Rheometer and Mooney Viscometer

Rheometer is use to determine the rheological properties of a rubber compound. The machine expresses the properties in test time, ts2, tc10, tc90, ML, MH etc. Mooney viscometer is use to determine the flow properties such as viscosity and also scorch time of a rubber compound.

There are some common problems/issues associate with rheometer and Mooney viscometer, whether problem is from the machine or from other factors, we will share some of the problems and how we solve it.

1. Die unable to heat up

This is the most common problem we face with a Rheometer and Mooney viscometer. There are some potential root causes to this problem.

The most frequent item that cause this issue is the heater/heating element. The heating element is a consumable. It will experience aging and deteriorate after some time and eventually burnt/stop working. Replacing the heater will solve the issue.

2. Die unable to clamp/come down

When we have this problem, the first thing to check is incoming pneumatic supply. We need to ensure the inlet pressure is sufficient.

We also need to check if the silencer is in good shape and not blocked/clogged.

Next, we check if the solenoid/control valve is in good condition. It should receive a signal when we press down. If there are no incoming signal, the control part is having problem. If there is signal but the valve does not work, either the valve is stuck or the coil was burnt.

Another possible reason is the main air cylinder was corroded/dirty. Usually incoming pneumatic supply contains moisture, if the machine does not equip with water trap and air lubrication system, the cylinder will contain moisture and lead to corrosion. The solution is to remove the cylinder and perform repair.

3. Air Leaking Noise

If we hear air leak noise form the machine, we need to check all the pneumatic hoses. Over the time, the hoses will age and starts to crack.

We also need to inspect if the noise comes from the control valves or the cylinder. There are rubber seals inside control valves and cylinder. We can replace the seals with new part.

4. Result too high/low

When we face this problem, we need to perform several checks to the machine.

The first thing to check is the incoming air pressure, the pressure should have a minimum of 4.5bar.

The second thing to do is to clean all the residue rubber in the die/cavity. Especially the case for Mooney viscometer, there can be stuck rubber in the rotor housing and increase the friction. We should also check the rotor condition for deformation (Mooney Viscometer)

Next, perform a calibration to the temperature and torque. We can verify the temperature with a thermocouple or infrared thermometer.

Another possible reason is the die gap, the nominal gap is 0.45mm(Rheometer). Over the time, the gap might get out of spec and cause result variation in result.

5. Abnormal mechanical noise

If we hear abnormal loud noise from the machine, we should stop the machine immediately.

The noise usually comes from the bearings in the machine. It could be the bearing of the torsion arm, the bearing of the main rotor, bearings of the driven gear, motor bearing or the reducer/gearbox. Troubleshoot by remove the part and check for looseness and free-play. The bearing should feel coarse and gritty when we turn by hand. Replace the faulty part and confirm if the noise disappears.