Universal Tensile testing Machine Troubleshooting
Universal Tensile Testing Machine (UTM) can perform many kinds of test according to the required test standard. It can perform tensile test, compression test flexural (bending test) and so on.
There are some common problems/issues associate with Universal Tensile Testing Machine, whether problem is from the machine or from other factors, we will share some of the problems and how we solve it.
1.Test result too low or too high for tensile strength or elongation
When we have this kind of issue, we need to understand the basis of the test unit.
For example, if we have low result in tensile strength for rubber glove (flat dumbbell specimen). The formula for tensile strength is force/ Area (thickness X width). From here, we check each of the component.
For force, we verify the load cell by hanging a standard weight/load cell. If the load is within 1% difference, the calibration is correct and unlikely to cause problem
For width, (rubber glove) we need to follow dimension from each cutter’s calibration certificate (ASTM D412, type C, width = 6mm) for other rigid specimen, we measure with calliper and make sure the value is entered correctly into the software
For thickness, we check the specimen with thickness gauge and ensure the correct value is key into the software
If we have low elongation result, we need to understand how the machine calculate the elongation. The formula for elongation is deformation/initial length.
If we use a long travel extensometer, we need to check the condition of the extensometer grip, usually it has a rubber O-ring or friction pad. When the O-ring/friction pad were worn, the extensometer does not follow the movement of the gauge length.
If the movement is fine, we need to verify the extensometer calibration. With a ruler or measuring tape, we compare the deformation display on software and actual readout. If the error is more than 10%, it is time to carry out calibration.
We also can check if the deformation channel is selected correctly. If the software uses the machine stroke for calculation, the elongation result is usually too high.
For initial length, we refer to the gauge length. Depends on the sample type, if we have D412 type C specimen, the gauge length is 25mm, for ASTM D638 type II, the gauge length is 50mm, we need to ensure the value is key in correctly. A different value will cause big error in the calculation.
Once all these basic troubleshooting technics have been carried out but still fail to identify any cause of the error, then it has high chances that your Universal Tesnsile Testing Machine is having complicated issues. Please get help from professional service technician for a detailed troubleshooting on-site.
2. Sample cannot break
Sometimes the test specimen is unable to break as expected, it may due to several reasons, depend on the various situations:
The Universal Tesnsile Testing Machine starts and move for a brief moment and stop
For this symptom, it may due to impact sensitivity setting, the machine detected the load cell is experiencing impact/overload, we need to adjust the sensitivity so that it reacts correctly.
Another factor is due to the load cell signal noise, the machine detected there are big fluctuations and then it stops the test. We should check the ground connection of the machine and load cell and try to eliminate the noise. If the noise is still present, we may need to change a new load cell or try to adjust the preload and start point settings.
The Universal Tesnsile Testing Machine pulls the sample until certain height and then it stops
For this symptom, we can have multiple reasons. The first reason is the software setting is incorrect. We need to check the deformation limit. Usually, the setting should enable the crosshead to move to its maximum position.
The second reason is the software’s load limit setting. We need to check if the setting is too low, we may adjust the value close to 95% of the capacity.
The third reason is due to the machine limitation, the sample elongation may be too large. The machine reaches it maximum crosshead position and unable to pull any further. For this problem, we may reduce the sample size (change sample type) or reduce the width or gauge length. We can also use a smaller fixture to improve the crosshead’s travel distance.
The fourth reason is the sample is too thick, the machine reaches the maximum capacity of the load cell, for protection purpose the machine stop itself from continuing the test.
3. Machine does not auto return after sample break
Usually, this issue is due to software and load cell issues.
The first reason is the break detection setting, if the setting is incorrect, the machine unable to detect the sample was broken hence it continue running.
The second reason is auto return function wasn’t activated/selected; we need to check the setting.
The third reason is the load cell or the connection is damaged/broken, the machine unable to detect any load so it continues running. To solve the problem, we need to verify if the load cell and connection is still in good condition. If the load cell is in good physical condition, it may due to software or electronic interface issue. Please get help from professional service technician
4. Machine abnormal or loud operating noise
This problem usually associates with moving mechanical parts such as bearings, belts, roller and guides.
We need to check which parts is emitting the noise. The most common source is from the bearings due to long time usage or incorrect belt tension.
If the problem is from the guide, we can lubricate the moving parts and adjust the clearance.
5. Load cell damaged/machine overloaded(crashed)
When the machine is overloaded, it may due to mishandling, software and hardware problem.
We can check the condition of the limit switch, if the limit switch is not activated (wrong position), the cause is due to mishandling.
If the limit switch was activated but the load cell still damaged, the problem might due to internal hardware problem which might need to be inspected.
If this situation occurs, the machine will unable to operate. We need to disconnect the power connection. Open the motor and pulley cover, carefully rotate the pulley to release the pressure applied to the load cell. Check the condition of load cell and test jig. If the load cell is damaged, we need to replace with a new unit.
6. Machine unable to turn on
When we have this issue, the first thing we need to inspect is the power supply. Is the power socket plugged in properly and turned on? If we have a test pen or multimeter, we need to measure if the incoming power supply is sufficient (240V for single phase and 415V for 3 Phase).
Next, we check if the fuse is burnt. If both is in good condition, we then check if the emergency button is activated. Some machine has multiple E-switch, we may need to deactivate all in order to turn on the machine.
Usually, there is a DC power supply inside the machine. We can check this item as well. Visually, we can check if the led light is lit.
With a multimeter, we measure the output voltage whether 12V or 24V is present. If all still unable to work, you are advised to contact the supplier.
7. Hydraulic Clamp not working
When we face this issue, the first thing we need to check is the power supply.
Hydraulic clamp usually has an independent power pack. We need to check if the power supply and fuse is in good condition.
Next, we check if we able to turn on the motor pump. If the pump is running but the clamp/grip still unable to function. We then check if the solenoid valve is activated when we pressed the button. If there is no activation, it means the remote control is damaged. If signal is detected, but the valve does not operate. It may due to burnt coil or the valve is stuck mechanically.
The most common cause is a burnt coil.