Thingiverse
CTC Heated Build Platform Thermistor Fix by slippyr4
by Thingiverse
Last crawled date: 4 years, 1 month ago
Many, many owners find that the Heated Build Platform on their CTC Dual Printer (which is a clone of the Flashforge Creator, which is in itself a clone of the Makerbot Replicator Dual), is woefully badly calibrated.
The HBP is based on the original Replicator HBP ( http://www.thingiverse.com/thing:16061 ), but the PCB layout is tweaked to make space for a largish (~7mm) thermistor, or a 1206 SMD part (only 1 should be fitted though).
In many ways, it doesn't really matter if the displayed (set) temperature doesn't match the real HBP temperature, so long as it's consistent. However, on my CTC, it was out such that a set temperature of 90C resulted in a platform temperature of about 60 degrees, and the maximum allowed set temperature of 130 degrees resulted in an actual platform temperature of 90 C. That's not good enough - the inaccuracy means the HBP isn't really hot enough for reliable ABS prints.
The reason for the discrepancy is that CTC chose the wrong part for the thermistor. I'm not sure what the part is they used, but it's beta is way out of the required beta.
I'm running Sailfish 7.7, and according to the source code, the firmware is designed to work with a 100k thermistor with beta 4066K with R2 at 4.7K.
So, replacing the thermistor with a better part will fix the problem.
I chose to use an EPCOS B57540G0104J thermistor. Which is absolutely tiny, but works very well. You should be able to find one on RS, Digikey, Farnell, the usual suspects.
The HBP is based on the original Replicator HBP ( http://www.thingiverse.com/thing:16061 ), but the PCB layout is tweaked to make space for a largish (~7mm) thermistor, or a 1206 SMD part (only 1 should be fitted though).
In many ways, it doesn't really matter if the displayed (set) temperature doesn't match the real HBP temperature, so long as it's consistent. However, on my CTC, it was out such that a set temperature of 90C resulted in a platform temperature of about 60 degrees, and the maximum allowed set temperature of 130 degrees resulted in an actual platform temperature of 90 C. That's not good enough - the inaccuracy means the HBP isn't really hot enough for reliable ABS prints.
The reason for the discrepancy is that CTC chose the wrong part for the thermistor. I'm not sure what the part is they used, but it's beta is way out of the required beta.
I'm running Sailfish 7.7, and according to the source code, the firmware is designed to work with a 100k thermistor with beta 4066K with R2 at 4.7K.
So, replacing the thermistor with a better part will fix the problem.
I chose to use an EPCOS B57540G0104J thermistor. Which is absolutely tiny, but works very well. You should be able to find one on RS, Digikey, Farnell, the usual suspects.