Surely the angle is given by arctan. For small angles arctan and arcsin will give similar answers but they will quickly diverge as the angle is increased. Imagine going up 20mm and along 20mm, 20/20=1,  arcsin(1) = 90° but arctan(1) = 45°

The Gcode used for this function in Mach3 is ATAN. Examples of using this in Gcode can be found in the user manual under "Unary Operation Value". For the given example using Mach3. Decide on a parameter for the angle eg #51 for the angle and the angle will be given by #51=ATAN[3/20] . You can also use parameters for the Z move and the X (or Y) move. So if you have #52=3 and #53=20 you then have:

#52=3
#53=20
g01 z #52
g01 x #53
#51 = atan[#52/#53]

What you do with that value is up to you. If you want to you can set up a DRO on the screen using something like the program Machscreen to edit the Mach3 screens to display it during running of the program.

:

On Mon, Feb 5, 2024 at 12:52 PM, Andy Wander wrote:

If you are traveling along 20mm and going up 3mm, why not just use Pythagoras rule? a squared + b squared = c squared.

hi
simply because I'm terrible at math

c squared = my angle??

Sorry about the mix up, I thought you were chasing a length. 

Pythagoras will give you the distance between the start point and the end point. So if D is the distance between the start and end points up 3mm and across 20mm then D²=3²+20²    D²=9+400=409    so D is the square root of 409 which is 20.22mm and is not an angle. It is not what you asked for.

Are you using a probe to check stock angle? For example descend until the probe makes contact, set z axis to zero, rise something like 20mm, move across 20mm then descend until the probe touches, note reading on z axis. If so then ATAN is what you should use. The problem is MACH3 does not make it easy to then do something based on the result, there is no IF option in MACH3 but you can do it in a macro so you could have something that puts out the message "The angle is" or lets you know if the part is simply too steep or too shallow. So if you are writing a macro then that should make what you want to do possible.

Example macro, note I have not checked but I think 802 is the correct value for the Z axis. What you do in the macro after calculating the angle depends on what you propose to do with the information. I also have not checked what I have written it is just based on things I have done in the past for probing.

Angle = -89
Hfeed = 20
Feed1 = 30
Feed2 = 200
NegMove = -50
Posmove = 20

On Tue, Feb 6, 2024 at 01:18 AM, Martin Connelly wrote:

I just like to declare variables to remind me what is in a macro. I also like to put a really unlikely value in something that is going to be calculated so I can tell when it has been changed in the macro. If you write a long macro you do not really want to search for the point at which you first set a variable to some value so it is better to list them all together at the beginning but it is not a necessity. You can also add comments to the line with the declaration in if you want that reminds you later, maybe a year later for example, of what that variable is for.

The order of probing is a personal choice and depends on what you are doing. As I don't have a full understanding of what you are doing I just chose a general probing order.

I have been thinking a little bit more on this. It occurred to me that you may be better just reading the Z axis DRO into two variables and using the difference between those two values to calculate the angle. That way you would not loose your Z axis setting. Like this:

Angle = -89
Hfeed = 20
Feed1 = 30
Feed2 = 200
NegMove = -50
Posmove = 20
Zdro1 = 0  
Zdro2 = 0
Zdifference = 50

Much simpler is go to this Website and enter the dimensions you have and get the result immediately.
https://www.engineersedge.com/calculators/triangle_solution_3.htm

Emgee

On Wed, Feb 7, 2024 at 06:12 AM, Martin Connelly wrote:

I have been thinking a little bit more on this. It occurred to me that you may be better just reading the Z axis DRO into two variables and using the difference between those two values to calculate the angle. That way you would not loose your Z axis setting. Like this:

thank you Martin for this reflection,
I will test all this by replacing the Z with the Y
I will keep you informed of my tests

Note, if you get a negative value for the angle when you want it to be positive then use Zdifference = Zdro1-Zdro2

it all depends on how the piece is fixed on the table

It never occurred to me that they did not implement Atan in Mach3 scripts since it is a standard VB function. There is a simple work around though using what are known as the Taylor Series for trig functions so the solution for finding the angle in degrees is:

Glad I could help with the angle calculation. Here is something to consider. If you are not currently using the A axis you can make use of it. The A axis is rotation about the linear X axis and uses DRO 803. You can set the A axis to be active, write a value into the A axis DRO and then when you leave the script it will be there for you to see on screen.

There is also the option to do the angle calculation in Gcode using G31. When you probe using G31 the values of X Y and Z at the probing point are written to parameters #2000, #2001, #2002.

For example set up parameters

#50 = 0 (X axis change, you could set this to 20)
#51 = 0 (Y axis change, may not be needed)
#52 = 0 (Z axis change, you could set this to 3)
#53 = 0 (slope, may not be needed)
#54 = 0 (angle)
#1000 = 0 (temporary variable)
#1001 = 0 (temporary variable, may not be needed)
#1002 = 0 (temporary variable)

So go to your first probing point, set your own temporary variables to the values at the probing point.

#1000=#2000
#1001=#2001 (may not be needed)
#1002=#2002

Go to your second probing point then the axis changes will be given by:

#50 = #2000 - #1000
#51 = #2001 - #1001 (may not be needed)
#52 = #2002 - #1002

You may need to change the order of the variables in the subtraction if the angle comes out as negative when you want it to be positive.

You can then calculate the angle of the probed face using Atan in Gcode

#54 = Atan[#52]/[#50]

Once again I have not checked this out on my machine.

If I was setting this up I would probe using Z axis movement, not X axis movement. For a shallow slope a small variation in Z axis positioning will give a large variation in the X axis result, in this case at a ratio of 20:3. So if you move the Z axis and it is 0.01mm out of position then the X axis probe error will be in the ratio of 20:3, 0.0667mm. If you move the X axis and have an error in position of 0.01mm then probe in the Z axis then the error will be smaller in the ratio of 3:20 so 0.0015mm

If doing this in Gcode and not using the A axis you can also use G0 A #54 to set the A axis DRO to the calculated angle (make sure you are in G90 absolute mode for this or you will get odd results).