I have been a member at Protospace for quite a while. There are no charges for use of equipment and never has been.
The only exception is the Trotec laser cutter where you are limited to a few hours a month of free usage. The Rabbit laser cutter is always free.
There are some small charges for consumables like welding gas and welding wire. If you use shared filament on the 3D printers, there is a per-gram charge that covers the cost of the material used.
I teach the manual lathe and manual mill classes, which are very cheap ($10 each). For people that have significant experience, I will generally give them a pass on the training requirement. Those classes are each about 6 hours long and try to cover enough to get you started on safely using those machines. Most other courses are in the same price range (welding is a bit more since it uses more materials), and are one day or less.
Weekend day-time is the busiest times in the Protospace shop, followed by weekday evenings. Equipment access is usually not an issue. The laser cutters are often the busiest tools.
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