How accurate are the estimated machining times?
The estimated machining times are just a straight calculation of how long it would take to move along the total toolpath length at the given feedrate. Your actual times will always be longer because the mill takes some time to ramp up from a stop and back down at the end of a move. Since the acceleration time is completely dependent on your exact machine it cannot be calculated by MeshCAM.
The estimated machining times are useful to verify that you did not make any mistakes when entering the toolpath parameters and to judge the relative speed of one toolpath compared to another.
Are the machining times in seconds or minutes?
The short answer is, “That’s totally up to you”. MeshCAM does not keep track of time units internally; the feedrate values are passed right thru to the post processor where they are only converted to/from inches or mm if required.
For instance, if you enter a feedrate of “10 in” then it is passed right to the post processor and put into the gcode as “F10” if you’re using an inch post processor.
Unless you’re one of the (relatively few) people who have a milling machine configured for mm/sec then count on using the feedrates in “minutes”.