pilliars and circle getting squished and layer splitting ?

hi

after a buch of headaches and google searches i finally decided to ask for some expert advice i have a box frame prusa i3 and i am printing with 1.75 abs if i print small objects they come out perfect and strong but as soon as i try printing anything big like a y axis bracket its extremely fragile the layers split from each other easily so then i found that it might be the layer height so i printed 0.5 wall's till i found the best layer hieght (i am using repetier and sli3er) so i fought why not try printing something long and circled. 10x10x20 circle

the first few layers went well then it started looking like the infill gets thicker each layer and then it started looking like it was not even printing a new layer put squeezing the plastic into the previous layer

the i tried using curaengine to slice the print (cura used a different infill method then sli3er) but the print came out excellent

so i presume something is set wrong in sli3er?

as well as my bottom and top layers look almost squished (did check the z end stop and its fine) and again when i printed something bigger like a cube 20x20x20 it came out perfect accept for the top and bottom layers that look squished

would appreciate any help
best regards
Ruan

Have you calibrated E steps per mm and set the correct Z steps per mm? It sound like you're over-extruding, which would fit the description of smaller objects coming out OK but bigger looking like they do.

hi yes the z axis and E steps are well calibrated the E steps might be out by maybe 1 or 2 mm but would not be more than that
bigger objects come out fine if uploaded a picture of a y axis bracket i printed its just very fragile and splits layers easily which i
don't understand as well or is abs just not that strong?.... there are 3 circle prints 1 is a 5x5x20 which you can clearly see theres squeezing
and the 1 which is lying on the phone was printed using sli3er which squeezed as well and the other one that came out beter was printed using curaengine
so i don't think its e steps or zsteps?

Insufficient layer adhesion can be caused by printing at too low a temperature. What temperature are you printing at? With ABS you need to be especially careful of drafts. A lot of people find an enclosure necessary to maintain a constant temperature as uneven cooling can cause ABS layers to warp and separate. Do you have a fan pointed at the print?

From what I can see of the top surface of your print, it does look like you're over-extruding slightly, but that won't account for the squishiness. The bottom layer will be squished more or less depending on how far your nozzle is from the surface of the bed. It does need to squish a little so the print will stick to the bed properly, so it's reasonable to expect a small lip on the bottom surface of your prints. When printing tall thin objects, you can expect some deformation as individual layers don't have enough time to cool properly before the print head passes over them again and deforms them with too much heat. I'd also look to the temperature of the stepper motors and stepper driver to see they're not overheating and missing steps. Where the column has broken off the round piece, this may be due to layers warping as they cool, but it's difficult to tell.

Things to try / check:
1. Printing temperature - if it's too low, layer's won't stick. Try the temperature calibration tower. [www.thingiverse.com] - you'll need to adjust for higher ABS printing temperature.
2. Drafts. Eliminate if at all possible.
3. Distance of nozzle from bed for first layer - do the paper test: place a piece of paper under the nozzle in the middle of the bed and home the Z axis. If you can move the paper but feel slight drag from the nozzle, you're good. No drag and you're too high. Can't move the paper and you're too low. Adjust height as necessary.

hi 3dkarma

now everything is more clear to me as for the pillar that broke off it's it must be like that because its a temperature calibration piece but i could not print it because of to much squeezing but i think your right about the cooling because when i stop the print i can totally squish the howl pillar with my fingers till about 3 mins then its rock solid and yes i do have a fan pointing at the heater barrel so i was thinking of adding another fan that points at the tip? as for the stepper motor's there's just one running hot sometimes and that's only with long prints and that's the extrduer motor i havn't checked the motor controllers yet il check them later and as well id go check the drafting later on i think that might be my problem as well

i am printing at 225 for now and the squeezing at the bottom layer just has a small lip i fought it shouldn't have one at all as far the fragile abs that wraps i think i am going to change to PLA for now because my printer is well still in a beta fase there are still a lot of bugs to fix like z wobble extruder and extruder fans x and y belt tensioners etc..al the fun goodies

i have both my z motor's wire's connected to one might that be a cause ?

thanks a lot for the help i really appreciate the input so fast

PLA is going to be easier to print with and responds well to having a fan directed at the business end. A lot of your "squishiness" will disappear as a result.

Having both your Z motors connected to the same driver is fairly standard, but you need to make sure you have the reference voltage on the driver set correctly. If you think it's missing steps (which you can detect by moving the Z axis up and down a few times by the same amount and measuring how much it actually moves) you can try increasing the vref (very slightly - no more than 1/8th of a turn at a time) until you're happy with the result. Be careful, though, as over-driving the steppers creates a lot of heat in both the stepper motors and driver and can burn them out or shorten their working lifespan.