Unless you’re using a servo, press consistency is crucial to length accuracy in flying punch and cut applications. Without servo positioning, timing variances in the press will directly relate to length tolerance error, and the faster you run the line, the worse even small timing variances will affect length.
For instance, if you’re running a roll former at 400 fpm, that’s 80 ips. At that speed a timing variance as small as ±0.003 s will cause a total length variance of ±0.24″!
Even the best 24 VDC relays have a switching time of ± 0.003 s. Thus, running a press fire output through an electro-mechanical relay could easily induce a total length variance of almost 0.5″. That assumes you have no encoder tracking issues.