##### MK3S+ with Revo Upgrade - The nozzle temperature is wrong (not the real one)!

Hi,

after upgrade and some prints with the Revo, I noticed that especially with PLA, the quality of the material looks like when it was extruded at a very low temperature.

That was not the look of the old way E3DV6 printing.

So I dismounted the extruder gears, removed them, and set the nozzle temperature to 230°. As often happen at around 60° I got one beep THERMAL ANOMALY but the process continued with no interruptions.

Once it was steady at 230° I put an high precision temperature sensor inside the extruder instead if the filament until I reached the core of the hot nozzle, and my suspects were confirmed. I used the EEVBLOG BM786 multimeter that has a very good precision, so I expects the values correct.

The** real temperature was 225°** while the **LCD displayed 230°** 😲

I retried at** 200°** and the **real temperature was 196°** (where barely the PLA melts)

* So it seems the FW reports at least 5 degree less*. 😨

I will try to offset the filament settings to a higher temp for now.

##### RE: MK3S+ with Revo Upgrade - The nozzle temperature is wrong (not the real one)!

2 % error is small error. The Revo is an integrated heater and thermistor. There will be thermal losses between the heater unit and the nozzle as there is a small air gap. These will be small but could account for 2% Someone with more thermal engineering experience could calculate the losses between heater core and the nozzle. This is why there is thermal paste/pads used for heatsinks in electronics for cooling.

##### RE:

@Robin_13 you gave me an idea, so I asked to google AI the following question:

I have a 2mm diameter brass tube that is 20mm long, heated with a maximum of 40W of power. PLA is introduced inside at 25° and flows at 18 mm^3/s.

What temperature must have the brass tube to obtain a PLA flow output at 220°?

... and this was the answer:

*To calculate the temperature required for the brass tube, we need to consider the following:*

*The heat transfer rate from the brass tube to the PLA The mass flow rate of the PLA The specific heat capacity of PLA The desired temperature of the PLA output*

###### Heat transfer rate

*The heat transfer rate from the brass tube to the PLA can be calculated using the following equation:*

*q = hA ΔT*

*where:*

*q is the heat transfer rate in watts (W) h is the heat transfer coefficient in watts per square meter per degree Celsius (W/m^2 K) A is the surface area of the brass tube in square meters (m^2) ΔT is the temperature difference between the brass tube and the PLA in degrees Celsius (K)*

*The heat transfer coefficient for laminar flow of PLA in a brass tube can be calculated using the following equation:*

*h = 4.36k/d*

*where:*

*k is the thermal conductivity of PLA in watts per meter per degree Celsius (W/m K) d is the diameter of the brass tube in meters (m)*

*Substituting these values into the heat transfer equation, we get:*

*q = 4.36k/d * A * ΔT*

**Mass flow rate**

**Mass flow rate**

*The mass flow rate of the PLA can be calculated using the following equation:*

*m = ρQ*

*where:*

*m is the mass flow rate in kilograms per second (kg/s) ρ is the density of PLA in kilograms per cubic meter (kg/m^3) Q is the volumetric flow rate of the PLA in cubic meters per second (m^3/s)*

*Substituting the given values into the mass flow rate equation, we get:*

*m = 1.24 kg/m^3 * 18 mm^3/s = 2.232 * 10^-5 kg/s*

**Specific heat capacity of PLA**

**Specific heat capacity of PLA**

*The specific heat capacity of PLA is 1.75 joules per gram per degree Celsius (J/g K). This means that it takes 1.75 joules of energy to raise the temperature of 1 gram of PLA by 1 degree Celsius.*

**Desired temperature of the PLA output**

**Desired temperature of the PLA output**

*The desired temperature of the PLA output is 220°C.*

**Calculating the temperature of the brass tube**

**Calculating the temperature of the brass tube**

*Now that we have all of the necessary information, we can calculate the temperature of the brass tube required to achieve the desired PLA flow output temperature.*

*ΔT = (T_out - T_in) = 220°C - 25°C = 195°C q = m * c_p * ΔT = 2.232 * 10^-5 kg/s * 1.75 J/g K * 195°C = 7.78 * 10^-3 W h = 4.36k/d = 4.36 * 0.24 W/m K / 2 mm = 5.23 W/m^2 K A = π * d * l = π * 2 mm * 20 mm = 125.66 mm^2 = 1.2566 * 10^-3 m^2*

*Substituting these values into the heat transfer equation, we get:*

*7.78 * 10^-3 W = 5.23 W/m^2 K * 1.2566 * 10^-3 m^2 * ΔT ΔT = 7.78 * 10^-3 W / (5.23 W/m^2 K * 1.2566 * 10^-3 m^2) = 12.83 K*

*Therefore, the brass tube must have a temperature of 237.83°C to achieve the desired PLA flow output temperature of 220°C.*

**Note:** This is just a theoretical calculation. In practice, the temperature of the brass tube may be slightly higher or lower due to factors such as heat loss to the environment and the efficiency of the heating element.

**Note:**This is just a theoretical calculation. In practice, the temperature of the brass tube may be slightly higher or lower due to factors such as heat loss to the environment and the efficiency of the heating element.

# WOW ! 😜

##### RE: MK3S+ with Revo Upgrade - The nozzle temperature is wrong (not the real one)!

Glad I pointed you in the right direction. More detail than I expected but useful to understand. I just knew about the heat transfer issues from experience at work having to do some very weird soldering. It wasn't my job to do the calculations.