Building from Scratch or follow some plans?

[routercnc]

Hi Monk,

Firstly just looking at the section sizes, given that it will be 1200mm long, would seem a reasonable start. It will depend on how far down the cutting is taking place away from this section, since this will lead to a twisting torque, along with the deflections Irving mentioned above. Any ideas on the height down to the workpiece?

I need to dash off now, so will get back to you with some proper analysis. Really you need to use what is called the 'parallel axis theorem' which works out how to combine the two shapes (or any number of shapes), and find the neutral axis. This will be slightly below 'half way' in your L case. Then you can calculate the total section 'I' value, second moment of area, in mm4. From here it is then possible to get the deflection, and given a bit more data from you, the twisting.

The Hepco 40x80 shows an Ixx value of 61.4cm4, which if my brain is working is 61.4x1e4 mm^4. This is a start, hope to be back with some better answers tomorrow unless someone jumps in . . .

Ah, Ross, you jumped in while I was typing. Here is the Hepco catalogue link:
http://www.hepcomotion.com/en/litera...m-pg-16-get-31

Yes, watch those units. Should be consistant really.