Printhead¶

When you try to assemble that cap (which is attached to the ribbon cable) onto the plug once you put it into the connector, you might have a hard time doing so - at least I had in the beginning.
So there's a little trick to get everything together - it's kinda difficult for me to explain it properly, but I'll try:
After you plugged the plug into the connector, bend that ribbon cable where that textile tape (or whatever that is) is located a bit downwards.
Pay attention that those levers at the sides of the connector are clipped into the plug's side.
Then carefully push down that cap while paying attention that it really goes across the plug in the back as well.
Once everything looks fine so far, push down the cap until it finally goes over the plug and clips onto it. Don't try to force it too much - you do need a bit of force, but you have to make sure that everything is in place.

• Take the height gauge from Anycubic.
  If you don't have the height gauge, take a sheet of paper and the bigger two-sided open-end wrench that came with your printer.
  If you also don't have that, take something with a flat surface that is ~2mm thick.
• Put on the spring steel plate on the heated bed and place the printhead about the center of the bed.
• If you're using the height gauge, put it under the printhead and lower the head by turning the z axis rod manually. The nozzle should then touch the lower/thinner part of the gauge while the proximity sensor should touch the higher/thicker part of it as the following picture of a different printer model illustrates.
  
• If you don't have/use the height gauge, place a sheet of paper under the printhead now. Then lower the head to make the nozzle touch the sheet of paper. You should still be able to move the paper but you should feel a minimum amount of resistance as a sign that the nozzle is touching it.
  Now place the wrench flat under the ABL sensor. The sensor should touch the wrench.
• If the sensor is too high or too low, you need to adjust the position of the sensor. Therefore you need to loosen the screw which clamps down that plastic bracket which holds the ABL sensor:
  
  
• Once you loosened the screw enough, pull that plastic bracket slightly apart and adjust the position of the sensor by moving it up or down. When you found the correct position, tighten up the screw of that bracket again.
• After completing the beforementioned steps, take all parts off the bed and start a calibration process for having the z-offset and the new bedmesh generated. Keep an eye on your first layer and adjust the z-offset on the fly if necessary.

• First disconnect the belonging connector at the distribution box. Be careful to not rip off the wire nor the connector itself!
• Now measure the distance between the tip of the sensor and the lower side of the bracket, so that you can install the replacement part at the exact same height later.
• Now unscrew the belonging screw and take out the sensor.
• Voilà - you're already done!

For remounting, just follow the steps of dismounting in reverse:
- Place the sensor in the bracket and mind the correct position which you measured before taking the old one out.
- Make sure you're using the right screw and don't overtighten it though - as my father (R.I.P.) used to say: "After tight comes loose!" (roughly translated ;) ).
- Reconnect the wiring.

• When you take off the blue plastic cover of the printhead (Attention: disconnect the part cooling fan cable when taking off the head's cover!), you can see the extruder gearbox above the black metal heatsink. The following picture shows the gearbox with the three corresponding screws being marked.
  
• If you're really careful to not rip off any wires, you can leave everything besides the ABL probe connected and leave the breakout board in it's location as well.
• Unscrew those three screws and carefully take off the corresponding lid of the feeder gear box as shown in the following picture. When doing so, be careful to neither lose any parts nor rip off any wires or connectors!
  
• Now you can see the interior. The following pictures show some close-up views of the parts, starting with the lid where you can also see the lever and the corresponding spring.
  
  
  
  

Whatever you now have to do about further disassembling, pay special attention to the location of the parts before taking apart anything and make sure to not lose anything!

For reassembling, just put everything back together by proceeding the steps of disassembling in reverse.
Make sure that everything is in the correct location and that everything aligns how it should.
When putting on the lid, make sure it really sits in the correct position and that there's no gap when putting in the three screws to secure the lid.
When screwing in the screws that hold the lid in place, don't overtighten the screws - as my father (R.I.P.) used to say: "After tight comes loose!" (roughly translated ;) ).

If you need to dismount the heatsink, you need to take out the two screws which are holding it to the gearbox.
After doing so, you can just take it out - make sure to also get out the PTFE tube which is stuck into the heatbreak!

If you need to dismount the heatsink cooling fan, you can't do so right away as one of the screws is blocked by the metal plate where the extruder motor is mounted to.

So for being able to unscrew the screw in the upper left corner, you need to unscrew the two screws in the front which hold the heatsink in place (you don't have to dismount the hotend though).

Then you can pull out the whole heatsink-hotend-setup out of the feeder gearbox and reach the necessary screws.

Now you can unscrew the fan from the heatsink and take it off.

For reassembling the heatsink cooling fan, just proceed with the steps of dismounting it in reverse.

Sometimes it may happen that melted filament builds up on top of the heater block to a large clump. The reason for that is that the heatbreak and the end of the nozzle don't touch tight enough, so that the melted filament can squeeze out. It also may be caused by bad and cheap parts where the threads aren't just as good as they should be.

So if you encouter this problem, here is what I recommend to do (based on my own experience with this dilemma).

• Take off the plastic cover first to get better access to the whole area.
• Heat up everthing.
• Once the filament starts to melt and became soft, I'd suppose to turn off the printer, just to make you don't cause any shortcuts in case you harm the wires.
• Then grab a wooden stick and take away as much as possible carefully. Don't use a screwdriver or something like that to do so as you might harm the wires and/or cause a shortcut at e.g. the contacts of the cartridge heater.
  Be really careful when taking away the clumps to not harm or rip off any of the wires! You can also use a cloth to wipe off the melted filament from the heater block and so on, just make sure you don't burn yourself!
• For the next steps you need to be a bit quick in proceeding them, so if this is the first time you're diassembling the hotend, take a look at the sections here at the page and read them first so you'll know where the screws are located and which steps you need to take. Then proceed with the following steps.
• So, once everything is as clean as possible, heat everything up again. The turn off the printer and loosen the two grub screws inside the heater block to take out the thermistor and the cartridge heater. Give it a quick wipe with the cloth if they're covered by a lot of filament, too (but don't waste too much time here as the filament is becoming hard again now pretty quick!).
• Then disassemble the hotend (see description below), so take out the nozzle from the heater block and unscrew the heater block from the heatbreal. Pay attention if you can feel that the heatbreak was loose in the heater block to check if that was the reason for the filament being able to squeeze out and build up.
• If you were using a cheap nozzle and have a spare one, just throw away the old one. If it's a good or your only nozzle, try to get it back to work again by giving it a proper cleaning and doing some cold pulls when it's installed again.
• Now put all the metal parts (heatbreak, heater block and probably the nozzle) in a glass with acetone. close the lid and let it sit there for about 24hrs. The acetone won't dissolve PLA filament or so automagically like it does with ABS, but it'll make it soft and easier to clean.
• In the meantime you can take care of the thermistor and the cartridge heater. Scratch off the hardened filament from the metal parts by using a cutter for example, but be really careful to not slip off and harm any wires! I personally didn't take care of the little clump at the part where ther wires are coming out of the metal part because I didn't wanted to risk harming the wires, so I just let it sit there.
• When you're about to clean the meatal parts which soaked in the acetone, I'd recommend wearing disposable gloves as acteone isn't really healthy for your skin. So put on those gloves and start cleaning the parts by carefully scratching off the rest of the filament. Use a cutter, a brass brush etc., but always be careful to not really harm anything. Pay special attention to all the threads and the holes of the heater block where the thermistor and the cartridge heater will take place. If you don't get everything cleaned up at the first time, just put it back in the acetone, wait again and then repeat the cleaning steps.
• Once everything looks nice and clean, rinse off the acetone with clear water and let it dry. This is especially important for the inner side of the nozzle - you don't want to have acetone in there.
• Then reassemble the hotend (see description below) and put it back in place. Read the notes in the specific sections here about how to reassemble the specific parts and what to pay attention to.
• At the end when everything is reassembled and you heated up the hotend to finally mount the nozzle and load the filament, extrude filament to see if everything is ok.
• If so (I hope it will be!), don't start printing right away - execute a PID tuning for the hotend first.
• Also check if you need to re-level the ABL sensor in relation to the nozzle due to a probably different position of the hotend now.
• Execute an ABL and take care of your Z-offset, most likely the position of your nozzle will be different due to a different position of the whole hotend.

When I need to disassemble the hotend, I first take off the blue plastic cover (including the part cooling fan which you have to disconnect from the breakout board) of the printhead, so I'd suggest to do the same. Then proceed as follows.

Attention: you'll handle HOT parts now, so be really careful to not harm yourself by accidentally touching any parts or your surrounding by dropping any parts!
Also make sure to be quite quick as you need to disassemble the parts while they're still hot. So make sure to read through the following steps and have the belonging tools on hand already.

• Before you start to disassemble the hotend, heat it up to about 240°C first. Once it reached the temperature, turn off the printer.
• Unplug the connectors at the breakout board of the heater cartridge and the thermistor.
• Now I personally take out the whole hotend from the heatsink, so I'd suggest to do the same. For doing so, just loosen those two grub screws in the center of the heatsink while holding the heater block with an adjustable wrench to prevent the hotend falling down.
  
• Once you have the whole hotend in front of you, pull out the PTFE tube which is located in the heatbreak, it should come out easily. If it's somehow not there, you'll have to check in the extruder system later if it somehow got stuck in there.
• Now loosen the nozzle by holding the heater block in place with an adjustable spanner or wrench and carefully loosen the nozzle by turning it counter-clockwise with a 7mm wrench.
• Once you unscrewed the nozzle a bit, carefully grab the heatbreak then instead of the nozzle by using an adjustable wrench and turn it counter-clockwise.
• Then take out both parts completely from the heater block while everything is still hot - pay attention to not burn yourself and to not drop any hot parts on a temperature sensitive surface.

• Screw the heatbreak into the heater block to the corresponding depth and screw in the nozzle from the other side until they touch. Don't tighten up the nozzle yet!
• Put back the new PTFE tube in the heatbreak.
• If you took them out, put the thermistor and the heater cartridge back in place and secure them by carefully tighten the belonging screws. Don't overtighten the grub screw of the cartridge heater and don't pich the thin wiring of the thermistor.
• Then push the heatbreak back into the specific hole of the heatsink - make sure you push it deep enough (I personally push it as far into it as it goes).
• Turn the hotend so that the wires which are coming from the heater block are hanging freely and aren't bent too much.
• Then tighten up the two grub screws at the heatsink which hold the heatbreak in place, so that the hotend doesn't turn or wiggle anymore (but don't overtighten the screws though).
• Plug in the cartridge heater and thermistor back into their corresponding connectors.
• Turn on the printer and heat up the nozzle to ~230-240°C. Once the temperature is reached, tighten up the nozzle with about 1.5NM force.
  Make sure to hold the heater block in place with an adjustable wrench or spanner and strictly avoid any movement of it - make sure to not pinch or harm any wires while doing so!
• Once everything is done, reconnect the part cooling fan to the breakout board and mount the plastic cover.

• Before dismounting the heatbreak from the heater block, I personally use to heat up the hotend to ~240°C with the plastic cover (including the part cooling fan - don't rip off it's wires!) of the printhead already being taken off.
  Once it reached the final temperature, turn off the machine and disconnect the connectors of both the thermistor and the heater cartridge at the breakout board, labeled as "T0" (thermistor) and "H" (cartridge heater).
• Then you need to take out the hotend from the heatsink by loosening those two grub screws in the center of the front of the heatsink which hold the heatbreak in place for being able to actually reach the screw which holds the thermistor in place.
  
  Attention:
  Be very careful when doing so, as the heatbreak will slip out of the heatsink and the whole hotend will fall down immediately! As these parts are heated up, you can severly harm yourself and the surrounding! So better use a decent pair of adjustable pliers and/or some thick leather gloves to hold the hotend in place and avoid that it's falling down!
• You will now have the whole hotend in front of you.
  
• If you now have to dismount the heatbreak from the heater block, hold the heater block in place using an adjustable wrench or an adjustable pair of pliers and grab the heatbreak with another pair of (adjustable) pliers. It might be a good idea to put a piece of cloth between the jaws of the pliers and the metal parts to avoid scratching them as much as possible.
  Be careful to not harm any wires by accident!
• Now unscrew the heatbreak from the heater block by turning it counter-clockwise.

If you need to get the reverse bowden tube out of the PC-4 couplers, you need to push down the black plastic part towards the metal part of the coupler.
At the printhead's coupler there's an additional blue plastic clip in between the metal and the black plastic part - make sure to remove that one first and don't lose it. Once you're done with dis- and reassembling of the tube, put that clip back in place.

For accessing the PTFE tube in order to inspect and/or replace it, you need to take out the whole hotend from the heatsink. It's not a complicated task, you literally only need to loosen two screws (well, and you have to take off the plastic cover from the printhead in the first place).

• Take off the plastic cover of the printhead first of all. Pay attention to not rip off the wires of the part cooling fan, and unplug the connector from the breakout board.
• Disconnect the connectors of both the thermistor and the heater cartridge at the breakout board, labeled as "T0" (thermistor) and "H" (cartridge heater). You might be able to take out the hotend with those wires still being attached, but you don't want to risk ripping any wires off, so better disconnect them completely.
• Then you need to take out the hotend from the heatsink by loosening those two grub screws in the center of the front of the heatsink which hold the heatbreak in place for being able to actually reach the screw which holds the thermistor in place.
  
  Attention:
  Be very careful when doing so, as the heatbreak will slip out of the heatsink and the whole hotend will fall down immediately!
• You will now have the whole hotend in front of you.
  
• Now you can pull out the PTFE inliner from the heatbreak. Usually it comes out without any problems. If it doesn't come out, it might already be deformed, melted or somehow 'glued' due to molten filament - in this case you need to connect the thermistor and the cartridge heater again and heat up the hotend. Be careful to not harm yourself!
• Once you pulled the inliner out, inspect it and replace it with a new one. It's advisable to use Capricorn XS tubing here.
• If you had trouble getting out the inliner, you might have to clean the heatbreak in the inside as well. Therefore you'd have to unscrew the heatbreak from the heater block. To do so, you have to heat up the hotend to minimum 220°C - pay attention to not harm yourself!
  Refer to the section about the heatbreak and read the tips and the violet expandable textbox there as well for further instructions.

Before attempting any measurements, do a visual check if the insulation of the thermistor's wires is still intact.

If you can see bare wire shing through due to a melted and/or displaced insulation, change the part immediately!

Don't try to cover it up with some kind of insulation, even though Kapton tape should stand the heat. You'll risk a shortcut which then will harm your motherboard and might even cause more severe damage!

Generally speaking, you can check the wiring of the thermistor by measuring the electrical continuity of the wires. If your multimeter doesn't have this function, you can measure the resistance instead.
However, it's advisable to measure the resistance, even though your multimeter offers the function of probing for continuity, because it might be the case that a wire still passes the check for continuity, but that individual strands of the wire are broken. This causes problems if those strands lose contact permanently or during movement of the head, as it leads to a higher resistance and therefore a wrong temperature being reported.

The difficulty here though is to actually measure one wire by itself, because you can only access one end of the wire (at the connector), the other end is inside of the thermistor's capsule. So if you measure the resistance probing at both contacts of the two wires, you already measure the thermistor itself as well.
However, by doing so you could still be able to tell if the wiring is faulty when you move the wires around while probing and see if the resistance value will spontaneously change. It actually wouldn't really help you in the end though to know if it's either the wiring or the thermistor itself, as you can't just change the wiring. Due to the construction of the thermistor and it's wiring, you'd have to replace the whole unit anyway though.

You can check if a thermistor is working or if it's somehow broken by measuring the resistance of it using a multimeter.
As mentioned above, at a temperature of 25°C the resistance should be ~100k Ohm (nominal restistance: R^25°C = 100 kΩ ± 1%).
If the temperature is lower, the resistance value will be higher; if the temperature is higher, the resistance value will be lower.
The following table gives you some typical resistance values of a 100K thermistor type 3950 (generic) for temperatures around room temperature. The values might slightly vary from the one you'll get, but they should be pretty close.

Set your multimeter to resistance testing for a higher Ohm range - in most cases the multimeters have different settings, usually 200/2000/20K/200K/20M -> use the setting "200K" here.

You can measure by probing the belonging wires at the plug of the breakout board (unplug it!), that would be the connector labeled as "T0".
Keep in mind though that by doing so you also measure the wiring itself. Means, if there are e.g. broken wires, the thermistor won't work even if the thermistor itself is still fine. Due to the construction of the thermistor and it's wiring, you'd have to replace the whole unit anyway though.

• If you need to change the thermistor, take off the blue plastic housing of the head first (including the part cooling fan - don't rip off it's wires!).
• It's advisable to already disconnect the connectors of both the thermistor and the heater cartridge at the breakout board, labeled as "T0" (thermistor) and "H" (cartridge heater).
• Then you need to take out the hotend from the heatsink by loosening those two grub screws in the center of the front of the heatsink which hold the heatbreak in place for being able to actually reach the screw which holds the thermistor in place.
  
• So loosen those two screws and take out the whole hotend - be careful when pulling it out to not rip off any wires if you didn't disconnect them already.
• Once you took the hotend out, you can already spot the black head of the hex screw which taps the thermistor and holds it in place.
  
• Take out that black hex screw completely and you can pull out the thermistor.
  
  Attention: be careful when trying to loosen that screw, it might be that it won't come loose unless you heated up the hotend first!
• Now take your new thermistor and repeat the steps in reverse for reassemble everything.
  Make sure to not pinch the thin wires of the thermistor with the head of the black hex screw and to connect the wires back to the breakout board once you installed the hotend back into the heabreak.

Before attempting any measurements, do a visual check if the insulation of the cartridge heater is still intact.

If you can see bare wire shing through due to a melted and/or displaced insulation, change the part immediately!

Don't try to cover it up with some kind of insulation, even though Kapton tape should stand the heat. You'll risk a shortcut which then will harm your motherboard and might even cause more severe damage!

Generally speaking, you can check the wiring of the 24V line by measuring the electrical continuity of the wires. If your multimeter doesn't have this function, you can measure the resistance instead.
However, it's advisable to measure the resistance, even though your multimeter offers the function of probing for continuity, because it might be the case that a wire still passes the check for continuity, but that individual strands of the wire are broken. This causes problems if those strands lose contact permanently or during movement of the head, as it leads to a higher resistance.
At the 24V wires this can lead to the circumstance that the wire will get hot at that spot, that the insulation will melt, that a shortcut might occur and it might even occur that it causes a fire.

The difficulty here though is to actually measure one wire by itself, because you can only access one end of the wire (at the connector), the other end is inside of the hetaer cartridge's capsule. So if you measure the resistance probing at both contacts of the two wires, you already measure the cartridge heater itself as well.
However, by doing so you could still be able to tell if the wiring is faulty when you move the wires around while probing and see if the resistance value will spontaneously change. It actually wouldn't really help you in the end though to know if it's either the wiring or the cartridge heater itself, as you can't just change the wiring. Due to the construction of the cartridge heater and it's wiring, you'd have to replace the whole unit anyway though.

You can check the 24V heating circuit of the cartridge heater itself. Besides inspecting it closely if any visible damages like scratches or abraded spots are visible, you can measure the continuity and resistance of the circuit as well.

If the circuit and the cartridge heater is ok, continuity will be given and a resistance of about 10.5 Ohm should be reported.

• If you need to change the thermistor, take off the blue plastic housing of the head first (including the part cooling fan - don't rip off it's wires!).
• It's advisable to already disconnect the connectors of both the thermistor and the heater cartridge at the breakout board, labeled as "T0" (thermistor) and "H" (cartridge heater).
• Then you need to take out the hotend from the heatsink by loosening those two grub screws in the center of the front of the heatsink which hold the heatbreak in place for being able to actually reach the screw which holds the thermistor in place.
  
• So loosen those two screws and take out the whole hotend - be careful when pulling it out to not rip off any wires if you didn't disconnect them already.
• Once you took the hotend out, loosen the 1.5mm hex grub/set screw at the heater block which holds the cartride heater in place.
  
  Attention: be careful when trying to loosen that screw, it might be that it won't come loose unless you heated up the hotend first!
• Now you can take out the cartridge heater.
  
• Now take your new cartridge heater and repeat the steps in reverse for reassemble everything.
  Make sure to screw the grub screw in tight but not too tight (as you don't want to harm the unit) and to connect the wires back to the breakout board once you installed the hotend back into the heabreak.

• For cleaning the nozzle and getting rid of excessive filament during the printing process or right before printing starts as the extruder is heating up, you can use a long and thin wooden stick like a skewer. A wooden toothpick also works fine - just make sure you don't burn yourself as it may be a bit short. I personally use these long pipe cleaners which have this kinda cotton stuff all around them. It doesn't melt when touching the hot nozzle and filament sticks great to it.
• Before and after each print I recommend to wipe away the melted filament at the nozzle with a 'cotton' pipe cleaner, a paper towel or a cloth - but don't burn yourself! This procedure keeps the nozzle clean and the rest of the filament won't burn black onto the brass which makes it hard to remove later.
• If the nozzle is already too smeared and has too much filament burnt onto the surface to be cleaned with a paper towel, you can use a small brass brush. Be careful though to not harm the tip of the nozzle by scrubbing too hard across it! Be careful to not touch any wires or contacts during brushing at it may cause a shortcut and blow off your mainboard! So I'd suggest you heat up the nozzle and then turn off the printer before starting to brush.
• If the nozzle is clogged, using a needle with the correct diameter to stick it into the hot nozzle for cleaning it sometimes works. Just stick in in the heatened up nozzle and poke around. Be careful to not harm the tip of the nozzle though!
• You can also use certain filament which is made for cleaning. You load it and let it run through.
• If the nozzle is clogged and therefore the cleaning filament can't run through, you could also try to do a "cold pull". To do so you heat up the nozzle to about 220°C, load the cleaning filament and manually push it through a bit. Then let the nozzle cool down to about 90-100°C and rip out the filament. You may have to repeat this procedure a few times until the cleaning filament can run through again. However, be careful not to rip off the filament by doing the cold pull as you then definitely have to disassemble the hotend.
  Attention: don't do cold pulls when using any kind of coated nozzles! This also involves hardened steel nozzles! The manufacturers say that it might harm the coating of the inside of the nozzle!
• If you still encounter problems with the flow of the filament though or if you even can't load new filament, most likely the little PTFE tube inside of the heatbreak is clogged. Scroll down to the "Disassembling" section where you'll find a little guide about how to get it out and clean it.
• If you took out the nozzle from the heater block and can't get it clean, heat it up with a hot air gun. Then you can poke out the soft filament. You can also try to put it in acetone and let it sit there - the longer the better (I'd say minimum 24hrs). This method works especially great with ABS as that just dissolves, but it also works at least a bit with other types of filament like PLA (although not as good as with ABS at all) and makes it a bit softer. Then you can try to poke the filament out. This also works with the heater block and the heatbreak if you want to clean them also. Make sure to rinse them with water before installing though.

• If you just want to change the nozzle, take off the silicone sock of the heater block, then heat up the extruder first about 5-10°C above your regular printing temperature and pull back the filament a bit once it's warm enough.
• Once the extruder heated up, let it sit at that temperature for about a minute or two to make sure that even the last amount of filament which might stick somewhere in the gaps or the thread is melted.
• Then turn off the printer and ideally unplug it from the power outlet. Don't fiddle around while it's turned on - in case you slip with the wrench and harm the wires you could create a shortcut which most likely will blow something up of your mainboard.
• Then grab the heater block with a wrench to hold it in place and screw out the nozzle carefully. Use a sufficient tool like a wrench or a socket wrench for the nozzle - don't use a pair of pliers as it may/will round off the screw nut.
• Make sure you don't turn the heater block at all to not loosen it from the heat break! Just hold it in place.
• If the nozzle won't come loose, heat up the extruder again, raise the temperature a bit and let it sit longer to melt the filament in the gaps which seems to block. Before trying to unscrew the nozzle, switch off the printer again.
  If that still doesn't work, you could take a piece of damp cloth and hold it against the nozzle (not the heater block, only the nozzle!) for a moment to cool it down. Due to the sudden decrease of temperature the metal of the nozzle will contract a tiny bit which may result in being able to unscrew it.
• For installing the new nozzle, screw it in and turn it back about one rotation once you feel it hits the heatbreak. I personally do this after everything cooled down until it's safe to touch because then I can screw in the nozzle by hand and therefore I can feel right at the start if it doesn't sit correctly.
• Check if you didn't harm any wires!
• If everything is fine, power up the printer and heat up the extruder again. Most nozzle manufacturers say that you should heat it up to about 250°C, but that might already harm the PTFE tube. So go with 230-240°.
• Then carefully tighten up the nozzle, but don't overtighten it though. However, you need to make sure that it's tight enough (about 1.5NM) and that it really touches the heatbreak! There shouldn't be any gap between the heatbreak and the nozzle inside of the heater block!
• Don't get irritated by the fact that there's a little gap between the head of the nozzle and the heater block oncce you installed everything correctly - that's totally fine and it's supposed to be like that as the following picture shows.