# Specific 3D Printers, Scanners, & Hardware > CTC 3D Printers >  Z Axis Offset

## patele

Hi, 
somehow my Z Axis is in the correct height at bed leveling, but when I start my print, there is an almost 1mm gap... 
Do I have to change the Offset to the positive or negative. 
I don't really see a difference by making these changes.

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## patele

Just tried to print a Hollow Test Cube. I Have no Idea what that guy is doing. The nozzle is way to much in the air. And then at some point the extruder stopped extruding. I think I have to clean the feeding gears. But that does not solve the problem of the first layers... 
Just have a look, you can even look through the layers... How do I get that stupid nozzle down. Tried Offsets from 2 to -2mm with no noticable difference... Am I missing something?

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## bigo93

Are you leveling the bed when it is cold or hot?

If cold then that is the problem.
You should level the bed when it is hot as the heatbed can expand and warp slightly when it's hot.

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## patele

> Are you leveling the bed when it is cold or hot?
> 
> If cold then that is the problem.
> You should level the bed when it is hot as the heatbed can expand and warp slightly when it's hot.


Gonna try this later today. But I doubt its getting smaller when its hot. Cause its also not touching the board at any point. 
Could this also be a Makerbot fail, which sets the first layer at a wrong height. Is there any way to check this?

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## TiredJuan

What software are you using? 
If you're using Makerware, I would try the same print in ReplicatorG to see if it changes. RepG is terrible software, but IMHO it's been better than Makerware. Especially if you don't mind getting your hands a little dirty with code. Like many here, I've switched to Simplify3D. It fixed 90% of my issues. Also there's this guide which can help, even if you're not using their software.

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