OCM cutting data calculator (#167 / #1-02-1)

Fundamentals of the OCM cutting data calculator

Introduction

The OCM cutting data calculator is used to determine the Cutting data for Cycle 272 OCM ROUGHING. These result from the properties of the material and the tool. The calculated cutting data help to achieve high material removal rates and therefore increase the productivity.

In addition, you can use the OCM cutting data calculator to specifically influence the load on the tool via sliders for the mechanical and thermal loads. This allows you to optimize the process reliability, the wear on the tool, and the productivity.

Requirements

 
Machine

Refer to your machine manual!

In order to capitalize on the calculated Cutting data, you need a sufficiently powerful spindle as well as a stable machine tool.

    • The entered values are based on the assumption that the workpiece is firmly clamped in place.
    • The entered values are based on the assumption that the tool is seated firmly in its holder.
    • The tool being used must be appropriate for the material to be machined.
 
Tip

In case of large cutting depths and a large angle of twist, strong pulling forces develop in the direction of the tool axis. Make sure to have a sufficient finishing allowance for the floor.

Maintaining the cutting conditions

Use the cutting data only for Cycle 272 OCM ROUGHING.

Only this cycle ensures that the permissible tool contact angle is not exceeded for the contours to be machined.

Chip removal

 
Notice
Caution: Danger to the tool and workpiece!
If the chips are not removed in an optimum manner, they could get caught in narrow pockets at these high metal removal rates. There is then a risk of tool breakage!
  1. Ensure that the chips are removed in an optimum manner, as recommended by the OCM cutting data calculator.

Process cooling

The OCM cutting data calculator recommends dry cutting with cooling by compressed air for most materials. The compressed air must be aimed directly at the cutting location. The best method is through the tool holder. If this is not possible, you can also mill with an internal coolant supply.

However, chip removal might not be as efficient when using tools with an internal coolant supply. This can lead to shortened tool life.

Operation

Opening the cutting data calculator

  1. Select cycle 272 OCM ROUGHING

  1. Select OCM cutting data calculator in the action bar

Closing the cutting data calculator

  1. Select APPLY
  2. The control applies the determined Cutting data to the intended cycle parameters.
  3. The current entries are stored, and are in place when the cutting data calculator is opened again.

  1. or

  2. Select Cancel
  3. The current entries are not stored.
  4. The control does not apply any values to the cycle.
 
Tip

The OCM cutting data calculator calculates associated values for these cycle parameters:

  • Plunging depth(Q202)
  • Overlap factor(Q370)
  • Spindle speed(Q576)
  • Climb or up-cut(Q351)

If you use the OCM cutting data calculator, then do not subsequently edit these parameters in the cycle.

Fillable form

The control uses various colors and symbols in the fillable form:

  • Dark gray background: entry required
  • Red border of input boxes and information symbols: missing or incorrect entry
  • Gray background: no entry possible
 
Tip
  • The input field of the workpiece material is highlighted in gray. You can only select it through the selection list. The tool can also be selected through the tool table.
  • Use the +, -, *, /, (, and ) keys for calculations in the numerical input fields.

Workpiece material

To select the workpiece material:

  1. Select the Select material button
  2. The control opens a selection list with various types of steel, aluminum, and titanium.
  3. Select the workpiece material
  4. or

  5. Enter a search term in the filter mask
  6. The control displays the materials or material groups that were found. Use the Delete button to return to the original selection list.
 
Tip

Programming and operating notes:

  • If your material is not listed in the table, choose an appropriate material group or a material with similar cutting properties
  • You will find the workpiece-material table ocm.xml in the TNC:\system\_calcprocess directory

Tool

You can choose the tool either by selecting it from the tool table tool.t or by entering the data manually.

To select the tool:

  1. Select the Select the tool button
  2. The control opens the active tool table tool.t.
  3. Select the tool
  4. or

  5. Enter a tool name or number in the search field
  6. Confirm with OK
  7. The control applies the Diameter, the Number of teeth and the Tooth length from the tool.t table.
  8. Define the Angle of twist

To select the tool:

  1. Enter the Diameter
  2. Define the Number of teeth
  3. Enter the Tooth length
  4. Define the Angle of twist

Input dialog

Description

Diameter

Diameter of the roughing tool in mm

Value is applied automatically after the roughing tool has been selected.

Input: 1...40

Number of teeth

Number of teeth of the roughing tool

Value is applied automatically after the roughing tool has been selected.

Input: 1...10

Angle of twist

Angle of twist of the roughing tool in °

If there are different angles of twist, then enter the average value.

Input: 0...80

 
Tip

Programming and operating notes:

  • You can modify the values of the Diameter, the Number of teeth and the Tooth length at any time. The modified value is not written to the tool.t tool table!
  • You will find the Angle of twist in the description of your tool, for example in the tool catalog of the tool manufacturer.

Limits

For the Limits, you need to define the maximum spindle speed and the maximum milling feed rate. The calculated Cutting data are then limited to these values.

Input dialog

Description

Max. spindle speed

Maximum spindle speed in rpm permitted by the machine and the clamping situation:

Input: 1...99999

Max. milling speed

Maximum milling speed (feed rate) in mm/min permitted by the machine and the clamping situation:

Input: 1...99999

Process parameters

For the Process parameters, you need to define the Plunging depth(Q202) as well as the mechanical and thermal loads:

Input dialog

Description

Plunging depth(Q202)

Plunging depth (>0 mm to [6 times the tool diameter])

The value from cycle parameter Q202 is applied when starting the OCM cutting data calculator.

Input: 0.001...99999.999

Mechanical load on tool

Slider for selection of the mechanical load (the value is normally between 70% and 100%)

Input: 0%...150%

Thermal load on tool

Slider for selection of the thermal load

Set the slider according to the thermal wear-resistance (coating) of your tool.

  • HSS: low thermal wear-resistance
  • VHM (uncoated or normally-coated solid carbide milling cutters): medium thermal wear-resistance
  • Coated (fully-coated solid carbide milling cutters): high thermal wear-resistance
  •  
    Tip
    • The slider is effective only in the range with a green background. This limiting depends on the maximum spindle speed, the maximum feed rate, and the selected material.
    • If the slider is in the red range, the control will use the maximum permissible value.

Input: 0%...200%

Process parameters

Cutting data

The control displays the calculated values in the Cutting data section.

The following Cutting data are applied to the appropriate cycle parameters in addition to the plunging depth Q202:

Cutting data:

Applied to cycle parameter:

Overlap factor(Q370)

Q370 = TOOL PATH OVERLAP

Milling feed(Q207) in mm/min

Q207 = FEED RATE MILLING

Spindle speed(Q576) in rpm

Q576 = SPINDLE SPEED

Climb or up-cut(Q351)

Q351= CLIMB OR UP-CUT

 
Tip

Programming and operating notes:

  • The OCM cutting data calculator calculates values only for climb milling Q351=+1. For this reason, it always applies Q351=+1 to the cycle parameter.
  • The OCM cutting data calculator compares the cutting data with the input ranges of the cycle. If the values fall below or exceed the input ranges, the parameter will be highlighted in red in the OCM cutting data calculator. In this case, the cutting data cannot be transferred to the cycle.

The following cutting data is for informational purposes and recommendation:

  • Lateral infeed in mm
  • Tooth feed FZ in mm
  • Cutting speed VC in m/min
  • Material removal rate in cm3/min
  • Spindle power in kW
  • Recommended cooling

These values help you assess whether your machine tool is able to meet the selected cutting conditions.

Process parameters

The two sliders for the mechanical and thermal load have an influence on the process forces and temperatures prevalent on the cutting edges. Higher values increase the metal removal rate, but also lead to a higher load. Moving the sliders makes different process parameters possible.

Maximum material removal rate

For a maximum material removal rate, set the slider for the mechanical load to 100% and the slider for the thermal load according to the coating of your tool.

If the defined limitations permit it, the cutting data utilize the tool at its mechanical and thermal load capacities. For large tool diameters (D>=16 mm), a very high level of spindle power can be necessary.

For the theoretically expectable spindle power, refer to the cutting data output.

 
Tip

If the permissible spindle power is exceeded, you can first move the slider for the mechanical load to a lower value. If necessary, you can also reduce the plunging depth (ap).

Please note that at very high shaft speeds, a spindle running below its rated speed will not attain the rated power.

If you wish to achieve a high material removal rate, you must ensure that chips are removed optimally.

Reduced load and low wear

In order to decrease the mechanical load and the thermal wear, reduce the mechanical load to 70%. Reduce the thermal load to a value that corresponds to 70% of the coating of your tool.

These settings utilize the tool in a manner that is mechanically and thermally balanced. In general the tool will then reach its maximum service life. The lower mechanical load makes a smoother process possible that is less subject to vibration.

Achieving an optimum result

If the Cutting data do not lead to a satisfactory cutting process, then different causes might be the reason for this.

Excessively high mechanical load

If there is an excessive mechanical load, you must first reduce the process force.

The following conditions are indications of excessive mechanical load:

  • Cutting edges of the tool break
  • Shaft of the tool breaks
  • Excessive spindle torque or spindle power
  • Excessive axial or radial forces on the spindle bearing
  • Undesired oscillations or chatter
  • Oscillations due to weak clamping
  • Oscillations due to long projecting tool

Excessively high thermal load

If there is an excessive thermal load, you must reduce the process temperature.

The following conditions indicate an excessive thermal load on the tool:

  • Excessive crater wear at the cutting surface
  • The tool glows
  • The cutting edges melt (for materials that are very difficult to cut, such as titanium)

Material removal rate is too low

If the machining time is too long and it must be reduced, the material removal rate can be increased by moving both sliders.

If both the machine and the tool still have potential, then it is recommended that the slider for the process temperature be raised to a higher value first. Subsequently, if possible, you can also raise the slider for the process forces to a higher value.

Remedies for problems

The table below provides an overview of possible types of problems as well as countermeasures for them.

Condition

Slider Mechanical load on tool

Slider Thermal load on tool

Miscellaneous

Vibrations (such as weak clamping or tools that project too far)

Decrease

Perhaps increase

Check the clamping

Undesired vibrations or chatter

Decrease

-

Shaft of tool breaks

Decrease

-

Check the chip removal

Cutting edges of the tool break

Decrease

-

Check the chip removal

Excessive wear

Perhaps increase

Decrease

The tool glows

Perhaps increase

Decrease

Check the cooling

Machining time is too long

Perhaps increase

Increase this first

Excessive spindle load

Decrease

-

Excessive axial force on spindle bearing

Decrease

-

  • Reduce the plunging depth
  • Use a tool with a lower angle of twist

Excessive radial force on spindle bearing

Decrease

-