High Speed Machining (HSM) Seminar On  High Speed Machining (HSM) Submited To : Submited By www.mobikida.wordpress.com Ghaytadak Satish Laxman 1 1

Contents Introduction and Background HSM / Hard Milling Components of HSM HSM aspects outside your CAM system HSM aspects inside your CAM system References

High Speed Machining What is it? Different materials (aluminum) 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 Firstly, as with each section lets be sure we know what we are addressing:

High Speed Machining Value Challenges 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?” Why are customers interested? See slide Challenges: Customer are new to these processes. However, its not simply a case of buying a HSM and pressing the “go faster” buttons! First out they typically start breaking tools – can damage the part, anyone who has the guard wedged open, and their wallets. They can also get surface imperfections, exactly what they didn’t want in looking for a high quality finish and avoid slower methods.

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. HSM - High Efficiency Hard Milling HSM Capable Machine Tool Cutting Tool Controller HSM capable CAM System Programming Know-how “It is only as good as the weakest link.”

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.)

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.

Hard Milling – Cutting Tools Tools capable of handling very high surface temperature. Available High Length to Diameter ratios for reaching into intricate cavities TiN Gold coating High surface hardness Lubricity TiCN Blue-gray coating Moderate temperatures TiAlN High Temperature applications Forms Al Oxide coating -low thermal conductivity Longer tool life

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.

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.

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

Hard Milling - Machine 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.

Hard Milling – Machine Controller NURBS

Hard Milling - Machine Controller Smooth Interpolation Exact positioning

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

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.

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

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.

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 For tool-paths – we have continuously invested in this area over the last several releases. We NX 3 we reached a point where we know we are competitive with the specialist vendors that focus only on mold and die. The key issue is achieving a constant rate of material removal. We want to avoid paths that leave sudden steps, or extra depths in the material that will be “hit” by the tool on the next path or operation. That would be a good way to break the tool. The key issue is achieving a constant rate of material removal

Trochoidal Toolpath

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

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

MRR & Vertical Engagement Angle

MRR & Vertical Engagement Angle

Metal Removal Rate Order your flowcuts

Metal Removal Rate - Uniform Blank Cut between your Z-Levels

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.

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

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

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.

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.)

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

References www.google.com www.wikipedia.com

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