cant cut a perfect square

[b.ackerman@live.ca]

no matter what i try, my machine cant cut a square, ive tryed calibrating everything i can think of and i cut a square out and check its out in the corners, maybe 1/8 over 16 inches. i have a hypertherm 1250 and mach 3 setup
any suggestions would help
thanks

[plain ol Bill]

Sounds like your number of steps in motor tuning isn't right on to me. You should be able to move precisely a given distance on x or y axis by adjusting the number of stepsx

[b.ackerman@live.ca]

ive tryed that i calibrated the x axis upto 46 inches and it travelled a perfect 46 and the y to 78 inches worked perfect just cant cut a square

[Gamelord]

Is it out on all four sides the same amount? If so it may be that your software is adding in extra width for the kerf of your cut. You may need to dial that back a little bit to get it exact. if it is out on two of the four corners, then that may be a couple things...

1 - your table may not be square to your gantry
2- your motors may not be calibrated correctly
3 - your pulleys/gears may be slipping a little. double check your gears, even if they seem tight, check them again. many problems have been from slippage from the gear to the motor or loose belts/chains/gears etc...

[jimcolt]

If you describe what happens when you try to cut a square it will help us help you. Pictures, dimensions, etc.

Jim Colt

ive tryed that i calibrated the x axis upto 46 inches and it travelled a perfect 46 and the y to 78 inches worked perfect just cant cut a square

[b.ackerman@live.ca]

here is a pic all 4 corners are out sometimes and only 1 or 2 other times ive cut how squares trying to get it but cant figure it out.

[Gamelord]

Is it cutting the exact same every time? Or is it intermittent? If it is intermittent, I would say gear slippage.

[Diverdude]

are you cutting on thin material close to the edge? I've seen the heat pull the materal with those conditions causing that kind of problem.

[b.ackerman@live.ca]

i would have to say it cuts like that all the time and im cutting 1/4 inch and times in a straight cut. the cut line is all over the place wavy, oh my just terrible.

[plain ol Bill]

Is your gantry squared up?

[Gamelord]

If you are getting waves in a straight cut, then something is loose on your machine. Either your gantry has some slop in it, or your slats in your table are moving, or something.

it can only be the above, or your software/computer is sending some bad info....this would be extremely rare and not what I would even consider.

Something has to be lose.

[Loyd]

Is your square square? Just a thought....
Loyd

[Gamelord]

good point Loyd, I have seen squares that are not .... square.

To check, draw a straight line, place the edge of your square against it, draw the perpendicular line down on the side sticking up. then flip your square to the other side of the perpendicular line, place the edge of the square against the same first line and check to see if it lines up with the perpendicular line you drew. If it is not perfect, then your square is not square.

Here's a video showing what I am trying to explain.
http://www.youtube.com/watch?v=DxNriQsxalo

Usually you can tap the center corner of the square to open it up a little (where that little half circle hole it), or just bang the ends to close it if needed.

[Largemouthlou]

Another way to ck a square is with a 2' level.. On a wall do a plumb line and a intersecting level line,, that will be a tru2 90.. As long as the level is good!! LOL

Another way to ck lines and objecst for square is by measuring 3' up on edge nd 4' up the other and the connecting point will be 5', or you can diaglal a box by measuring cornewr to corner on both sides and the measurement should be the same..

[plain ol Bill]

Ok, back to step one. Is your gantry square with the sides? If not you will not be able to cut square.

[b.ackerman@live.ca]

thanks for all the reply's, i did find some loose bolts on my gantry and im going to try cutting a square.
mainly i think its the cut quality going on bevels and little jagged, im thinking that might cause it
to be a little unsquare as well?

[Gamelord]

Bevel is on the edge, perpendicular to the length of the side. Bevel will not effect the square of an object. Even with severe bevel, your machine should still be able to cut a square...square. The only way your object will not be square is if your gantry is moving in a direction it is not suppose to be moving while it is cutting.

[MQUICK]

I had the same problem about a year ago. As always it's the last thing you check. Check to see if your table is level. Table showed square but the table was not level. Causes a twist in the gantry.

[Fountaine]

Lots of good advise here I had a similar issue when I first set up my table: is the table square? If all sides measure exactly equal, ie. your two x sides are equal and your two Y sides are equal.....Then you can take a measurement diagonally one way and another the opposite in other words a X, if the sides are equal and the X is the same both ways.......Then the table is square.

Every time I start up my table I check a measurement from the gantry to the front of the table, to cut strait both sides have to be the same.

It does not matter if the material is square to the table or not, if all is set properly you would cut your square even if the material is canted sideways.

Another thing I will point out. I have all but eliminated: Angular cuts, wavy lines and out of round circles by cutting at 30 amp instead of 40 amp. I am also using a lead ion to get rid of a pierce hole.

Hopefully some of this will help you.

[b.ackerman@live.ca]

Thanks for all the replys i have a to do list on the old table this weekend and then try some more cuts, ill let you all know.

[Stout]

Like Bill said. It sounds like your gantry is not square on the table rails. Easy to check with a bit of geometry.

If it is the gantry, squares will look like a tilting polygon. Two corners will be >90 and two <90 degrees.

[b.ackerman@live.ca]

found my problem a couple loose bolts and the y axis gear is a little worn, got it working good for now but i am going to replace the gear. its the original one and it has 2600 hours on it, well spent money i guess. THANKS FOR ALL THE IDEAS!