issue with DIY Kossel 3d Printer

[eMole]

This seems to be layer-shifting problem.
One of the possible causes:
- printhead crashes into printed object (long quick nonprinting head jumping is not “completely flat”… or any model portion rises) and

1. motor step skips
2. belt skips (wrong belt tension)
   Solution:
   - for fast prints use larger z-lift, around 3x layer height

- increase current on driver (careful to motor limit!)
- well tighten belts
- avoid model twisting (good glue, ideally tempered chamber)

[ImpulsiveJames]

If rods weren’t parallel or same length, wouldn’t the parts end up more oval or start peeling up from the bed instead of shifting half way through?

[ImpulsiveJames]

Ok, apparently I have a lot of competition on this page… If you don’t have a parts fan, the PLA is cooling unevenly which causes it to warp upwards. When this happens, your nozzle crashes into the warped edge and the rest of the layers are shifted, just as your picture describes.

[CpunktRistian]

It seems that your stepper missing some stepps. Maybe you should reduce the extrution and rice the retracrion. Greez

[drakkn]

Start from the beginning and make sure the bed is totally level in each direction and your print head is about a piece of papers thickness away from the bed when your print starts.

[TECH_GEEK]

I think your belts may have slipped at that point. Try tightening the belts until they “twang” like a piano sting.

[paenian]

This is your printer skipping steps, due to too much sideways resistance on the extruder.

There are many possible mitigations, but the first I’d recommend for a deltabot pure software - make sure your printer ‘hops’ from one object to another.

In Slic3r the setting is in the printer - set “lift Z” to 2, and then every time the printer retracts filament, it’ll pop up 2mm before traveling to the next object, then set back down to print.

If that doesn’t work, you might want to improve your print cooling, lower the travel speed, or increase your motor voltage.

Paul

[JackP]

Your axis might be slipping. Does it always happen at the same spot? If not, It might be in your software. Also, your extruder might be getting stuck on your print and skipping steps.

[SEngineering]

Add a cooling fan to reduce warping and lower your travel velocity to 100mm/s. As someone else suggested, adding z-lift with retractions. Also, if this is a generic kossel kit, check your X,Y and Z acceleration. 9000 is typically too high for average stepper motors. Lowering to 7000 will give you more reliable printing and higher quality prints.

[SummersideGuy]

Ok, let me get into some more detail, it almost never happens in a single print with very few seperate points. Ive printed the G Rocket fine, vases fine, more kossel parts fine, etc etc. My rods are not quite perfect to each other, they came premade in the kit so I went with it. I have 2 at 216mm, 2 at 215.5mm and 2 at 215mm. Also I know the print is going to end up this way in advance where I hear the print head running into the part and when I examine the situation it looks as if the PLA has curled up a bit at the point of contact. Ive tried various temps from 185-up to 220 for the pla to cure this and I have 2 fans on my print head, one to cool the heat sink and one directed at the hot end itself.

[SummersideGuy]

I was think this but I do have a 30mm fan cooling the PLA and still getting curls(but not all the time) On some models no curls at all and on other lots of curls. Ive tried varying temps but it makes no different. I do have any examples atm to show as I usually toss them. Currently print BB-8 and he is coming out flawless so far, not oval or anything so this discounts someone else comments about rod length issues. I might most some examples of successful prints with multiple points here and then try one I know fails and post a pic.

[C_D]

On a DELTA printer, a layer shift due to a motor skipping steps or cutting out will make the print shift away from a particular tower. When it skips a step its usually trying to move up, or if it cuts out for a millisecond the carriage will drop down slightly. Both of these actions result in one axis being a few steps below where it should be, which in turn pushes the platform AWAY from that tower.

If your layers are shifting like your photo shows, have look which direction the part has shifted (maybe take a photo from directly above). This should point to which tower has the problem.

[SummersideGuy]

Ive done this many times to ensure bed calibration is right on. I even have buttons setup in Pronterface for X,Y,Z,Center Position locations. Always fine tune until a piece of paper just barely scrapes the head

[C_D]

Pictures always help. The more pictures you can post the better the chances someone can spot your issue =)

[SummersideGuy]

I was actually considering trying this out a few times but unsure of the feature. I may give a go tonight on something I know fails to see how it goes.

[HooeyB]

Hey, first check to make sure all belts and pulleys are tight. Als make sure the print has isn’t wobbling then if that fails u may need to adjust the current to the stepper drivers

[edakmiller]

A shift like that is typically caused by the bed moving because parts are attached to it and being hit by the head. Secure the bed as best possible and use the zlift feature as previously mentioned. My kossel mini prints multiple objects like a champ, my only issue is stringing which I can’t eliminate.

[SummersideGuy]

My Glass bed is secured down and cannot shift side to side as I have tabs fixed to the 2020 fram with rads exactly matching the diameter of the glass bed. There is no play. I never have a problem with stringing unless I am printing in flexible filament. My printer has good days where it prints great and mediocre days where it prints soso. I have been into this now for about 5 weeks and had to do a lot of research and reading up to get it this far. It is a DIY kit that had no firmware when I got it. If I can get past this one last obstacle I’ll hopefully be fine

[edakmiller]

If your printer is homed, can you shift the head by Hans such that it doesn’t move back?

[SEngineering]

It definitely sounds like your move speed is too high (not your actual printing speed, but the speed for moving between parts) and/or your motor acceleration values are too high in firmware. To test lower acceleration speeds without having to reflash your firmware, go to control -> motion -> scroll down until you see acceleration and lower to 2000. Than scroll down further and change each of the individual motor (x, y, z) acceleration values down to 7000. Start there and see if it is improved.