Centroid Community CNC Support Forum

Posted: **Fri Jan 26, 2018 8:52 pm**

As I impatiently wait for the drives to come in for my Acorn tabletop router project I've been looking over some of my 4th axis ideas and trying to settle in on a decision so I can write a Vectric based Rotary_Wrapped post processor.

Based on the "normal" convention since my rotary axis will use X wrapped around Y, I would consider the rotary axis B. Is there anything in the Centroid control that would make this not the best choice? Are there others using a rotary axis with a router or mill? Clarify, horizontal rather than rotary table.

TIA for any replies.

Posted: **Fri Jan 26, 2018 10:13 pm**

http://www.cncexpo.com/Cartesian.aspx

Z axis is ALWAYS the axis along which the primary spindle is. With a
vertical mill, this would be the vertical axis. With a horizontal
mill, it would be front to back, and on a Lathe, it is left to right.

The X axis is generally the axis remaining, with the longest travel,
and at right angles to the Z axis.

The Y axis is the last remaining axis at 90 degrees to the Z.

Axes U, V, and W are sub-sets of the above (U-X, V-Y, and W-Z).
Sometimes these are actual axes, such as the knee on a vertical mill
(usually the W), or sometimes, these are incremental movements of the
primary axes.

Rotational axes are A, B, and C. A would be rotation around X, B
around Y, and C around Z. A rotary table mounted on the table of a
vertical mill, with the plane of it's table in the horizontal plane,
would be a C axis. If the rotary table is mounted with the plane of
the table vertical, and the face of the table pointing towards your
right, it would be the A axis.

Posted: **Sun Jan 28, 2018 9:16 am**

tblough wrote: ↑Fri Jan 26, 2018 10:13 pm http://www.cncexpo.com/Cartesian.aspx

Z axis is ALWAYS the axis along which the primary spindle is. With a
vertical mill, this would be the vertical axis. With a horizontal
mill, it would be front to back, and on a Lathe, it is left to right.

The X axis is generally the axis remaining, with the longest travel,
and at right angles to the Z axis.

The Y axis is the last remaining axis at 90 degrees to the Z.

Axes U, V, and W are sub-sets of the above (U-X, V-Y, and W-Z).
Sometimes these are actual axes, such as the knee on a vertical mill
(usually the W), or sometimes, these are incremental movements of the
primary axes.

Rotational axes are A, B, and C. A would be rotation around X, B
around Y, and C around Z. A rotary table mounted on the table of a
vertical mill, with the plane of it's table in the horizontal plane,
would be a C axis. If the rotary table is mounted with the plane of
the table vertical, and the face of the table pointing towards your
right, it would be the A axis.

Very well explained Tom.
Marty

Posted: **Sun Jan 28, 2018 10:35 am**

I must have missed Tom's post in all the forum activity of late. Tom, thanks for posting.

I understand the convention as per the linked doc. My question was: In many cases, maybe even most that I am familiar with, programmers and machine builders adjust the function of certain axes to add feature to specialized machines. Since Centroid builds some very elegant machines, I was wondering if that was the case.

Most of the non-conformity I speak of has been done by CNC router mfgrs for what I would call lazy reasons. One for example always calls the rotary axis A, no matter the orientation. Reason was that when the rotary axis was called B (for Y parallel orientation) the A axis display of 0.000 could not be eliminated, apparently causing confusion.

I didnt think our friends at Centroid had built in any of these quirks, but thought that I would ask.

Posted: **Sun Jan 28, 2018 10:10 pm**

I guess machine builders can do whatever they want, but what I summarized was from ISO Standard 841:2001 "Industrial automation systems and integration — Numerical control of machines — Coordinate system and motion nomenclature"

https://www.iso.org/obp/ui/#iso:std:iso:841:ed-2:v1:en

Posted: **Sat Feb 10, 2018 8:00 pm**

Speaking of rotary axis make me want to ask. The Acorn board is a four axis output I was thinking of a way to run a rotary A axis but Because I want to do it on a router table is there a way to run your y axis in one output freeing up the other axis without pairing the last output and still run two steppers on the Y axis , could you run two drives with one axis output , also if you had to reverse one of the motors is there a way to invert the direction output to one of the motors ? I guess you could do it with gears if you had too just thinking, David

Posted: **Sun Feb 11, 2018 9:12 am**

David...
Most anything is possible if you take the time to work out the variables involved. Two drives can be "sistered" and use the same step & direction signals, but autosquare ability will take some extra work. There are a number of ways to reverse a stepper, software, switch on the drive, invert A or B pair at the drive or motor.

Unless there is a switch on the drive (closed loop drives) my most common method is to swap the B+ and B- wires at the drive, as this keeps the inversion visible and accessible.

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