Substitution of grinding processes in crankshaft machining – NILES-SIMMONS Industrieanlagen GmbH introduces new technology hard milling

Dipl.-Ing. Michael Kamm, Dipl.-Ing. Eric Rein­warth, NILES-SIMMONS Indus­trie­an­la­gen GmbH

In today’s mar­ket place, the most important dri­ving forces in the field of auto­mo­tive indus­try are sus­taina­bi­lity, resource con­ser­va­tion and eco­no­mic effi­ci­ency. These trends do not only drive the deve­lo­p­ment of new inno­va­tive tech­no­lo­gies and final con­fi­gu­ra­ti­ons for new pro­ducts, but also push the ever-incre­asing requi­re­ments of the manu­fac­tu­r­ers to find new cost-effi­ci­ent manu­fac­tu­ring con­cepts for the pro­duc­tion of the exis­ting com­pon­ents in production.

In order to meet these mar­ket requi­re­ments, NILES-SIMMONS have deve­lo­ped the new tech­no­logy “hard mil­ling” for the machi­ning of har­dened cranks­hafts for truck‑, con­s­truc­tion machi­nery- and agri­cul­tu­ral machi­nery engines.

This tech­no­logy allows for the sub­sti­tu­tion of a grin­ding pro­cess for machi­ning of large cranks­hafts by the imple­men­ta­tion of an effi­ci­ent mil­ling pro­cess. In turn, the enorm­ous pre- grin­ding efforts, which had been requi­red for machi­ning of cranks­hafts after har­dening is remo­ved and the pre­pa­ra­tion for the finish grin­ding pro­cess is per­fectly con­trol­led to reduce finis­hing requi­re­ments to a minimum.

Hard mil­ling of a 6‑cylinder cranks­haft for trucks

 

The pro­cess is spe­ci­fi­cally adapted for the machi­ning of 4, 5, 6 and 8 cylin­der-cranks­hafts with a maxi­mum length of up to 1350mm and a maxi­mum fly­ing cir­cle of up to 310mm. It is available on both NILES-SIMMONS mil­ling cen­ters N20CM und N30CM.

 

NILES-SIMMONS Mil­ling-Cen­ter N30CM 

 

These spe­cial pur­pose machi­nes, which belong to the NILES-SIMMONS crank mil­ling (CM)- series, are inher­ently equip­ped with a distance bet­ween cen­ters of up to 2000mm tog­e­ther with a maxi­mum dia­me­ter of up to 780mm and carry out highly relia­ble dry-mil­ling machi­ning pro­ces­ses with extra­or­di­nary long-life pre­cis­ion at extre­mely high-pro­duc­tion levels. Thanks to their fle­xi­ble auto­ma­tion opti­ons, the machi­nes run with mini­mal ope­ra­tor inter­ven­ti­ons. The most favored loa­ding con­cepts are for ins­tance the work­piece loa­ding by over­head gan­try via an inte­gra­ted hatch­way or work­piece loa­ding by robot via the machine’s front doors.

For the imple­men­ta­tion of the spe­ci­fic pro­cess “hard mil­ling” for large cranks­hafts as a clo­sed pro­cess, the machi­nes are equip­ped with main- and coun­ter spind­les with a maxi­mum tur­ning moment of 930Nm (100%) each as well as two mil­ling units with maxi­mum tur­ning moment of 3350Nm (S1-100%) each.

 

Machine con­fi­gu­ra­tion NILES-SIMMONS N30CM for the pro­cess hard milling 

 

The mil­ling tools used are sup­plied by the com­pany ‘Inger­soll Werk­zeuge GmbH, with tool dia­me­ters of 700 – 800mm and a cut­ting width up to 95mm they are equip­ped with spe­ci­fi­cally deve­lo­ped cera­mic cut­ting inserts. By using these, the mil­ling pro­cess of the main- and pin bea­rings runs with a radial cut­ting depth of up to 0,5mm at hard­ness of up to 59 HRC. The cut­ting speeds applied are bet­ween 250 and 275m/min and the feed rates are set bet­ween 0,23 – 0,35mm. The tool con­s­truc­tion is pos­si­ble both in mono­bloc-design and  in cartridge-design.

 

Mil­ling tools with spe­ci­fic cera­mic cut­ting inserts of the com­pany ‘Inger­soll Werk­zeuge GmbH’

 

For clam­ping of the work­pie­ces, we use com­pen­sa­ting mil­ling jaw chucks in main and coun­ter spindle. Those spe­ci­fic, power-ope­ra­ted lever chucks with a dia­me­ter of 320mm, have a sen­si­tive adjus­t­ment of less or equal 20µm on the clam­ping dia­me­ter and con­se­quently allow a highly effi­ci­ent com­pen­sa­tion of dis­tor­tion due to the har­dening.  For addi­tio­nal back­ing, we use two self-cen­te­ring mil­ling ste­ady rests with pin loca­tor jaws.

On top of that, the machine has an inte­gra­ted touch probe for exact and pro­cess relia­ble iden­ti­fi­ca­tion of the work­piece position.

With that, dia­me­ter-accu­ra­cies of 25µm, round­ness-accu­ra­cies of 10µm and posi­tion-accu­ra­cies of the pin bea­rings of 0,1mm are accom­plished. As a result, the finish- grin­ding pro­cess is per­fectly prepared.

 

Inte­gra­ted touch probe for exact iden­ti­fi­ca­tion of work­piece position

 

Pro­gramming of the pro­cess takes place by use of the spe­ci­fi­cally deve­lo­ped crank mil­ling soft­ware of NILES-SIMMONS. This soft­ware allows for com­ple­tely inde­pen­dent pro­gramming for machi­ning of main- and pin bea­rings, cen­tric ele­ments, cheeks and spe­ci­fic cheek con­tours. The ope­ra­tor can easily imple­ment neces­sary cor­rec­tions by use of cor­re­spon­ding input fields and is extre­mely ope­ra­tor fri­endly. The ope­ra­tor can also import form cor­rec­tion tables directly from the mea­su­ring machine and by doing so the pro­gramming is easy and quickly completed.

The pro­cess runs enti­rely dry, wit­hout any pro­cess fluids and is the­r­e­fore much more sus­tainable than grin­ding pro­ces­ses, which had to be used up until now. Con­se­quently, the main­ten­ance requi­re­ments and manu­fac­tu­ring run­ning costs decrease significantly.

With the use of the new hard mil­ling tech­no­logy, the finish grin­ding requi­re­ments for machi­ning of large cranks­hafts can typi­cally decrease by up to 75 per­cent. The invest­ment costs for the num­ber of machi­nes decrea­ses remar­kably by up to 50 per­cent. Inte­gra­tion and adapt­a­tion of the machi­ning pro­cess into exis­ting manu­fac­tu­ring lines is easily pos­si­ble. Hard mil­ling alre­ady runs suc­cessfully within cranks­haft pro­duc­tion lines in the mar­ket and achie­ves pro­cess-relia­ble cycle times of six minutes.

 

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