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Squaring up Axis

Posted: Wed Mar 04, 2015 2:31 am
by TReischl
How to get X and Y square to each other comes up regularly, or even how to check them.

I just finished getting a new shop built and reassembled my machine after the move. Of course it had to be resquared.

The process is pretty simple and is a variation on the old draftsman's trick of checking to see if a triangle is square.

I used a piece of 1/4 MDF measuring 24 X 36 (my machine is a 3 X 4).

Fastened a piece parallel to the fixed axis and machined the edge I would butt the MDF against.

Then created a program to cut two short slots through the MDF as far apart as practical perpendicular to the fixed axis.

Cut the two slots, then flipped the sheet over keeping the same edge against the machined edge.

Cut the two slots again about an inch away from the first set of slots.

Got out the dial calipers, and measured the distance between both sets. One was about .904, the other was .875.s

Adjusted machine and repeated the process. After 4 interations I got it to where there was only a thou or so difference. Not bad over 34 inches.

The beauty of this method is that it shows double the error.

Measuring across corners is great if you are building a cabinet or house, but for accurately adjusting a machine? Nahhhhh.

Re: Squaring up Axis

Posted: Wed Mar 04, 2015 3:57 pm
by kaetamer
Nice technique.

Paul Rowntree does essentially the same thing in software with Skewcalc.

Re: Squaring up Axis

Posted: Wed Aug 12, 2015 5:30 pm
by AlanS
I recently moved my machine and have been trying to figure out a way to square it up. While I have read your post I am not able to envision what is being done. Would you have some pictures that would show what you are doing?

Thanks,
Alan

Re: Squaring up Axis

Posted: Wed Aug 12, 2015 5:46 pm
by GeneMpls
kaetamer wrote:Nice technique.

Paul Rowntree does essentially the same thing in software with Skewcalc.
Where is this? I looked on Paul's site. Thanks Gene

Re: Squaring up Axis

Posted: Wed Aug 12, 2015 7:40 pm
by TReischl
Alan:

Here is a pic:
Capture.JPG
Just fasten a scrap board parallel to your fixed axis (that is the one bolted to your machine frame. Then machine a straight edge on it.

It will be exactly parallel to your fixed axis.

Then butt a sheet of something against it. Cut two slots as shown in the picture.

Flip it over keeping the same edge against that machined edge.

Cut the next pair of slots fairly close to the first ones so you can measure them easily.

The difference will be twice the error. So this is a very accurate method.

Gene: I looked all over Paul's site too, no luck at all.

Re: Squaring up Axis

Posted: Wed Aug 12, 2015 9:04 pm
by PaulRowntree
The SkewCalc program is really just a way to measure the out-of-skew angle directly, for use in the WarpDriver program. SkewCalc uses the measurements of the diagonals, which can be quite accurate if done with USB microscope cameras. WarpDriver can use this angle to skew the output GCode to correct for imperfections of the machine's X-Y orthogonality.

That said, it is far better to correct the machine itself, if possible, and the flipped piece with slots is a better way to see if everything is all squared up than diagonals because you can use verniers to measure small errors more accurately than using tapes to measure large diagonals.

Cheers!

PS : SkewCalc is buried on the WarpDriver page because they work together ...

Re: Squaring up Axis

Posted: Thu Aug 13, 2015 12:25 pm
by AlanS
TReischl,
Thanks for explaining it for me. I will use this method to square my machine up.

Alan