reprap:anet:a8:improvements:understanding_my_heatbed

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reprap:anet:a8:improvements:understanding_my_heatbed [2018/12/30 09:57] – [Heat-bed Power] cj_elec_techreprap:anet:a8:improvements:understanding_my_heatbed [2018/12/30 10:19] (current) – [The optimal wire] cj_elec_tech
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 {{ :reprap:anet:a8:improvements:mypicture2.gif |}} {{ :reprap:anet:a8:improvements:mypicture2.gif |}}
  
-Resistance is calculated by dividing the voltage by the current, which leads to the following resistance{{ :reprap:anet:a8:improvements:mypicture3.gif?direct&400 |}}+Resistance is calculated by dividing voltage by current - this lead to the following resistance{{ :reprap:anet:a8:improvements:mypicture3.gif?direct&400 |}}
  
 This gradient nearly fits the gradient expected for copper with an temperature coefficient of approximately 0.0039 1/K This gradient nearly fits the gradient expected for copper with an temperature coefficient of approximately 0.0039 1/K
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 This is probably the reason why there are values of 1.2 to 1.6 Ohms mentioned in some forums and sites for this heat-bed. This is probably the reason why there are values of 1.2 to 1.6 Ohms mentioned in some forums and sites for this heat-bed.
 ==== Simulating the heat bed ==== ==== Simulating the heat bed ====
-In  order to undertstand the heat bed behavior in more datail I made a {{ :reprap:anet:a8:improvements:warm_up_2.xlsx |heat bed simulator}} in excel (dispite I don't like to this software for simulations). It fits quite well to the measured data, therefore it seems to be not so bad. But keep in mind that it is a model and not the reality.+In  order to understand the heat bed behavior in more detail I made a {{ :reprap:anet:a8:improvements:warm_up_2.xlsx |heat bed simulator}} in Excel (despite not liking this software for simulations). It fits quite well to the measured data, therefore it seems to be not so bad - but keep in mind that it is a model and not reality.
  
 {{ :reprap:anet:a8:improvements:mypicture4.gif |}} {{ :reprap:anet:a8:improvements:mypicture4.gif |}}
  
-The cool thing about simulations is that you can evaluate heat fluxes which are difficult to measure and to make a serios of variations which would require months of testing in a few minutes.+The cool thing about simulations is that you can evaluate heat fluxes which are difficult to measure and to make a series of variations which would require months of testing in a few minutes.
  
 {{ :reprap:anet:a8:improvements:mypicture7.gif |}} {{ :reprap:anet:a8:improvements:mypicture7.gif |}}
  
-When the steady state is nearly reached the initial 110W of electric power are reduced to 0 by the following contributions (for a heat bed without insulation). It can be seen that a large portion of the heat is irradieted by infrared radiation. This should possible to easily reduced by a factor of 8 to 9 by applying a aluminium foil(emissivity 0.11) beneath the heatbed or insulation.+When the steady state is nearly reached the initial 110W of electric power are reduced to 0 by the following contributions (for a heat bed without insulation). It can be seen that a large portion of the heat is radiated by infrared radiation. This should possible to easily reduced by a factor of 8 to 9 by applying a aluminium foil (emissivity 0.11) beneath the heat-bed or insulation.
  
 {{ :reprap:anet:a8:improvements:mypicture8.gif |}} {{ :reprap:anet:a8:improvements:mypicture8.gif |}}
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 ==== Analysis with the simulator==== ==== Analysis with the simulator====
-It can be seen with these curves that quite thick insulation is nescessary for a large effect onto the heat curve.+It can be seen with these curves that quite thick insulation is necessary for a large effect on the heat curve.
 {{ :reprap:anet:a8:improvements:mypicture9.gif |}} {{ :reprap:anet:a8:improvements:mypicture9.gif |}}
  
 {{ :reprap:anet:a8:improvements:mypicture13.gif |}} {{ :reprap:anet:a8:improvements:mypicture13.gif |}}
  
-Nearly half of the of the heat is lost by infrared heat radiation. Therefore an aluminum foil at the bottom is more effective than 6mm of kork. To reduce the heatloss even more combine them.+Nearly half of the of the heat is lost by infrared radiation. Therefore aluminum foil on the bottom is more effective than 6mm of cork. To reduce the heat-loss even morecombine them.
 {{ :reprap:anet:a8:improvements:mypicture14.gif |}} {{ :reprap:anet:a8:improvements:mypicture14.gif |}}
  
  
-It can be seen with these curves that increasing the voltage on the heatbed increases the speed and max temperature. This can be achived by 3 measures: +It can be seen with these curves that increasing the voltage on the heat-bed increases the speed and max temperature. This can be achieved by 3 measures: 
-  * Use thicker wires between HB and board and board and power suplly.(see the optimization chapter below) +  * Use thicker wires between heat-bed and the boardand board and power supply (see the optimization chapter below). 
-  * Solder the wires directly onto the heatbed (some soldering practice needed) +  * Solder wires directly onto the heat-bed (some soldering practice is needed). 
-  * increse the voltage of the power suplly. This might be risky and is only recomended if you have [[reprap:anet:a8:replace_connectors|replaced the orignal connectors]]. The power suplly might exeed its limits, therefore a power suplly with 30A at least is recomended by some users if 14V is used. Thoretically the arduino in the Anet board can go up to 18V but only 12V is recomended for arduinos. So it should be possible but it is your own risk.+  * Increase the voltage of the power supply. This might be risky and is only recommended if you have [[reprap:anet:a8:replace_connectors|replaced the original connectors]]. The power supply might exceed its limits, therefore a power supply with 30A at least is recommended by some users if 14V is used. Theoretically the Arduino in the Anet board can go up to 18V but only 12V is recommended for Arduinos. So it should be possiblebut it is your own risk!
 {{ :reprap:anet:a8:improvements:mypicture11.gif |}} {{ :reprap:anet:a8:improvements:mypicture11.gif |}}
  
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-==== Some research in the net==== +==== Some research on the Net==== 
-The heatbed for the A8 was increased to 220x220mm from the original Prussa i3 design with 200x200mmAparently the power was not not scaled accordingly. +The heat-bed for the A8 was increased to 220 x 220mm from the original Prussa i3 design (200 x 200mm)Apparently the power was not scaled accordingly. 
  
-Some recomendation say you need 0.6 W/cm² for a heat bed. This would mean 290W for the A8 heat bed. But it has not even half(110W) of it.+Some recommendations say you need 0.6 W/cm² for a heat-bed. This should mean 290W for the A8 heat-bed, but the A8 is not even half that value (it's only 110W).
 ==== The optimal wire ==== ==== The optimal wire ====
-The original wires from the Anet printer are thin and therefore have an resistance which lead to an power reduction of the heat bed. If you use extremly thick wires you it will be a mechanical issue for the Y-axis stepper and as cables are made of very good thermal conductors it will remove heat from your heatbed by conduction. This rough estimation shows that AWG 9 would be an Optimum from the thermal point but the difference from an AWG 14 is minimal and AWG14 is conciderable more flexible and can be crimped with blue pre insulated crimps. Also the 1 W more for AWG16 would be ok as this as 1W would increase the max heat bed temperature by only 0.5K. +The original wires from the A8 printer are thintherefore their resistance leads to an power reduction to the heat-bed. If you use extremely thick wires you will create extra mechanical loads for the Y-axis stepper andas cables are made of very good thermal conductor, thicker wires will remove heat from your heat-bed via conduction. This rough estimation shows that AWG 9 would be an Optimum from the thermal point but the difference from an AWG 14 is minimal and AWG 14 is considerably more flexible and can be crimped with blue pre-insulated crimps. Also the extra Watt of power saved by using AWG16 wire would only increase the max heat-bed temperature by 0.5K. 
-recomend silicone wires with thin strands due to their flexibility.+recommend silicone wires with many thin strands as they are much more flexible.
  
 {{:reprap:anet:a8:improvements:optimum_cables2.jpg|}} {{:reprap:anet:a8:improvements:optimum_cables2.jpg|}}
  
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