Z Height between layer help

Hey guys, I have my new prusa type build up and running, well sort of.. it's doing everything it should, firmware all good, pronterface happy, stepper speeds and axis max/min's set..

The issue I have is the Z layer height. I am waiting for a new hot end, so I have it printing invisible stuff right now, but it seems to be jumping like 1cm between printing layers, so instead of 0.1 it jumps 1.0..

I tried using josef prusa's calculator, but the prob is my steppers are so cheap and nasty, there is like no info on them at all, no serial, nothing... I am pretty sure they are sainsmart, so I went off those settings but still..

Is there something really incredibly obvious I missed in my eager rush to get it built? :o

What does this line look like in your configuration.h file? (Assuming its Marlin firmware???)

#define DEFAULT_AXIS_STEPS_PER_UNIT {78.7402,78.7402,200.0*8/3,760*1.1} // default steps per unit for Ultimaker

Because if it is off by 10x, obviously, that line would have to be adjusted. If it is off by 10x something is turning (or moving) way more than you expected!

And one more set of questions: Are you using the exact same motor for the X & Y? Does the X & Y movement position accurately (like no 10x movement) ? (Because if you are using the same motors and they move correctly, at least the number of steps per revolution is known.)

It isnt very scientific, but measuring how much the Z-Axis moves compared to what you actually told it to move should let you scale that constant to what it needs to be.

oooer... How did I get my config so wrong...

My axis steps are similar, in the 79's except of course for the Z height, I some how had a value of a 1000, which it was at 4000 so I assumed lowering it would lower the z height, but you have 200.0*8/3

That's sorta where I got lost... and I cut some decimals too, I guess that was a bad idea lol...

#define DEFAULT_AXIS_STEPS_PER_UNIT {79.2, 79.2, 1000, 700} // default steps per unit for ultimaker

So yeah.. I screwed up clearly... I had to play alot with the Z speeds to make sure the rods were both screwing at the same time, and I have them now moving really smoothly using
#define HOMING_FEEDRATE {50*60, 50*60, 2*60, 0} // set the homing speeds (mm/min)

I am back working full time, got a job working IT in a bank, so it's been pretty full on training, this weekend will be about my first chance to get back on it :/

Just for reference... This is how my Configuration.h comes up with the numbers. That one line I posted is actually commented out in my Configuration.h file. It is for the Ultimaker. My Z-Axis threaded shafts are English threads so that makes things a little less clean. But the numbers won't be radically different for metric:

#define MICROSTEPPING_RATIO 0.0625 // Enter microstepping ratio of electronics. Printrboard and Pololu = 1/16, Gen6 = 1/8, etc.
#define Z_MTR_STPS 200 // Enter number of steps per one revolution of the Z motor(s). Print calibration cube of 10-20mm to compute xyz steps

#define BELT_PITCH 2.5 // Enter pitch of X and Y belts in millimeters (space from tooth to tooth). XL belts = 5.08mm
#define GEAR_TEETH 16 // Enter number of teeth on X and Y gears
#define Z_ROD_PITCH 1.05833333333 // Enter pitch of Z rods in millimeters. Pitch = 1.25mm for directly driven M8 rods, 1.41111111mm for directly driven 5/16-18 rods.

#define DEFAULT_AXIS_STEPS_PER_UNIT { ((XY_MTR_STPS/MICROSTEPPING_RATIO)/(BELT_PITCH*GEAR_TEETH)),
((XY_MTR_STPS/MICROSTEPPING_RATIO)/(BELT_PITCH*GEAR_TEETH)),
((Z_MTR_STPS/MICROSTEPPING_RATIO)/Z_ROD_PITCH),
((PACKING_DENSITY*EXTRUDER_MTR_STPS*EXTRUDER_GEAR_ RATIO*(1/MICROSTEPPING_RATIO))/(PI*BOLT_DIAMETER))}

What this means is my X & Y number are at 3200 (much higher than the UltiMaker #'s) And my Z is at 3023. More steps per unit of movement should help precision (assuming all the mechanical stuff is tight with no slop).

Why not just connect the printer to pronterface, have it home then have it go down to bed. Measure with the butt end of a caliper the distance from the bed to a known part on the printer head, lets say its 80mm, then give command to move up on z axis by a set amount and measure. Once you have those measurments you know what ball park your in. For example you tell it to move .1mm and it moves 1.00mm your about 10x off on your calculations, so multiply those out by 10 and test again.

my .02c

You can use Josef Prusa's reprap calculator to get a much more precise setting for x, y and z steps per mm.

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Originally Posted by 3dkarma

You can use Josef Prusa's reprap calculator to get a much more precise setting for x, y and z steps per mm.

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I tried using josef prusa's calculator, but the prob is my steppers are so cheap and nasty, there is like no info on them at all, no serial, nothing... I am pretty sure they are sainsmart, so I went off those settings but still..

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Anyway, Roxy, thank you, you have made simpler what was to me becoming a little frustrating. Yep, I have the mechanics to a point where it can shoot the Z axis up and down on the twin rods very fast and it doesnt slip, belts dont slip at full speed, tensions seem good( X and Y have always been solid) it was just that z speed that really needed work as for some buggering reason it would shoot up to the top of the Z axis before a print..

ie. It would home, and do the bounce on all the end stops, and then WHOOSH up to the top she went and off the Z rods, right off the machine lol!

I found out it was some crappy gcode being inserted from slicer or prioterface and removed it, seemed to be ok after that.

@Jaguarking I will try that too, so far the tutorials for pronterface have been nothing short of terrible. I really wonder how people who have little knowledge of computers sort themselves out with all this.. I mean I get what's going on, I've used arduino for years, ive programmed in about 7 languages, and have been building computers since I was 7 when the internet didn't exist lol and we were using decouplers on our phones to download 256bit images of photoshopped naked swimsuit models off a dodgy bulletin board... and I am finding it challenging, but it's fun and if you are like me fixing problems is a sort of bad fun time :)

I went to the pains of manually tuning my printer the best I can, I tried to make things work from a base stand point. I did this because of two reasons, usually the harder road gives the best result and secondly learning how this firmware works is part of the deal for me. I did a bunch of reading to get things built right. Have I succeeded? At this point I feel about 80% satisfied. People seem to build 3d printers so they can build 3d printers. I personaly have other intentions in mind besides upgrading parts. I am spending time learning how to properly design things and testing out ideas. This involves improving my own 3d printer, as well as building parts for my other projects. Its a bunch of fun for me, also very challenging. I like to think I have the whole system mentality vs the component mentality. Sometimes its fulfilling, other times it is frustrating.

As for the documentation being horrible? Yes it is, however coming from a linux/unix background, its nothing new. The documentation starts to make more sense once you know what is going on, learning curve is very high.