Category Archives: maintenance

My Filament is Not Coming Out : Why?

no filament out of the nozzle- find out why...

Filament problems with your 3d printer – find out what causes them and how to fix them.

It’s always the case – the print that matters – you have setup the printer and made sure everything is working – you go to print and even the perimeters are not printing  -now what…..

The filament is not coming out of my hotend : There are a few reasons that filament may not come out of your hotend: nozzle too close to the print bed, extruder not working, clogged throat or the filament not loaded correctly.

But all of these problems are solvable, once you sort out the main reason, in this article I take you through the possible causes of the filament not coming out of your nozzle and the solutions….

  1. Extruder motor not working
  2. Extruder gear not turning
  3. Extruder gear misaligned
  4. Not enough tension on filament
  5. Filament not loaded correctly
  6. Throat clogged
  7. Nozzle cold
  8. Nozzle jammed
  9. Nozzle height too low

Let’s have a look at each one, what you see and how to correct it.

Extruder problems

Extruder motor not turning

After you have determined that the printer doesn’t have any filament coming out of the nozzle, look at the extruder gear /shaft and see if it is turning.

If you cannot see these due to the fan obstructing them then hold the filament gently and you will feel it being tugged into the extruder.

And you will feel the motor stepping.

If you don’t feel the motor moving there can be two causes.

  1. The G-code has become corrupted and no extruder information is in there
  2. There is a problem with the motor driver, motor wiring or motor.

After halting the print you can examine the G-code to determine whether it is correct, it is always worth just checking the G-code to see what you are sending to your printer – i tend to use ideamaker or craftware ( my favorite as you see the G-code).

The printer may have just had a glitch and restarting it will print ok, but go through the rest of this article and make sure everything else is ok before restarting the print.

To test the motor use the manual movement menu to move the nozzle away from the bed.

Navigate to the extruder menu and retract a couple of mm and see the filament move – or at least try to ( but only if the nozzle is up to temperature – see below).

If the motor doesn’t move then you need to fault find on the motor system.

See my motor system fault finding article for more information.

But the basics are :

  • Check the wiring for open wires
  • Check the motor for open windings
  • Check the motor driver for correct operation

You can swap the extruder motor for the x motor ( if you know that is working correctly) to test for wiring and motor problems.

Remember to swap it back afterwards.

Extruder gear not turning

This is a commonish fault, where the grub screw works its way loose.

The motor is turning, but the gear is not turning – so no filament is being fed into the hotend.

Use the movement menu to move the extruder ( again if the hotend is up to temp) both forwards and backwards to make sure that the gear  rotates correctly.

Re tightening the grub screws fixes this.

Make sure one of the grub screws it located on the flat of the shaft –

tip for seeing whether the shaft and gear are turning in synch - add a linethis way it takes a lot more to have this fault.

One tip is to use an indelible pen to mark the gear and shaft to see if they are rotating together.

This way, when you carry out your routine maintenance ( you do do it don’t you) you can see at a glance that the gear is rotating with the shaft both on load and retraction.

Extruder gear misaligned

This fault is common when you build the printer.

You push the gear onto the shaft and tighten it

When you load the filament you don’t notice that the filament is not catching on the teeth, but on the shaft and cannot be fed into the hotend due to no force on the filament.

You can visually see this when you remove the cooling fan.

Repair is to loosen the gear and realign it with the friction wheel.

Check that when you load the filament you can feel the motor turning when you pull on it gently ( and a visual check is worth it)

Not enough tension on filament

This fault shows no flow of filament from the nozzle.

The filament is catching the teeth of the extruder gear.

There is no clicking of the extruder motor.

There is no grinding of the filament.

There are no marks when it is unloaded.

This would indicate that there is not enough tension on the filament and the gear is slipping over the filament.

To test that filament is coming out of the nozzle, making sure the nozzle is up to temperature, push on the lever to release all the tension and gently push down on the filament, forcing it out of the nozzle.

Correction is to increase the tension on the filament by adjustment of the screw on the spring for the pinch roller.

Filament not loaded correctly

This is another problem you come across when starting out.

Feeding the filament into the extruder and down to the hotend can be problematic.

Knowing whether it has entered the hole for the throat and has gone in far enough to reach the hot end without hitting an obstruction.

If you suspect this then mark it at the top of the extruder and withdraw it.

Measure the depth of the extruder and hotend to the nozzle and see it this measurement ties up with the mark on the filament.

If it is a lot short there maybe an obstruction in the throat or a misalignment of the liner to the nozzle – something that prevents the filament reaching the hotend and then coming out.

A thin wire or toothpick (preferred) can be carefully inserted into the throat – feeling for any obstructions – this is carried out after removal of the extruder motor.

Mark the toothpick and if necessary disassemble the hotend noting whether there is any obstruction at the height you measured.

Reassembly and readjustment of the z height will be necessary before you print again – so this one is a last resort if possible.

Hotend problems

Throat clogged

If your filament rises too far on retraction it can drag heat too far up the throat and on cooling the filament can start to cause a problem feeding the filament down.

If your hotend is too hot, the heat can rise through conduction melting the filament above the hotend causing a blockage – preventing the filament being fed through the nozzle.

You may hear a ticking as the extruder gear jumps on the filament, it is a regular tick….tick as the gear tries to feed the filament into the hotend.

To test for this – release the pressure on the pinch wheel and push gently onto the filament – forcing it down.

You will feel whether it is moving or not.

If it doesn’t move then try retracting it.

This is done with the hotend hot.

If it wont retract then it maybe jammed in the throat.

Removal of the extruder motor and lifting the extruder gear and pinch roller off the filament before cutting the filament and stripping down the hotend is the only way to cleat the blockage.

Make sure the nozzle is hot when you remove it as i have sheared one when trying to remove it full of filament.

You maybe able to force the filament down through the hotend to get it out.

This is one of worst faults as you need to reset the whole of the hot end and bed height, it all takes time.

Do check your retraction lengths and temperature you are running your material at.

Make sure there is adequate cooling at the extruder – put the fan back on….

Nozzle cold

If the extruder doesn’t start to click and the print starts to fail with no filament coming out, then flick your eyes up to the nozzle temperature before you abort the print.

If the temperature is below 180 degrees then there is a safety cutout where the software stops feeding the filament below that temperature.

This maybe due to a hotend heater failure or an intermittent connection.

With the movement you get on the hotend, unless the wires are secured the movement can cause a rapid failure at stressed points – like where the wire comes out of the heater.

This connection maybe made when the nozzle is on the bed, but open when the z height raises, causing a little confusion as to where the problem is.

A gentle tug on the wiring will determine whether it is secure into the heater or comes away easily.

Replacement of the heater cartridge or heatblock is the only course of action – making sure you secure the wires to reduce this in the future.

Replacement of the heatblock will mean that you have to check the bed clearance again….

Nozzle jammed

So with the above fault you were not able to withdraw the filament from the throat.

With this one you can.

But still pushing down on the filament, with the hotend hot nothing is coming out.

You may get the same ticking from the extruder as in the fault above.

Ok, so you now have a blocked nozzle.

Thee are two ways you can deal with this.

With the nozzle hot – replace it.

Or try a cold pull to remove the material from the nozzle and hopefully the debris.

To carry out a cold pull take the nozzle temp down to 100c with the filament still inserted.

Once it is there – release the tension on the pinch roller and give the filament a hard yank – but don’t damage your printer.

Hopefully the filament has come loose from the nozzle and reformed itself into the lining of the throat before it cools.

When it comes out it should look like the inside of the nozzle shape on the end.

Thee maybe little black bits on it – these could be burnt filament or other debris gone down into the hotend causing it to be jammed.

It maybe that the filament comes out but it doesn’t feel like all of it came out, to test this cut the end at 45 degrees and reinsert – if it doesn’t go all the way down then you have a piece stuck in the throat.

Using a drill smaller that the throat you could try to force the filament down to the hotend and try the cold pull again – or remove the nozzle and then force the filament down the throat.

Whichever way you do it – remember there maybe debris on the end that will cause a blockage again – so don’t just force it down and carry on printing…..

The easiest way is to carry stock of the common nozzles you use and replace it if it jams. They are cheap enough to carry a few in stock.

There are on the market nozzle cleaning kits.

These are made up of very thin steel wires used to force the filament out of the nozzle when it is jammed.

For me i wonder at the damage you can do the the brass nozzle ( which is very soft compared to the steel) waggling the pin around trying to clear the jam.

But really all you are doing is to move it to one side, waiting for it to clog the nozzle again- or partially clog it in a few minutes or hours…

Now you go back to printing with an unknown nozzle size and wonder why your prints are not as good as they used to be.

As you can tell I am not really a fan of these as they can do more damage than they fix.

If you take off the nozzle you can then clear it out from the rear without damaging the accurate exit hole.

Bed height

Nozzle too close to bed

This fault is one most beginners get , I still get it occasionally, but i know quickly what to do.

The first layer starts to print – you have spent hour s leveling the bed and it is perfect.

But no filament is coming out.

Then you hear the extruder gear clicking.

And you think you have a clogged nozzle .

So you abort the print – raise the nozzle and push the filament through.

Only to have it come out of the nozzle quite happily -dropping straight down.

This maybe a case where the blockage is the bed itself.

With the nozzle too low no filament can be forced onto the bed.

When you get a little more experience then you will be able to use the time your printers takes to print the perimeter lines to adjust the bed.

Knowing that a whole turn of the bed screws adjust the bed down 0.45mm to 0.5mm depending on whether you have 2.5mm or 3mm screws.

You know that there is quite an adjustment if you don’t see any filament come out, then you see the filament ooze around the nozzle and know that it will not stick to the bed.

You could try pinning it down with a scalpel to try to drag it off the nozzle, but 9 times out of 10 I halt the print and clean off the nozzle and give the bed screws half a turn to move the bed downwards – wondering why it has moved again.

Checking the z endstop tightness to see if that as caused this problem…

And Finally

I hope reading through this has helped sort out thing to try to clear the fact that the filament is not coming out of the nozzle.

Let me know if you find any more which can cause this and i will add it to the list.

Thanks for reading



Anet A8 hotend problems : leaking filament

This article is how to find out whether your Anet A8 hotend has been assembled correctly.

 Common Problems with the Anet A8 hotend

There are three main problems associated with the hotend which anet a8 hotend :leaky nozzlewill be dealt with in this article.

  • Filament leaking from the top of the heat block
  • Filament leaking from the bottom of the heat block
  • Hotend loose when heated.

When you receive your Anet A8 the hotend will probably be assembled, mine was. What you don’t realise is that it is probably assembled wrong – as mine was!

You assemble the unit onto the printer and start printing.

After a short while there appears at the top of the heatblock some molten filament.

If you are unlucky this can increase and drop down onto your printed model and either catch with the nozzle or cause detaching problems when the nozzle knocks your print off.

In the best case where it doesn’t drip you are left with a lot of filament stuck to the top of the heat block, requiring cleaning up.

Or the filament starts oozing from the top of the nozzle and drips onto your model causing problems.

Or after heating up the printer you start printing and notice that the heatblock is spinning around and causing printing problems with your model.

Whichever it is this needs to be rectified.

 What is the hotend made up of?

The Hotend is contructed of a few parts. these include:hotend components

  • The throat
  • The liner
  • The heat block
  • The cartridge heater
  • The thermistor
  • The nozzle

The liner is usually made out of PTFE material, slippery and heat proof. This is the insulation while the filament goes through the extruder.

The PTFE tube is fitted inside the throat, made of stainless steel. It goes right down to the bottom to be butted up against the nozzle. The throat forms the connection between the extruder and the hotend. It also forms the heatbreak to prevent heat from the hotend from backing up the throat causing blockages.

The metal heater block holds all of the parts of the hot end block together.

The Cartridge heater, a 12v 40w heater raises the temperature of the heat block above the melting point of the filament.

The thermistor gives the controller some feedback on the temperature of the heat block. Once close to temperature the heating is cut back so that it doesn’t overshoot. It closes the loop of the cartridge heater into the heatblock to the thermistor, back to the controller.

The nozzle is the melt zone. Once liquid the filament is forced through the opening in the tip of the nozzle. The semi melted filament forms a plug which pushes the molten filament out of the nozzle.

How to disassemble your hotend properly

Once you have used your hotend it will be full of filament.extruder assembly removed from printer

If you try to disassemble this when it is cold then you stand a good chance of breaking it.

If the nozzle has stuck this can shear off when trying to unscrew it.

Or the throat may snap, again with the filament stuck to it.

So what do you do?

I tend to cut off the filament at the top of the extruder rather than trying to remove it by pulling out.

Switch your printer on and warm it up, it doesn’t have to be at the melting temperature, just above the transition temperature from rigid to flexible – which on PLA occurs at about 50C.

So set the printer to preheat PLA – if PLA is what you are using, and go back to the main screen. Watch the temperature until it rises above 60C and you can then switch the printer off.

To remove the nozzle at this time, use a pair of molegrips ( visegrips) to hold the heatblock- carefully avoiding the heater cartridge and themistor.

With the correct size spanner unscrew the nozzle. This should turn relatively easily now the plastic is warmed.

Place it down on something that can withstand the heat without melting or being damaged. – I put it on the printers bed.

On the Anet A8 the hotend is held in place with the lower bracket of the extruder motor.

If you undo the nut and the allen bolt holding this bracket to thehotend removed frame and the two screw holding the extruder motor you can remove the throat/heatblock/retainer completely.

Now while it is still warm the nut can be tightened up to the mounting block and the heatblock gripped in the molegrips again.

The throat can be removed from the heatblock at this time.

If it proves difficult then remove the mounting block and add throat removedanother nut to the throat.

Tighten the two nuts together, and using a spanner on the nut closest to the heatblock, use the molegrips to remove the heatblock from the throat.

You may need to clean out the threads of the heatblock or replace it if there is damage to the threads.

Check the throat for damage to the threads or to the PTFE liner. If it is blackened it may have been overheated or bits of filament may have overheated – these can break off and cause partial blockages in the nozzle while printing.

As they are only a couple of dollars then replacement would be the

removed nozzle
all the black is overheated filament ready to block the nozzle

best move – keep these in stock as consumables.

Remove any remaining filament and make sure that all of it is cleaned before reassembling.

 Assembling Your 3D Printers Hotend Correctly

To assemble your hotend correctly make sure you have all the pieces available.

Nozzle, throat, heatblock and that’s it. If the heatblock has the hotend partscartridge heater and the thermistor installed make sure you are careful with the wires. You don’t want to reassemble the hotend onto your printer just to have the wires break.

Personally I reassemble the hotend cold and have had no problems, others are not so lucky and perform the last stage hot. This is something you will need to try and see which way works best for you.

Taking the nozzle, screw this into the heatblock by hand until it goes


Then unscrew it by 1/2 a turn.

Now take the throat and screw that in until it is stoped by the nozzle.

Using the molegrips, hold the heatblock to stop it rotating while using a spanner to tighten the nozzle onto the throat.

Don’t over tighten the nozzle, it need about 1/16th of a turn to take up any slack in the threads and to prevent it leaking from the joint between the nozzle and throat.

After you have tightened this examine the nozzle to see that there is still a small gap between the body of the nozzle and the heat block.

Now the nut to hold the hotend to the extruder can be screwed down the throat, if it was removed.

And the mounting block screwed onto the throat.

The throat end should come to the top of the mounting block or slightly protrude. The wires for the heater and thermistor will orientate themselves to the correct position as they were when you took the assembly off.

Offer the assembly up to the extruder and screw in the allen bolt – do not tighten. Align the mounting block and tighten the nut up to the extruder mount. Tighten the allen bolt.

Place the spring for the extruder in the correct position and holding hotend installeddown te extruder motor screw this back in with the two allen bolts. It is easier to locate the one furthest away from te spring first and using that as a pivot locate the one closest to the spring – then tighten both up.

You now have a reassembled hotend which should not leak.

Note: if your hotend becomes loose when you have heated it then hold the heatblock in molegrips and tighten the nozzle  – make sure it is not tight against the heatblock when fully tightened.

Testing your hotend

Switch on your printer and make sure that it starts up ok.

Locate the hotend temperature menu and start the process.

Go back to the main screen and watch the temperature rise on the hotend.

Make sure it stabilises where you set it.

Straighten the end of your filament and feed it into the extruder. Pressing down on the tension spring will allow you to feed the filament in without turning the motor.

Manually push it through until you see filament coming out of the nozzle.

Stop pushing. and release the tension spring.

Look for signs of leaking, both at the top and bottom of the heatblock.

If there are then hold the heatblock with the molegrips and tighten the nozzle.

You now have a working hotend on your 3d printer which will not leak.

After clearing and reassembling your hotend you will need to go through leveling your bed as the height of the nozzle will not be the same as before.

Other solutions for the Anet A8 hotend

I have heard that people are putting teflon tape around the threads to prevent leakage- if you get the joint tight between the nozzle and the throat then you really don’t need anything else.

And don’t use thread lock on the threads of the throat as you may not be able to disassemble it in the future. If there is still a problem then the joint between the nozzle and the throat is not correct and needs attention.

If you really cannot get it to stop leaking then try to flatten the faces nozzle flattenedof the nozzle and the throat on some wet n dry paper – if you don’t get it really flat it may cause more problems than solving.

The complete new assembly is available relatively cheaply to purchase from Amazon. Don’t forget to check it before fitting as most manufacturers don’t assembly these properly from the factory. Go through the assembly process of loosening the nozzle and tightening the throat down onto the nozzle.

If you find that the teflon tube is blackened at the end where it meets the nozzle, it will be worth checking your temperature settings for the material you are using. too hot and it will start to overheat and stick internally leading to more blockages.

I tend to polish the inside of my nozzle before the first fitting – does this do anything? well I have very few problems with partial blockages so every little helps, and it only takes a few minutes.

Thanks for reading and please fill in the survey whether you tightened your anet a8 hotend hot or cold.

[poll id=”3″]


Anet A8 Bed Leveling : How do You do Yours?

Having had my anet a8 for over a year now I am getting quite used to it.anet a8 bed leveling : smashing printer

I am just going through a mod for adding an e3d v6 all metal hotend clone, with interesting results, but that’s another story.

One of the main things I with my anet a8 at the start was bed leveling.

I would go through the Anet A8 bed leveling process and the prints would not stick (nozzle too high) or the filament would not come out (nozzle too low).

What was I doing wrong? Why wouldn’t it work properly?

But I understood that bed leveling was nothing to do with using a spirit gauge to get the bed perfectly level. It was to do with getting the nozzle the same distance above the whole of the bed. So you are adjusting your bed to the height of the nozzle with the Z axis set to 0.

Make sure your Z axis height is the same on both sides first.

Before You Start the Anet A8 Bed Leveling Process

Well there were a few things I had to do first to stabilise my machine before the leveling worked.

One of the main ones was to add a base and screw it down.anet a8 screwed down

If you move the front up by 0.4mm then the bed leveling will be out- and this may happen with the weight of the bed moving back and forth if you don’t bolt it down.

Create a Solid Base for the Anet A8

So screw it down to a flat piece of wood or a cabinet top.

I created a box for mine so I had storage underneath it.

The top was is made of laminate floorboards.

The sides of the box are made out of tongue and groove floorboard with the groove modified to accept the top ( the inner part of the groove is gone and the top rests on the ledge left).

A brace has been put across the top at the front to stiffen up the structure. As can be seen in the picture above.

Sort out the Z Axis Stop

z stop mod
Anet A8 Z endspot holder for 2017 version by daveposh

The other one which makes all the difference to stock parts is to change the z stop. Mine would always start to work loose, so the z zero height would be adjusting, messing up the bed leveling.

So I used this anet a8 z stop.

Make sure the screw goes into the plunger straight – mine is crooked, as this can give you unexpected results when adjusting the z height.

With this mod one turn of the screw will adjust the Z axis about 2mm. So you need to be light with the adjustment.

If this is the adjustment before your first print then tighten up the z stop as much as possible and use the bed adjustment to bring the nozzle close. Once printing, make it a priority to print off the z stop adjuster.

Check your Bed Flatness

Another thing to do is to check your bed for flatness with a steel ruler – you may find that at the very edges it does bow up or down as well as a little bit close to the hole where the thermister is.

You can either accept this as I have or flatten it on a piece of float glass with a sheet of wet n dry taped to it – don’t forget to add water with a little dishsoap as a lubricant.

I have not tried this but it should give you a flat surface to work with if the bow it too much.

Clean Your Nozzle

Before leveling the bed check that the nozzle is clean of any filament clean the filament offsticking out. This will cause an error to the height adjustment and will cause failed adhesion prints- from experience!!

If there is filament sticking out then switch on the printer and go to control → temperature and set the nozzle to 190. Press back until you get to the home screen and wait for the temperature to stabilise.

Wipe the nozzle with a clean paper towel or cloth, making sure you don’t burn your fingers.

Set the temperature to 0 and allow to cool, make sure there is no ooze as it was cooling down!

Tip for the Threaded Bottom Plates

If you have one of the older Anet A8’s then you may have the screws going through the bed and threaded into the lower plate. If this is the case and they are stiff to turn then carefully remove them and add a bit of grease ( I use (#amazon link) lithium grease) to the threads and put them back in. This will prevent the threads from binding and stripping. Makes it a lot easier to adjust as well. I used a spray can as my screws were starting to bind and this could spray between the spring. It worked and they are loose.

If you have one of the newer ones with a clearance hole and wing nuts underneath the lower plate then it might be worth considering printing off the easy to use round adjusters. The only thing I would add is some kapton tape over the lower part of the bed where the washers go to add another layer of insulation, I have heard of the bed shorting out with the washers.

Anet A8 Bed Leveling Process

Switch on the printer, leave it cold.

Make sure there is no filament sticking out of the nozzle.

Send the printer to its home position.

Manually raise the z by 2-3 mm.

Move the X axis by 25mm.

Move the Y axis by 25mm.

Move the Z axis slowly down to the bed and place a piece of paper between the bed and the nozzle. Or a feeler gauge of 0.2mm.

There should be drag on the paper or feeler gauge.

Looking down from the top

Turning the screw adjuster anticlockwise will raise the bed and turning clockwise will lower the bed.

With the nut adjuster turning anticlockwise will raise the bed and clockwise will lower the bed.

If there is a large gap then you will have to go around two or three times before it settles.

Don’t press down too hard as this will possibly put pressure on the lower plate and throw out the adjustment.

Once you have adjusted this corner then raise the Z axis by 1mm and move the x axis to 175mm ( you don’t need to be exact).

Lower the Z axis to 0mm.

Now adjust the front right adjuster to feel the drag on the paper.

Raise the Z axis by 1mm.

Move the Y axis to 175mm.

Lower the Z axis to 0mm

Adjust the rear right adjuster for drag on the paper.

Raise the z axis by 1mm

Move the X axis to 25mm.

Lower the z axis to 0mm.

Adjust the rear left adjuster for drag on the paper.

Raise the Z axis by 1mm.

Now adjust the Y axis to 25mm.

Go to the home position then raise the Z axis by 1mm and go back to X 25mm, Y 25mm.

Lower the Z axis to 0mm.

Check and readjust if necessary for drag on the paper.

If the drag is still the same as it was then good. If not, it is a pain, but go around again and readjust all four corners until you are confident that the gap is consistant.

After the Manual Process

Test print

I use a single layer circle test print 100mm diameter 0.2mm thick.

Download the test circle.

If you now load up the test print, wait for it to start printing.

You will see what is happening with the nozzle as it comes down to make the first part of the print.

If it doesn’t stick then adjust the corner to either raise the bed if the nozzle too closenozzle is too high or lower the bed if the nozzle appears to be too low.

If the print hasn’t stuck after the first half circle then abort the print.

Remembering that a turn of the screw is 2mm tweak the adjusters in the direction you need to and start the print again – after wiping the printers nose.

Once this test print sticks and prints completely then use a marker pen and mark the forward direction so you can orientate the print. Peel it off carefully and measure the thickness of it. Measure in the two axis – both diresctions – is it consistant at 0.2mm (ish).

Use this test print to more accurately setup your printer – don’t be too obsessive.

Print it again and check for consistancy.

Once you are at this stage then you know that any print you do now should stick with a first layer squished down.

Remember to go slightly more squished rather than less as once your model goes upwards it has less chance of detaching if it is adhered to the bed more.

Every few prints ( preferably before every print) clean your print bed.

Did you manage to get Your Anet a8 bed leveled?

Good luck with this, and leave some comments if you feel that you have a better method for anet a8 bed leveling.

Thanks for reading


Solution for Blown Anet A8 Bed Mosfet on Main Board

anet a8 bed mosfetMy Anet A8 bed mosfet has blown up  – what now?

I have been asked about this question about the anet a8 bed mosfet a few times now.

So my advice was to add an external mosfet and use the output of the controller to switch it on and off.

Thanks to GearBest my order of spare main boards was delayed until a few days ago, and my printer is normally on the go – so I didn’t want to strip it down.

So the first thing I did was to run a new main board up with a power supply – to test it.

I was under the impression that you could run the whole board off the usb, same as the mega. But this is not the case you need power to the board from the 12v dc input.

Now getting the computer to recognise the board was easy – with the ch340 driver installed.

Connecting through the serial port at 115k baud the computer recognised the board in pronterface , but the ‘printer’ was not working – it had errors.

You need to connect the two thermisters, one for the bed and the other for the hotend before you can fool the board into thinking it is a working printer.

So with these now connected, I was able to switch on and off the bed with pronterface.

Switching it all off and now connecting the external mosfet as I had described in an earlier post.

Connect the control wires across r42, the gate resistor for Q1 the bed mosfet.

First thing I had to do was find r42, the second was to solder wires wires across r42either side of it.

Being an 0805 surface mount resistor you don’t have much space between the pads of the resistor, but it is possible to solder either side of it.

Note: an easier place to connect the wires is across the bed mosfet – the two legs are the same terminals as the resistor and wider easier method of wiringspaced.

Wiring in the supply to the mosfet board and putting a load on it of a car led indicator lamp – closest thing I had to hand which worked at 12v easily!, I switched it all back on.

Reconnecting the computer I switched the bed on and … nothing- no light – the onboard mosefet switched on but not the external one.

Ok so what is wrong.

Looking at the circuit, the control voltage goes through a full bridge – to make it polarity independent.

This will take 0.6v off either pin – so from the 5v controller output you need to subtract 1.2v – we are left with 3.6v.

This is fed through a 10k resistor (R5) to the opto device to pass current through a led – this in turn switches on the opto transistor, eventually switching on the output mosfet.

The point of this is, that with 12v on the control input there is enough current through the led to activate the device, but with 5v there isn’t.

Damn – what now!

Calculating the current through the 10k resistor with 12v ( (12-1.2- 1)/10k= 1mA) and with the 5v input ((5-1.2-1)/10k= 0.3mA) we can see why the opto switch is not working.

Note the extra 1v drop in the above equation is for the led internal to the opto device.

So working it the other way round – we need a minimum of 1mA to operate the opto device we can use the voltage to calculate the resistor value.

5-1.2-1 = 2.8v

To have 1mA flowing and calculate the resistor value we divide the voltage by the current.

2.8/0.001 = 2800 or 2k7

I am very lucky to have an 0805 resistor kit, so I looked through this and found the closest value was 2k7 (preferred value). Removing the fitted one and replacing it with the 2k7, reconnecting and switchingreplace 0805 resistor the bed on and off it worked.

So if your anet a8 main board has blown its bed mosfet you have three choices.

  1. buy a new main board – be it ramps and mega or(#amazon link) standard replacement.

  2. Replace the Bed mosfet(ebay link)– see below for directions on how to do this easily.

  3. Use the controller voltage but change the resistor value on the external mosfet board.(#amazon link) resistor kit

Replacing the onboard mosfet easily.

Note: remember these devices are static sensitive – pick up the device and then touch the board with a finger to get both the board and device to te same potential- reducing the chance of it blowing up!

I have just been reminded that you need to know the device number to replace it!
The device is an IRLR7843 mosfet.

Can be obtained  ebay sources in the UK or elsewhere dependant on time scales.

The onboard bed mosfet is located where the designator says Q1. It is under the silver heatsink.

This heatsink is held in place with thermal silicon adhesive.

To remove this heatsink, take a flat screwdriver and carefully lever the heatsink away from the device. This may pop off easily or be very difficult. If you use the board as a lever by the green connectors it is controllable – but be careful you don’t damage the board.

Once this is off you can see the device is held down to the board with two legs and the back pad.bed mosfet exposed

To remove this device easily – carefully cut the legs of the device close to the package.

Use a soldering iron to remove the cut legs- don’t damage the pads on the board.

To remove the main body, hold the tip of the soldering iron against the metal tab at the top of the device and feed a bit of solder onto the iron.

You will see the solder flow onto the tab of the device – when this happens it is ready to be removed.

Use a pair of tweezers to lift the device off the large rear pad and you have done it – congratulations.

All you have to do is to clean up the large pad – make the solder flat – and replace the device with a new one.

To remove the solder from the pad I use (#amazon link) solder wick.

To use this lay the solder wick over the solder you want to remove and press on top of this with the soldering iron, you will see the solder melt and flow into the solder wick.

Remove the solder wick from the area before the solder solidifies.

If the solder solidifies then remelt the solder with the soldering iron and remove it quicker.

Remember that this wick is copper and it will conduct heat – so keep your fingers a little away from where you are going to remove the solder. Or get asbestos fingers!

To replace the device

Melt a little solder onto the large pad. And I mean a little.

Place the device onto the pad and heat the tab.

Feed a little solder onto the iron while it is in contact with the tab and the large pad to assist reflow.

When the solder melts then position the device carefully with tweezers – making sure the two legs are on the correct pads, remove the iron.

Solder the two remaiming legs to their respective pads.

Now all you have to do is to glue the heatsink back on with this (#amazon link)thermal compound.

And you are done.

Now test the board – without loading it with the bed to start with.

So there you have it – how to replace your bed mosfet and how to wire in an external mosfet if your anet a8 bed mosfet blows!

It sounds complicated but really isn’t.

If you have a go at replacing your Anet A8 bed mosfet and have problems then why not comment in the box below and we can try to sort the problem out.

Thanks for reading


Anet A8 bearing replacement- SB1

Service Bulletin 1 (SB1)Anet A8 upgrades : Anet A8 3d printer

This service bulletin details how to check and perform Anet A8 bearing replacement on the X and Y axis.

What are the symptoms which require Anet A8 bearing replacement

After you have bought your 3d printer and used it a fair bit you may notice a few strange noises.

Where the print head used to glide across the printer, you notice a knocking noise as it changes direction.

When the bed changes direction there is a visible jump.

Well the main cause for this could be wear on the linear bearings. Continue reading Anet A8 bearing replacement- SB1

Why you need a multimeter if you have a 3d printer!

What a digital multimeter can tell you.

You know that time when your printer went wrong and you sat there looking at it?

You were frustrated because you knew it was not mechanical, there was something wrong with the electrics or electronics.

Someone on a forum said – ‘ Have you checked the voltage at …’ and you thought huh?

Well that was the time when you could have done with a multimeter to measure the voltage.

The problem got solved eventually with a friend coming round with a meter and with a couple of checks he said ‘Yep I agree with them, it is the …’.

You just sat there and nodded.

So why not change that?

Anet A8 upgrades : Anet A8 3d printer
See what people think at Amazon – click the picture. (#amazon link)

You know how to put the printer together and operate it.

You have had a go at the cad thingy they are all talking about, and yes it’s ok – maybe with a bit more practise it will get easier.

But what if it goes wrong again?

What will you do then?

Well you could do worse than invest in a multimeter – or meter for short.

What does a multimeter do?

The most basic multimeter will measure voltage, current and resistance.

Any other ranges will be a bonus.

Meters now are capable of measuring capacitance, frequency, temperature and a lot more, all of this for really not a lot of money.

What would be the best multimeter for the 3d printer?

What would you like to measure?

The low voltages around the circuit.

The resistance of the bed and fuses.

The temperature of the hot end and bed.

Checking the cables of the motors and other items.

Checking whether the mosfets are working.

So you can see with a meter you can do an awful lot to fix and test your printer.

Which one is the best one – the one you use – if it is too complex you will look at it and put it to one side, never to pick it up again.

So go for one which will do the job, not the one that has x thousands of ranges to measure between here and the moon, you just need a meter which will measure what you want.

I would recommend something like this (#amazon link) Tacklife DM01M

With this one you even get a light to see what you are measuring.

With this meter you need to be aware of what you are about to measure – if you try to measure 12v on the 6v range it will just show overload, so you need an idea of what you are just about to do or measure.

But this is true when fault finding- if you don’t have any idea of what should be there, then anything you measure will be correct, as you don’t know it is wrong.

So on this meter for measuring the 12v power supply set the dial to 60v dc range.

Connect the black probe to the negative of the power supply ( black lead on the main board input) and the red probe to the positive of the power supply( red lead on the main board) and with the printer switched on the meter should read about 12v – there will be a little bit of fluctuation and you will probably be able to hear that fluctuation in the voltage on the fan on the extruder – this should be in the order of 0.1-0.5v.

Do use the meter when the printer is working so you have an idea of what voltages are expected where, so on the power input of the main board , when switched on, you will get 12v.

On the mosfet output to the bed you may not get 12v until it is on for a certain time period – the meter needs a certain time period to read the voltage. So it may try to fool you by showing 3 or 4V up to 12V and be varying. Watch the led on the bed and if you measure it after switching on the bed you should find it to be 12v, when the led is flashing on/off quickly the voltage will drop, maybe even down to 0v. This is quite normal, as I said the meter needs the voltage to be stable for a time period for it to measure the voltage correctly.

So have a poke around the circuit – do not short anything out ( connect two points together unintentionally) or you may let the magic smoke out -this would not be good, as you cannot catch all of it and put it back.

multimeter resistance measurement 1
Mine read about 130k

With your printer off you can measure the thermistors resistance, along with the bed resistance and the heater resistance.

All of these checks will allow you to determine whether the items are in good order.

The thermistor, when at room temperature will be about 100kr.

To measure this switch the meter to the 600k range, plug the leads into the com ( black) and the red into the one above that.

Unplug the thermistor from the main board and place a probe on each of the connections. As I said the meter should read about 100k.

Note; if the thermistor is hot the resistance comes down rapidly – this is how the controller is able to ‘see’ what the temperature is and switch off the heater.

You can measure the resistance of the print bed – again unplug the bed and measure between the two outer pins on the bed connector.

You should read about 1r, this may be more or less.

Or how about unscrewing the hotend heater and measuring the resistance of that.

heater multimeter measurement
my heater resistance was 3.3R

As it is a 40w heater run from 12v the resistance will be about 3.6r.

Get yourself a log book and start noting these measurements down for the time when your printer goes wrong.

You should also be noting down the filament type and what parameters you change in your slicer and printer to make it print properly, but that is another post!

If one of your motors stops working – you can measure the resistance of the windings and then check the continuity of the cable.

So you can see with a multimeter you can diagnose a lot of the faults, and I will try to list out some of them in another post and how to check for them. So why not sign up to be kept up todate with the posts in the box at the top right.

Why not hop over to Amazon and order one today.

If you do need help measuring anything with your multimeter then get in touch via Facebook, 3deeprinter, or add a comment below and I will be able to help you.

Thanks for reading


Anet A8 upgrades : External Mosfet for the Bed

Anet A8 upgrades : Anet A8 3d printerA lot of people are interested in the Anet A8 upgrades, especially the mosfet mod for the heated bed.

The reason for this is a lot of misinformation out on the web about the mosfet on the main board being too small and causing fires.

If you really want to carry out this mod then follow the directions in this post.

We will go through everything you need to do to carry this procedure out safely. Continue reading Anet A8 upgrades : External Mosfet for the Bed

Ups for a 3d Printer: Do you need one?

Why would you need a UPS for a 3d printer?

UPS for a 3d printer can be useful to prevent interruptions (#amazon link)

Why do you need a UPS for a 3d printer?

Let me describe the scenario…

You have spent a lot of time on your 3d printer, adding this and that mod, improving the quality and repeatability of your prints. So now you can slice a model and print it knowing that it will be as good as it can be.

Ok, now for the big one. The 100 hour print,the one you keep putting off knowing it will tie up your printer for over 4 days – but it will be worth it. Continue reading Ups for a 3d Printer: Do you need one?

3D print Nozzle secrets

All about a 3d print nozzle

3d print nozzle : main

Continue reading 3D print Nozzle secrets

3d print problems : Become an investigative detective

 Are you a destroyer or a detective?

You know what it is like when you have 3d print problems.

3d print problems : first failure

You come back to the printer after waiting 12 hours only to find this heap of spaghetti.


You rip it off the printer and throw it into the corner – where it bounces back and sits on the floor laughing at you!!

I know the feeling – I have been there many times – and yes I have done the same.

But after a while you get to thinking – if you don’t change anything you will get the same results. Continue reading 3d print problems : Become an investigative detective