Gantry alignment... How do ya?

[ChrisInEstes]

What's a good way to make sure my gantry Y-Axis is as perfectly 90 Degrees perpendicular to the X-Axis? I had to have both drive belts off my machine to make a repair, and while it will go back together really close to how it was, it's reasonable to assume it won't be right on.

Any ideas for me?
Chris

[FixitMike]

One way is to carve the largest rectangle that you can. (Or just the 4 corners.) Check that the diagonal measurements are equal.

[ChrisInEstes]

I can cut a tad bigger than 4' x 8'... I'm gonna need bigger calipers!

Chris

[FixitMike]

Or just a large square. You don't need the actual diagonal dimension, just the difference.

[PaulRowntree]

Jerry Burke had a neat idea over at the 'Zone. He used a USB microscope mounted on the router support to view a good metal straightedge, which gives good distance measures (good to 0.005"). If you combine this with accurate grid paper it can give very good (x,y) measurements. Two good measurements [ set the origin as (0,0), a point along Y motion, a point along X motion] gives very good angles. here is the XL sheet I used to do the math, rename from txt to xlsx

The image is an example of the USB microscope image. The lines on the paper are 0.008" wide.

[rsetina]

One way is to carve the largest rectangle that you can. (Or just the 4 corners.) Check that the diagonal measurements are equal.

He means that after you cut the rectangle you can measure the diagonal corners with a measuring tape. If the measurements are equal, you have a perfectly perpendicular X and Y. If not, then your rectangle will be a parallelogram and X and Y are not perpendicular.

[Norb]

There isn't really any need to cut a square or rectangle. My table is 5' x 10' so I use a rectangle of 4' x 9' on the computer but the toolpath consists only of 3mm holes at the exact position of the 4 corners. I have 3mm pins (but you can use of course the drill bit up-side-down) which will act as temporary stops for the tape measure when taking diagonal measurements.

If measurements show that gantry is out of square, I 'cross' the holes with a pencil do some adjustments to gantry, move the toolpath about 5mm in either Y or X and start over again.

That way you won't make unnecessary grooves in the spoilboard.

[Leo]

The best way I know of is with a 3-4-5 triangle

http://mikelindstrom.wordpress.com/2007 ... triangles/

You CAN do it with a tape measure - and get the hypotenuse probably within 1/64 - with a tape measure. Over a 3 foot x 4 foot x 5 foot triangle - that would be really close

Of course you could do a little arthritic and get the 3 foot leg to be 4 foot and the corresponding other legs to fit - and get a little closer.

You could make some really accurate length measuring gages directly on your machine to get you closer than 1/64.

That's my take on it.

Ohhh and yeah - you could program a trace pattern

[ChrisInEstes]

Lots of ideas... I'll let you know what I end up doing and how it comes out.

Thanks!
Chris

[daniellyall]

stick a pencil in in your spindle draw a line along the x axis then down the y axis put a big squire on the x line see how it lines up to the y axis line then adjust from there