Printing tweaking guide

This is my problem:

I've been playing around with 3D printing since I've got my gMax. I have printed fair amount of things and while doing so I have tweaked and changed various settings in slicer trying to get satisfactory end results. Now, all that tweaking is basically time consuming shooting in the dark most of the time. Like, let's change this and see what happens. What does this setting mean? Hmmmm, internet says it is this or that. Let's change it and see what happens. And on and on and on.

I have yet to produce anything besides rude and off prints on my gMax. It is good to make 3D models real so I can actually feel them in my hands and figure if design will work, but other than that (like printing parts for gMax), no way. I can tell it is possible to 3D print good plastic parts, (my gMax is made of them!) but they are just not coming out of my acrylic bed yet.

Question for you lass' and lads: is there a book or a web site or something where I can find explanations, aka theory, aka concepts behind 3D printing and how it works.
So that I actually can understand what all those words mean (infill, raft, travel speed, extrusion multiplier, etc etc) and so that when I notice something in my 3D print that is off (very thick and deformed 5 bottom layers, head scrapes over first 3-4 layers while printing, some layers shrink in X-Y plane some don't and I get kind of wavy wall instead of straigh one, etc, etc.) I can actually do some diagnostics and say something along the lines of: ahhhh, this looks like infill travel raft speed of stepping groove should be set to 0.025 lillyputs. Or something :)

Any thoughts and comments are welcome :)
Slic3r manual may be of help to you:

The questions you ask are covered in the expert section on the left.

As for the other stuff, like head scraping on the bed, this is a machine-specific issue and will be cured by
1) adjusting the z height (leveling the bed in respect to the nozzle and then slightly increasing the screw that hits the Z-axis endstop as necessary)
2) adopting one of the community solutions to ensuring a flat(er) bed by means of MDF, sheet metal, or glass. All of those mods are in the forum and reasonably well documented.
First things first:

- manual says check all bolts and nuts and tighten them up after few weeks or a month. Plastic parts need some time to settle after you assemble printer. Do it. I didn't and it does make a difference

- Check positions of critical parts: are both Z rods parallel to each other? are X-axis guides tightened (4 small bolts from bottom) so stepper motor and wheel on right side are not wobbling?

- Are all 4 Y-axis wheels below bed tightly in their aluminium guides? Mine were not, they had cca 0.5 mm of free travel. I have calibrated bed on Z-axis with wheels pressed down and after first print they travelled up for about 0.5 mm when I was removing first print. It screwed up all prints after that in very weird ways and it cost me weeks of useless fiddling with settings.

And at the end, here are some links I have found useful for printer calibration: ... rial_Guide

RepRap guides can help a quite, since gMax is reprap kind of animal :)