Current issues with FLSUN printer

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If you have any problem the printer - shoot.

For me - my PSU works only for limited time - it stops on second print - I've upgreaded it server PSU, and now it works fine.

Ordered my kit. Have it all wired up correctly (I think) switched the switched to 110v but I have no power. When I plug the usb into my laptop the LCD screen lights up but no fans come on. No movement what so ever. Any ideas??

Double check the wiring to the PSU and from the PSU to the MKS Gen-L. USB will only provide 5V power to the board, enough to light the LCD. Won't power fans or motors.

Ordered my kit 2/8. It was delivered 7/8. Parts were well packed and nothing was missing. Plenty of extra fasteners.
The instructions cover all the details, but had to move frequently between video description and the pdf. Making a lot of notes helps.
Had problem getting Repetier Host to connect to the printer. Flsun were very helpful and we thought it might be the Marlin firmware. Reinstalled from the online website, but it caused the LCD screen to go blank.
Flsun then emailed correct version of Marlin and the screen display was restored. Thinking the Repetier communication problem might be due to Windows 10, tried with another PC and it was the same. The problem was because Repetier Server had been installed as well with Repetier Host. After deleting the Repetier server installation the communication was fine.
It is best to adjust the Bed level sensor position with the nozzle very close to the bed. Then the Z Offset is small and can be easily set using M851, M500, M501 and M503.
(Tip: Fix Bed Level Sensor in its lowest position, then move it down to activate and use old credit cards to measure the gap, sensor - bed, and nozzle-bed. Subtract nozzle gap and readjust sensor fixing.)
My first print was a Bracket for the Bed Level Sensor.
Now working on guard for the Extruder fan and also the motherboard fans.
Here is link to my first print:https://youtu.be/pHbfcw6nCL4

Comments deleted.

Hi all.
I've just ordered a FLSUN i3 Prusa, after reading about them. I chose this printer as I like the aluminium frame.
I've already seen a few 'upgrades' that I'll be doing, but I'm wondering if one of the upgrades should be the PSU? Am I right in assuming that a PC PSU would be ok? I have a couple lying about, from previous computer builds, so could possibly use one if they are the thing to use.
I'm relatively new to 3D printing & am always learning, so any advice etc. will be gladly received.
My current printer is the 'Create & Print V3'. It was built from scratch as part of a magazine subscription. I find it a good printer, if treated carefully. But I'm now wanting a larger print area, hence the purchase of the FLSUN.

HI, i'm extremely new to this, I've completed the building of my printer, and need to set up the software, my lcd display is lit but has nothing on it. also with the repetier software running having followed the provided instructions. when sending the axis home the z-axis moves upwards and not towards the micro switch (it moves about 15mm and stops). if you can understand what i'm saying I would really appreciate some help. Thanks in advance.

I had the FLSun printer for about two months now. I placed corkboard under the heat bed and covered it with aluminum foil to raise the bed temp to about 117deg C. I also bought a zonestare duel color print head and added that. I will post some pictures. I am attempting to connect a BLTouch sensor and want to know what pins to connect to on the main board? Can someone lend a hand on the pin Outs?
Thanks in advance.

Some notes: I turned software min endstops off. I connected the Z prob to z min. Easer to set leveling and layer height. The zonestare dual print head is $45 + shipping but it is a quality print head. I also added a single nozzle to it. All I had to do was printout new X axis rod holders with the 8 mm rods stacked on top of each other with the hole spacing at 45 mm. I printed 4, one for each side of the Y axis carriage. I the used tyraps to ho tighten the new rod holders together. Works great. I got 2 bad pieces of glass for my printbed and that's why I am adding the BLTouch for better bed leveling. I think once I an done with this the printer will become a solid print platform. Also had to add a second extruder and bought two exact extruder gear sets so the E value will be the same for both filaments.

Im new in 3d printer . I bought flsun prusa printer a week ago i assembly it but nose and the(z) axles are not calibrated to print. Can somebody help......

Were you able to find the PS_On pin on the board or is your PSU on all the time?

Mine PSU is on all the time. Should wire it properly, but no time for that :P

Look for D12 on the board. It is PS-on pin. And just use
M80 ATX_Power_On
M81 ATX Power Off

Mine came with the MKS GenL v1.0. from what I can tell, there's no pin D12. I'll be setting up a raspberry PI with octoprint soon so I guess I'll just use that to control the PSU.

I just got mine all togeather last night. The 2020 X axis fan mount snapped during assembly but wasn't a big deal.

Unfortunately, the X axis and Extruder doesn't work from the manual operation in repieter-host. I can get the motors to work if I plug them into the Y or Z motor controller ports (just to test the steppers.

Build went past 2am so I gave up for the night, going to try swapping the stepper driver boards to see if the driver boards are toast.

Can't wait to get this thing going.

***Update: it's not the stepper driver... anyone have some idea for me?

Yeah, my 2020 fan acrylic plate cracked too.

I thought the same thing too, you have to heat up the hotend; the extruder motor won't work if the hotend temperature is not high enough to melt the plastic, this prevents it trying to push when it can't and burning out.

I appreciate the response. unfortunately for me it's not the cold extrusion protection. I heated the nozzle and bed manually and via a small test print off the SD card. X axis and Extruder motors just won't go. FLSUN is sending out a new board should be here in a few days. I can't wait!! =)

Hi seannoseworthy, do you have the contact details for FLSUN, I am having issues with my i3 large and have tried emailing them with the email address on their website but not getting any response. Any help much appreciated.

Hi David,. Sorry I do not. I used the Amazon marketplace to flag an issue with the shipment. All correspondence was via that system. In the near 40 messages back and forth there was no contact methods mentioned what so ever.

I would try to contact them via Amazon. They where pretty quick to respond via that considering the near 12 hour time difference.

Thanks very much for the quick reply. I did see on their Facebook page a contact for technical and after sales when I was considering buying and doing some research, I have looked again and tried searching but cannot find it again.

No problem wish I could have provided some asistance. What is the issue?

A few issues really, I have found that one of the z lead screws is bent (I did a 12 hour print which was large and the model ended up stepping out while printing), there was also no mount for the auto level when using with the dual extruder (I went for the full package chimera, cyclops and single extruder with touch screen and auto level) and the main problem now is I went to change the firmware (already changed successfully twice to use different extruders, just experimenting with it) to the single extruder but didn't realise that there was an error in the provided single extruder firmware until after I had flashed it on the sd card they provided and it has ended up turning the mainboard into a brick. I've been researching it and trying different things for a couple of days but looks like the boot loader is corrupt now and will not let me change anything and just times out. From what I have found the only thing I can do is buy a Arduino Uno board and use that to flash the boot loader on it or replace the board.

i have one problem with my FLSUN 3D printer.when i give print X axis only moved other two axis does not works.but when i give auto home the three axis moves well.Please can any one help me o solve a problem.

The firmware is setup so that you have to home the printer before you can move the axis manually. That is something that confused me as well after I first built the printer.

Mine was doing the same thing. Turned out it the Psu switch was on 220 not 110.

I just got the printer this week, put it all together, installed the software, uploaded the marlin firmware and nothing seems to work the way it's supposed to. The LCD is blank, the extruder motor doesn't turn, the fan ramps up to 100% as soon as it's powered on, and the X, Y, & Z motors seem to turn one direction but don't want to go the other way. Any thoughts would be greatly appreciated!

So, here's a brief explanation: The board is not quite a ramps board. It's very, very similar but some pins have changed.

Here's my firmware with the configuration files. https://github.com/hominidae/Marlin

Basically, it should work with the usual configuration changes you'd go through but you'll need to select the board with the abstracted configuration for the changed pins for the LCD.

Power connector heated up and blue plastic melted, any of you guys experienced? I was having issues with bed not heating, so I wiggled the power wires and bed would turn on, turns out to be lose power wire, then later on I decided to inspect it further, that's when I discovered the melted plastic housing on the screw wire terminal. Unfortunately, I inspected it during a print and did a slight tug on the wire, it came out and touch something on on the board causing spark. I quickly isolated that, turn power off, hopefully it is still good, now I got to tear it down and check. Don't know if it's a board thing or power supply thing.

Ouch mate. I had issues with connectors. I've heard about melting issues there. Those connectors are not rated for the current. Best way would be to use a relay. Biggest issue there is moving bed - as it's moving it wiggles the cables out. If you will use solid state relay you will move the moving cables away from the ramps. You should also get connectors like this: 1065pcs/set 3 colors 22~12AWG Wire Copper Crimp Connector Insulated Cord Pin End Terminal Bootlace cooper Ferrules kit set
(from AliExpress Android)

A relay will limit you to flash bang heat mode only. If you want to enable PID you'll need a mosfet board.

Which type of relay and how would or where would you wire it in?

I crimped on similar crimp connection but the flat blade after that occured.

I swap out the PS that came with it with an ATX pc PS but it seems to be weaker when powering both extruder and bed at the same time.

I see where the wire shorted the board by touch, looks like it burned an inductor coil, but it still seem to operate. I did run through a print and about 18 step up the Z axis in the print job it stall and became non - responsive. I rebooted the printer and pickup on as close as possible where it stalled to resume print. It finished there after with decent finish.

I do have 12 AWG wires for the board to PS.

Hi Dirt_Builder,

For the relay just go to your automobile store (sometimes in big malls like Walmart) and grab 12-14V car relay ;) they are rated for 30-40A and have nice screw hole - so it could be mounted to 2020 extrusions ;)

For the connectors - it's good - it has to get flat - every time you are taking it apart - you should use new one so it will hold the cables in place.

Good your ramps live on :D you are lucky ;) you should have send lottery ticket :P

So, let me try to understand this, on our board we got 2 inputs from PS, 1 for board/motors/nozzle and the 2nd one for heat bed, correct? Then there is 2 output, 1 for nozzle and 1 for heat bed....so to wire the relay, would you use the heat bed output to control the relay gate switch which is connected directly to the PS that way the bed draws power directly from the PS instead of through the clone ramps board? I understand that the relay will be controlled on/off, but I can only figure the controller must come from the board to controller it automatically. If that is the case will you still need 2 power inputs? ..... please clarify. ....

I love the wire crimp terminal for the loose end wires, it was that I had to order crimper and crimps after I already got my printer I'm a poor college boy. So my printer was already built and operational and just didn't have time to haggle with it. But now I must as I was going to redo wiring to motor with cat5/6 cables cut to proper length to clean it up.

I was also thinking about using 2 m6 or m8 nut solder together side by side to create nut that would lodge and lock up inside the frame. Those nuts/bolts are expensive and I can't buy in bulk locally.


The heat bed is an output. Don't put power in.

Why complicate things. Obviously the connections were just loose causing too much resistance and heat. I tinned the ends of the wires and have them nice and tight, have the bed wires wrapped in the spiral loom and zip-tied over that to the bed and top corner of the control board for strain relief (temporarily) no loosening up or heat issues at the connectors. The psu-to-board wires themselves, however, get warm and need to be thicker, i've got some 12 gauge ready to put in.

The board connectors are not designed to carry alot of current. My wires were fine at 12awg, but the connector block on the board did melt. I'm just taking precautions for the future as it seems to be a issue with those block connector type.

Hi all!

I'm considering buying this printer, can you tell me your thought on it? Would you buy it again? Is the build volume large enough for you? How is your print quality? Also, I cannot tell from images I've seen, are the X & Y axis belt drive? Is the Z-Axis on threaded rods or lead screws?

I have a Geeetech Prusa i3 M201 already but want something more customize-able.



Like others have mentioned. .... not the best but not the worst. .. it is a great beginner for wanting to understand 3d technology as well as learning to upgrade or redeveloped the parts. But if you don't want to tinker and learn the developmental diy aspects, spend a little more. Another advantage of these is you can use the core parts to expand on. Improve its capabilities with various different parts such as fans, board, PS, motors, bed, frame, nozzel, and practically all. IT'S just what you want to do. It is OK to start off with but does require calibration to setup and get decent usable prints. You will not be able to get decent prints right at the start, so be prepared to tinker. That is how I learned 3d printing, from youtube video to building, now it's about calibrations, printing techniques, and understanding the programming.

Have fun

I wouldn't see it as being a huge step up from your Geeetech. Like most direct from china printers it has design flaws and the user has to fix them and fine tune it before getting good quality prints. I avoided the Geeetech because of the acrylic frame. In answer to your questions:

  • approx 200mm x 200mm x 200mm build volume, large enough for anything i have wanted to print so far
  • good print quality after you stiffen up the frame, adjust things properly, and get the right slicer settings
  • Both Y and X axis are belt drive
  • Z axis uses two 8mm leadscrews


How would you rate the quality of the main components? Good steppers? Is the control board a single board or an Arduino Mega and Ramps 1.#?

The reason I ask, is that I want a design based on the 2020 or 2040 v-slot rails so I can adapt the parts to the Prusa XL I'm building. It will be 1m x 1m x 1m with an 800mm x 800mm x 800mm build volume. I already have the 2040 v-slot assembled, 6.35mm aluminum bed and 110v silicone heater, and 1m lead screws. I was going to build a coreXY but the bed assembly was going to be too heavy, requiring 4x $150 steppers. Also, a big part of this is, the firmware on my Geeetech M201 is proprietary and is only available in compressed/encoded HEX.



  • The control board is a single board called the BT7272A and comes preloaded with marlin. It is of very good quality.
  • The steppers are good. My friend who has a printer says that mine are much quieter than his.

The printed components that come with the kit are of ok quality. But the design is somewhat lacking. Based on your description, you would be basically buying it for the 2020, some bearings, the control board, the power supply, and the five steppers. Although the ones that come with the kit are good, it may be cheaper to buy these things individually.

I have uploaded the files (parts list, manuals) that come with the printer here so you can judge for yourself:

Flsun Prusa Original Parts, Manuals, and Software
by jmzjamz

Hi, the printer is fair good. This is my first experience with 3Dprints, and I have to recognise that quality is good since first day, after a pair of weekends of setup, I didnt have problems with definition as people coment here. Obviously, it has parts to improve, like wobble in z axis, and I personaly dont like the X bars position (non vertical nor horizontal). Other thing is the components, I am having trouble heating the bed, it takes more or less 15 min to reach 80 degrees, and the highest temperature ive reached is 97 after 2hours of print and a blanket covering the printer. Maybe it has less resistance than a 1st quality component. The PSU is just ok. Another little problem is the electronics, being a quite hard to find resources on the internet cos its not normal RAMPS.
On the other hand I am very glad to see how much increased the activity of people form last 3 months (when I took it in November, there was nothing about this prusa) and hope to find many things, mods or improvements from now.

My prints lean in the Y- direction. I tear down all the printer to asure all parts of the frame are tight and square, also I will boost the current for the y motor. I will tell you as soon I finish re assembling

Do you use micro stepping?

Any of you have the motors data sheet?

Thank you in advance.

can you post some pictures?
How's your belt tension? Do not use springs.

I'm not using micro stepping - didn't go that deep with the software, I just started modding software.
My motors are sl42sth40-1504a
I've found datasheet for mine here:


i found that the motors will only move in increments of 6 microsteps.
(the boat jumpers are setup for 16 microsteps).
The 6 microsteps is very odd.
I cannot find anywhere in the firmware or the menu where this might be setup.

What pictures exactly do you want?
I think the belt tension is medium-high, I am not using springs.

Today I finished assembling the printer again, I noticed the y rods were loose. I made a wooden bed support, I hate de acrylic. I also boost the y driver to 1 V Vref. I tried to align all tight and square. I did a test print and the problem appears to be solved, but the printer needs deepest tuning.

Also I soldered the pins for the microstepping, my board did not have them, I am planning to try micro stepping for X-Y axis soon.

My motors are the same, thank you for the link.


Thanks for joining the group! Hopefully we can get a vibrant community going around this printer.

The PSUs that come with some kits are known to be unreliable. I have not had any issues with mine, but it seems like a common problem. Just be aware that it could mean there is an underlying problem with your printer that is causing it to draw too much current and overload the supply.

I picked up this printer off ebay, owned for about a month now. I did cracked the psi that was supplied, discovered a loosed solder joint on one of the diode, re - solder and seems to work decent so far. Gotta be careful with these low quality parts they toss in.

That is why I got myself 39A server power supply ;) I think it will be enaugh for now.


Did it improved your heating bed capabilities?

Yes it does. Those 20A power supply has very big voltage drop when heat bed is on. Here on the server PSU no drop at all. Recommended upgrade 11/10 ;)