While eagerly waiting for my Maslow4 (I am part of batch #3), I want to start designing a frame out of 39x89mm SLS (equivalent to 2x4”, I guess). To save space, I want it to be as vertical as possible.

I started thinking about the effect of the angle on downforce. Can anybody help with guesstimates?

How much downforce is needed to keep the sled on the workpiece and to drive the bit into the material, 2-3kg?

Contributing factors are:

- Gravity
- Belt tension
- Suction force from shop vac for dust extraction

For pure horizontal 100% of gravity = downforce, for pure vertical, 0%. 10deg~17%, 15deg~26%, 20deg ~34%, …

What will be the weight of the sled incl all parts as delivered? 4kg?

I found 1,9kg for the dewalt router but guess that includes the plunge base. So 1,5kg without?

Total 5,5kg would give 1,4kg downforce for a 15deg angle. Not enough, I guess.

Belt tension helps when the belts are angled down towards the anchors.

In the middle of the workspace, each belt is about 7’ long, assuming 12x8’ between anchors (8x4’ + 24” in each direction ~ 14’ diagonal).

Assuming anchors at level of the spoiler board, I estimate the spools are on average 4” higher. That gives an average angle of 2,7deg meaning just under 5% of belt tension contributes to the downforce.

What is a good estimate for belt tension? I think I read max 30lbs ~ 14kg.

Assuming an average of 10lbs~2,5kg, downforce for all 4 belts would be 0,5kg.

I realize that reality is (much) more complex: each spool is on a different height, gravity results in higher tension in the upper belts, tension changes with sled position, … but want to get a feel for numbers.

My conclusion so far is that, unless some of my estimates are off, the contribution of belt tension is about the same as what I can get from additional 5deg angle.

Will the spools be happy with out of plane forces? If not, I’d rather keep belts parallel to the work surface and live with a larger angle and footprint.

I’d rather not count on suction force.

Comments are appreciated!

Will share my design (will use Fusion360) when I get somewhere.