Dwell Time Calculator

The Dwell Time Calculator built by LFA is designed to help you work out how long your tablet is under maximum compression. Understanding this will help you scale up from small scale R&D to batch production of your tablets.

The dwell time is calculated in the following way:

Where:

• dt = dwell time (milliseconds)
• Dhf = head flat diameter (millimeters)
• Dpc = pitch circle diameter of turret (millimeters)
• rpm = revolutions per minute (turret speed)

Dwell time is then expressed in ms (milliseconds).

The longer the dwell time, the harder the tablet will become. This is because the energy created when compressing the tablets has time to dissipate and does not allow for the elasticity of the powders to spring back.

To use the Dwell Time Calculator, take the following steps:

1. Select your machine from the drop down menu. If you are not using an LFA machine select "Other" and then enter the make and model of your machine along with the Pitch Circle Diameter in mm. The Pitch Circle Diameter is the distance from the centre of one die to the corresponding die on the other side of the press. If you do not know this it will be available from your manufacturer. 
   
   
   
   
2. Next, select the tooling you are using from the drop-down menu. If you are not using one of the standard tooling sizes listed, then select "Other". You will then be asked to enter the name of the tooling and the size of the head flat in mm. The head flat of your tooling is the size of the flat section on the top of the head of the punch, as shown below:
   
   
   
   
3. Finally, enter the speed in rpm that you are running the machine at. Then click "Calculate", and the dwell time will be displayed.