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How Do I Set the Machine Stiffness on Plus Series Test Machines

When using the test machine to measure very small distances, the extension readings can be incorrect due to the stiffness of the machine, load cell bending and grip pin movement.

To overcome this there is a setting for machine stiffness that can be set and the extension readings will be compensated for in the embedded software

The newly compensated extension readings are available as a scheme setting in both standalone mode (machine only) or with test software (NEXYGEN MT or NEXYGENPlus). There is space for 10 individual compensation settings.

The following graph shows one test with compensation and one without. It can clearly be seen that compensation makes a considerable difference to the extension readings. This test was performed with a 100N load cell in compression.

How do I set the machine stiffness on Plus Series

How to set the machine stiffness on your materials testing machine 
For Tension a solid metal bar must be gripped between eye ends. For Compression, machine eye ends or compression platens can be pressed together.

With the correct load cell fitted, switch on the test machine and allow it to initialize.

From The top level Test / Edit screen on the test machine console:

Select Edit

Select Global

Press the > key twice

Select Set Machine Stiffness
If no schemes are currently set the display will show Empty 1….10
A previous scheme can be edited to use again.

Select the desired scheme to be configured using the < > keys

The scheme can be given a name usually associated with the load cell type for example T100N or C100N for tension or compression.

Select Setup

Select the test mode either Tension or Compression 

Select Set Preload Value 

Select Preload and enter the force to start the extension readings. This is recommended to be 0.5% of the load cell value. Example 1000N load cell, preload = 5N. Other units can be used such as gf or lbf.

Select Speed and enter 1mm/min. (it is highly recommended that no higher speeds are used). 
When preload and speed have been set press the Enter key once.

Select Set Limit Value

Select Limit and set this to the target load needed. This can be full range of load cell or a percentage of (if the test does use full load).

Select Speed and enter 1mm/min.

When limit and speed have been set press the Enter key.

The settings are now complete.

Select Perform. The display will show ‘Performing Test Machine Stiffness’

The test machine will do two cycles. The first cycle checks the physical deflection in the machine and load train. The second cycle performs the measurement compensation for the movement found.

When fully complete the display will return to the Select Scheme name screen.

To return to the console top-level menu press the Enter key three times.

Using the scheme in a test (stand alone test machine only)
The stiffness compensation scheme that has been set will be stored in the test machine console memory and can be selected in any test set up.

From the top menu select the test to edit using the < > keys

Select Edit and then Setup

Select Test Type

Press the > key once

Select Machine Stiffness

Use the left hand up arrow key ^ on the console to select Enable or Disable scheme

Use the < > keys to select the scheme name and setup to be used

Press the Enter key to exit

Select all other test parameters as normal

When a test is now run this scheme (if enabled) will be used and extension readings and results will be compensated.

Note: As the machine memory holds the Stiffness scheme, to clear it from a test setup, it can be disabled in the settings as mentioned above or a Ram Dump of the machine can be performed.

Using the scheme in a test with software (NEXYGEN MT or NEXYGENPlus)
With the test machine switched on and PC connected, open the correct console (EZ and Plus Series

How do I set the machine stiffness on Plus Series

Right Click on the console and select Machine Setup Schemes

How do I set the machine stiffness on Plus Series

Select + button next to Machine Stiffness and from the drop-down menu select the scheme name required.

Select Save As... to save the console and use this Machine Stiffness setting.

When you open a batch file and run a test, the software using the saved console’s extension readings and results will be compensated.