Machining trit slots is not that difficult if you got your machine setup. I have recentlly had 14 trit slots machined into a Sunwayman V10R Ti and it was a lot easier than I thought it would be. On this torch the time taken was not for cutting the slots but the time it takes to position the torch for the milling head.
To cut a 1.55mm slot 1.8mm deep takes my guy 9 passes - not 22 passes.My local guy is comfortable that 9 passes is all it needs. Each pass mills 0.2mm off material (which is miniscule if you think about it) and the feed rate is set a reasonable rate of 20mm/min and cutter is spinning at 4000 rpm. This rate does not cause the tool any stress. Each pass takes about 20 seconds (5mm to travel) Each slot takes approx 4 minutes (when you factor in opening doors, blowing off coolant, pressing buttons etc) . I can upload a video if anybody wants to see the slot cutting in progress.
What takes time and is repetetive is to rotate the torch on the indexing head for the next position. This takes about 2 minutes (time to open the CNC doors, blow the coolant off, rotate the indexing head, clamp the head, close the doors and press the 'Go' button).
All together you are looking about 6-7 minutes per slot. It took about 2 hours to cut 14 slots in 2 different axis on the Sunwayman. There are CNC machines out there that will rotate the torch in the Z axis (along the axis of the torch) but my local guy doesn't have such a machine. If you have a CNC machine that rotates the torch on the Z axis it would take less than 45 minutes to mill all the 14 slots in my estimate and it would be unattended.
My local CNC machine costs are approx $50 per hour. I got charged $100 approx in Sterling pounds for 2 hours work. That worked out $7 dollars a slot. It would make no difference if the slots were longer, or if there were several along the same axis as the machine would only take a few minutes longer. If the machine can be left unattended the costs will be half of this as the operator can get on do other jobs and it would be just the cost of using the machine and some machine operator time.
I have now started to mill the slots by hand. It takes a lot of concentration but it is fun to do... if you are careful the end result is pretty good and not really far off the result of the CNC.
Mohan