[maly-miller]

A centre screw works ok when cutting in the middle of the table, however when cutting out at one side (one end of the gantry) there is racking, where one end of the gantry gets pushed further along the bearings than the other. Basically if you push on the front of one end the gantry will move relative to the other. Wider spaced bearings will reduce this but not eliminate it and means a smaller cutting area.

Another problem is table rigidity, which is much harder to achieve with the centre screw as you need the beam underneath. You can easily name a much more rigid table if you don't need this.

I've built a centre screw machine - never again.

Other than the centre screw, I think your basic design principles are good - you've used thick gantry uprights (most people still use thin plate).

The other thing is, if you can at all afford it, is to use profile rails. I haven't bought from them but BST automation on aliexpress have very cheap hiwin rails, other cnczone members have recommended them.

pippin88,

very comprehensive feedback. Thanks. The design concept below is very versatile. If you look below you will find that the Y-Axis is separate on a thick 40-4080 piece of extrusion. Adding a second screw is a matter of unscrewing the middle screw extrusion from the main frame which will remove the screw, stepper and everything related as one piece. Then I have to place this one piece axis to the left of the table and just create a similar one piece access and screw it to the right of the table and voila, you have a dual screw machine.

For the regidity of the table, my bad I didn't include the drawing with the MDF bed removed. There is a piece of 40-4012 in the middle to support the bed. I can add as many as I can to support it.

I will check these guys on aliexpress.



Here is a more detailed photo

Attachment 232892