How to check for gantry squareness?

[15mgtar]

Guys is there anyway that you can check if your gantry isn't pefectly squared?
I'm running 2 motor for the Y axis.

[ger21]

Cut a square and see if it's square.

[spoiledbrat]

You could place a mag-base dial indicator on your Z or y axis. Clamp a machinist' square to your table, and trace both edges.

[TOTALLYRC]

To expound on Gerry's suggestion, cut a square and not only measure the width and length but specifically measure from point to point. If the length and width match but diagonals are off, you have a parallelogram.

If the length and width don't match, then you have a mess and it could be your steps per inch that is wrong.

Mike

[15mgtar]

ok thank you guys

[RomanLini]

Cut 2 squares out of thin sheet, stacked on top of each other so they are cut together. Make them as big as you can.

The take out the 2 identical squares, and flip one over and put them back together, then stand them up on the table so their bottom edge are both aligned on the table surface.

Any trapezoidal error will be shown doubled because it wil be + on one sheet and - on the other, so you can easily see (or feel with your finger run down the edge) if they are not square.

[jhowelb]

A triangle measuring 3x4x5 (mm or miles, no diff) will have one square corner.

IE: y+3, x+4 should make the distance from start to finish in a straight line measure 5

[willstony]

Try this old trick used on pillar drills. Use a cranked bar in the collet and a dial gauge at the far end so that it describes a large circle touching the bed - the larger the circle the more precise your adjustments will be.

[YZF]

Here's a different way of doing this...

If you mount a camera with a microscope where your tool goes and have some accurate reference you can directly measure the squareness (and accuracy) of your machine. There are some pretty cheap USB microscopes around.
Any LCD monitor can provide a really accurate reference (to a few microns over the area of your typical monitor) but you have to figure out how to mount it on your table. A laptop could probably do the trick.