# Thread: Machine not moving correctly

1. ## Machine not moving correctly

I am trying to mill a circle in a piece of MDF for a project I'm working on. If I use a compass and draw a circle on the MDF then using a 1/8" 4 flute flat bottom bit and do and Outside cut using Cut2D, the bit doesn't follow the line I drew with the compass. It will start out in the correct place but as it moves around the outside of the circle the bit will move away from the line by 1/16" and then move back to the line, cross the line on the inside of the circle by 1/6" and back to the beginning. I am using Mach 3 Version R3.043.022

I went back and double checked my X, Y movement and both axis's move the distance I tell them.

So I started from the corner of the MDF and made a mark in the X at 4.5" and from there made 2 marks in the Y direction. One at 2.5" and the other at 4". I drew a line from the corner to each mark so I could see if the bit followed it when moving from 0,0 to 4.5,2.5 and 0,0 to 4.5,4

With the 1/8" bit setting at 0,0 centered on the corner I used the MDI to move to the 4.5,2.5 location and the center of the bit followed the line . When I went from 0,0 to the 4.5,4 the center of the bit was off by about the thickness of the bit.

Is there a setting in Mach 3 that I may have missed that will correct this?

John Frankforther

2. I went back and double checked my X, Y movement and both axis's move the distance I tell them....................................
..............................When I went from 0,0 to the 4.5,4 the center of the bit was off by about the thickness of the bit.
If the first statement above is true, then the second one can't be true. Either it's moving the amount you tell it to, or it's not.

It's possible that you're occasionally losing steps.

But, based on your circle example, either the machine has some flex in it, or possible something is loose mechanically.

Are the X and Y axis perpendicular to each other?

3. Originally Posted by ger21
If the first statement above is true, then the second one can't be true. Either it's moving the amount you tell it to, or it's not.

It's possible that you're occasionally losing steps.

But, based on your circle example, either the machine has some flex in it, or possible something is loose mechanically.

Are the X and Y axis perpendicular to each other?
Hello Gerry

I went back to the basics of the machine setup and found that when I changed the leadscrews several months ago I had some how inadvertently and unknowingly got the table out of skew by, yes about 1/8" counter-clockwise. I found this out tonight by placing a block of MDF squarely on the table. The I milled the left side (Y) and bottom (X) edges and saw the error right away.

Thanks for the suggestions

John