A look into the issues surrounding Anet 3D printer fires – by Dr. Phil3D

“Friends don’t let friends buy Anet”

After seeing numerous incidents of Anet printers catching fire I decided to do some investigating of my own. I have a nearly brand new Anet A8 that was given to me after its frustrated owner gave up on it and gave it away. I had planned to strip it for parts, but instead, I will attempt to make it catch fire in the name of safety.

The results are quite interesting and ultimately the risk of fire comes down to poor design and the factory trying to save money on production costs.

Design and Manufacturing Flaws

When a PCB is designed to be produced at very low-cost small irregularities and underrated or counterfeit components will push an already stressed circuit over the limit. Changes not foreseen by the engineer are made to reduce cost. For example, capacitors or resistors may be changed to a different brand which can save a fraction of a penny. On a large production scale, the savings add up. Now, this may be ok for knockoff android phones, but when it comes to a machine that moves and runs endlessly at high temperatures cheaping out on parts to save pennies will inevitably cause property damage and injury.

https://reprap.org/wiki/Safety

The first thing that stands out is the wiggly power connectors, this is never a good sign. I held a light to the back of the PCB and was shocked to see how thin all the traces are.

This printer was designed to make a profit at the cost of safety

Everything is at the absolute minimum, through-hole components are poorly soldered at too low of a temperature.

Testing for overheating

Using a CAT S60 thermal imaging camera I closely monitored the Anet’s control board for signs of overheating in multiple scenarios, printing PLA with and without the heated bed to more extreme cases that are common for materials like ABS, Nylon or Polycarbonate.

I’m familiar with the mandatory heated bed MOSFET upgrade, however, after reading the Reddit post linked above I believe the fire was caused by an underrated 5-volt regulator. I was surprised to find the 5-volt regulator reaching temperatures of 64˚c under normal operating conditions generating substantially more heat than the heated bed MOSFET.

If the power supply voltage is increased to 14.5 volts the temperature of the regulator rises. After an hour and a half runtime at 14.5 volts, the 5-volt regulator reached a temperature of degrees 112˚C or 233˚F

Make sure to properly adjust your power supply!

Stepper Drivers

The minimal amount of copper in the two-layer PCB does not provide sufficient heat dissipation for the A4982 stepper drivers.

Heated Bed Wiring situation

Unsecured wiring will fray and break.

Conditions for thermal runaway which may lead to fire

Worn out wires and loose connectors

Unsecured print bed and hotend wires

Power supply voltage set higher than 12.5-volts dc

Heated bed temperature set too high 85 ˚ c or more

Hotend temperature set too high 230 ˚ c to 250 ˚ c and higher is risky

Rapid acceleration and deceleration

Lengthy and large prints

Modifying Firmware settings for Jerk, Acceleration or Feedrate beyond their stock limit. (some slicers may do this automatically)

Heated bed thermistor location causes incorrect temperature reading

I discovered setting the heated bed to 85c or higher causes a dangerous situation as the firmware attempts to reach temperature the thermistor which is located on the bottom of the heater PCB does not read the actual surface temperature of the bed which is substantially higher.

Setting the bed temperature to anything higher then what can be reached leaves the heated bed MOSFET endless in the ON state.

In this photo the bed temperature is set to the maximum of 120˚c, the LCD reading is 100˚c, however, the actual surface temperature is exceeding 150˚C

The 5v power regulator is running hotter than the heated bed MOSFET. This would explain how someone could have their printer catch fire even after the MOSFET upgrade.

5-volt Regulator under normal conditions (heated bed off) reads 46.4˚c

Maximum Temperature set, 5-volt regulator is reading 111.6˚ c



Reaching Temperatures of 113 ˚ c

Conclusion

I believe many people have been given a false sense of security with their Anet printers, the heated bed MOSFET upgrade does not solve serious product safety issues associated with this low-quality board.

After a quick google search, my suspicions have been confirmed. Numerous posts on Reddit and other forums regarding accounts of voltage regulators failing. One, in particular, stated that they heard a loud pop noise before the printer stopped working.



This printer is unsafe under any operating conditions! As these machines age and accumulate use, unfortunately, I am certain that we will see more many preventable accidents occur.

Merry Christmas, Be Safe!

And remember Friends don’t let friends buy Anet

Here are some simple solutions

If you decide to continue using your Anet printer without changing to a new controller here are some simple upgrades that will help.

Improve heat dissipation by adding adhesive heatsinks to the back side of the board directly over the bottom of the stepper drivers, 5-volt regulator, and heated bed MOSFET.

Add a cooling fan

Add a smoke alarm

Zip tie loose wiring harness on the heated bed and hotend

https://reprap.org/wiki/Safety

https://3dprint.wiki/reprap/anet/a8

https://letsprint3d.net/2018/05/30/critical-safety-mods-upgrade-anet-a8?fbclid=IwAR3uk-WbsJopmbKb7Aq4yA1-oAiGxLkGQVAGSL1OUhoNbjioVURiXfj3o1U

5-Volt Regulator Datasheet AMS1117

Maximum Voltage: 18V

Operating Temperature -20˚c to 125˚c Max

As reference voltage increases temperature increases







12-volt Regulator Datasheet

Maximum Voltage: 30V

Operating Temperature: -20˚c to 175˚c Max

Sources

Reddit: Here’s a reminder to not leave your printer unattended.

Fire Hazard

Reddit: Anet Burns down half the house

Thermal Runaway test youtube

Reddit: House fire thanks to a cheap printer