The Process Of Machining Titanium Using Modern Machinery

precision titanium machining

precision titanium machiningTitanium has become one of the most popular materials used in aerospace applications.? The reason for this are the special properties titanium possesses. Titanium has a relatively low mass for a given strength level and it also is highly resistant to high temperatures.

These properties make it a very good choice for an aerospace material because materials need high temperature resistance and light weight but great strength at the same time.

Titanium is used in the front sections of an aircraft engine and are becoming more and more common in structural and landing gear components.? The one big drawback to using titanium is that the materials is very difficult to machine.

Machining Titanium

Machining titanium is very demanding and requires he right machine tools for the job. It often requires the removal of up to 90% of the weight of the workpiece. When titanium is machined it produces a high-chemical re-activity that causes the chip to weld to the tool which leads to cratering and quick tool failure.

Titanium laso has low thermal conductivity which does not allow the heat generated during machining to dissipate from the tool edge. The inability to dissipate heat causes high tool tip temperatures and excessive tool deformation and wear.

Correct Use of Coolant

Using Coolant in the machining processThe most important factor to consider when machining titanium or titanium alloys is proper coolant delivery.? The goal is to create a low coefficient of friction.? This results in lower temperatures so the workpiece does not get soft and the tool life is extended rather than shortened.

With pressure and direction, the coolant knocks chips off the cutting edges and provides anti-corrosive benefits for both the machine tool and the workpiece.? Research shows that there is a high correlation between the amount of coolant delivered and the metal removal rate.

Using a high coolant concentration provides lubricity that helps extend tool life, chip evacuation and finer surface finishes. High –pressure coolant through the tool or through an adjacent line parallel to the tool should also be considered to increase tool life and production rates.? Multi-coolant lines should not be used. It is better to use a single line with 100% of the flow capacity to evacuate the chips from the work area.

Synthetic or semi-synthetic coolants should be used at proper volume, pressure and concentrations levels.? 10-12% coolant concentration is mandatory.? The flow to the cutting edges should be maximized with a recommendation of 3 gallons per minute or 13 liters per minute at 500 psi for through tool flow.

Machining Tips

  • Rigidity is paramount
  • Coolant, coolant, and more coolant
  • Speeds and feeds have to reduced significantly below what they are for softer metals
  • Cutter material is critical-Use coated carbide cutters
  • Reduce tool stickout-vibrations destroy the surface finish
  • Always utilize gravity to your advantage
  • Horizontal spindles help chips to fall away fro the workpiece
  • Horizontal fixturing requires the use of angle plates or “tombstones”.
  • Keep work closest to the strongest points of fixture
  • Keep work as close as possible to the spindle/quill
  • Know the power curve of the machine
  • Ensure sufficient axis drive motors for power cuts
  • Look for weak links and weak parts of machine structure that could compromise rigidity
  • Check for backlash in the machine’s spindle
  • Identify your drawbar’s pull-back force
  • Watch the adapter for fretting and premature wear-signs of overloading the cutting tool and damaging the spindle and bearings

Non-Traditional Machining

Titanum alloy components often require the use of non-traditional machining methods such as electrochemical machining, chemical milling or laser beam torch.? Chemical and electrochemical methods of metal removal are likely to increase because of their many useful features.

They are particularly good methods for rapid removal of metal from the surface of complex shaped parts, thin sections and large areas and formed parts without damaging the mechanical properties of the metal.

Electrochemical Machining

ECM is the removal of electrically conductive material by anodic dissolution in a rapidly flowing electrolyte which separates the workiece from a shaped electrode. This method can generate very difficult contours and provide undistorted, high-quality surfaces.? When using it to machine titanium alloys the most common electrolyte used is sodium chloride in a concentration of 1 pound per gallon.

Chemical Machining

Chemical machining uses a strong chemical reagent. The part being processed is thoroughly cleaned and covered with a strippable, chemically-resistant mask. Areas where chemical action is desired are stripped off the mask, and then the part is submerged in the chemical reagent to dissolve the exposed material.

Laser Beam Torch Machining

Machining using this process involves removing material from a workpiece by focusing a laser beam and a gas stream on the workpiece. The laser energy? causes localized melting and an oxygen gas stream creates an exothermic reaction forcing the melted material out from the cut.? It is possible to cut titanium alloys at a very rapid rate using a continuous wave CO2 laser with oxygen assistance.

CNC lathes and machining centers can be used to machine titanium and many new models and CNC machining centers are dramatically increasing the milling efficiency of titanium and titanium alloys by including several key elements for efficient titanium machining including active dampening systems, rigid construction, high-torque, high-powered spindles, and high pressure, high-flow coolant systems.

Although titanium and titanium alloys present specific problems for machining, there are several different methods of competing titanium machining. CNC mills and lathes are being specially designed to address this growing segment of the machining market and many advances have already been made making the machining of titanium easier than ever before.

Leave a Reply