[mackie29]

We are buying an new large Gantry 5-axis for cutting molds. One of the options is an Renishaw Touch Probe. Is it worth it or just an waste of money.

[underthetire]

Probes are nice, especially for castings. They can really help center up rough castings, or even tell weather the casting has enough material to clean up. Downside is, takes a fair amount of macro programming, slows production down if it has to qualify every part, but on the flip side you may not scrap as many parts.

[fizzissist]

Depends on how sophisticated you'd like your manufacturing to be.

If you're talking about the spindle mounted probe, you should consider it for in-process QC, monitoring tool wear, positioning, casting verification, ... etc...

It will take some time to program, but in my opinion it's worth the expense if you're going to compete.. as long as you use it to its full capabilities...
...and your control will accommodate the input and the input into your program in a macro.

I think a probe for 5 axis work is a great help in locating a part that doesn't have easy reference points...and helping to eliminate tooling balls.