Building a machine to mimic a robot...

[sdimelow]

Evening all, I've been looking into buying an industrial robot but the cost of software just makes it unfeasible.

I'd really like one to machine large polystyrene sculptural pieces, like in this video...

https://www.youtube.com/watch?v=UwzwzobO5rs


Do you think it'd be possible to build an upright machine to do a similar thing, albeit with fewer DoF?

I've drawn up this simplistic sketch as a bit of a starting point. Green bit goes up and down, yellow bit left and right and the red bit turns to tip the spindle up and down. And there's a turntable...

The issues I see is rigidity as the X moves to its extent, although it could be lightweight as only going to be cutting poly.



Any help appreciated..

P.S. If anyone knows of any free robot software that'd save me building something 😂

[pippin88]

Workpiece mounted on blue rotates? A polar axis.

Currently you have X (yellow, side to side), Z (column up and down), and polar (blue)

Do you plan to do many flat surfaces?
If you want to do flat surfaces fast, you might want a Y axis as well.

Desired travels?

[sdimelow]

Yes you're correct, plus the red part could move too. I did wonder about Y, I initially thought a big 3 axis router tipped on it's end. So like my drawing but with two posts and a gantry between.

Z travel would be 2-2.5m, X maybe 800mm. I'll have to model it in a bit more detail and simulate cutting an actual model to find out required travels.

[sdimelow]

I've done a bit more of a drawing for how it could possibly be built including a Y axis.

It would have 5 axes in total, that's if I did go with an axis to rotate the spindle up and down.

As it will only be used to mill polystyrene I could use a really lightweight spindle, as long as it takes big enough cutters.


Any thoughts folks?

[m_c]

As it's only polystyrene, cutting forces would be very minimal, so well designed lightweight should be more than acceptable.



Robot control is all about kinematics.
As long as a robot could be controlled by fairly common steppers/servos, there are controller options about that could handle it.
If it's something you did want to consider, I'd suggest having a look at Dynomotion, as their default CNC software can be made to handle kinematics, and TomK (Who run's Dynomotion) does like kinematics.

The major benefit of having a good kinematics setup in the controller, is you can program the machine using conventional Cartesian (XYZ) moves/positions, and the controller will handle converting that to the non-linear movements that something like a robot arm needs.

[sdimelow]

Thank you, do you mean look into Dynomotion to make a controller for an industrial robot or for the one I've drawn up?

[sdimelow]

Hi guys and girls,

I've been thinking over my plan, and so far I've come up with the following for the machine frame.





As you can see she's going to be a big old girl!

I'm in the middle of modelling a 2-axis spindle head too.


My questions are;

1. What would be best for Z axis motion, ball screws, chains, R+P?
2. Would properly sized steppers lift the Z, or are we in AC servo territory?

Any input appreciated.

Edit to add- Obviously I've made no effort in this model to make this actually buildable, I'll work out the details later.