Z length

I’m starting to assembly my very first MPCNC. I’m planning to use this machine for milling wood but also need some aluminium parts crafted from time to time. Now I’m trying to find some balance between travel length and rigidity of the machine. I ended up with X and Y dimensions of 864 mm x 1,164 mm (longer axis will be supported from the middle).

The needed Z axis height got me confused. I’m using Cut Calculator and there’s an input for Z-Axis Desired Work Height. I try to aim for as rigid machine as possible for this size so the Z axis would need to be on the short side. My question is: What I need to include in the desired work height dimension? Naturally milled material thickness will be there but do I also need to calculate endmill height or some other factors along with this (a little bit of empty space between endmill and worked material et cetera…)?

If you add 3/4" you should be safe, most endmills are that length. Just realize this is also about as deep as you can ever cut before the spindle gets in the way. You can account for this for deeper cuts but I consider this an advanced topic.

Go short, making it longer is very easy to do, but you will have a much better experience with a short z axis.

Thanks for the tip. On the other hand I can also add a little more length than planned and later cut it down if needed for more rigidity. I’m using stainless steel from a local hardware store but would save some time (and little bit money) when I wouldn’t have to take extra trip to the store in case I change my mind on length needed.

Even that endmills are not usually any longer than 3/4 inch in size I’m thinking that couple millimeters of free space between work piece and the endmill is still needed. Also now that I think of it there might be some pieces I’m going to mill that will be deeper than the length of my endmills. This means that material won’t be cutted through. Rest of the cutting could be made later on with a plunge router if needed.

So this in mind I could first try with 3 inch (c. 75 mm) working space for Z depth and cut it down if and when needed.