LUREN Precision Co.LTD.

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1 Precision Co.LTD. Head Office: Li Hsing Factory Location: Hsin Chu Science Park - Taiwan Head Office: Via Marconi, 8 Viganò Brianza (LC)- Italy

2 Luren Hob Resharpening Machines CNC Hob Resharpening Machines producing by Luren LHG LHS LHG LHG 1520

3 With this presentation we want to inform about: Basic of hob resharpening operation Working condition Description of Luren hob resharpening machines The most important characteristic of Luren resharpening machines are: High performances High tech design and components High flexibility Easy to use Low cost

4 Basic technical information about of hob resharpening operation The accuracy of the hobbing process to a large extent on good hob resharpening and the performance of hob is very much affected by the type of resharpening carried out. If a hob is resharpened under incorrect working condition, it may at times result in tooth breakage. We examine now some aspects of this important operation. The maintenance of the hob is a very delicate operation that must be carried out by a efficient machinery and modern equipment. First examine the definition of the errors that may be generated when resharpening according to the DIN 3968 normative.

5 The error of profile and position of the tooth face u = the movement of the resharpening face in relation to the radial plan when sharpening with a positive rake angle. In radial sharpening the u value is zero. h = useful tooth depth e = profile error found Gash radial alignment (microns) Module 0, ,6 1,6-2,5 2, ,3 6, ,1-16 AA Class A B

6 Error of profile generated on the workpiece Negative rack angle Positive rack angle

7 The indexing error between two consecutive flutes Must be measured half way up the tooth Indexing between gashes (two adjacent teeth) (microns) Module 0, ,6 1,6-2,5 2, ,3 6, ,1-16 AA Class A B

8 Spacing between two non adjacent flutes This is the cumulated indexing error of the flutes Maximum indexing error between any two teeth (microns) Module 0, ,6 1,6-2,5 2, ,3 6, ,1-16 AA Class A B

9 Error of profile generated on the workpiece Indexing error of the flutes produces irregular profile

10 The direction error of the flutes This error is measured in a length of 100 mm Accuracy of gashes over 100 mm (microns) Module 0, ,6 1,6-2,5 2, ,3 6, ,1-16 AA 50 Class A 70 B 100

Interference between grinding wheel and hob Hob Gear Sharpening a hob with helical gashes using a grinding wheel that has a rectilinear cutting line, the face that is generated will be slightly

11 Interference between grinding wheel and hob Hob Gear Sharpening a hob with helical gashes using a grinding wheel that has a rectilinear cutting line, the face that is generated will be slightly crowned because of the interference of the grinding wheel with the helical gash. The larger the helix angle of the gash and the larger of the diameter of the grinding wheel, the greater this convexity of the resharpening face will be. This is why resharpening machines which works helical hobs must be equipped with a special dressing unit to profile the grinding wheel, so as to generate the same convexity and compensate for the interference phenomenon. A hob with a convex cutting face will produce a gear tooth with more material on the tip and at the root.

Working condition in resharpening The u movement of the grinding wheel in relation of the hob depends both on the rack angle and on the hob diameter where

12 Working condition in resharpening The u movement of the grinding wheel in relation of the hob depends both on the rack angle and on the hob diameter where the following applies: a)- Movement below centre which generates a positive cutting angle b)- Movement above centre which generates a negative cutting angle

Working condition in resharpening Ra = 0,15 Rz = 1,12 The sharpened surface roughness must be as low as possible so that the cutting edge is not irregular.

13 Working condition in resharpening Ra = 0,15 Rz = 1,12 The sharpened surface roughness must be as low as possible so that the cutting edge is not irregular. If this were the case, wear and chipping would form with more ease. The tolerable roughness is a maximum of R a = 0,20 microns If the roughness is higher the wear of the cutting face proceeds faster Ra = 0,35 Rz = 2,18 In order to obtain a lower roughness the working conditions must be chosen properly

14 Working condition in resharpening The roughness is strongly influenced by grain size of the grinding wheel abrasive The grain size is identified by a number, but this number has a different meaning for Aluminium Oxide and CBN (or Diamond) abrasive The two following slides show the standard size

15 Grit specification of Aluminium Oxide abrasive Approximate diameter of the grain Indicative FEPA Number Diameter in mm Diameter in inch Indicative FEPA Number Diameter in mm Diameter in inch 36 0,500 0, ,080 0, ,350 0, ,070 0, ,300 0, ,060 0, ,250 0, ,050 0, ,210 0, ,040 0, ,180 0, ,030 0, ,150 0, ,020 0, ,130 0, ,014 0, ,100 0, ,010 0,0004

16 Grit specification of Diamond and CBN abrasive Diamond FEPA DIN 848 CBN FEPA DIN 848 Nominal width of the mesh (µm) ISO 565 USA - ASTM E11-70 (Mesh) Mesh per 1 Japan JIS dimension µm Russia Gost dimension µm D251 B D213 B D181 B D151 B D126 B D107 B D91 B D76 B D64 B D54 B D46 B B D

Working condition in resharpening Resharpening with CBN grinding wheel of High Speed Steel Hobs Some manufacturers prefer to remove all of the stock (from 0,20 to 0,40 mm) in just one pass using a

17 Working condition in resharpening Resharpening with CBN grinding wheel of High Speed Steel Hobs Some manufacturers prefer to remove all of the stock (from 0,20 to 0,40 mm) in just one pass using a reduced feed speed Cutting speed = 30 m/sec Feed speed = 200 mm/min Cutting depth = 0,20 mm Size of grit = Concentration = Resin alloying element Due to the low feed it s produced a large amount of heat because the wheel works in the same area for a long time

Working condition in resharpening Resharpening with CBN grinding wheel of High Speed Steel Hobs The following working condition are suggested with CBN wheels This type of grinding wheel generally has

18 Working condition in resharpening Resharpening with CBN grinding wheel of High Speed Steel Hobs The following working condition are suggested with CBN wheels This type of grinding wheel generally has a diameter of around 150 mm. Phase Stock removal per stroke Feed mm/min Roughing 0,03 mm 2500 Pre-finishing 0,01 mm 2500 Finishing 0,005 mm 2500 Fast passes with limited stock removal and change of gashes so as to prevent the grinding wheel from heating up the hob teeth.

19 Working condition in resharpening Resharpening with Diamond grinding wheel of Carbide Hobs The following working condition are suggested with Diamond wheels for carbide hobs This type of grinding wheel generally has a diameter of around 150 mm. Cutting speed = 30 m/sec Phase Stock removal per stroke Feed mm/min Roughing 0,03 mm 2000 Pre-finishing 0,01 mm 900 Finishing 0,005 mm 600 Size of grit = 64 Concentration = 100

Working condition in resharpening Resharpening with Ceramic grinding wheel (HSS Hobs) The following working condition are suggested with ceramic wheels Grinding wheels have a standard diameter in a

20 Working condition in resharpening Resharpening with Ceramic grinding wheel (HSS Hobs) The following working condition are suggested with ceramic wheels Grinding wheels have a standard diameter in a range from mm. The size of the grit may range from 60 to 80 Cutting speed = 30 m/sec Feed speed = Cutting depth = 0,03 0,05 mm (for modules up to 3 mm) For modules over 3 mm cutting depth reduced to 0,01 0,02 mm. The same characteristics are applied during the return stroke Coolant must be abundant

21 Working condition in resharpening Coolant must be abundant A very thin emulsifying oil which has strong cooling and rinsing abilities although care must be taken not to cool the work area too drastically. Even when the amount of material removed is limited and the feed is quick, notable temperatures develop at the point of contact. If this area were cooled too violently by the liquid jet, the change in temperature would be too drastic and this could be damaging. It is better to use a low viscosity oil which has good cooling abilities but which is a little more gentle. The best oil must be a viscosity between 5 and 10 cst at 40 C In the Luren Hob resharpening machine, the capacity of the tank is 300 Liters. The quantity of the coolant in the working area is: 120 liters/min

22 Luren Hob Resharpening machines Luren is producing now four model of hob resharpening machines: Mod. LHG : universal hob resharpener for spur and helical hobs Mod. LHS 3040: simplified hob resharpener only for spur gashes hobs Mod. LHG 2540: universal hob resharpener with different capacity Mod. LHG 1520: resharpening machine for limited diameter hobs Four models with different performances and different price in order to optimize the cost of resharpening operation

23 Luren Hob Resharpening machines General characteristic CNC-FANUC with the last digital technology (mod. 21.iMB) Linear Motors and Direct Drive Motors High flessibility : resharpening spur and helical hobs, HSS and carbide Hobs, with ceramic and CBN wheels. The machines can be used like a profile gear grinder or like a shaper cutter grinder. TFT colour flat screen 26,4 cm (10,4 ) Graphical operator guidance Dialog imput tailor to hob resharpenig Dialog for hob-related programming CNC with Windows based operating system combined with PC for program calculation and information storage Quickly and easy change of grinding spindles High rigidity

24 Luren Hob Resharpening machines High Rigidity Use high rigidity T shape structure that is used on CNC Relieving Profile Grinding Machine Selecting high quality steel casting, ensuring stable productivity

25 Luren Hob Resharpening machines Precisely Driven System High-precision, high efficiency, no backlash Minimum mechanism linkage Lower heat generated Lower induced vibration Build-in Motor Direct Drive Torque Motor Linear Motor

Rated Torque : 1200 Nm 260 Nm Rated Speed : 250 rpm 300

26 Work-piece Spindle Luren Hob Resharpening machines Direct Drive Torque Motor Low Speed High Torque -FANUC - Rated Torque : 1200 Nm 260 Nm Rated Speed : 250 rpm 300 rpm Absolute Accuracy : 15 arc-sec Repeat Accuracy : 1.3 arc-sec

27 Luren Hob Resharpening machines Oil Cooling Linear Motor No backlash, High reliability, Less components, Easy installation, Long Life-time. CNC Control System FANUC Motor MAX. Thrust 3000N

28 Luren Hob Resharpening machines Linear Motor vs. Ball-Screw Drive Linear Motor Air gap A =0.5mm Coil Magnet Coupling Ball-Screw Drive Servo motor Support Units Holder Support Units Ball screw Nuts Bracket for Ball Screw

3 Nm) 21 Kw (35 Nm) Speed (rev/min) 2.000 10.000 2.000 10.000 CBN wheel =.

29 Luren Hob Resharpening machines Build-in Motor of Grinding Spindle Liquid cold Standard Standard Rated capacity 4.6 kw (5.3 Nm) 21 Kw (35 Nm) Speed (rev/min) CBN wheel =.D. 150 mm 150 mm Dressable grinding wheel 125 mm 230 mm

30 Luren Hob Resharpening machines Arbor of Grinding Wheel Easy changeable (BT30) Dressable Grinding Wheel CBN Grinding Wheel Diamond Grinding Wheel HSK63A

31 Luren Hob Resharpening machines CAM Integrated System IPC Ethernet Fanuc Control

32 Luren Hob Resharpening machines Latest CNC Control CNC Control Integrated with Standard PC - Windows R XP based environment - User oriented operator interface - Easy to upgrade the grinding program - Combine with PC for program calculation and information storage.

33 Luren Hob Resharpening machines Smart Dialogue Interface Dialog input tailor to workpiece

34 Luren Hob Resharpening machines (Standard Type) LHG-3040 A-axis N-axis (D.D.-AC Servo Motor) X-axis B-axis Dressing Unit Y-axis Tailstock Grinding-Wheel Z-axis(Linear Motor )

35 Luren Hob Resharpening machines (Standard Type) LHS-3040 N-axis ( Build-in Motor) A-axis (DD-AC Servo Motor) Y-axis Tailstock Grinding-Wheel Z-axis Linear Motor

36 Luren Hob Resharpening machines LHG LHS LHS AXIS Dimension Front Width: 4074mm Side Long : 3876mm Height : 2443mm Weight : 7000Kg

37 Luren Hob Resharpening machines LHG LHS-3040 Main specification Max. workpiece diameter: 250mm Min. workpiece diameter: 20mm Max. gash grinding depth: 35mm Max. number of lead: 99 Max. between center distance 550mm Max. grinding slide stroke: 400mm Max. grinding wheel speed: 10000rpm CNC control system FANUC 21i-MB

38 Luren Hob Resharpening machines LHG-2540 Min./Max.workpiece Max. grinding length Max. module Max. grinding depth 20mm / 250 mm 350 mm M10 30 mm Min./max. number of gashes 1/99 Max. gash lead angle Min./max. gash lead Min./max. distance between centers ± / 80~450mm Max. grinding axial slide travel Max. workpiece weight 400 mm 30 kg

39 Luren Hob Resharpening machines Min./Max. grinding wheel diameter : 70/150 mm Max. grinding wheel speed : 10,000 rpm Max. grinding wheel width : 20 mm motor : 4.6 kw(7.5kw) Voltage : 3Ø/220 V Voltage : 40 Amp Ambient temperature : 10 C~40 C Relative humidity: 85% Total connected load of machine : 10 kva CNC control: FANUC 0iMD Overall dimension(lxwxh) : 2350 x 3600 x 2000 mm Weight : 4000 kg LHG-2540

grinding length 20 mm / 150 mm 30 mm / 125 mm 300 mm Max. module M8 (DP3.175) Max. grinding depth 30 mm Min./max.

40 Luren Hob Resharpening machines LHG-1520 Main Specification Min./Max.workpiece diameter (CBN wheel) Min./Max.workpiece diameter (Ceramic grinding wheel) Max. grinding length 20 mm / 150 mm 30 mm / 125 mm 300 mm Max. module M8 (DP3.175) Max. grinding depth 30 mm Min./max. number of gashes 1/99 Max. gash lead angle ±35 Min./max. gash lead 1000 / Min./max. distance between centers 80~500mm Max. grinding axial slide travel 400 mm Max. workpiece weight 30 kg

grinding wheel width: 20 mm Capacity of the grinding wheel drive motor: 4.

41 Luren Hob Resharpening machines LHG-1520 Min./Max. grinding wheel diameter : 80/150 mm Max. grinding wheel speed : 10,000 rpm Max. grinding wheel width: 20 mm Capacity of the grinding wheel drive motor: 4.6 kw Voltage: 3Ø/220 V Current requirement: 30 Amp Ambient temperature: 10 C ~40 C Total connected load of machine: 15 k VA CNC control: Fanuc Overall dimension (LxWxH) : 2350 x 3600 x 2000 mm Weight : 4000 kg

42 Luren Hob Resharpening machines LHG-1520

43 Luren Hob Resharpening machines Example of spur hob LHG-3040 Module 2.35 Pressure Angle ' 00" Flute Lead Angle ' R Gash Lead 0 No. of Start 5 No. of Gashes 17 Outside Diameter 90 mm Length 190mm Gash Depth mm CBN grinding wheel

Luren Hob Resharpening machines Example of helical gashes hob LHG-3040 Module 12.

44 Luren Hob Resharpening machines Example of helical gashes hob LHG-3040 Module Pressure angle 19 45' 00" Flute lead angle 16 45' 00" R Gash lead 1332L No. of start 3 No. of gashes 9 Outside diameter 165 mm Length 200 mm Gash depth 29.5 mm Ceramic grinding wheel

45 Luren Hob Resharpening machines Example of helical gashes hob LHG-3040 Module Pressure angle Flute lead angle Gash lead 15 13"10" 40 27" 00" L R No. of start 6 No. of gashes 5 Outside diameter 53.1mm Ceramic grinding wheel

46 Luren Hob Resharpening machines Example of helical gashes hob Hob Data O.D. x Length 90 mm x 190mm Module 2.35 Lead angle 8 9 " R Pressure angle 20 Gashes 17 Material ASP30 Grinding Data Grinding Wheel Grinding Speed Removal In-feed speed Cutting time CBN 5800 rpm 0.15m m 3000mm/min 9 min. 33 sec.

47 Luren Hob Resharpening machines Example of special worm hob LHG-3040 m:1.193 No. of start: 3 Lead angle: 17 21'00" Pressure angle: 19 05" 24" Lead of gashes: L Outside diameter: 15mm Ceramic grinding wheel

48 Luren Hob Resharpening machines Example of carbide hob Hob Data O.D. x Length 32mm x 60mm Module Lead angle 1 54 " R " LHG-3040 & LHS-3040 Pressure angle 20 Gashes 12 Material carbide Grinding Data Grinding Wheel Grinding Speed Removal In-feed speed Cutting time Diamond Wheel 7200 rpm 0.05m m x 4 trip =0.2 mm 1000mm/min 12 min

49 Optional -LHG-3040 / LHS-3040 Helical Shaper Cutter Spur Shaper Cutter Module: Inner Hole: 44.90mm Lead Angle : Sharpening Angle :28 Shank Shaper

Hob Sharpening Machine -- Optional Shaper Cutter O.D. 157.78 mm Module 1.88 Lead angle 35.

50 Hob Sharpening Machine -- Optional Shaper Cutter O.D mm Module 1.88 Lead angle Gashes 66 Sharpening Angle 28 Material ASP30 Inner Hole Diameter Grinding Data Grinding Wheel Grinding Speed Removal In-feed speed Cutting time 44.9m m Abrasive Wheel 2000rpm 0.03m m x 10trip=0.3mm 5000mm/min 27 min 30 sec

51 Hob Sharpening Machine (OPTIONAL) LHG LHS-3040 Gear Grinding Spline Grinding

52 Thank you for your attention

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