Small but strong cnc machine

[routercnc]

Hi Alex,

This is how I did it . . . .
http://www.mycncuk.com/threads/7155-...ight=stiffness

Attach a DTI to the collet (mm) and push it with some scales (reads kg so *9.81 to give N). Divide one by the other to give N/mm. Repeat for vertical, fore/aft, and side to side directions. This gives a rough stiffness figure. You will see the sorts of figures achieved by the DIY machines in the post. They will all cut aluminium.

There are some guideline cutting force levels for different materials:
5N wood
50N alum
75N steel

This will of course vary in practice, and the steel force is probably on the low side, but I think it is enough to get a feel for things. You can then estimate the deflection due to the cutting force by inverting the stiffness (do 1 over the stiffness value to give mm/N) and multiplying this by the cutting force (N) for the material you want to cut. This will give (mm) of deflection during cutting. You will have to decide if you think this is acceptable based on the accuracy you want.

Your machine does look on the low stiffness side, but it is small so that will help. Plus it is beautifully made so well done on that front.