Help in response to laser beam alignment tutorial

[SWMS]

Hi Marco, that's a great tutorial. I learnt this the hard way. I have a problem with my machine in that I cannot get Top right and Bottom right to align on the vertical axis of the apeture. I have a 5-7mm difference between the two with it being in the centre of the z axis midway between the top right and bottom right.

The frame is level, as is the gantry at all points both at the front and back.

I think I can rule out the carriage it is running on on both ends of the gantry and also the laser head carriage as if they weren't built correctly the error would not be noticeable as calibration would have sorted this out.

Therefore I can only think that if the frame is level then the y axis frame on either end of the gantry has a tiny twist in it? Does anyone have suggestions?

Btw the gantry is around 1.2m long.

I attached a picture of what is happening. I should say this is a home brew machine that I bought.

Thanks

[Techgraphix]

With a water-level
( )
you can sort out a lot.
It even is possible that your machine is placed at an un-even floor and that it is not set properly.

Also check if the lasertube is alligned, so that the centre of it is at the same hight as the centre of mirror1, mirror2 and mirror3
A flexible transparent hose filled with a fluid can be handy to level out parts over a distance or around a corner..

Kees

[SWMS]

Thanks for the help. I have checked that its level using a water level, a pretty expensive one too! That's why I have written that they are all level on the diagram. I have also checked that the machine is level from corner to corner to check for twist. The machine is leveled by screw feet.

The aperture from the laser tube is about an inch to two inches away from mirror 1 and it is striking the centre of mirror one.

At left top and left bottom the laser strikes the same place on mirror two.

At right bottom it strikes the aperture for the laser head slightly low, hits the middle of the aperture when positioned between right bottom and right top and hits it slightly high at top right.

If mirror two is aligned so that the laser hits the centre of the apeture in the same place at top left and top right then between top right and bottom right is low and bottom right is even lower. See diagram attached.

However, all the frame is level. There is no rise or fall on either end of the y axis supporting the gantry.

So all I can think of is minor twist that is of course exaggerated by distance from origin to laser head aperture. When I say twist, I mean along one of the y axis runners for the gantry maybe caused by some previous torsion?

[Techgraphix]

can be.. You can check that too with a waterlevel.. Put it on top of you second mirror and slide it from top to bottom. if the airbubble stays on the same spot, there is no twist probably..
Is the gantry in level, on all positions (top to bottom)?

Kees

[SWMS]

I'm not near it at the mo, its 40 mins away. I was considering getting bolt on v rails. Then even if there is a twist I might be able to compensate for it by packing one end of the rail.


Actually I was thinking, if I stick the level on top of the mirror with a little double sided sticky tape at a right angle to the y axis that the gantry runs on and roll it front to back on both sides of the gantry I should be able to see if there is a twist somewhere?

Thanks for help

[Tech_Marco]

What about the beam from the 1st mirror to the 2nd mirror (2 -> 1)
BTW, I have hard time to follow your numbering ... (2,3,1) got my head dizzy


Marco

[SWMS]

From the first mirror to second mirror the beam hits exactly the same point. Sorry about numbering. I added the third number in after whilst I was drawing it out.

Rename 2 to 3 and 3 to 2 in your head. Ha ha.