There has been a lot of talk on the internet about the Anet A8 problems.
I disagree that it is in itself dangerous.
The Anet A8 printer has sold in its thousands and is continuing to sell.
There will always be problems selling a product in this quantity and due to the fact you put it together there is another factor at play.
I have one of these machines and at the moment it is working fine.
The areas that are of concern are :
With all of these known problems it is a wonder that it sell in the quantities it does!
Lets take them one at a time
The supplied power supply is a 12v 20a supply or a 240W power supply.
This has been talked about as being inadequate for the job – not having enough current.
With the heated bed heating and the nozzle heating and the motors moving the total current requirement is about 18A peak.
Yes it is close to it’s limit but it is still within its capability and noting that the bed and nozzle will not be on all the time it is well adequate for the job.
What I would suggest is to add a fan to cool this unit, prolonging its life.
There have been the ones which blow up, unfortunately the manufacturer of the printer has no control over the quality of the power supply manufacturer. So with the quantity supplied you will probably find that it is in the order of less than 1% failures.
When you have built your printer and operate it, you will find that the fan on the extruder comes on immediately,
When the heated bed turns off you will notice a different pitch in the fan noise and speed, this is quite normal and the dip due to the heated bed is only 0.2V, nothing to worry about.
If your power supply does give up the ghost, then it would be worth replacing it with a higher current one like this (link to 30A psu).
With the standard power supply you can run lighting to the extruder to see what is going on, but it must be low power led lighting – if you start using car led lighting then this may overload the power supply.
To control the heating of the bed and the nozzle a ‘switch’ is turned on by the controller.
This switch has to be able to handle the current required for the heating of the bed or nozzle.
The ideal switch will have no resistance, therefore not heat up at all, but in real life all semiconductor switches (mosfets) have a small amount of resistance.
This resistance will cause a small voltage drop and a small amount of power will be dissipated in this mosfet.
The power will cause a temperature rise in the device and it is fitted with a heatsink to get rid of the heat quicker.
A lot of people cannot believe that the small device on the board can handle the current of the heated bed, but due to the fact that it is very low resistance when switched on and only drops a little voltage it only consumes a little power.
The data sheet for the device says it will be an on resistance of about 0.003 ohms when fully switched on and can pass 113A max – well above the 11A required by the heated bed.
So from this there is nothing wrong with the onboard mosfets.
As for bigger is better, I totally disagree, the larger the heatsink the more the expected power dissipation – the more losses.
People have reported better heat up times when fitting external mosfets, this may be due to the improved path for the voltage to get to the mosfet and back to the power supply – the wires! These tend to be a lot thicker than the tracks on the circuit board and will have less losses. The wires from the mosfet to the heated bed are normally upgraded as well at this time, again less losses.
All of these gains ( less losses) will add up to improved times for heating.
If you have a problem with the bed not heating then fitting an external mosfet may bring your printer back to life, fitting one of these is dealt with in my post here.
The heated bed on the Anet A8 is fitted with a 6 pin connector.
This is a 3.96mm pitch connector rated at 10A, so it is being used at its maximum rating, not always a good thing.
The connector has the positive, negative and the two wires for the thermistor, with two pins unconnected.
The connectors datasheet says it has a contact resistance of 0.02R, trying to reduce the power losses in the connector.
This power loss will heat the connector up slightly.
As the connector is in direct contact with the heated bed then whatever temperature the bed is at the connector will be at, so if the bed is run at 60C then the connector will be at 60C, if the bed is run at 105C then the connector will be at 105C.
As the connector maximum temperature is 85C then you can see that running the bed at 105C is taking it outside its limit.
With the heated bed moving while the print is going there will be movement on the connector, this may cause partial disconnects and arcing build, leading to increased resistance and increased heating.
It is not uncommon, in the forums to see connectors with brown marks on the sides where the connector has overheated and burnt the shell material.
Is this connector suitable for the job, yes it is just ( again, as with the power supply). My reasoning is that the bed will heat – so it is on continuously, then it will switch off until the bed temperature drops, when it will switch on again. So the current then becomes cyclic rather than continuous, allowing the connector to cool.
If you are printing ABS, however, the bed temperature is up at 110C, so you can see this is already outside the operating temperature of the connector and on top of that the bed will struggle to maintain this temperature, so the current will be on for longer.
With the increased temperature the connector will expand, loosening its grip on the pin slightly increasing the resistance , which in bad cases could lead to thermal runaway, where the increased resistance causes increased heating- this in turn causes more expansion, increasing the resistance … until failure of the part in either melting of the housing or loss of contact with the bed pin.
What is the answer?
Don’t exceed the temperature of the connector and stop the wires moving the connector while printing.
Insulate your bed to prevent heat losses from underneath – I will be investigating different types of insulation in the near future.
If you are going to be printing abs or other filaments which require a bed temperature of 60C or greater then it maybe worth replacing your connector on the bed with soldered joints, this can be a bit of a pain due to the thermal mass of the bed ( heatsink effect) but it can be done with preheating the bed with a hot air gun or even a spare hotend, another post will show how to do this successfully.
Securing the wires to the bed so the connector does not move while printing may prove interesting, there are supplied ‘p’ clips for securing the wire, also cable ties. Both of these are nylon and will withstand 85C, so again not suitable for ABS work.
You could secure it to the lower plate by a nylon cable clip, as this plate does not get hot, it will need to go on the top of the plate as this goes very close to the rear frame.
The Anet A8 has a frame made of acrylic, not known for being the most robust of materials but a little more stable than the early wooden frames offered.
The construction of the A8 does leave a little to be desired, but with a few modification you can get a very good printer for a little money.
One of the major items is to put it on a stable base and secure it to it. This will stop the front frame and rods from flexing, so your Z height calibration will stay correct.
The other major weakness of the frame is when you tension the belts, as the Y axis belt is secured in the middle of the frame this part flexes when you tension the Y axis belt.
Starting a print and holding a ruler to the front frame you can see every time the bed goes towards the rear and stops the frame flexing, a very good idea is to get some right angle aluminium and secure this to the front and rear frames.
Out of the box the printer can be used, these modifications are to improve the performance.
Can you use the Anet A8 3D Printer ‘out of the box’
There are those who proclaim on the forums ‘ it’s a fire risk’, ‘a danger’ , ‘not up to the job’ , ‘ you need a fire extinguisher next to it’, are they right?
Well I personally would take care with anything I have built myself, especially if it involves electricity and heat.
I would run it for longer and longer, rather than downloading the biggest stl which will fit on my machine and run it for fourteen hours or more straight after building it. I still haven’t left the house with the printer running, even though I have tested the ‘weak’ points and they are all alright. Is it paranoia – I don’t think so, to me it is common sense.
There have been problems with some kits supplied and people have built them and they have failed. But it is a cost effective kit and things like this will happen. You need a mindset of – ok so this has broken, I can fix it with…
There are mods you can do to help yourself soon after you have built the printer and get a feel for setting it up, see my post here on 5 mods for your anet a8 printer.
It does have limitations but can perform as well as other printers costing 5 or 6 times as much.
A little understanding of what you have purchased and a lot of time learning about the printing process will not go amiss.
This is a very capable printer which you can modify if you want to, or you can operate it out of the box. If it goes wrong then fix it, the parts are available easily on the net and information on sites like this one and in the forums will help you get out of trouble.
So should you buy it – yes of course you should. It is a cheap printer with good performance, needing a little care, but they all will.
Are they dangerous, a fire hazard – well anything which involves heat up to 200C and electricity is a fire hazard, would you leave your cooker on for 14 hours? Be respectful and it will reward you with many thousands of fine prints, once you get it set up.
What Anet A8 problems have you come across – have you had any problems other than the ones listed above? Leave a comment in the box below so we can all learn about the new risk.
Thanks for reading and I hope I have put your mind at rest over the hyped risks with the Anet A8 problems.