The speed of a CNC is usually measured in in/min (inches per minute) or mm/sec (millimeters per second), if metric. This refers to the feed rate of the machine. Meaning how fast the cutter can move though material.
A STEPCRAFT CNC (version 2) will move at a rate of 50 mm/sec or 117.6 in/min.
Just because that is the maximum speed of a CNC machine does not mean that is the speed you will run at all the time. In fact, many materials will require you to run much slower than that. For instance, cutting a piece of 1/4″ plywood would require a feed rate of about 25 mm/sec, whereas cutting 6061 aluminum would be slower at around 15 mm/sec depending on the bit you are using. If you were cutting or carving foam, then you could most likely run at full speed. However cutting hard wood like maple will require you to run much slower.
A general rule of thumb with a STEPCRAFT is for most materials to start running at 20 mm/sec and then adjust the speed while the job is running in UCCNC to obtain the best performance and cut quality and the best cutter life. Once you determine the optimal feed rate you can calculate that and set it up on a cheat sheet or in the tool library for future use.
For example, if you setup a job to run at 20 mm/sec and once running you find that you can go faster and you increase the feed rate to 140%. Then you can setup the tool in the Vectric tool library (or tool library for your CAM program of choice) with a new feed rate of 28 mm/sec (20 mm/sec x 140%). Now you can recall that tool the next time you run that material and it will automatically have the correct feed rate programmed in so you don’t need to remember.
When you are working with a hobby, light duty or non-production CNC, then the max feed rate is not as important as ease of use, accuracy and reliability. If you were running a production shop with a high end CNC mill that costs upwards of $100k, then max speeds would be more of a consideration.
Take care of your machine and do not push it beyond its capacity and it will last you a long time with very little maintenance requirements and your tools (bits) will last much longer as well.