Rotary Brake Torque

Applies to machines built from:
January, 1989
This document includes these topics:
• How to calculate the rotary brake torque at pressures other than 100 psi (6.89 bar)
• How to calculate the minimum rotary brake torque for your application
• Example

How to calculate the rotary brake torque at pressures other than 100 psi (6.89 bar)

Each rotary unit has a specified rotary brake torque, which is measured at 100 psi (6.89 bar). For most rotary units, the brake torque changes with air pressure. But some rotary units are internally regulated. These rotaries include:

• HRT 450 (prior to May 2015)
• HRT 600 (prior to May 2015)
• Some built-in rotary axis
Use this formula to calculate the rotary brake torque when you have these conditions:
• The air pressure to your machine is not 100 psi (6.89 bar)
• The axis is not internally regulated

• A is the specified brake torque for the rotary table. Find this value on the specification chart for your particular model.
• B is the air pressure to your machine (in PSI). Use the air pressure gauge on the machine, or an external gauge.
• C is the brake torque the rotary unit supplies.

How to calculate the minimum rotary brake torque for your application

Before you select or install a rotary unit, make sure it can supply enough brake force for the work. This can become a problem when you do one of these operations:

• heavy drilling
• heavy milling
• drilling or milling far from the rotary center.
Use the this formula to calculate the minimum brake torque for your application.

• D is the distance (inches) away from the rotary center. You must measure this distance differently for different types of tool paths. See the following illustrations for reference. The illustration on the left shows you how to calculate D for milling applications. The illustration on the right shows you how to calculate D for drilling applications. The illustrations show the rotary center (1) and the feed direction (2).
• E is the cutting force (lb) necessary for the operation. This information is available from your cutting tool manufacturer.
• F is the minimum rotary brake torque. (ft-lb)

Generally, the actual brake torque (C) should be larger than the minimum brake torque (F) by a reasonable margin. For example, if (F) is 100 ft-lb (135.6 nm), then (C) may be 120 ft-lb (176.3 nm) or greater.

note: Do not adjust the air pressure to the machine to change the brake torque. The machine operates in a range of pressures. If you change the pressure, this has an effect on other systems on the machine. This information is to select the best rotary unit for the work, and to make adjustments to the program.

Example

Here is an example of an A-Axis milling operation:

• 1018 mild steel
• .5" (12.7 mm), 4 flute square end mill, 4600 rpm
• .5" (12.70 mm) width of cut, .15" (3.81 mm) depth of cut, .007" (.18 mm) feed per tooth
• Cutting force = 190 lb (supplied from cutting tool company based upon cutting parameters)
• Air pressure = 85psi
Use the formula to find the necessary brake torque:

• D is 5" away from the rotary center
• E is 190 lb (supplied from cutting tool company based upon cutting parameters)
• F is calculated to be 79 ft-lb of minimum brake torque. 95 ft-lb or more of brake torque is best.

Because of the part's size, an HRC 210 or HRT 210 are the best selections. But the air pressure is 85 psi. We must calculate the supplied brake torque to be sure it is sufficient.

• An HRC 210 supplies 114 ft-lb at 85 psi
• An HRT 210 supplies.170 ft-lb at 85 psi
In this example, any 210 mm or larger rotary table will work for the application.

Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.