How to make axles nicely perpendicular?

[Witsenburg]

Hi,

after some test-routing, I noticed the X and X and Y axis are not really perpendicular, and Y movement changes the Z coordinate (not in the software, but in real life). OK, so there must be some settings for that. I clicked Config -> Screwmapping, which opens the Screw Mapping Correction window. Now that looks the business to me. However, I cannot get it do work for me, so I must be doing something wrong.

Here are the measurements I took:
Over +250 mm of Y axis movement, I loose 4 mm X.
Over +250 mm of Y axis movement, I gain 2 mm Z.
Over +1000 mm of X movement, I gain 2 mm Z.
And, logically, doing negative movement turns gain into loose and visa versa. In all, I have a pretty linear machine, but it's crooked.

Would someone please be so kind as to tell me how to fix this?

Thanks,

Hugo

[MichaelHenry]

It sounds like your mill is out of tram. If that is the case, Mach probably can't help you out and you will have to resolve the problem by shimming one or parts of the mill. Or is this a router?

Mike

[ger21]

Originally Posted by Witsenburg Over +250 mm of Y axis movement, I loose 4 mm X. Over +250 mm of Y axis movement, I gain 2 mm Z. Over +1000 mm of X movement, I gain 2 mm Z.

If this error is consistent along the entire axis (if use lose 2mm at 125mm of Y), change your steps/unit to adjust for this.

This is not the same as not being perpendicular. You'll need to mechanically adjust your machine to fix that.

[HuFlungDung]

Screw mapping is designed to map errors in accumulated movement in the same direction as the screw itself. There is no association made between errors on the Y axis screw and the other two axis.

Some kind of complex transformation equations could likely be created to apply to your program to correct it when run on the machine. But, that sounds like more of a nightmare than just fixing the alignment of the axis.

Pick the least adjustable axis on your machine to serve as a baseline. Square the other axis to it. Probably one method to do this is write a program to drill holes at the corners of a right triangle, insert pins, measure the seperation of the pins at the hypotenuse. One favoured combination of sides for such a right triangle is 3,4,5 units, because any triangle with those specs contains a perfect right angle. So program 3" in X and 4" in Y and then measure the third side accurately with a digital caliper. Adjust one axis to try to reduce the error.

The longer the sides of the triangle you use, the more accuracy you can achieve. You can scale up the 3,4,5 triangle to 6,8,10 or 9,12,15

[Witsenburg]

Yeah, I was machining a 3-4-5 triangle to find out the X/Y misfit.

Anyway, thanks for the input, all, I will mechanically alter the machine to fix it. Just have to think of how...

Cheers,

Hugo

[widgitmaster]

Have you ever used a "Dial Indicator", they are the perfect tool for measuring the problems you are experiencing!

Simply make a 90 deg attachment to go into the spindle, position the spindle in the center of the X & Y travel. Then with the dial indicator on the other end of the 90 deg arm, manually rotate the spindle 350 deg. the dial indicator will show you where the high and low spots are. Then by shimming and adjusting the machine components, you can get the error minimized.

Then mount the indicator in the spindle, and move the x-axis back and forth.
then the y-axis back and forth. when everything is trammed perfectly, your machined parts should be much better.

lastly, the screw mapping can be used to calibrate each axis so the machine is moving the amount you told it to!

Widgit

[MichaelHenry]

Here's a picture of the setup I used to tram my mill:

http://member.newsguy.com/~mphenry/T...Tram-01JPG.jpg

The 1-2-3 block was used to avoid dropping the indicator tip into the table slots when the arm was rotated about the spindle to obtain readings along the +/- X and Y axes.

Mike

[JerryFlyGuy]

I'm setting up for the process of tramming all three axis of my machine. My mill is a gantry unit w/ drives at either end of the gantry. The gantry travels in the X direction. I'm going to use the machine to cut some mat'l which I can then measure to figure out how sqr the axis is.
I've attached a drawing showing how I plan to accomplish this. This is not an original idea but one passed onto me by someone on the 'zone' a year or more ago..

Getting the Y axis perfectly level is the next challenge I have to work on for my project. I plan to get the Z axis plumb by using a precision plumb bob, but first.. the Y axis must be leveled.. I still don't have a precise way to do this [that I'm happy w/]

Suggestions??

Jerry

[primotool]

just tram the machine with an indicator. Their making it sound harder than it really is.

PS.. Tool & Die Maker 25 years @ GM engine plant #4

[JerryFlyGuy]

Primo I used the proceedure outlined above and it worked very well to tram/sqr my y axis. [I forgot to note that the pc needs ot be fliped as well or it will be a // shape instead of a /\ shape] anyway, I'm curious to learn how you'd have simply used an indicator to sqr the system. Btw, the y axis on my machine is over 10feet.

Also, I have to tram my z axis post [it's only 55"long] to be perp to the table. Can you tell me how you'd use an indicator to do this?

After that step, I can chuck up an indicator and sweap the table to get the spindle perp to the table as well.

Thanks in advance!

Jerry

[JerryFlyGuy]

Well, just to re-cap. I've got my machine all nice and trammed. I did end up using a dial indicator for the Z axis. I got to thinking about it some more and realized there was a way to do it. First off I used the machine to machine a section of the bed flat. Then I used a sqr w/ a dial indicator in the chuck and traversed the z up/down the sqr and adjusted accordingly. I checked it from front to back and side to side [two ways on each direction] and it looks like I'm less than 0.002" over ~24" of Z travel which I'm happy w/. Now I've just got to work out why my z is getting harmonic problems and the machine is done.. it's only been 3 years in the making.. sigh..

Jerry