Edge Rounding and Polishing of Tools Process and application Straubenhardt, 2 June 2008 Dipl.-Ing. (FH) Martin Bott OTEC Präzisionsfinish GmbH Dieselstrasse Straubenhardt

2.) Processes for rounding the cutting edges - Sandblasting - Brushing - VIBRATORY DRAG FINISHING 2

3 3.) Drag finishing

4 3.1) Process description Since the workpieces can not come into contact with each other, the result is a finishing process which is gentle on the workpiece surfaces. In this process, it is impossible for the workpieces to collide. The drag finishing process enables multistage processes such as fine grinding and polishing to be carried out.

3.2) Drag finishing - processing goals 3.2.1) Edge rounding achieves the following:  Removes grinding burs  Stabilizes the cutting edge  Gives uniform surface structure at the cutting edge  Extends tool life  Gives better bonding for coatings  Reduces jaggedness at the cutting edge  Reduces chipping at the cutting edge  Reduces build-up edges 5

3.2.1) Edge rounding Example of a die 6

) Edge rounding Example of an end milling cutter Workpieces: Chip removing tools of all kinds requiring edge rounding. Material:All materials used, but mainly carbides Processing goal: Rounding of the primary and secondary cutting edges for immediate use or prior to coating Media: HSC granulates in the case of required edge rounding of up to 10 µm SIX granulates in the case of required edge rounding of up to 30 µm QZ 1-3 in the case of required edge rounding of more than 30 µm Direction of rotation: 100% clockwise Processing time:1 – 20 minutes depending on degree of edge rounding required

) Edge rounding Example of an end-milling cutter

) Edge rounding unprocessed cutting edge

) Edge rounding processed cutting edge

3.2) Drag finishing - processing goals 3.2.2) Polishing achieves the following:  Improves the surface quality  Reduces roughness  Improves chip flow  Improves flow characteristics when drawing  Extends tool life  Gives better bonding for coatings  Reduces cutting forces needed  Reduces tendency to cold welding 11

3.2.2) Polishing Example of forming dies 12 Unbearbeitet Before processingAfter initial grinding After polishing

3.2.2) Polishing Example of a forming tool unprocessed processed 13

3.2.2) Polishing Example of a forming die 14

3.2.2) Polishing Example of a tool holder 15

3.2) Drag finishing - processing goals 3.2.3) Droplet removal achieves the following:  Improves surface quality  Reduces roughness  Improves chip flow  Improves flow characteristics when drawing  Extends tool life  Reduces cutting forces required  Creates microscopic lubricant pockets 16

3.2.3) Droplet removal Example of an end milling cutter 17

) Example: smoothing of a coated surface As a result of the PVD coating process, droplets (tiny balls of material embedded into the surface) often become lodged in the protective coating. This in turn causes friction. The drag finishing process removes these droplets. The miniature “pockets” that remain improve the wetting properties of the surface. These “pockets” serve to store lubricant.

3.3.1) Machine parameters )Speed )Processing time )Direction )Immersion depth )Angle of holder )Control functions ) Key factors

3.3.1) Machine parameters Overview 20 Parameter input

) Speed Higher speeds give greater rounding values N.B. The rounding at corners increases more quickly 21

) Effect of speed

) Processing time and direction The processing time and the direction of rotation can be controlled during the process. 23

) Effect of processing time Longer processing times give higher degrees of rounding. The increase in rounding values is not linear to the processing time. N.B. The rounding at the corners increases faster than at the edges. Depending on the media, the maximum value can vary. 24

) Effect of processing time

) Effect of direction The choice of direction of rotation affects the flow of media against the workpiece. A change of speed is absolutely essential for homogeneous media flow and uniform processing. Uneven finishing, which is more pronounced on one side than the other, is often undesirable. Differences between the workpiece and the speed or direction of the rotor affect have an effect on edge rounding. (Low workpiece rotations give a uniform finish) (High workpiece rotations give a more pronounced rounding of the corners)

) Immersion depth Different immersion depths can be achieved by preselecting the operating modes. 27

) Effect of immersion depth Because of the static pressure, the contact pressure of the media increases with the immersion depth. In general we can say that a difference of 100 mm in the vertical results in a difference of about 25% in the amount of material removed. In the case of lightweight media with a low bulk density, this effect is less pronounced.

) Effect of the angle of the holder and/or workpieces An angled position for the holders and/or the workpieces offers advantages for the processing of the workpiece face and of large flat areas. 29

) Control functions In addition to the adjustable machine parameters, the following additional parameters are monitored: -Media life for 5 different, freely selectable, media types -Workpiece length (Sensor for avoiding collisions) -Media level (Sensor for measuring the level) Goal: reliable processes

3.3) Key factors 3.3.2) Media H granulates polishing HSC granulates gentle edge rounding µm K granulates gentle edge rounding < 15 µm SIX granulates more pronounced edge rounding up to 30 µm QZ granulates more pronounced edge rounding over 30 µm 31

3.3.2) Media H granulates - Finishing of HSS tools -Polishing, gentle deburring -Gentle edge rounding -Low rate of chip removal, depending on grinding or polishing additive 32

) Media HSC granulates -Finishing of HSS and carbide tools -Polishing of coated tools and removal of droplets -Smoothing and polishing of carbide tools -Edge rounding of carbide materials up to max. 15 – 20 µm -Removal of solder residues -Rate of chip removal medium to high depending on grain size -Creates very high surface qualities (Rz 0.5 for an initial value of Rz 2.5)

) Media K granulates -Finishing of HSS and carbide tools -Polishing of coated tools and removal of droplets -Smoothing and polishing of carbide tools -Edge rounding of carbide materials up to max. 10 – 15 µm -Natural granulate bonded with PP1 polishing powder

) Media SIX granulates -Finishing of carbide tools -Deburring and edge rounding of HSS tools -Smoothing and edge rounding of chip removing tools in carbide up to max. 30 µm -Finishing of inserts -High rate of chip removal -Creates high quality surfaces

) Media QZ granulates -Finishing of carbide tools -Gives especially high degree of edge rounding over 30 µm -Rate of chip removal approx. twice as high as with SIX granulates -Carborundum with grain size of 1-3 mm -Very high rate of material removal -In the case of small edge radii under 30 µm; gives rougher surfaces than SIX or HSC granulates.

) Media - Changing the media It is a quick matter to change the media by simply changing the process container. This makes it possible to carry out multi-stage processing very efficiently. The drag grinding or drag finishing process is the only type of vibratory grinding that enables targeted surface finishing such as deburring, grinding, polishing and targeted edge rounding – all from the same machine.

3.3.2) Media - Changing the media 38

3.3) Key factors 3.3.3) Workpiece ) Workpiece size ) Workpiece geometry ) Workpiece materials 39

) Effect of workpiece size In the case of single-drive DF machines, the transmission ratio between rotor and workpiece can not be adjusted. Here the diameter accounts for only about 10% of the effect. In the case of dual drive versions with two motors, the satellite speed can be set independently of the rotary speed. Areas of application: Thread-cutting taps  high satellite speed, low rotor speed Carbide drills  low satellite speed, high rotor speed In the case of high satellite speeds, the diameter of the workpiece has a much greater effect than it does with low satellite speeds.

) Effect of workpiece geometry Larger workpieces displace more media, which ‘glides’ over the edges and removes more material. The processing has little effect on the central areas of large, flat workpieces. “Scooping” workpieces push the media away from themselves. This reduces the effect of processing. Inner surfaces can be processed to a limited extend. With small bore holes, the media grain size should not be too large.

) Effect of workpiece materials Workpieces made from hard materials can be rounded more accurately than soft ones. 42

3.4) Machine specifications 43 DF-3DF-4DF-5DF-6DF-10 Maximum immersion depth 250 mm Holder connections Maximum workpiece diameter 250 mm210 mm250 mm210 mm200 mm Maximum holder weight 15 kg Adapter interfaces for 4-way / 6-way holders 12 / 1816 / 2420 / 3024 / 3640 / 60 Maximum workpiece diameter with 4-way / 6-way adapter 85 mm 55 mm 82 mm 55 mm 85 mm 55 mm 82 mm 55 mm 65 mm 55 mm Maximum workpiece weight with adapter 0.5 / 2 kg Extra drive optional Connection voltage400 V Power requirement depending on configuration 2-3 kW 3 – 5 kW 3.5 – 7 kW

3.4) Machine specifications Independently rotating holder systems Holder type 4-way 2B up to 500 g Holder type 6-way 2B up to 500 g Holder type 4-way 2B up to 2 kg Holder type 6-way 2B up to 2 kg Holder type 4-way 2B SL Holder type 6-way 2B SL Special types on request 44

4.) Outlook DF-3/4 and DF-5/6 with angled holders 45

46 4.) Outlook DF-6 Automation