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High Speed Machining

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  1. High Speed Machining Reference using UGX and NX CAM by Siemens PLM Software (formerly known as UGS PLM Software http://www.plm.automation.siemens.com )

  2. Contents • Introduction and Background • HSM / Hard Milling • Components of HSM • HSM aspects outside your CAM system • HSM aspects inside your CAM system • Case Study • Q&A

  3. High Speed Machining • What is it? • Very high tool rpm, small depths of cut and high feed rates • Mostly used in milling hard mold and die steels (hence term “hard milling”) • Also appears in airframe work for different reasons • Different materials (aluminum) • Used to reduce heat and material stress during machining

  4. High Speed Machining • Value • Maximizes overall productivity – fewer process steps, faster machining • Machining Mold and Dies made of very hard materials (P20, H13, D2, etc.), deep cavities and fine details typically require time consuming EDM processes. • HSM produces high quality finish on milling machine – reduces need for EDM electrodes, burning and hand finishing • Challenges • How to drive HSM machines to capacity without breaking tools • Tool makers cutting data ranges from very safe to highly optimistic - “what data do we use and why doesn’t this data always work for me?”

  5. Hard Milling HSM Capable Machine Tool Cutting Tool Controller HSM capable CAM System Programming Know-how HSM - High Efficiency Hard Milling Machining Mold and Dies made of very hard materials (P20, H13, D2, etc.), deep cavities and fine details typically require time consuming EDM processes. HSM helps users bypass EDM with out-of-the-box “hard-milling” solutions. • “It is only as good as the weakest link.”

  6. Hard Milling • Do you have all the components you need? • Increasing spindle speed and feed while decreasing chip load is just the beginning step of successful high speed programming. • Further understanding of the cutting action is essential. (chatter, vertical engagement angle, material removal rate, effect of surface speed on the finish, etc.)

  7. Hard Milling - Machine HSM Capable Machine Tool • A stable machine capable of running at high speeds and feeds without the machine dynamics coming into the machining equation. • The cutting forces and vibration caused by the actual contact between the tool and the material becomes the primary action. • High Speed Spindle retrofits are not High Speed Machines.

  8. Hard Milling – Cutting Tools Cutting Tool • Tools capable of handling very high surface temperature. • Available High Length to Diameter ratios for reaching into intricate cavities

  9. Hard Milling – Cutting Tools • Ball End Mills rough closer to the part than End Mills with small corner radius. • Original Part and Blank • 30mm End Mill with 1mm Corner Radius • 30mm Ball End Mill • Ball End Mills produce consistent finish along the entire slope spectrum.

  10. Hard Milling – Cutting Tools • End mills always get stressed at the same point. • Effective engagement of ball end mills is distributed • Contrary to popular beliefs, ball mills cut more effectively at the tip than end mills. While it is correct that ball end mills do not have surface speed at the center, it is true for flat end mills as well. Unless you are cutting flat horizontal faces, there is no need to use flat end mills for finishing.

  11. Hard Milling - Tool Holder • Holders capable of very low run-out at high spindle speeds and acceleration. • HSK • Shrink fit • ‘Tribos’ • Dynamic vs. static run-out. • Example holder standards. 3Gs

  12. Hard Milling - Machine Controller Controller • Support for various high speed interpolation types • Look-ahead • Corner acceleration and deceleration curves. • Distinction criteria for Linear Vs Spline interpolation. • NURBS (Non-Uniformal Rational B-Spline) Non-Uniform Rational B-Spline: This is a mathematical representation for smooth curves and surfaces. A type of curve or surface for which the delta (difference) between successive knots need not be expressed in uniform increments of 1. This non-uniformity distinguishes NURBS from other curve types. B-Spline: A particularly smooth class of approximating curves. B-Splines are fully approximating: such a curve generally passes through its control points if several of them are in the same location. B-Spline curves are converted to NURBS curves when imported into Industrial Design softwares for example 3D Studio MAX.

  13. Hard Milling – Machine Controller NURBS

  14. Hard Milling - Machine Controller Smooth Interpolation • Exact positioning

  15. Hard Milling - Machine Controller • Discrepancy between actual and requested high feed rate. • Is SuperGI (Geometric Intelligence) or similar algorithm turned on ? • Is SuperGI disabled due to programming/post errors? • Subroutines within a Super GIMakino block • Cutter Compensation • Using multiple Super GI modes for finishing, roughing and non-cutting moves (M250, M251, M252Makino) Bi-directional copy-mill example

  16. Hard Milling - CAM HSM capable CAM System Programming Know-how • Consistent use of chatter free machining parameters. • Do not exceed the intended Metal Removal Rate. • Leave uniform amount of stock after every tool. • Consistent finish in both steep and non-steep areas. • Smooth, continuous cutting. • Fine tuned HSM data for CNC controllers • Divide and conquer. Do not apply templates to the entire part.

  17. Hard Milling - Chatter Chatter Zone • Chatter is the #2 cause of tool failure in hard milling applications. (It is also the most overlooked) • Process for avoiding chatter

  18. Proven Integrated Machining Data Integrated, customizable machining database enables storing, retrieving and associatively using the data in tool path operations. NX-CAM for example includes proven machining data for commonly used raw materials. P20 in NX3 More materials coming up in NX4.

  19. NX Milling – what can you do? • Avoid over-loading the tool while maintaining high feed rates • Controlling tool step-over, managing tool embedding • Z-level plus path • Enhanced trochoidal paths • Efficiently locate the optimum machining areas • Use the in-process workpiece The key issue is achieving a constant rate of material removal

  20. Trochoidal Toolpath

  21. Material Removal Rate - Roughing • Typical roughing path exceeds requested metal removal rate at corners and fully embedded first cuts.

  22. Metal Removal Rate - Roughing • Without trochoidal, if you are not breaking the tool, you are not cutting efficiently.

  23. MRR & Vertical Engagement Angle

  24. MRR & Vertical Engagement Angle

  25. Metal Removal Rate • Order your flowcuts

  26. Metal Removal Rate - Uniform Blank • Cut between your Z-Levels

  27. MRR & Z Level Operations • Easy control of vertical and horizontal engagement angles. • Z-lock provides much better Super-GI performance at the controller. Watch out for Z level passes near horizontal corners.

  28. Metal Removal Rate & Finish On part stepover option enables constant metal removal rate and uniform surface finish

  29. Cleaner Toolpath • Too many engages and retracts are unsafe and should be avoided. • Level based Rest Milling is faster too.

  30. Constant Surface Speed ?? • Varying RPM as the effective cutting diameter changes. • This is important for good surface finish. • Chatter characteristics could be ignored since the depth of cut is really small.

  31. Tool Length • Keep the tool length as short as possible. • Increased tool length causes increased deflection. • Even in big tools this makes a difference. • Even if there is insignificant un-measurable deflection, you need only a small disturbance to start vibration. (which is very bad for the coating.)

  32. Divide and Conquer • Different machining regions require different strategies. • Mass machining of the entire part does not produce efficient HSM tool path.

  33. Case Study - HSM on Connecting Rod Die Measurement NX2 NX3 Operations required 11 7 Rest mill path 4:30 1:30 generation time Overall Programming 6 hr 2 hr Time • Improved In-process work-piece performance • Automatic cut levels in cavity milling • New Z-level Plus path to contour floors while roughing • Trochoidal cutting to avoid over-embedding tool • Holder checking for multiple tools How did we do it?

  34. Case Study - HSM on Connecting Rod Die Measurement NX2 NX3 Operations required 11 7 Rest mill path 4:30 1:30 generation time Overall Programming 6 hr 2 hr Time • Improved In-process work-piece performance • Automatic cut levels in cavity milling • New Z-level Plus path to contour floors while roughing • Trochoidal cutting to avoid over-embedding tool • Holder checking for multiple tools How did we do it?

  35. Articles, papers, presentations • “Faster and Finer” • “Is Your HSM Investment Paying You Dividends”- by Edwin Gasparraj • “Constant Material Removal – The Key to Hard Milling” - by Edwin Gasparraj • “Critical Machining Data for HSM Process Specification”- by Edwin Gasparraj • Customer facing presentation – “Die/Mold and HSM”

  36. Website reference • UGS PLM Software http://www.plm.automation.siemens.com • Vibrafree.com http://www.vibrafree.com/UHSHM/UHSHM.htm • For more case studies please visit Vibrafree.com. There a lot of case studies about HSM in pdf format.