Roger and others
I will try to answer your questions as best as I can. When I first built the machine, I did a test on aluminium and steel 6mm. I found that providing the feed rate was modest it cut just fine. Note, I just cut a straight line for the test. However (there is always a however) in practice this was not the best strategy. I had a learning curve re suitable cutters and I use a maximum of 6mm. Basically not all cutters are suitable. The next issue is in machining a complex shape, sooner or latter you will be climb cutting which you have to allow for. I am certain that there are people out there who could offer far better advice on cutting methods however this is my experience in isolation. Cutting steel which is the most difficult, I use a twin flute carbide cutter and for five mm steel (the most common for me) I make three 1.25 mm deep roughing cuts with 0.2mm clearance. The final cut (on line) of 1.25 also cleans up the the overall piece. The ability to do rough cutting followed by a finishing cut is a feature of Cambam. I am sure other software will do the same. The time taken to do four cuts is about the same as doing it in one cut.
The other issue, is securing the work piece. If making a deep cut and the work piece moves by the smallest amount it is bin material. Straight lines are easy, it is the curves that put the load on the machine and in particular the cutting bit. If the cutting rate on a curve is too great, the cutter snaps, the machine does not slow down. I have a number of broken cutters as a result of my learning. If I have the time, I will change the bed from aluminium to steel making the T slots out of bright flat bar. The aluminium seemed like a good idea at the time as it had the T slots incorporated however. I don't think that you get the same purchase as with steel just my thoughts.
Aluminium cutting is easier especially if you use a single flute carbide cutter however, I still do a minimum of two cuts to improve the final finish. I was asked to repair two model railway carriages (about one meter long) and it required making new sides which I cut out on the router which included all of the windows and doors etc. I then changed the G code from cutting internal to the line to cutting external to the line. The end result, all of the windows just pressed in exactly. I could never have achieved that doing it manually.
The spindle I use (which was given to me) is good for 1.5 hp and is three phase via a single to three phase converter. These converters have a speed control to adjust the frequency and thus the speed of the spindle. The spindle is designed to run at a maximum of 400Hz and they are two pole motors. Their upper speed is 24,000 rpm and in theory should run down to about 50Hz or 3000 rpm but you need to be careful of the heat. Water cooling is a benefit here. I run my spindle between 3 and 8 thousand rpm. This requires some changes to the controller settings to ensure the power curve remains constant. Basically as the frequency is reduced, so is the voltage so if the settings are not changed, at 200 HZ you have half power and at 100 Hz you have quarter power (approximately).
The higher cutting speeds require plenty of coolant and I use a coolant mixed in with compressed air which is used to remove the cuttings. If anyone is interested in more detail of the build etc send a personal email.
As for video of the machine working, I as yet haven't made one. I have made then of some of my engines but have found the files so large you can't up load them to these forums.
All the best for the festive season.
Bruce