Work Area

I was looking at work area issues and like other SCARA types the optimum work area occurs when the arms are of equal length. No that important however to be exactly equal.

Force Transmission

For efficient force transmission I selected a minimum far arm angle of 45 to 135 degrees.

This however is pretty inefficient with regard to work area. To improve the work area I adopted a square area rather than a 2:1 rectangle. Here is the result:

Note: The arm lengths allow proper folding for "storage".

The small work area pretty well explains why the this SCARA configuration is not in "common" use for router applications.

Alternatives

I have found a variant with a powered far arm:

But this does not offer any real advantage over a convention (single arm) SCARA except it is more rigid (particularly for twist) and subject to less vibration due to the second arm.

Aside, the above SCARA would benefit from increased work area if the spacing between the fixed arms was reduced. The bed lift mechanism should be replaced with a vertical bed lift mechanism. But I understand that the current lift mechanism can be fixed in software.

The 30 degree 5 Bar SCARA

Here is the 30 degree SCARA:

Okay, I will have to proceed on the 30 degree SCARA basis.

It all in software anyway, a laser could run at 15 degrees while a router could run at 45 degrees:

And if I really have to I could power both far arms!

Compromise

I can use 45 degrees when out reached (need more force in this case) and 150 degrees (or more) when reaching inwards:

Alan