If they throw a hussy fit, I usually pull out the firm reasonable babysitter voice.

"Look. It's hot (or cold or busy or slow or whatever else), you'regrumpy, I'm grumpy everyone in here is grumpy. This is what I need, and this is what you are doing. I have to get this thing done. Play nice and I will stop bugging you so much"

That usually works a bit better than threats or pretty pleases for me, but sometimes the Machine is just in a "NO!" Mood.