I noticed a few of the extrusion based designs have something in common with house wall design. The extrusions/boards meet at 90° angles but have no diagonal braces and no other braces like a triangular wedge to ensure it does not lean. Why is that? Wouldn’t the walls and CNC machines be stronger with such support?
I’d say this is mostly due to the available joint types and extrusion cuts offered.
That’s correct. It’s simply easier to connect at 90 degree without doing any cut. One already has to drill and tap holes.
If you cut a square sheet in two, stack them and drill 4 holes, you have 2 braces. You just have to drill the holes in the right places.
I think people use T slot L shaped corner bracket like this one.
http://www.aliexpress.com/item/T-Slot-L-Shape-Type-90-Degree-Aluminum-Profile-Accessories-Inside-Interior-Corner-Connector-Bracket-for/1513536335.html
Once something is strong enough making it any stronger is a waste. It is interesting to note that the less accomplished one is engineering the more they tend to over engineer things to compensate for their lack of ability. Anyhow, as I understand it those extrusions are designed at the outset to connect how they connect. So the engineering is basically done for you. That is their main selling point. Now if you can simply cut them at a right angle then you’re good to go.
But yes you’re right, gussets, or braces do add considerable strength to members connected at angles to each other. There is more to machine design than just torsional strength though. One has to consider harmonics, and dampening masses too. So building the strongest machine for weight might not always be the best solution. Such a machine might resonate like a fine violin, and also chatter like one does too.
@Peter_Fouche1 So you mean lap joints? If you do then yes, lapping components is one way to avoid worrying about angles.
@Peter_Fouche1 That is a lapped gusset, as opposed to one positioned on a center line.
file:///tmp/AngleBracketwithGusset01_Right.png7a8dec7a-0eb6-4174-bd59-c3056fec2342Large.jpg
@Paul_Frederick you gave us a link to a temporary file on your computer. That does not work too well. lol
@Peter_Fouche1 yeah. That first image is exactly what I was thinking should be on the bottom of the corners for alot of the extrusion based CNC machines. As for lap joints, I have seen them in the middles of wood based CNC machines.
@NathanielStenzel
Yeah dumb browser opened it that way sorry
http://www.123dapp.com/123d-3D-Model/Angle-Bracket-with-Gusset/594071
@Paul_Frederick that last image would probably work well enough too.
@NathanielStenzel It would work well enough, but they are more trouble to make than overlapped parts. A center line gusset is the ideal form by all metrics. But to make one it is quite a bit more trouble as opposed to a gusset attached to the sides of the members it braces. Debatably more trouble than it is worth too.