Aluminium Extrusion Router Build

[JAZZCNC]

Hi Jazz, reading a few of the forum threads, I think most people use the 5mm pitch HTD pulleys with 15mm wide belts. Is there a certain number of teeth engaged with the pulley for best torque transfer, as I was looking at maybe the 20 tooth pulley, which is 26mm wide.

They say should have 6 or more teeth engaged on the smallest pulley.
Regards the 20T then yes these are fine and what I often use. However it does depend on the Motor shaft to some degree because of the Boss diameter. If using large motors you may have to increase pulley size to suit a Boss that gives enough material left for grub screws after being bored.

On the ballscrew shafts do you file flats onto the end to give the grub screws a better bite on it?

Yes and I use 3 Grub screws in each pulley plus I locitite them on using Strong loctite.

As for the ATC spindle my take on this is that I would need the ATC spindle, some form of linear or round tool holder, a compressor as I think that the tools are held in the spindle with pneumatics.

Yes need compressor for draw bar that pulls toolholder into spindle and also some have Air purge on the taper to keep clean.
The tool holders you can buy. Like these.!
https://www.aliexpress.com/item/High...ceBeautifyAB=0

How do the tool changes work, are they programmed into the G code that Mach 3 processes. I Have seen that each tool on a linear tool holder has a seperate set of coordinates and the tool height is reset each time and with the circular holders you need to rotate the holder to select tools, how is this programmed in. It all seems a bit complicated to me.

Not in the G-code but into the M6 tool change macro which mach3 uses every time you call for tool in your G-code.
In the G-code each tool change will be called with command like T1 M06. This then tells mach to run M6 macro and change to tool #1.

The M6 macro is where you put all the code required to operate the tool changer. Depending on the type of tool changer will determine how difficult. For instance rack mounted tool holders are easier to code because you just provide coordinates each tool is located in the rack.
Obviously you have to keep track of current tool and tell it where to put back before going to get new tool. Also need to operate few external bits of hardware like Air solenoids at the right times and tell how far lift up and put down etc but in general it's not massive job to create a tool change macro for rack mount.
Now carousel type gets little more involved because lots more going on. Got things whizzing in/out and spinning round which need to be monitored before next step can happen. Then got to keep track of tool again so gets put back in empty holder then decide which way to spin for next tool etc.

So yes could say "It's all bit complicated" but still do-able. Basicly just copy some body else M6 macro and make it fit your needs..Lol