This is my take on the proposed kinematics project.
Using the photo in this link -
https://www.dropbox.com/s/zpxqzl4q1n2gssa/IMG_20200404_160947.jpg?dl=0
The photo shows the elements I believe are necessary to calculate the
forward and inverse kinematics. You should need to use only two
lines(vectors). The line labelled B Axis in the Hiteco drawing and my
sketch is one of the necessary lines. The other necessary line is the
spindle center line I reference in my sketch. Where the two lines meet is
the important point. This would be referenced as the pivot point. Prior to
having the computing power(speed) the pivot point was the point XYZ of the
gcode program for a particular machine configuration. With dynamic pivot
length compensation and dynamic tool length compensation the tool tip
should be the XYZ point of the gcode program. Regarding gage point(pivot
length) and tool length the only important consideration is the pivot
length and tool length sum to the total distance from the tool tip to the
pivot point.
In my sketch the Z axis is parallel to the 51 dimension. The X and Y axes
are determined by where the C axis is homed. As sketched, if the 40
dimension and the B Axis as shown in the sketch are parallel to the X axis
then the Y axis is perpendicular to the paper. This would cause, according
to normal symbolic assignment, the rotation of the tool around the X axis
to result in the symbol of A assigned to the rotational tilt of the tool.
I would not try to use the 50 degree tilted axis as a the B axis. I
reference the B axis in the drawing only to communicate what part of the
drawing I am talking about as that is labelled in the drawing from Hiteco
and my sketch.
I would program kinematics from the center line of the spindle (tool) as
that is where the numbers from the CAM system will reference.
The CAM system should output tool tip (XYZ) and tool orientation (AC)
values. I would cause the kinematics to determine the position of the
machine elements to satisfy the tool position as programmed in the XYZAC
configuration.
I would calculate the kinematics using trig but it is also possible using
DH parameters.
https://en.wikipedia.org/wiki/Denavit%E2%80%93Hartenberg_parameters
thanks
Stuart
On Tue, Mar 31, 2020 at 9:32 AM andy pugh wrote:
> On Tue, 31 Mar 2020 at 15:14, Tomaz T. wrote:
>
> > is there maybe 5-axis kinematics module suited for this kind of 2-axis
> head design which has A (or B) axis at an angle, for example 50 degrees,
> like the on from following link:
> >
> https://www.hiteco.net/en/products/bi-rotary-units.c8396/serie-orbital-j-50deg.8398/orbital-jqx-50-compressed-air.101428
>
> They seem to be 2-DOF serial kinematics + cartesian.
>
> Inverse kinematics is easy, but forward seems a bit harder.
>
> I don't think that genserkins can be forced in to that shape due to
> the non-serial prismatic axes.
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
>
>
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