Gantry alignment... How do ya?

Gantry alignment... How do ya?

Postby ChrisInEstes » Tue Jan 14, 2014 9:57 pm

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
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Re: Gantry alignment... How do ya?

Postby FixitMike » Tue Jan 14, 2014 10:26 pm

One way is to carve the largest rectangle that you can. (Or just the 4 corners.) Check that the diagonal measurements are equal.
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Re: Gantry alignment... How do ya?

Postby ChrisInEstes » Tue Jan 14, 2014 11:55 pm

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

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Re: Gantry alignment... How do ya?

Postby FixitMike » Wed Jan 15, 2014 12:47 am

Or just a large square. You don't need the actual diagonal dimension, just the difference. :wink:
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Re: Gantry alignment... How do ya?

Postby PaulRowntree » Wed Jan 15, 2014 1:39 am

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.
Attachments
X.jpg
TreeSoft SkewCalc - Copy.txt
(10.77 KiB) Downloaded 154 times
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Re: Gantry alignment... How do ya?

Postby rsetina » Wed Jan 15, 2014 7:16 am

FixitMike wrote: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.
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Re: Gantry alignment... How do ya?

Postby Norb » Fri Jan 17, 2014 1:14 am

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.
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Re: Gantry alignment... How do ya?

Postby Leo » Fri Jan 17, 2014 2:45 am

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
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Re: Gantry alignment... How do ya?

Postby ChrisInEstes » Fri Jan 17, 2014 5:00 pm

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

Thanks!
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Re: Gantry alignment... How do ya?

Postby daniellyall » Sun Jan 19, 2014 9:07 pm

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
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