3D-Print
Layer
choose the layer height corresponding to the steps of your drive and spindle. So you don't end with different micro-stepping on each layer. So your stepper has 200 steps per rotation and your thread is a T8 lead screw with 4threads×2mm pitch so each rotation moves 8mm. So your layer height should be a multiple of 8/200=0.04 like 0.08, 0.12 or 0.16…
slicing
slicer have 3 modes to slice objects into layer, either you make sure the layer base starts and ends in your object or the top (or something in the middle). When you have a taper then the top of your layer is either smaller or bigger than the base.
here an example of exclusive smaller and inclusive (bigger than your object) slicing of a prism with 45° sides . The difference depends on the angel and layer height here for .2 layer, keep in mind this will happen on both sides so a cone with 45° will have .4mm difference in diameter
Flow
To get a nice print you have to ensure an equal flow. Beside the speed, movement and extrusion which is controlled by software, the main factors are filament and nozzle diameter (your slicer doesn't need the nozzle diameter as the extruded volume will be line width×layer height). Both are not that fixed as you might think, how you can adapt the flow rate could be seen here:
So it is very important to get the filament diameter right, and if you print a .6 wall with a .4 nozzle at .3 layer you need to keep in mind that bridging will not work as it is over extruding (the layer has more volume than the diameter of the nozzle so in mid air not a string is pulled but more like spaghetti drop down), also if the layer is very low your bridge string can gets very thin and break. Top layer (skin) are also bridges! - This happens when your layer is over 80% of the nozzle and walls equal nozzle diameter.
E-steps calibration
While the Slicer need the exact filament diameter to calculate the volume of plastic, you printer doesn't knows the extruded length of filament, only how many steps are send to the extruder stepper. To be precise you have to configure how many steps are needed to transport filament 1mm - this is done in the printer menu. (or with M92 gcode) and need to be stored in the EEPROM (saved).
Why can this differ?
The Stepper is turning the sprocket, maybe via a gear, depending of the size the circumference could differ. also wear and tear could change this value. Also a very soft filament may be indented more, different pressure on the spring load.
How to measure?
First heat up the extruder and load filament. Now use a marker and ruler to mark 25cm on the filament (keep it straight) from the extruder inlet. Now extrude 200mm via menu or a G1 E200 command and measure the distance to the mark - it should be 50mm (5cm). If there is less lets say you have 40mm left to the mark - then your extruded length is 200+ 50-40 =210. If there is more like 60 ⇒ 200 + 50 - 60 =190mm extruded.
Calculation
As the printer software only knows steps we first need to calculate how many steps were send. So check the Value for e-steps/mm and multiply that with 200mm (the extruded length commanded). Lets say you have 157 configured then this would be 31400 steps (157×200). Now take your measured length
e.g. 215mm ⇒ So your new E-Steps 31400 steps / 215 mm = 146 steps/mm
e.g. 209mm ⇒ 31400/209 = 150.24
e.g. 188mm ⇒ 31400/188 = 167.02
Now repeat the measurement to ensure it is now a match and save the configuration to the EEPROM after.
Your extruder is now calibrated for best printing accuracy.
Surface
Printing without raft on glass or kapton results in a nice smooth surface.
Using wider lines for the bottom reduces number of lines.
Reducing the space for the first layer (or set higher flow multiplyer) will generate a helpful over extrusion to fill gaps or if you use a pattern print sheet.
You can print a pattern or letter 1layer thick and foil with kapton tape - these pattern will transferred as imprint for following prints.
Also using a filament with iridescent particles (metallic) could give nice patterns as they get oriented by the printing process, using a concentric bottom pattern can intensify the effect.
Adding some distortions like small holes or cuts ( 0.05 mm ) will not leave a gap but cause the slicer to calculate the path around - so you can generate pattern or even a text when cutting it as a thin outline into your model.
G-Codes
M170 S60 ;Bed temp NO wait
M190 S75; Bed temp wait
M104 S140;Extruder temp NO wait
M109 S200;Extruder temp wait
M82; absolute Extrusion
M83; relative Extrusion
G28; move to Endstop (XYZ)
G90;absolute position
G91;relative position
G92; set position XYZE (zero)
G4 P4000; Pause for P in millisec
G1 X10 Y10 Z10 E10 F10; move XYZE F=speed
M106 S0;Fan 0-255
M117 Hello World; display message
M25; Pause for resume
M26 S0;fileposition S0 (byte) for loops
Toothed belts
If you notice that models are distorted, it may be that the belt has changed in length. This happens only on segments, not equal over the full length - so prints could be fine if printed on one position and get bad dimensions on another. Print this calibration bar twice (at the same location) and hold them together - one turned 180° after printed. If they doesn't match you have probably a belt problem. You need to repeat this for the other belt - on CoreXY or H-drive print it diagonal.