marlin firmware and half height prints

[bigmikeinil]

#define DEFAULT_AXIS_STEPS_PER_UNIT {98.98, 98.98, 4007.32, 700} // default steps per unit for ultimaker
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.


copied/pasted direct from arduino app and is current, when i measure 100mm command send from pronterface it measures out to 100.02mm which is quite good.

printbus: i think the allthread is one of the weakest links in the chain have been giving thought to upgrading them to direct drive acme screws like the ones used in the davinci xyz (dad has one) so far ive replaced bed rods and bearings (went through 36 linear bearings to find 3 that had no wobble) 2 stop switches, and various other hardware. to be honest, the drill rod stock shipped with the unit is not what a drill maker would consider first quality and are probably seconds as i found variations throughout the length of the rods.. the endstop switches were rather junky (replaced with 69 cent bulk ones)
as far as the ramps chips i have been thinking about swapping out the stock chip for the higher current one just to be safe, it is running 2 steppers on the same chip as the others that are running 1.

mjoliner: used this http://youtu.be/wAL9d7FgInk as my guide for calibration and that calibration took me from rather poor prints to rather nice prints with sprinter firmware.

as for now im going to crank out 2 consecutive 20mm cubes just to verify consistency and i have one i printed with the exact same filament before the firmware change ill post a pic of all 3 when done
thanks guys

[bigmikeinil]

heres the results:
left cube was printed the other day under sprinter
middle cube today first print
right cube last print

[Roxy]

What is the height of the right one? It looks like you need to scale up your Z-Axis DEFAULT_AXIS_STEPS_PER_UNIT. And until I had things working right, I would bump down:

#define DEFAULT_MAX_FEEDRATE {500, 500, 2, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,30,10000}

[bigmikeinil]

roxy thats the wierd thing, with that setting for z-axis default steps when i move it up 100mm in pronterface it measures out to 100.02mm but when i go to print something i get 50% print height

[Roxy]

roxy thats the wierd thing, with that setting for z-axis default steps when i move it up 100mm in pronterface it measures out to 100.02mm but when i go to print something i get 50% print height

And that is a big reason why you ought to try the smaller numbers for Feedrate and Acceleration. It is possible your stepper motors can't keep up. Pronterface isn't going to use highly aggressive numbers for manually moving the carriage around. They are going to use numbers that work for everybody. So if it works when you are manually moving things around in Pronterface but not with your GCode... It is possible the GCode numbers are too aggressive.

I'm not saying this is the problem. But I am saying I would back off my numbers until the problem is understood.

[printbus]

I agree with Roxy. For comparison, here are the numbers MakerFarm uses as their values, and their printers can likely be assumed to be close to what you have.

#define DEFAULT_MAX_FEEDRATE {250, 250, 2, 22} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {1000,1000,5,1000} // X, Y, Z, E maximum start speed for accelerated moves.

These are considerably slower than what appear to be Marlin defaults that you're using now.

On the Pololu driver boards, I assume you're referring to Pololu Black as the higher current driver board? I think the only difference is a more efficient heat dissipation scheme on the board. IMO, unless you've noticed the heatsink on the driver board running hot (well, I'm assuming nwreprap has you put heatsinks on the driver chips), buying the fancier driver board won't get you much. You can always set the Z-motor driver for 2x the setting of the drivers with one motor if you haven't already.

If you go to the Acme screws, remember you'll have to go back in and readjust the Z value in the DEFAULT_STEPS_PER_UNIT since they have a significantly different thread.

Have you been in touch with nwreprap at all over this, since they say the firmware files they provide are pretailored for you?

[bigmikeinil]

ive changed the values in arduino, re-uploaded the firmware, and am printing another cube now. ive yet to talk to a human at nwreprap, they have a nack for calling back while im at work and have just received a reply to an email to them on the subject... response so far "you have to calibrate #define DEFAULT_AXIS_STEPS_PER_UNIT {98.98, 98.98, 4007.32, 700}" even tho in the email i had said i had that within .02 mm of perfect, will let you know how this cube comes out
thanks

[bigmikeinil]

just finished printing my cube... its now shorter by about 1.5mm than the last one!

[stargeezer]

Hi Mike. I have those couplers sitting on my bench. I think they will make a world of difference. Those three cubes above are all different sizes and the two smaller ones were made with no changes between them - that can only mean those couplers are slipping or you are losing steps. I know how loose the slip coupler seemed to me, that's why I ordered the couplers. Swing by and pick them up in the morning. BTW, I printed out a couple knobs for the top of the 5mm threaded rod so that it will be easier to adjust them on the fly. I can't address the software issues, you know that's where I'm weak, but that stuff you are seeing appears hardware related to me.

Dad

[bigmikeinil]

ok this morning ive made up my mind that i would rather be able to print stuff than have a working screen and not be able to print stuff so im going to reup my original firmware and fix the bedsize issue and then dig through the marlin code a little more to see if i can figure out whats causing the issue with print height. ill keep you guys posted on how it goes. thanks!