120 volt vs 240 volt makes no freaking difference, in theory.
120v @ 40 amps = 240v @ 20 amps
(same amount of energy, watts)
Anything that requires a lot of power (stove/oven, clothes dryer, hot water heater, baseboard electric heat) is going to be 240v because it is less expensive and more efficient to run wires for it than for 120v at twice the amperage. You may have noticed that the wire that feeds power into the transformers on your street isn't very large, yet it powers the whole street. It is probably running at around 600v, then the transformer steps it down for your house. Volts is like
the pressure pushing the power through the wire, so higher volts can push more power through a smaller wire.
Anyway, you are setting about to milk the wrong end of the cow ;-)
Ask not what voltage you need.
Rather, how much energy do you need, and think of that as watts--and conveniently everything from lightbulbs to conveyor dryers state how many watts they require.
Also consider what capacity you have available. Is there an unused 240v outlet for a clothes dryer? Typical 120v household circuits are 15 to 20 amps ... which isn't going to run much of a dryer, especially since there will likely be other things already running on the circuit.
I cure with a heat press on a dedicated 120v 20 amp circuit. It is a different workflow than a conveyor, but it takes up a lot less space, costs a lot less, and can do other things ... like heat press vinyl and transfers. YMMV
Some of the smaller conveyor dryers may be compatible with 120v 20amp, don't know. I'm sure it says in their specs. Most will require 240v, so that opens up more options to choose from.
Explainer on watts vs amps vs volts: