Nozzle too high when print begins

I have a mendel max 1.5 and am using a modded 0.4 mm mk7 extruder from folger tech. The extruder is rather tiny and was unable to touch the heated bed when the Z axis minimum is 0> TO fix this I set the Z axis minimum to-20 and it is able to reach the bed fine. As you know, when you start a print everything homes and then the extruder rises a little bit to allow it to extrude properly. When mine homes the nozzle raises too much and the plastic is too high to reach the bed. I am thinking the problem is that it still think the z axis minimum is ) but am not sure how to fix this.
Thanks in advance!

Can you adjust your Z end stop down any?

Also are your Z axis steps per mm set right?

Edited 1 time(s). Last edit at 11/18/2014 06:31PM by zerodameaon.

My z axis is at the correct height for when it homes, but when it rises a little it goes too high

Did you have the printer working before you changed the extruder?

If not, what software are you using? Try raising the extruder 10mm and measure, if it raises anymore your step/mm have not been calibrated right. What are you using for Z axis drive screws?

I think my z axis steps per mm may be way off because when I press the 10 in pronterface for 10 mm it barely goes 2 mm and I have to press the one 40 times for it to reach ten mm. Although wouldn't this be out of line with my problem?

The issues would be compounded. First you should calibrate all your axes.

[prusaprinters.org]

I don't really understand how to calibrate the axis. I saw the calibration guide, but didnt fully understand how to set the steps for the z axis besides adjusting the pots

What firmware are you using? It is a value you have to change in firmware for your axis.

Make sure that the springs of the bed are as loose as posible, use a drop leveler to make sure that the bed is leveled both X and Y points, then try moving very carefully the microswitch that stops the motors of the extruder, until when stopped by the microswitch the extruder slightly touches the bed and make a milimetric fraction of pressure on it; have no fear of breaking the glass since the springs as very loose. Then, when the extruder touches the bed and automatically moves up and down a little, try to calculate the distance with a little piece of letter paper passing in between with no pressure. You finally are going to find the best way to calibrate your hot end and bed distance. Remember that there are certain glitches that make the Z motors fail to reach the perfect distance every time.

Edited 1 time(s). Last edit at 11/26/2014 12:59PM by veteran54.

do not forget to check with the drop leveler both rails were the extruder travels back and forth.

Hi,

I'm having the same problem and I didn't want to spam the forum with a similar thread, so here it goes.

In my case I have the bed leveled and the nozzle is at max 0.1mm from the bed in all four corners of the bed and also in the middle. The printer is also leveled using a spirit level. The X-, Y- and Z- steps are well calculated on the Marvin firmware using the Prusa Calculator (http://prusaprinters.org/calculator/). For that matter, also the E-Step is well adjusted. I am using Slic3r and the Z-offset value is at 0. For the last few prints I'm using 0.3 mm layer hight with a width of 0.45 (hight x 1.5). Both Z carriages are at the same hight as I adjust it regulary.

When it starts printing and the printer beginns to extrude, I can see that the nozzle is much higher that it should be. It's hard to say but like 1 mm or even more. I can see clearly the the filament is beign deposited over the surface, not squished over it. It's really frustrating.

Any further ideas?