Prusa I3 Z axis problem

So I've been having some troubles with my prusa i3's z axis. My first print was all smashed by the hot end. I went into the Marlin config file and found that the default steps per unit were set at 2000 when its supposed to at 4000.

I change the default steps per unit from this:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, (200.0*8/0.8), 700}
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25}
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,300}

To This:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, (200.0*16/0.8), 700}
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25}
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,300}

When I went back into pronterface and moved the z axis up and down it was a bit louder and not as smooth but still worked. Then I hit the Z home button and that's when it started to get really weird. The motors make noise but do not move until I hit the end stop with my finger, then they run really smooth as shown in the video.
Z Axis Problem Video

I thought that maybe it had to do with the stepper driver not giving enough current, so I tried to adjust the potentiometer but it had no effect on it at all. It runs fine during a print and it just won't home right after I changed the default steps per unit. The print on this 10 mm cube was 1000 time better with 4000 steps per unit.

Did you reflash your firmware or something before the problem started?

I assume that when you say "10mm cube" that that's as defined by the STL model or whatever. So what is the measured height of the 10mm cube? Is it actually 10mm?

Regarding the weird Z-home thing... sounds like the polarity of the Z-home switch is inverted... there is a setting for that in Marlin's Configuration.h file.

So before I went in and changed the default steps per unit for the Z axis, i printed the one on the right, my j-head hot end was not raising high enough for the next layer to print and squished the entire print. Then I went in and only changed the default steps per unit for the Z axis to equal 4000 and re-flashed it. Before I changed anything, The z motors worked great and ran smooth and the end stop worked just right as well when the default steps per unit were 2000.

As for the cube, the one on the left printed how it was supposed to, it is 10mm by 10mm

Thanks,
-Stack

Edited 1 time(s). Last edit at 05/31/2015 09:36PM by Stack.

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#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25}

Change this line to :
#define DEFAULT_MAX_FEEDRATE {500, 500, 3, 25}
This will make the stepper work again. With "5" it was to fast ( and noisy )

Every time you change and reflashed the firmware, you have to use M502 & M500 command to store the new values in Eeprom.
-Olaf

-if you have 5mm lead-screw with 1.8degree and 1/16 microstepping, your steps per mm is 4000

-can we assume you are slicing the object at like 20% infill and not 100%?

-can we assume your extruding temp. is normal for your material, pla temp for PLA and ABS temps for ABS.?

-you should also change you acceleration down from 9000 to 5000

-instead of (200.0*16/0.8), you should just put 4000

-what is your layer height? 0.4mm?

-in your video, sounds like your motors are either receiving too much, or not enough power.
you can adjust the pot on the driver with a non-metal screw driver ..see [reprap.org]

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o_lampe

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#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 25}

Change this line to :
#define DEFAULT_MAX_FEEDRATE {500, 500, 3, 25}
This will make the stepper work again. With "5" it was to fast ( and noisy )

I changed it to 3 and it really helped but was sill a bit loud and then changed it to 2 and now it works like a dream runs smooth and homes like it should.

Thanks A lot
-Stack

Glad to hear!
Have you checked the two z-sides, if they run parallel?
I found my M5 nuts on the z-leadscrews were not aligned and all the weight rested on one z-rod. That can cause noise too.
When I adjusted the balance between the two z-rods, I had to level the heated bed afterwards.
-Olaf

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o_lampe
Have you checked the two z-sides, if they run parallel?
I found my M5 nuts on the z-leadscrews were not aligned and all the weight rested on one z-rod. That can cause noise too.

I have and I printed out a spool holder and it came out great, But I ran in to another problem, I tried to print an arduino holder but it came out mirrored and the board wouldn't fit. Does this have something to do with the y axiz? I built the Prusa i3 Rework and it has the y motor in the front with the end stop also in the front. Any Ideas?

-Stack

It is mirrored because of the end stops and how they home. In your firmware they home at min. Or max. Because it thinks you are starting in the other corner. You can solve this in repetier host. By changing how your homing is defined.
it would probably be mirror imaged on the x-axis. So start there. (Hint. Home x @ 200 with endstop in max position)

Whe you change a endstop to be defined as "max" then you also have to wire it accordingly on the RAMPS board.
When a stepper runs the wrong way after redefinition, you can turn around it´s cable or better do all the definitions in the firmware.

#define INVERT_X_DIR true
...
#define X_HOME_DIR 1

-Olaf

oh yes, nearly forgot about wire on ramps board

So generally speaking, when I move the motors in pronterface in the positive direction they move:

X: to the right
Y:backwards
Z:up
Is this right?



According to this picture I have my end stops set up in the firmware and on the board as:

X:Max
Y:Min
Z:Min

If you have the y-endstop as shown in the picture, you should define y as max ( not min, as you wrote )
-Olaf

I don't believe Olaf is correct. As you can see in the picture, when the Y-endstop is triggered, the extruder Y position will be at 0, which is min.

On mine, it is:

Y MIN : BACK
X MIN : LEFT
Z MIN: LEFT BOTTOM

Disabled Max so I can use a manual bed tramming probe. Honestly I don't even use Z min anymore so I have moved it all the way to the bottom. I have my startup Gcode to only G28 X0 Y0 and manually set Z.. I also rarely turn off my printer so I don't have to do the Z tramming all the time.

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wolfend
I don't believe Olaf is correct. As you can see in the picture, when the Y-endstop is triggered, the extruder Y position will be at 0, which is min.

In the picture, the green arrow represents the 0,0,0 position. When an endstop is at the opposite side, it is a MAX. endstop. It is even written y-max. on it.
-Olaf

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o_lampe

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wolfend
I don't believe Olaf is correct. As you can see in the picture, when the Y-endstop is triggered, the extruder Y position will be at 0, which is min.

In the picture, the green arrow represents the 0,0,0 position. When an endstop is at the opposite side, it is a MAX. endstop. It is even written y-max. on it.
-Olaf

The green arrow represents x=0, y=0. y=0 is achieved by moving the bed towards the back, so that's a MIN endstop. Max Y is achieved by moving the bed forward. The diagram is incorrectly labelled for normal usage. Whoever created tripped over the reversal due to the relative motion of moving the bed instead of the head.

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JamesK

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o_lampe

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wolfend
I don't believe Olaf is correct. As you can see in the picture, when the Y-endstop is triggered, the extruder Y position will be at 0, which is min.

In the picture, the green arrow represents the 0,0,0 position. When an endstop is at the opposite side, it is a MAX. endstop. It is even written y-max. on it.
-Olaf

The green arrow represents x=0, y=0. y=0 is achieved by moving the bed towards the back, so that's a MIN endstop. Max Y is achieved by moving the bed forward. The diagram is incorrectly labelled for normal usage. Whoever created tripped over the reversal due to the relative motion of moving the bed instead of the head.

So true!

I got confused by the label " y-max."
My apologies
-Olaf

My apologies for not being that descriptive, I just use the picture as a reference. My X end stop is a max (Like the pic) My Z is a min (like the pic) but my Y is a min (different from the pic). My home position is diagonal from the one in the picture. I have all the switches pluged in the right spot on the ramps board and also configured right in the firmware.What I think is causing the problem is that I built the Prussia i3 rework. In the rework the y motor is mounted on the front.

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Stack
My X end stop is a max (Like the pic) My Z is a min (like the pic) but my Y is a min (different from the pic). My home position is diagonal from the one in the picture.

When your 0,0,0 position is at the opposite corner, but your x-stop is at the same place as in the picture, the x-stop is a min-stop

The position of the y-stepper is not important. It is only relevant, if the stepper pulls the table to the endstop during "home" command. If not, you can turn around the cable or reverse direction in FW.
If you have the chance to put the y-stepper to the back it would be easier to install a belt tensioner ( in the front for convenience ).
-Olaf