So I have a glass plate on the bed now and I increased bed temperature to 65 to account for the heat loss through the glass (printing with PLA). Have not had a successful print yet. There seems to be some curling of the print and at some point the nozzle catches on a curled corner and pulls the whole piece off the bed. Is the curling because of excess or insufficient heat? Any other suggestions? It is worth noting that the preheat function on my printer doesn't seem to work. When I go to preheat and select on for the print bed, nothing happens. Is there a trick to doing a preheat?