Fixed z axis to gantry design

**Lachlan** · 19-10-2015

That makes sense, I will use two ballscrews on the z axis and brace the sides of the gantry front to back.

**Robin Hewitt** · 19-10-2015

Loved the movie, someone has actually sat down and thought about it rather than following the herd.
The gantry connects to the bed. Presumably linear blocks are screwed to the gantry, linear rails are screwed to the bed.
If you want to add dead weight to cancel out vibration, by all means bolt the gantry to the building.
Maybe I an missing something, but I don't see any need for bracing because the bed does not reference anything apart from the gantry.
Cutting steel badly indicates that it might cut aluminium alloy reasonably well

**routercnc** · 19-10-2015

Hi Robin,

What I meant by bracing was if you view the machine from the side the 'bed' is effectively a capital "L" shape, with the stiffness of the vertical part dictated by the stiffness at the joint to the horizontal part. Better to join the top of the L to the front of the L to form a complete triangle.

**Robin Hewitt** · 19-10-2015

But the horizontal part should be a mere decorative trim. It shouldn't connect to anything

Edit: It does have a purpose, it stops you putting your tea cup where it will get knocked over

**JAZZCNC** · 19-10-2015

Originally Posted by Robin Hewitt

But the horizontal part should be a mere decorative trim. It shouldn't connect to anything

Edit: It does have a purpose, it stops you putting your tea cup where it will get knocked over

How do you work that out then.? It's the foundation of the whole machine and what the Fixed Gantry connects too. Rob is correct in that the Fixed Gantry would benifit from bracing to form a triangle rather than just being a tall pillow.!

Regards twin screws on Z axis then 100% needed and it would fail badly without them. Personally if your only cutting aluminium then I would stay with 5mm pitch has you won't require the extra speed 10mm gives but you will benifit form the extra torque and resolution 5mm gives. Even geared 2:1 so doubling the Torque/resolution 5mm pitch will easily give higher feeds than are required for aluminium.

If your thinking about cutting woods/plastics then go with 10mm pitch.

**Robin Hewitt** · 19-10-2015

Originally Posted by JAZZCNC

How do you work that out then.? It's the foundation of the whole machine and what the Fixed Gantry connects too.

At first glance you might think that, but the foundation of the machine is actually the rectangular gantry.
Everything refers to the gantry, that is why it is such a rigid design. The overhangs are minimalized.
Okay, you need something to support it so it doesn't fall over, but a strut? Does that not detract from the beautiful simplicity of the design? That tower in Pisa would get a lot more benefit from a strut than this, but it doesn't mean you should fit one. I mean, how gauche

**JAZZCNC** · 19-10-2015

Originally Posted by Robin Hewitt

At first glance you might think that, but the foundation of the machine is actually the rectangular gantry.

No it's not. Watch this video and you'll see the whole structure.

The Gantry rectangle is only has strong has it's connection to the base hence the massive plates. It would greatly benifit from more bracing higher up with connection to the lower frame. Yes Maybe not looking has simplistic but what we building here.? machines to do a job good or poser machines.!!