FLSUN Kossel Building Tips and Problems

Alrighty, I have some small nuggets of wisdom to share with anyone building or using the FLSUN Kossel (I got mine from 3DPrintersBay). To put this in context, I'm a college student with lots of printing experience on a Makerbot in high school, but this printer is my first kit. I'll try to update this as much as I can when I think of something new.

BUILDING TIPS:
In my kit, there was an SD card with instructions. The 'instructions' were just links to youtube videos explaining the whole build process. I followed them to a T until they ended. The last video was the one that explained the wiring, but it did a pretty bad job. My kit came with some pretty long wires for some parts, and really short wires for the hotbed and screen, so I had to put the board on the bottom instead of the top of the printer. I decided to just leave the board sitting next to my printer (img1) because it's easier to access and find wires (but makes it a pain to transport). I would recommend attaching the board to the two included acrylic pieces, just so it's not out in the open. My kit also came with two extra 40mm fans to mount to the board, but as far as I can tell, there isn't a place on the board to plug them in. The stepper motor wires are incredibly long, so I wrapped each wire around each motor at least 6 times before routing the wire out to the board. Cable wrap is almost as useful as duct tape.
The 'turbo fan' for cooling the print doesn't quite fit in its slot in the print head. It's a little off kilter in mine, but it works.
I cut the filament tube down to around 70-80cm because it's a pain otherwise.
When assembling the heat block, the set screw you need to hold the heating element in is in the bag with the spare nozzle. Don't try to cut a M3x8 screw to fit, it doesn't work.

KNOWN PROBLEMS:
If you bought the version with a heated bed, be warned: mine couldn't reach 80C without modifications. PLA sticks to the bed alright, but ABS or HIPS won't. I ended up mutilating an oven mitt and putting it on the bottom of the build plate, which brought the max temp to 90C, which may work for ABS, but I have yet to try.
The 'turbo fan' blows on the print just fine, but it also blows on the heat block. If the fan is off and I'm printing PLA at 205C, there aren't any heating issues, but I get really bad warping on my prints. But if I turn the fan up over 60%, the extruder temp slowly drops, and if it's on 100%, the extruder drops all the way to 180C (and causes the print to fail). I might buy a new heating element (https://www.matterhackers.com/store/l/e3d-ceramic-heater-cartridge-12v-40w/sk/MGVJEE2H), or I might insulate the heat block with some spare oven mitt, or print a new nozzle for the cooling fan. My plan was to use this printer to print HIPS, which requires 240C, so more updates to come later.
The 'amazing auto bed leveling' is more of a pain in the rear than a benefit. On my printer, it's nigh on impossible to get the screws set right to make a gentle touch of the nozzle open the switch, yet still have the spring close it. Manually leveling the bed and changing the z-max position in Marlin work far better.
The entire print head has a bit of wobble to it. It's less than a mm in any direction, but it's really noticeable when printing. The prints end up alright, but I think I'll be adding springs to each of the arms to help stabilize it.

That's all I can think of for now. This seems to be a very well designed kit that works almost as intended, just with some heating issues. I'd appreciate any and all feedback!


EDIT 9/03
I made a new cooling fan nozzle that works much better than the previous one, since it doesn't blow on the heat block. It's on thingiverse! (https://www.thingiverse.com/thing:2515620)

Edited 1 time(s). Last edit at 09/03/2017 04:12PM by aflactheastronaut.

I just got one of these when 3D Printers Bay put the base model on sale for $160. I added the heated bed and slide rails to my buy. I needed some components for a custom build delta and it was cheaper for me to buy this kit and not use half of the parts than order ala-carte parts from around the globe!

I have custom corners, base plate hardware, extruder, end effector and and E3D 3mm filament hot end I will be using. I may keep the MKS board though, it is nice and small. I'll see how well it works.

Thanks for the pointers, I will learn from them. This is a very nicely packaged and complete kit, BTW, especially for the sale price of $169 (+ $75 for the upgrade parts I wanted). I will use these parts elsewhere. The end effector design is interesting and the rods are really solid and robust looking too.

This looks like a good value, especially for someone comfortable with hacking it!

DLC

First off, I got the FLsun Kossel kit just for the 2020 rails and the linear glides and steppers. I have my own hot end, plastic pieces and carriage parts from another project. This was just a way to get the other hardware "on the cheap".

Needless to say, I ignored all the build instructions (which are incomplete and pretty laughable actually) except for those involving the linear glides (which are kind of "notchy").
I am using the MKS gen_L ver. 1.0 board however, because I have it, and found some issues.
The first issue is that the board shipped with the kit is NOT the board in the instructions. There is no documentation included for either board, which is a bit of an issue when the instructions say "plug this in that place" when "that place" is unknown on the shipped board.
So.
I went looking and found very little documentation on this board - the reprap wiki has a little on the board in the build instructions, but nothing on the board actually shipped. This must be a pretty new one.

Once I found some graphics on the gen_L ver. 1.0 MKS board everything went pretty smoothly. Until I tried to get the part fan to work. I typically build up the electronics on a controller board first without installing the steppers since THAT requires that the endstops work properly and I like to see the fans work. Which the part cooler fan doesn't. There is a plug on the board that is noted as the part cooling fan connector, which nicely fits the part cooling fan's plug. But, when I tried to turn on the fan (using the firmware graphics screen commands) the fan blipped once and then stopped. It never moved again. I found a reference that this connector is PWM only, not a driver, which seems kind of dumb, but if that is the case then I probably just blew out the part "driving" that connector by connecting a fan directly that will want a couple of hundred mA and whose output is probably only able to supply 10mA. I do see a voltage level on that connector that matches the PWM "voltage", so something happens there, it just can't drive a fan.

This means that I will dump the firmware that is currently on this board and move to something that uses a RAMPS-style output which will put the part fan on the third PWM power output (extruder2 on the gen_L board.)

Can anyone confirm my findings? That the so-called part fan connector is not rated to power a fan directly?

(EDIT)
I found that the problem lies with the fan that FLSun sent. I don't think it will work with PWM signals. I found that the fan connector has a honking big driver transistor on it. If I put any other 12V fan on it then it works fine. So, either the 40mm fans that FLSun do not work with PWM signals or they are 24V fans. If I turn the fan on to a number > 128 then I can assist the fan to turn, but it won't kick off by itself. This means either it is 25V or it won't PWM, even at full 255 settings.
OK, that is good.

STATUS UPDATE:
The steppers all work fine. Both the bed and hot end properly heat up to set temperatures. All of the optical end-stops are working (I had to invert their signal values). Spankin'.
BUT
The extruder won't work, the display keeps throwing low temp errors when I test the extruder for extrude or retract. That is with the hot end set to 220C. The Marlin F/W has a 150C min extruder temp limit, so huh? What is going on here? It is NOT the firmware, I have used this exact code base in three other 3D printers with no issue, so something else is going on. Hmm, I just realized that I used the "1" setting for the hot end and I should have used "5" since I am using an E3D 3mm all-metal hot end. STILL, that thermistor was saying 220C, so I should not have gotten a false low-temp error flag.
Any ideas out there? I got nothin'. I will need to investigate more - I will report back when I figure it out!

(EDIT 2)
It turns out that the new pronterface I installed on this computer sent weird commands to the board. I got the older version that I have on another computer installed and everything worked fine then.
The latest Pronterface has a smashed-up busy interface that is hard to understand and drive.

thanks,
DLC

Thanks!
DLC

Edited 2 time(s). Last edit at 11/13/2017 06:35PM by dlc60.

gen l data sheet
4 fets 4 outputs D9 connected to the fourth fet , that white header above the drivers plain 12V or what ever your Vin is , you tested with another fan DLC.

That is one of the docs that I found. All in all I like this board. It is nicely integrated.

I set my stepper drivers like I set all my other StepStick boards. But my steppers are very loud and run hotter than they should so I don't think that these are biased the same. I will be dropping the setting from 0.81V to 0.61 and see how that goes. I am assuming these are set to 1/16 micro steps since my first poor ABS print is in the correct scale.

What do others out there set their NEMA 17 stepper current to?

Next step is to PID tune the hotend and bed.
I manually leveled the printer until I get some kind of zmin, zero offset detection setup crafted.

The cal cube is the next print...

Thanks,
DLC

Continuing the saga.

I have it printing. I replaced the faulty 40mm fan with the other 40mm fan FLsun sent. It works better. Everything is working, I just need to tune it up to work well.
My first successful 20mm cal cube measures 20.3x20.4x20.3. OK, those smooth rod guesses worked pretty well. I have the extruder pretty close and my steps/mm are obviously well on.
But...
My steppers get HOT in even a half hour print. I don't feel safe turning this thing loose on a 2 hour print when this happens. I started out with the drivers set to
.8V - super hot
.6V - super hot
.4V - super hot
sheesh! My little 800mA NEMA14 extruder motor is running set at .4V! What is with these NEMA17's? When you order stepper motors from "no name" outfits you expect issues, but all three super hot? Huh. I am wondering what stepper drivers these are, I can't read any of the text on anything so I don't know what the drivers actually are. I may just order up a set of StepSticks so I can start with something I am familiar with.
My next test is .25V as soon as the steppers cool down enough that I can touch them...

(EDIT)
0.25V bias voltage did the trick. After a two hour print run the steppers were just a little warm. Plenty of torque to move the end effector around. I also relieved tension on the belts, which eliminated the "notchy" sound (which was a big hint that I had the belts too tight...)


DLC

Edited 1 time(s). Last edit at 11/14/2017 11:20AM by dlc60.

What color are they? Have any pictures?

Quote
number40fan
What color are they? Have any pictures?

Sorry, what are you asking the color of? I will post pictures of my project as soon as I clean it up a little. I have the controller board mounted on the outside of the printer so that it is easy to "fiddle" with while I am tuning. Some of it is custom, some of it comes from other Thingiverse Things and some of it started as someone else's project that I modified to use with my own.

The one big tuning issue I have right now is top surface finish and layer adhesion. These are typically solved with tuning a combination of nozzle temperature, extrusion rate and print speed. Mostly the first two. I have 1.75mm filament tuning down cold on both Bowden-type deltas and Cartesian direct extruder printers. This Bowden setup is my first 3mm, and it clearly needs a different touch to tune it well. But hey, if it was simple, this wouldn't be any fun, would it? The joy is in the journey...

DLC

I was asking about the drivers to help identify them. .25v seems really low, but if they work....

Quote
number40fan
I was asking about the drivers to help identify them. .25v seems really low, but if they work....

The driver boards are blue, but they exactly match the green 4988 drivers. I checked that too. The docs imply blue is the 8825 driver, but that is very clearly not the case. 0.25 IS low, very low, and during one run a stepper skipped, which put the rest of the print off to one side. But now I wonder. The MKS board docs say that the "blue" boards should be jumpered "low, low, high" for 1/16 stepping. They were factory set to "high high high", which is 1/16 stepping for the green (4988 driver) boards. I would think that if the driver was trying to go 1/32 then my cal cube would not be even close to correct dimensions. That can't be it...

I turned the bias up to 0.3V and now the steppers get really hot again. The linear guides are very "notchy" and I wonder if their resistance is overtaxing the steppers such that they are pulling too hard and getting hot. But that doesn't make much sense because with the bias turned down that low they shouldn't be getting all that much current and if pulling, they should all skip a lot.

The only thing that I can think is that these stepper are POS and can't handle much current at all without overheating.

Anyway, I have attached a couple of pics of my setup. I still have the controller and PSU "outside" and not permanently mounted so that I can debug easier.



Thanks,
DLC

I think that I figured out the stepper problem. The super-heating steppers measure about 24 ohm across the windings. My other steppers are between 2 and 6 ohms. This leads me to believe that they sent me 24V steppers instead of ones better suited for 12V. I have looked at two other sets of steppers in printers and these are the only ones with such high winding resistance. The two ohm winding steppers are 1.5Amp NEMA 17, the 6.5 ohm winding steppers are 0.8 Amp NEMA 14 steppers.
Grump.
I seriously doubt that they will correct the issue, I bought the kit in September and just now built it. Oh well, another $40 for steppers, coming up. I guess I'll be making a 24V printer some time in the future...

Having fun,
DLC

Final report on this project.
I think that I mixed in some other "no name" stepper motors in my parts box and the FLSun ones are fine. My bad.
NEMA stepper motors measuring 24 ohms do not work at 12V, NEMA 17 steppers measuring 2 ohm, work fine.
My E3Dv6 3mm Bowden setup is using an "Itty Bitty Belted" extruder that I got on Thingiverse.
I am using the FLSun linear rails and heated bed.
I run Marlin firmware and use Simplify3D as my slicer/printer.

Pros:
* The kit is super well packaged and organized.
* The MKS gen_L ver. 1.0 Board is a fine board with nice options on it. It is working well, but is very susceptible to static hits on the Kossel frame. I need to do a more direct frame/Earth ground.
* My bed heater is hitting 90C with no problems.
* The unit works, it prints both ABS and PLA.
* Plenty of build hardware comes with the kit and it is well identified.

FLSun Cons:
* The linear glides are junk. These are noisy, "notchy" and occasionally catch. The whole reason I got this kit was to get those rails, and they are the single worst part of the kit! I am really considering just moving to the shower door rollers and calling it a miss.
* Need to replace the smooth bearings used as belt idlers, they are a bit noisy rolling the GT2 belt over them and I think that they will degrade the "teeth" in the belt.
* Build instructions are inadequate for a newbie builder. This is my third Kossel build, so no big for me.
* The 40mm fans are junk. There really is no other word for it. Neither of them will start without a "punch" and one of them won't run at any speed but "full on". I do not know if the 30mm fan or the 40mm blower will work.

E3Dv6 Cons (more tuning woes, probably):
* I am still working on an under-extrusion issue with the 3mm filament and E3Dv6. I have worked with steps/mm, temperature, cooling, multiple top layers, nothing seems to help (yet).
* 3mm filament (2.85mm) snags up when initially threading into the hot end. I have heard that a misaligned Bowden tube insertion can cause this, will work with that.

I wonder if the reason that I found it so hard to get 3mm Bowden fittings is because a 3mm Delta printer is a bad idea? I get 1.75mm stuff tuned in no time, this 3mm one is proving elusive.

Having fun!
DLC

Delta printers can give excellent results, but only if they are precisely engineered. Cheap delta kits rarely work well.

Shower door rollers are awful. Delrin rollers are better and can be made to work. But linear rails are best.

There are several posts on this forum by folks who have dismantled their cheap linear rail sliders, replaced the balls and repacked them with grease to get good results. You might want to try that. Alternatively, replace your linear rails and sliders with either Robotdigg 440C ones (if the size is compatible) or with western-manufactured ones.

Edited 1 time(s). Last edit at 11/20/2017 06:10PM by dc42.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Oh wow, I forgot I started this thread. It's been a while, and I'm happy to hear that you've solved a bunch of problems DLC!

As for me, I found some of the documentation that I was looking for in the original post. It was on the SD card that came with the printer, and I just hadn't looked for it there. Oops.

I've made it through half a spool of PETG, which has its ups and downs. It needs to print at 230+ C, and my hotend (with a ton of ceramic insulation and kapton tape) can barely stay above 235 with the cooling fan at 80%. I think the insulation just gets bad after a while, because it was holding 245 easily when I put it on the first time. More experimenting!

About your linear rail comments: I also had some issues with mine, where they would take extra force to move around. I ended up getting Slick 50 One Lube and generously applying it to the rails, and now they're smoother than butter! I'd recommend it, it was only $6. Someone else on this forum recommended it to me, since it has ptfe in it.

I have noticed my steppers getting warm, but not too bad. I did a 10 hour print last week, and they were hot enough by the end that I couldn't touch them for more than 5ish seconds. But I think my problem might just be that they're not getting any airflow and are sitting right next to the build plate/oven mitt combo, which was at 60C.

For the future, I may upgrade everything to a 24V system to let everything heat up a little faster. I'll definitely add a base to the printer to hold the power supply and controller and absolute mess of wires and some fans to cool it all. I also might upgrade to a (1.75mm) V6 extruder to see if that helps my heating issues. But it's printing alright for now, so I'm going to finish my Saturn V (https://www.thingiverse.com/thing:45316) which, btw, can be scaled 2.5X! Toodles and thanks for all the help you guys!

May your lines be straight and your extruders never clog,
Alex H

Quote
aflactheastronaut
Oh wow, I forgot I started this thread. It's been a while, and I'm happy to hear that you've solved a bunch of problems DLC!

As for me, I found some of the documentation that I was looking for in the original post. It was on the SD card that came with the printer, and I just hadn't looked for it there. Oops.

I've made it through half a spool of PETG, which has its ups and downs. It needs to print at 230+ C, and my hotend (with a ton of ceramic insulation and kapton tape) can barely stay above 235 with the cooling fan at 80%. I think the insulation just gets bad after a while, because it was holding 245 easily when I put it on the first time. More experimenting!

About your linear rail comments: I also had some issues with mine, where they would take extra force to move around. I ended up getting Slick 50 One Lube and generously applying it to the rails, and now they're smoother than butter! I'd recommend it, it was only $6. Someone else on this forum recommended it to me, since it has ptfe in it.

I have noticed my steppers getting warm, but not too bad. I did a 10 hour print last week, and they were hot enough by the end that I couldn't touch them for more than 5ish seconds. But I think my problem might just be that they're not getting any airflow and are sitting right next to the build plate/oven mitt combo, which was at 60C.

For the future, I may upgrade everything to a 24V system to let everything heat up a little faster. I'll definitely add a base to the printer to hold the power supply and controller and absolute mess of wires and some fans to cool it all. I also might upgrade to a (1.75mm) V6 extruder to see if that helps my heating issues. But it's printing alright for now, so I'm going to finish my Saturn V (https://www.thingiverse.com/thing:45316) which, btw, can be scaled 2.5X! Toodles and thanks for all the help you guys!

May your lines be straight and your extruders never clog,
Alex H

After many hours of service I had one of my linear rails "jam" on me. I took it off and using a paper towel, totally cleared the rails of gunk, and there was gunk! I then oiled the rail with RC car bushing oil. The linear bearing went directly to smooth as silk. So I did the other two rails as well. Now it is back in prime. I am using a 3mm E3DV6 head in mine. I cannot use anything but 2.85mm filament, the 3mm stuff jams in the Bowden tube, so that is right out. I have some issues with the filament catching on something when entering the heatsink and I have to fiddle with it to get it to go all the way into the hotend. It isn't easy to extricate it from my end effector, so I have not discovered what is going on with that...

Thanks,
DLC

Yeah, I'll be keeping a closer eye on my rails from now on.
Also, how close of a fit is the V6 hotend? I was looking into other effectors because I thought the stock one couldn't hold a V6.

Thanks,
Alex

Quote
aflactheastronaut
Yeah, I'll be keeping a closer eye on my rails from now on.
Also, how close of a fit is the V6 hotend? I was looking into other effectors because I thought the stock one couldn't hold a V6.

Thanks,
Alex

I have a custom end effector that I printed for my v6. There are plenty of them on Thingiverse. Mine does not have a bed detector, I manually level my beds.

DLC