This is a 2D optical 4th-order aspheric curve of the form Dx^4+x^2/(R+(R^2+x^2(k+1) )^.5) that I'm trying to sketch, then revolve:

y(x)= .0002629*x^4+x^2/(39.5194+(1561.78-27.7483*x^2)^.5) -11 <= x <= 11

and SW fails on it. Click on the green checkmark and it just disappears w/o a trace. Anyone know why? Is there a limit on the length of the equation or the number of of nested parentheses?

If I start plugging in the formula as written to an excel spreadsheet, several of the results for 1561.78-27.7483*x^2 are negative. Even after adding the 39.154 the square root will fail. Perhaps it is your order of operations.

I couldn't resist playing with this. Is it also possible that your conic value should be -.2517? That way -27.7483 would just be -.7483 and the curve would look like this:

Also, you might make your sketch from 0 to 11 so that you can revolve the curve about the center axis.