Re: [CAD_CAM_EDM_DRO] Re: CNC robotic welding arms

Hello Rab,
long time ago I worked in a valve factory and the best welding robot
system of all was a simple robot arm, that a good first class welder
teached in the first time and recorded every single swivelling. All
programed welder arms were a pain in the r.... He simply had to take
its hand and welded a valve body with it. The encoders and speed
generators
reported everything and go for 24 hour shifts.
Good luck
Sven Peter
rainnea wrote:

>
> Thanks for the info on the EMC files.
> As I understand it, EMC can handle all these calculations and would
> be the ideal method in theory, but has some rotational velocity
> issues in practice ?
> I'd imagine that it may just be easier and provide more flexibility
> to use a 3D animation program designed and perfected to handle very
> complex kinematics (and able to visualise them) to work out all of
> the joint / axis movements and then from there, output the
> coordinates that each axis has to move to in order for the toolpoint
> for follow a subdivided toolpath.
> >From this, the CNC controller would be able to handle the translation
> of these axis movement coordinates into step and direction signals
> while being totally unaware of the configuration of the machine if
> (and this is the problem) it could determine how fast each axis
> should travel for each move.
>
> One method that kind of works is to set a maximum feedrate per axis,
> for example, when using a 3-axis controller to do rotary machining
> where the Y-axis controls the rotation of the part and the controller
> doesn't know how far the toolpoint is really moving but calculates
> the feedrate based on the maximum feedrate set for the Y-axis as if
> it were a linear axis. This at least gives smooth and predictable
> movement but the axis feedrates would be the same whether the tool
> was cutting near the centre or at the outer radius of a rotary part,
> giving very different toolpoint velocities.
>
> Another method, not without its disadvantages, but that may be very
> effective is tagging the distance that the tool tip is actually
> moving relative to the material onto each line of G-Code containing
> the axis movements (as opposed to the tool movement). The distance
> value would be used to calculate feedrate or it could even be
> replaced with a feedrate or time value. Would this be enough for the
> controller to generate proper constant velocity movement at the
> toolpoint?
>
> For example, take a hexapod machining over a cusp or sharp point of a
> surface where the tool is changing angle rapidly but the toolpoint is
> actually moving very little in relation to the material. Using the
> above method would mean a series of six-axis coordinates for the six
> hexapod struts to move to, along with corresponding values that
> correspond to the distance that the toolpoint is actually moving. The
> controller would move the hexapod struts, coordinating their
> acceleration / deceleration, target and max velocity not knowing or
> caring about the physical arrangement of the machine, but just how
> long these axis movements should take. The same should hold true for
> other 4 and 5 axis arrangements.
> Could / should this method work ?
>
> Rab
>
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