Rohit Cutting Tools - Titanium Milling Made Easy: 11 Pro Tips for Machinists

Industries employing Titanium

• Aerospace and medical device manufacturing are two of the biggest industries using titanium milling.
• Aerospace companies machine titanium parts for aircraft, spacecraft, and missiles because the metal is both lightweight and durable. Titanium alloys can withstand high temperatures without corroding or fracturing under stress.
• Medical device makers mill titanium for implants like hip and knee replacements as well as dental implants. Titanium is biocompatible, meaning the human body accepts it without rejection or adverse effects. It’s also highly resistant to corrosion from bodily fluids.
• Titanium’s strength and biocompatibility come at a cost, though. The metal is notoriously difficult to machine and tool wear is rapid.

Pro Tip # 1: Select the Right Tooling for Titanium Milling

• When milling titanium, the right tooling is essential. Using regular high speed steel or carbide tools will lead to poor results and damage your workpiece.
• Invest in carbide end mills specifically designed for cutting titanium. Carbide can handle the high heat and abrasiveness of titanium alloys. Look for tools with a large number of cutting edges, like 5 or more flutes.
• More flutes mean more cutting edges and faster material removal.
• Employ special Tool Coatings as mentioned in Pro Tip # 9

Pro Tip # 2: Optimize Speeds and Feeds for Maximum Tool Life

• Feed rates for titanium should be around 1/3 to 1/2 those used for steel. Slower feeds decrease cutting forces and heat generation.
• Use high spindle speeds. Higher speeds, around 3000 to 5000 RPM, are more effective for milling titanium. The increased speed reduces heat buildup.
• Finding the Sweet Spot : You want to aim for the highest speeds and feeds possible without causing damage. Start conservatively, then slowly ramp up your speeds and feeds in small increments, testing after each change. Stop increasing once you notice excess chatter, vibration or poor surface finish. The settings that achieve the best results just before these unwanted effects are your sweet spot.
• For titanium alloys like Ti-6Al-4V, a good starting point is:
  • Spindle Speed: 150-300 SFM / 45~90 m/min
  • Chip Load: 0.001-0.003 IPR / 0.025 to 0.075 mm/rev

Pro Tip # 3: Use Copious Amounts of Coolant to Control Heat

• To combat heat buildup, flood the cutting area with copious amounts of coolant. Coolant cools the titanium, tools, and chips, preventing overheating. It also helps flush away chips, reducing chip welding and tool chip packing.
• For titanium milling, a water-soluble coolant works well. Apply it liberally through coolant nozzles, hoses, and coolant misters. Don’t skimp! The more coolant you can get to the cutting interface, the better with Coolant Mix %age to be higher at 10% instead of 6% used in Steel milling.
• Monitor cutting tool and workpiece temperatures closely. If temperatures start creeping up, increase your coolant flow rate or decrease your cutting speeds and feeds. It’s much easier to prevent overheating than recover from it.
• Keeping temperatures under control is key to successful titanium milling. Coolant is your best defense against heat, so use it generously for maximum effectiveness.

Pro Tip # 4: Use Variable Helix End Mills

• Variable helix end mills are versatile tools that can produce a smooth finish on titanium.
• The variable flute geometry reduces chatter and vibration.
• Use Variable-Helix End Mills in 4-flute Or especially 5-flute (You can ask for "ROHIT" make 330 Series - 4Flute Variable Helix Or 333 Series - 5Flute Variable Helix End Mills for Machining Titanium Alloys Or opt for newest series with Eccentric Relief for even higher performance & finish : 334 Series - 4Flute Variable Helix 

Pro Tip # 5: Employ Peck Drilling and Ramping Techniques

Peck Drilling

• Instead of drilling straight through the material in one continuous motion, peck drilling involves pulling the drill bit out intermittently. This allows chips to clear from the flutes and prevents overheating. To peck drill:
• Drill into the material for a few seconds.
• Retract the drill and clear chips.
• Repeat, pecking at the material until you reach full depth.
• Peck drilling requires more time but will prevent work hardening and keep the cutting edge of your tool fresher for longer.

Ramping

• Ramping involves gradually lowering the spindle into the cut. This allows you to take light passes at increasing depths, preventing shock loading on the tool. To ramp:
• Position the tool above the workpiece.
• Gradually lower the Z-axis while the spindle is running until you take a light cut.
• Raise the Z-axis, clear chips and repeat at a slightly lower height.
• Continue ramping to your final depth of cut.
• Ramping, like peck drilling, helps prevent excess heat and stress on the cutting tool when machining titanium. Employing these techniques will improve your tool life, part finish and overall milling efficiency.

Pro Tip # 6: Minimize Chatter and Vibration With Rigid Setups

Clamping is Key

• Clamp your titanium workpiece in a vise or fixture to keep it rigidly in place. Titanium’s slippery surface requires clamping force over a large area. Apply moderate pressure; too much can distort the workpiece. Locate clamps close to where you’re milling for best support.

Choose a Solid Setup

• A sturdy machine setup is a must for titanium milling or drilling. Chatter results from vibrations in the milling system, so use a solid spindle, toolholders, and machine bed. If possible, select a machine designed for high-speed milling of hard metals.
• For the best surface finish, mill titanium at high speeds with sharp cutters, and in a climb milling direction.
• Keeping your titanium workpiece secure through clamping and a robust machine setup helps ensure smooth milling by reducing excess vibration. With the proper precautions taken, titanium can be milled as efficiently as steel.

Pro Tip # 7: High-Speed Machining

Use high spindle speeds

• Crank up the RPMs on your mill to at least 12,000 RPM for effective titanium milling. Faster spindle speeds translate to increased cutting tool surface footage, which slices through the titanium more efficiently. The heat has less time to dissipate into the workpiece, preventing work hardening.
• For the best results, use a high-speed machining center designed for machining exotic alloys like titanium. These provide the power and rigidity needed for high-velocity milling, with spindle speeds of 20,000 RPM or more. If using a standard mill, choose the highest range that won’t damage your machine or tools. Apply cutting fluid generously to aid cooling and lubrication.

Pro Tip # 8: Tool Wear and Deflection

Tool Wear

• Check your tools frequently for signs of wear like rounded edges, cracks or chips. Dull tools require higher cutting forces, reducing tool life and part quality. Replace well before failure to prevent scrap.
• Consider more wear-resistant tool materials and coatings.

Tool Deflection

• The forces involved can bend and flex your tools, causing imperfect cuts and dimensions. Use the shortest, most rigid tools possible for the job. Keep extensions to a minimum. When possible, balance cuts on opposing sides of the workpiece to reduce deflection. Deflection is often highest at the tip of the tool, so consider back-tapered designs.
• Keeping a close eye on your tooling during titanium milling will help you achieve high quality results and less waste. With the proper precautions taken, you'll be milling titanium with confidence in no time.

Pro Tip # 9: Special Tool Coatings

• Special tool coatings are essential when milling titanium. The high heat and friction created can wreak havoc on your cutting tools. Using coatings specifically designed for titanium and super alloys will drastically improve your tool life and performance.
• These special coatings provide lubrication and help dissipate heat, preventing built-up edge.
• They also increase hardness and wear resistance. Using uncoated tools will lead to rapid tool wear, decreased tool life, and poor surface finish.
• Coatings like titanium-based coatings (TiN, TiCN, TiAlN), or aluminum-based coatings or new coatings like AL-PRO or TiSiN specially designed PVD coatings which prevents the titanium chips from welding to the tool.

Pro Tip # 10: Radial Engagement

• When milling titanium, radial engagement refers to how much of the tool’s cutting surface is contacting the workpiece. For titanium, use lower radial engagements, around 5-15% of the tool diameter.
• Too high of an engagement, like 25-50%, can overload the tool and cause chatter, poor surface finish, and reduced tool life. The heat and forces are too much for the tool to handle. Instead, take light passes with each tool path. Multiple finishing passes are better than trying to remove too much material at once.
• Think small bites, not big gulps! Lower radial engagements for titanium will lead to better success at the mill. Go slowly and be patient. Your tools and part will thank you.

Pro Tip # 11: Climb milling or Thick-to-Thin Chip Formation

Benefits of Climb Milling Titanium

• It requires less force to cut the material since the cutter isn't plowing into the workpiece. This reduces heat and tool pressure.
• It produces thinner, more uniform chips that are easier to evacuate.
• It leaves a better surface finish with less tool marks and burrs.
• It reduces work hardening of the material by cutting through the hardened surface layer.
• It lengthens tool life since there is less heat and rubbing.

Conclusion