I am having this ongoing issue with my DIY Kossel Mini. Let me try to explain what is going on. Lets say I am printing multiple items at a time or an item with multiple rising points at a time. What is happening as as the print head crosses from one point to the next it grazes the edge(now this could be cause of many reasons. I notice sometimes the pla curls up a bit) Well anyways as the print continues on and it graves edge after edge it begins to throw the print head out of the correct position and ruins the print. See the attached example illustration for what occurs as a result of this issue.
I would suggest two things, first try to use nozzle lift or how ever is called in your slicer maybe 0.2mm. Second I would look at steppers it self since I don’t think that’s enough force to skip steps, maybe increase current a bit. Also notice does it happens always on same axis if it does it might be one stepper skips.
I had the same problem once. It was mine mistake. I put the object to close to the edge of the bed. First layers were OK, after 50 mm there was overhang that was not in the printing area. The stepers didn’t know that and try to go outside the area and they loose few steps. The model came out like your picture, so you can check if you might be loosing some steps for some reason.
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
motor step skips
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)
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.
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.
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.
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.
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.
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.
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.
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.
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
