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Need clarification on GCode for 4th axis.
What is the "unit" of movement for a 4th (or any rotary) axis? Is the 4th axis measured in inches/millimeters (of head-relative movement) like X,Y, and Z, or degrees/radians (of rotation), etc. It is easy enough to make either set of calculations, but have not worked with (or seen) rotary axis code.
It could be machine specific. I use Haas machines with a 4th axis (A) and it is programmed in degrees. These machines have the ability to Circle Wrap which means they map the X or Y axis onto the A axis and for this you need to input a diameter value which the machine then uses to convert between linear measure and angular measure.
Either way, it is going to come down to calculating the amount of rotation necessary to "move" the head a specified distance. I am, in fact, doing a project that involves wrapping a 2D image around a cylinder. (Laser work)Quote:
Originally Posted by Geof
I had considered the axis-swapping approach, but still need to derive appropriate "units." Since I will be also building my own 4th-axis, it sounds like I can do it however I wish. Just did not want to do something totally contrary to the rest of the world.
Given your answer - that it is machine specific - I could write the application to allow users to choose their method, producing code that is likely to be compatible with their specific setup.
Thanks for the quick response - adds to my knowledge bank!
It depends on your machine, if your 4th Axis is Linear Axis unit would be in INCH/MILIMETER, and if your 4th Axis is a Rotary one unit would be in degree.
So, if user indicates they are mapping X or Y (I am working in 2D Laser), OR they have their Z axis directed to the rotary axis, then it is, by default, linear. BUT, it they indicate they are using the A (or B or C) axis, it should be, by default, degrees?Quote:
Originally Posted by Jitendra Tomar
That is what I really wanted to know, but did not ask clearly - "What is the normal unit of measure for the A, B, or C axes?"
Thanks! That is very helpful!
I have only setup and seen these axis in degrees. I would consider that to be the norm. But there is always someone to disagree.Quote:
Originally Posted by twehr
Stevo
From what I have seen, default to degrees motion. It sounds like you still need this, so add a G code to change behavior. Much like Geof described.
An example might be:
G0 X-3.0 Y 0.0 A85.0 (position Y0.0, center of cylinder at rotation for start of laser marking)
G201 Z2.0 (G201 made up code to trigger modal wrapping around A at 2.0 radius)
G1... (code in XY that the control translates to XA moves)
...
G200 (return to normal XY mode)
Hi
I found a youtube video that shows how to use a macro to do something like the question being asked. I had the same problem and right now I don't have
access to my 4th axis. Gcode on the fly for Rotary CNC - YouTube
If I get it to work, what I plan to do is add variables for diameter of material and length of material. That I am pretty sure that I can do manually,
Once I get that to work, I want to have a message so that I can enter this information. I'm looking at the M109 command. It looks like you can enter one
variable, I would like to enter at least 2 variables.
hy hmatyas :) 4th axis programing requires a bit of trials, so to find the correct formulas
i can help with code sugestions, going little by little, until solved, at least let's hope will figure it out
so far i solved for rotary on other machine, so there is a place to start / kindly :)
Hi,
I use Mach4 and all rotary axes are in degrees. This is a shame because I prefer radians. I use Fusion + Machining Extensions and Fusion can post either degrees OR radians, but Mach
can only handle degrees.
Mach does have a G93 mode which changes the angular velocity such the the peripheral speed remains constant. I have not used it in Fourth axis tool paths myself, thinking that G93 is
best suited to lathes.
Craig
hy joe :) if you need some feeds modified ( or someting else, etc ), i can help with
for example, let's say that you just generated program file cut-this.cnc; the moment you see it become cut-this-fixed.cnc, then all is ok ( thus a service runs in background, scans a folder for new files, and adjusts them as needed; no intervention necesary ) / kindly :)