WB 3/2014

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Page 3: Johannes Schneider and Tobias Hering Efficient machining ...

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MANUFACTURERi

Ceramtec GmbH73061 Ebersbach/FilsTel. +49 7163 166239www.ceramtec.de www.spk-tools.de

Picture 2 shows the BFL milling tool per-forming a plunge milling operation,achiev-ing a very high chip removal rate. Themilling tool is used here with axial feed, tomachine the contours of a GJS block (GGG50) rapidly. The BFL milling tool with sixinserts has a diameter of D = 80 mm. Theeffective entering angle in axial direction is75°. With a cutting width (radial depthof cut) of approx. ae = 8 mm and a feedper tooth of fz = 0.2 mm, an axial feedspeed of 2.4 m/min may be achieved. Thefeed speed is limited by the available ma-chine power. Several milling passes in theaxial direction ensure the required chip re-moval rate. The final surface quality isachieved with a finishing milling tool in alater operation. A mass of 13 kg of chipsper component may be reliably removedin production.

Finishing with adjustable Milling

Tools and combinations of

cutting materials

Milling tools with partially adjustablepockets or seats are capable of achievinghigh surface qualities during finishingmilling. The milling tool series PDK areoffering one to three adjustable inserts,de-pending on diameter, designed to fit in-serts made of ceramics, PCBN or Cermet(entering angle 90°). The limited numberof adjustable inserts has economic advan-tages and simplifies the handling and ad-justment of the cutter.The design also pro-vides for the finishing inserts to be set backradially and stand proud of the highest cut-ting position of a roughing insert by a few

thousands of an inch.. This ensures thatthe finishing insert will machine for sur-face quality on the face only. The geomet-rical layout of the milling tool also enablesa cost-optimized design of the finishing in-serts with a special fine-finishing featur-ing eight cutting edges.

The non-adjustable cutting inserts aremounted at 88 ° entering angles. Theyhandle the main chip-removal work. Theoption of fitting the milling tool withPCBN inserts for finishing only reducescosts considerably. Nevertheless it en-sures that the required high surface qual-ity is achieved. The user will realize fur-ther cost benefits by using finishinginserts made of mixed ceramics ratherthan PCBN. The milling tool and insertgeometries are designed to allow easy ex-change of cutting materials in these po-sitions (Picture 3).

For the finishing process, the PDKmilling cutter series offers many optionswhen selecting the cutting material, op-tions such as ceramics/ceramics, ceram-ics/PCBN, and Cermet/Cermet are allpossible. Depths of cut ap = 0.2 to 0.5 mmat feeds per tooth of fz = 0.14 to 0.30 mmare normally used. Cutting speeds rangefrom vc = 400 m/min (with Cermets) to 1200 m/min (with ceramics or PCBN cut-ting materials).

Using adjustable

cutters to cut machining

time in half

Picture 4 shows a typical finishing appli-cation: machining of the sealing surface of

a GJL crankcase. A milling cutter typePDK, diameter 125 mm, with 14 inserts isshown.The non-adjustable insert seats useSiAlON inserts geometry SNGN120412-Tand the adjustable PCBN inserts has a finefinishing geometry SNHX120412T125(grade WBN115). The depth of cut wasap = 0.5 mm, the cutting width was ae

= 85 mm and the feed per tooth wasfz = 0.18 mm. A feed speed of vf = 5m/min was achieved at a cutting speed ofvc = 900 m/min. Dry cutting was used.Compared to previous machining basedon tungsten carbide, the machining timewas reduced from 54 to close on 24 s – acritical operation in this case. The surfacequality achieved was in the range Ra = 0.5to 0.9 µm. The use of ceramics/PCBN in-serts virtually doubled the tool life com-pared to conventional machining withtungsten carbide inserts.

The results were similar in a case of fin-ishing milling of the lateral surfaces of aV16 truck cylinder block (Picture 5). APDK milling cutter, diameter 200 mm, wasused here, with 16 inserts, two of whichwere adjustable finishing inserts. The as-sembly was a combination of SiAlON andmixed ceramics (for finishing inserts). Thedepth of cut was ap = 0.5 mm and the cut-ting width ae = 160 mm.Although the ma-

The BFL type series milling tools can offer a very highmetal removal rate for plunge milling of GJS-500 blocks2 PDK finishing milling tool with adjustable inserts and mixed

ceramics/PCBN tipping for high surface quality3

WB 3/2014 www.werkstatt-betrieb.de

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Page 4: Johannes Schneider and Tobias Hering Efficient machining ...

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WB 3/2014 www.werkstatt-betrieb.de

chine limits allowed only a moderateincrease in cutting speed compared to for-mer tungsten carbide/PCBN combina-tion, the fine-finishing geometry of thefinishing insert and the additional optionof increased feed per tooth allowed themachining speed to be more than doubled.The machining time for this operationdropped from 4.3 to 2 min., with clearlyimproved surface quality (Ra = 0.60 µm)and at the same tool life quantity per cut-ting edge.

Milling with polygon

cutting inserts

Certain milling cutter series also makeprovision for the use of polygonal cuttinginserts with between 12 (HNGX 10…, 6-sided) and 16 cutting edges per insert (ON-HQ 06…, 8-sided), depending on config-uration. The type of the milling used isdetermined by the stock to remove.Millingcutters series PFK-HN are used for actualdepth of cut up to 6 mm. For depth of cutup to 4 mm however, milling cutters series

PFL-ON can offer an even larger numberof cutting edges to use.Both series are usedfor milling GJL workpieces at cuttingspeeds up to vc = 1 200 m/min and feedsper tooth up to fz = 0.3 mm. PFL-ON areavailable in diameters ranging from D =63 (6 teeth) to 160 mm (13 teeth). Theirrange of applications extends up to millingof GJL and GJS parts at medium depth ofcut,where high machining speeds and cut-ting insert efficiencies promise improvedefficiency and economy. Diameters ofmilling tools PFK-HN range from D = 80(8 teeth) to 160 mm (16 teeth). The seriesis designed for large chip cross sectionsand high metal removal rates. The ZZgeometry 47Z125 is furthermore availablefor the 6-sided version for particularlyhigh surface demands.

Minimal wear after 150 minutes

of machining GJL 250

Picture 6 shows a typical application – aGJL 250 compressor case machined witha milling cutter series PFK-HN. Roughing

of the surfaces was carried out with a cut-ting speed of vc = 800 m/min, a feed pertooth fz = 0,16 mm and a depth of cutap = 3 mm. The application of the poly-gon HNGX100512T cutting insert in-creased the previously eight cutting edgesto twelve per insert. Even after more than150 min. of machining, the SiAlON gradesSL808 exhibited only minimal wear on thecutting edge.

SiAlON ceramics also have benefitswhen milling GJS workpieces. A millingcutter series PFL-ON of 80 mm diame-ter with seven cutting inserts ON-HQ060616-T of the SiAlON grade SL808(Picture 7) was used for roughing thesealing surface of a GJS 700 cylinderhead. A tungsten carbide milling cutterwith nine inserts was the competition.No coolant was used. The cutting widthwas ae = 40 mm and the depth of cut justunder ap = 3 mm. Using a tooth feedfz = 0.21 and with the cutting speed in-creased only moderately to vc =400 m/min, the machining time perworkpiece was virtually halved to ca. 5min – despite the reduced number ofteeth compared to the tungsten carbidemilling cutter. The tool life quantity perinsert was also slightly increased by about10 percent.

Prospects of a wide range

of applications

Ceramics in conjunction with powerfulmilling tool concepts – especially SiAlONceramics – can offer interesting alterna-tives to conventional tungsten carbidebased milling of GJL and GJS work-pieces. High cutting speeds and feeds

Finishing milling the sealing surface of acrankcase using a ceramics/PCBN tippedPDK milling tool

4 Finishing milling the lateral surface of aV16 truck crankcase using a PDK millingtool and fine-finishing insert geometry

5

GJL 250 compressor case (left), machined using the PFK-HN milling tool and SiAlON grade SL808, also showing the state of wear ofthe inserts after 150 minutes of milling (right)6

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Page 5: Johannes Schneider and Tobias Hering Efficient machining ...

> Milling5 S P E C I A L

© Carl Hanser Verlag, München WB 3/2014

translate to short machining times, yetoffer highly reliable production. Imagi-native tool design and combinations ofceramic and PCBN cutting materials tosuit the application, enables finishingmilling with the high surface qualitiesdemanded. Holistic treatment of eachapplication and careful coordination ofcutting material, tool concept and ma-chining strategy will ensure great econ-omy and productivity at favorable pro-duction costs per piece. This opens upnew options for application in a widerange of machining of casings for the au-tomotive industry, in general mechani-

cal engineering and in gearboxes anddrives. ❚

> WB110926

A PFL-ON octagon milling tool managedto cut roughing time of a GJS 700 cylinderhead almost in half, compared to a tungstencarbide milling tool

7

Dipl.-Ing. Johannes Schneider is Manager ofStrategic Marketing in the SPK Tool Divisionof Ceramtec GmbH in Ebersbach/[email protected]

Tobias Hering is the Product Manager Mil-ling in the SPK Tool [email protected]

LITERATUR

1 J. Schneider, R. Ben Amor: Schnell und hoch-

produktiv beim Fräsen. In: WB Werkstatt+Be-

trieb 12(2006)139, S. 12-14

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