The science of Machining Dynamics is the vibration or frequency of the tool point self-generated during machining often resulting in chatter. Understanding Machining Dynamics will have the SINGLE GREATEST IMPACT on your milling operations.

1. ©Copyright 2010 BlueSwarf LLC Introduction toMACHINING DYNAMICS BlueSwarf® Technical Series

2. The science of Machining Dynamics is the vibration or frequency of the tool point self-generated during machining often resulting in chatter. Understanding Machining Dynamics will have the SINGLE GREATEST IMPACT on your milling operations

3. 4/18/2010 To begin to understand machining dynamics, you must recognize that the cutting tool is part of an entire cutting system

4. 4/18/2010 The cutting tool is gripped in a toolholder 1

5. 4/18/2010 2 The toolholder is pulled into a spindle

6. 4/18/2010 3 The spindle is rotating on bearings and is mounted into a the headstock

7. 4/18/2010 4 The headstock slides up and down on guide ways

8. 4/18/2010 3 2 4 Each of these connections creates a flexible joint 1

9. Force is applied when a tooth of the tool makes contact with the workpiece

10. The flexibility of the system allows it to deflect. The amount of the deflection, or the amplitude, is determined by the force applied which is in proportion to the depth of cut

11. When the tooth releases the tool then rebounds, or responds, back in the opposite direction, past the center line. Think of Newton’s third law of motion, “For every action there is an equal and opposite reaction”

12. Then the tool continues to vibrate back and forth until it is fully dissipated. The rate and duration of the vibration is the tool point’s natural frequency

13. An example of natural frequency is to hang a ruler over the edge of a table and flick the end with your finger. The ruler will vibrate at its natural frequency

14. The vibration is not allowed to fully dissipate. The next tooth impacts the workpiece and the process starts all over again. For example a four flute tool, running at 15,000 RPM, will have 1000 impacts per second

15. There is an up and back vibration and the tool is also rotating. If not perfectly in sync each tooth will impact the workpiece at different points within the up and back cycle. If the rotating tool tooth passing frequency is not perfectly in sync with the back and forth natural frequency, each tooth will impact the part at a different depth, changing the force applied

16. Here is the programmed chip thickness that is provided by the cutting tool manufacturer for maximum tool life 4/18/2010

17. 4/18/2010 If the tool rotation is not in sync one tooth will have a much smaller “instantaneous “ chip thickness

18. 4/18/2010 Another tooth will have a much larger instantaneous chip thickness

19. 4/18/2010 Tool Life This excessive instantaneous chip thickness will cause premature tool failure

20. 4/18/2010 Energy Use The excessive instantaneous chip thickness will also increase spindle load and energy consumption

21. One revolution of the cutter looks something like this. These rapid frequency change caused by the chip thickness variation results in audible chatter or feedback like a microphone

22. 4/18/2010 Because the unequal cuts leave a wavy surface, each subsequent pass creates even greater chip thickness variations and the chatter gets much, much worse. We call this regenerative chatter

23. 4/18/2010 The BlueSwarf® Tool Dashboard™ enables users to determine the maximum stable speeds, cutting depths and feed rates for any milling tool in any material We do this by measuring the tool point and synchronizing the tooth passing frequency (RPM) with the cutting system’s natural frequency

24. Results Up to 5X increase in metal removal rate DOUBLE tool life Reduce energy consumption by up to 75% Plus Improved Surface Finishes Reduced Maintenance Costs Lower Scrap Rates

26. Cutter Diameter

27. Cutter Projection

28. Number of Teeth

29. Spacing of Teeth

30. Tool Coating

31. Workpiece Material

32. Gripping Force of Toolholder

33. Weight of Toolholder

34. Run-out

35. Imbalance

36. Drawbar Force

37. Bearing Preload…and many more

38. No paper speed and feed chart can accurately predict the performance of every different cutting system combination and its unique tool point frequency

39. For more information: www.BlueSwarf.com