Newbie- How to make everything square and parallel

[eran k]

On my new machine i need to know how to make everything square and parallel, it's a dual x axis machine so it's very critical the the two axis are positioned as accurate as possible.
what tools do i need to use for this calibaration and what methods?

here is a picture, it's going to be mounted on a MDF base.



Thanks
Eran

[CarbonKevin]

I'm probably more of a newcomer to this than you are, so I'm curious - why are you using dual X axis?

Those also appear to be steppers, not servos, so how will your controller detect if one motor has fallen out of sync with the other?

[eran k]

Hi,
Im using a dual X just because i had tohose liner units and wnated to use them "As is" and take advantage of their accuracy, so th design of the machine was dictated by this.
i didnt think about the other thing you mentioned, hope it wont be a problam i saw other dual x machines with steppers

Eran

[Hirudin]

To try to help prevent this thread from going off topic I'll keep this short... CarbonKevin, what you're talking about is usually called "feedback". That is to say the motors "give feedback" to the computer so the computer knows the motors are working properly. Although it's possible to get feedback from steppers it generally isn't done. Steppers work on faith more or less - the computer tells the stepper to move and you trust that the stepper will carryout its movements correctly.

This topic has been discussed thoroughly, but here's a good thread to get a foothold on the differences between these two types of motors: Steppers and Servos....

[jsheerin]

To make your x rails parallel, there are lots of possibilities. The concept is to secure one rail and designate it the master. Then set the other rail in reference to it. Specifically, bolt down one rail and measure between the rails at both ends before bolting down the other. Since you already have them connected, you could bolt down one rail and then slide the y axis back and forth to get the other rail into alignment. Or other variations on that theme. You could measure with calipers, a dial indicator riding on the first rail, etc. It depends on what you have and how much you want to spend.

To square the y axis to the x axes, what I did was get it close by eye. That was easier for me because I had square surfaces to bolt the y to. In your case, you could use a machinist's square. Then you could tweak it in using the drive motors and your home switches. Mach (or whatever you use) has a homing sequence to home both x axes independently. So you can adjust your alignment by repositioning one of your home switches. To check alignment, I cut a square and measure across the diagonals to make sure they're the same. I'm sure there are other ways as well.

[amishx64]

Get a square. These things are available everywhere and will do wonders for your alignment. Just measure perpendicular to the edge of the MDF with one side, and you have a perfectly perpendicular line. Repeat a bit farther away on the same edge and you have two perfectly parallel lines.

[ger21]

I'd do as was mentioned. Bolt down one side, then slide the gantry along and bolt the other side as you move it, using the gantry to set them parallel. The only reason to use a square would be to line up the ends. Then, cut some actual square parts and check them with a quality square. If they are out of square, adjust as needed.

[rlwoodjr]

For the xy axis, a person can g-code a square or rectangle using a pencil or pin to draw on the table (XY Plane). Then measure cross the corners...if it is square these dimensions will be the same. If the dimensions are not the same then you have a parallelogram.

The bigger the rectangle the bigger the error so it would be easier to measure.


For flatness in the xy plane, a person can run the cnc to different positions with a bit a small amount above the table and measure bit to table distance.


As for the z axis, a square along side a long bit in your spindle.

[FandZ]

Originally Posted by eran k Hi, Im using a dual X just because i had tohose liner units and wnated to use them "As is" and take advantage of their accuracy, so th design of the machine was dictated by this. i didnt think about the other thing you mentioned, hope it wont be a problam i saw other dual x machines with steppers Eran

You shouldn't run into problems with it coming out of alignment. Basically you are going to use 2 different homing switches, so every time you hit home they both will be perfectly aligned. The question is how are you going to get both your homing switches perfectly aligned...lol

In my opinion dual drive is superior. It makes for a much stronger machine without any concerns of racking.

[jsheerin]

A more precise way to fine tune the Z axis is with a dial indicator mounted in your spindle. Sweep it front to back and side to side to see how to adjust the alignment. I put a 123 block on my mdf spoil board and indicated off of that when I aligned my z axis. This would be after you surfaced your spoil board - that will make it in the same plane as your x and y axes. Some might say that's overkill, but it got my cuts a bit smoother.

[FandZ]

Originally Posted by jsheerin A more precise way to fine tune the Z axis is with a dial indicator mounted in your spindle. Sweep it front to back and side to side to see how to adjust the alignment. I put a 123 block on my mdf spoil board and indicated off of that when I aligned my z axis. This would be after you surfaced your spoil board - that will make it in the same plane as your x and y axes. Some might say that's overkill, but it got my cuts a bit smoother.

I need to do that but I haven't looked into it with mach 3. Is there a command in mach 3 to do that? I was thinking about just running up some gcode for it but I'd think there would be something built in for it.

[jsheerin]

No - you don't move the axis with the motors. You just rotate the indicator in the spindle. The assumption is your table surface is flat and parallel to the x and y axes already and thus moving the spindle around in x and y is unnecessary. If your z axis is out, there will just be ridges or scallops in the spoilboard from surfacing it (how big depending on how far out of alignment the z axis is). The longer the arm the indicator is on (and the further away from the spindle's center line), the bigger the errors shown on the indicator. Ideally you would rotate the spindle and the indicator reading would never change as you swept a complete circle. If your z axis is not perfectly perpendicular to your table, then when you compare readings from +x and -x, there will be some difference and you can shim as appropriate. Same for y, although typically you would unbolt things and tap in the alignment in the y direction the way most router are built.