Hot-end sometimes hits bed clips

Hi all,

I have recently built a Prusa Air 2 and am having some issues.

The hot end will sometimes strike the bulldog clips used to hold the heated bed and glass, I have to remember to have the head in the middle of the bed before starting a job or homing - otherwise it can happen.

Any idea on how to prevent this?
Its very annoying as the printer can get damaged if I forget to centralise the head!

Thanks
Ash

Move the end-stop. Alternatively, on Repetier you can define the bed boundaries, I just don't think it will work when the printer is homing.

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Cheers,
Franklin Dattein

OK, but with the endstop in its current position the bed homes to the front left corner perfectly.
Surely if I change it this will be thrown out?

Maybe, you will have to test. If that is the case, you can limit the y-axis by changing it in the firmware.
However, I wouldn't limit the print size because a clip. I would rather try to find a larger glass or some other way that doesn't limit the print size.

In Repetier firmware you can tell th eprinter your front is x mm away from endstop. So after homing y it would go back x mm and define this position as zero. If you then position everything above y = 0 you should not have any problems. For the y max position you have to watch out or reduce the bed size to make sure objects are outside the critical path.

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I didn't want this issue, so I ran a thin bead of glue around the edge of the glass, and clamped the beds together until the glue dried. This was I have nothing protruding above the glass. I used UHU glue.

Does UHU handle the heat?

I just set up the firmware to have the origin in the middle of the bed instead of where the end stops are and home Z to the top to avoid the clips.

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[www.hydraraptor.blogspot.com]

Yeah it seems to, it's been at 70C (I only print pla) for what must be >500 hours by now. I don't know if it's lost some strength, but if I try and lift it, I'm wary about bending the 8mm smooth rods before I am of breaking the glue. homing z seems like a good solution - doesn't it add a bit more to the print time though or do you have very fast axes? I can't move my z axis that fast without the motors skipping (they don't have very good torque).

Ah yes 70C is no problem, I was thinking of 130C for ABS.

It does take a long time for the Z axis to decend 200mm but I switch the bed on first so no time is wasted.

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[www.hydraraptor.blogspot.com]

Thanks everyone, appreciate the input.

nophead Wrote:
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> Ah yes 70C is no problem, I was thinking of 130C
> for ABS.
>
> It does take a long time for the Z axis to decend
> 200mm but I switch the bed on first so no time is
> wasted.


I saw someone used Sugru (silicone putty) and it can handle up to 180c for extended time. I have some covering up my heated bed solder joints to prevent shorting and to give a physical connection. I had one wire break at one time.

The Sugru sticks to almost anything but can be removed with a razor if needed. It's like play doh or clay and he molded a rim around the glass without going above the glass.

Myself I like to change out my glass as I have several and I print, then set it on an aluminum sheet to cool as I pop in another glass to start printing again.