3D Machine

	Guideways & Costs
Frame & Motion converter

There are some different ways of lineair guideways:

Linear ball guideway
Supported linear ball guideway
Linear rail guideway

Beside this choice, also the support is important for getting the right stiffness. Here you could find an impression of different options. Below you could find a cost price calculation.

Inertia versus weight (single rod)

The inertia of the profile that is used, has a liniear influences on bending stifness. Here the inertia of one single tube with outer diameter of 25 [mm] and different inner diameters are compared. Also because of decreased cross section, the relative weight decrease is shown.


D [mm]	d [mm]	I [mm^4]	Inertia [%]	Weight [%]
25	0	19175	100	100
25	5	19144	100	96
25	10	18684	97	84
25	15	16690	87	64
25	20	11321	59	36
30	25	20586	107	44

Here you can see a tube with inner diameter of d=10 [mm], where stifness is decreased with only 3% and saves 16% in weight. Or when outer diameter is changed to 30 [mm] with inner diameter of 25 [mm], the stiffness is increased with 7% but weight is decreased with 56% !! This is a good way for finding the right stiffness/weight combination, when using tubes.

Rod support

The second important issue is rod support. There are different methods of clamping the rod, see picture below.

I will add stiffness numbers later on, but made alread a decision for creating some kind of support like #8. (Likely 2 symectrical supports.)

Combined supports

First of all, one single round rod will not support axial moments, therefore you need 2. In picture above with rod support #8, it's obvious to create a more stiff system with smaller rod dimensions and this means lower costs for those components!