From your answers I decided to purchase a 5w 5.6ohms and a 5w 6.8ohms. Those things are way bulkier than the one I had. Side by side I would have never though the smaller one was an 8w (and now I think it wasn't an 8w). I had to attach the 5.6 ohms to the heating block because it does not fit the hole on the block. This means a lot of the heat is going to inevitably go to the air. However, I did use thermal compound and attached it in such way that it is right next to the nozzle.
With regards to heat sinking a heating element, from what I gather, as soon as we attach/introduce it into the block of aluminium it will inevitably work as a heat sink. Traditionally, at least in my case, I want this heat to stay away of my CPU or any other electronics components, the difference here is that we want to use this heat for good. There are formulae to know how much heat a heat sink with fins can dissipate, and linking this to how much the extended surface of the heat sink increases the wattage of the heating element would be great.
I have been trying to find a simple way to know how much the wattage is increased with a specified material block, surface area and/or volume. Just to tell me if the aluminium block is raising the wattage close enough to ~26w (12^2*5.6), That way I can run my printer without fear that it might break down in the middle of a print. This is what I assume that NoobMan was making reference when he said it is '..not necessarily predictable'. One has to consider the increased area and conductivity to the heat sink to find the wattage increase. If anyone has a formula that can be simple enough to just ballpark it to this final wattage it would be good enough for me.
The easily predictable part is the temperature, like Traumflug explained. Looking at my initial test of the 5.6ohms, it took about 8 min to reach 200C. The dead one reached there quicker but since it is not placed in the same location I cannot say for sure that it had less resistance or that the thermal compound increased conductivity. To be on the safe side and avoid killing anything else I reduced the output at line 218 (..ish in my Marlin #define PID_MAX) from 255 being full power to 225 which according to my calculations should be ~20w (not fully sure). It now takes about 10min to reach 200. I am ok with that length of time but if I can speed it up knowing it will hold it would be great.
With regards to heat sinking a heating element, from what I gather, as soon as we attach/introduce it into the block of aluminium it will inevitably work as a heat sink. Traditionally, at least in my case, I want this heat to stay away of my CPU or any other electronics components, the difference here is that we want to use this heat for good. There are formulae to know how much heat a heat sink with fins can dissipate, and linking this to how much the extended surface of the heat sink increases the wattage of the heating element would be great.
I have been trying to find a simple way to know how much the wattage is increased with a specified material block, surface area and/or volume. Just to tell me if the aluminium block is raising the wattage close enough to ~26w (12^2*5.6), That way I can run my printer without fear that it might break down in the middle of a print. This is what I assume that NoobMan was making reference when he said it is '..not necessarily predictable'. One has to consider the increased area and conductivity to the heat sink to find the wattage increase. If anyone has a formula that can be simple enough to just ballpark it to this final wattage it would be good enough for me.
The easily predictable part is the temperature, like Traumflug explained. Looking at my initial test of the 5.6ohms, it took about 8 min to reach 200C. The dead one reached there quicker but since it is not placed in the same location I cannot say for sure that it had less resistance or that the thermal compound increased conductivity. To be on the safe side and avoid killing anything else I reduced the output at line 218 (..ish in my Marlin #define PID_MAX) from 255 being full power to 225 which according to my calculations should be ~20w (not fully sure). It now takes about 10min to reach 200. I am ok with that length of time but if I can speed it up knowing it will hold it would be great.