[peteeng]

Hi John - When designing a machine its sometimes easier to design the structure first and not get bogged down by the drives. The structure is what's important and it needs to be simple and really rigid. Once you settle down the structure you then add the drives. The drive is secondary to the structure and if you try to combine them too early you will compromise the structure. It takes several design rounds to boil down a design. Maybe 20 rounds for a really good design.. Z axis are usually underdone. It took me 3 machines to get the Z stiff enough to my liking. If you start designing from the outside in you generally run out of geometry for the Z axis and try to put too much into a small space. So once you have a basic frame philosophy sort the Z first then the machine is built around the Z axis. Make the Z axis as big and stiff as you can, the printnc has a very thin Z axis plate this allows it to flex to take care of other inaccuracies. Plus the Z axis drive is plastic and sits in a space with no screws so can wiggle. If you make a rigid Z then the rail foundation surfaces need to be accurate or the cars jam (this has happened to me) Peter

[Geordie1996]

Hi John - When designing a machine its sometimes easier to design the structure first and not get bogged down by the drives. The structure is what's important and it needs to be simple and really rigid. Once you settle down the structure you then add the drives. The drive is secondary to the structure and if you try to combine them too early you will compromise the structure. It takes several design rounds to boil down a design. Maybe 20 rounds for a really good design.. Z axis are usually underdone. It took me 3 machines to get the Z stiff enough to my liking. If you start designing from the outside in you generally run out of geometry for the Z axis and try to put too much into a small space. So once you have a basic frame philosophy sort the Z first then the machine is built around the Z axis. Make the Z axis as big and stiff as you can, the printnc has a very thin Z axis plate this allows it to flex to take care of other inaccuracies. Plus the Z axis drive is plastic and sits in a space with no screws so can wiggle. If you make a rigid Z then the rail foundation surfaces need to be accurate or the cars jam (this has happened to me) Peter

Your probably right with that haha, I do have a tendency to overcomplicate things sometimes. I think going back to your post of putting the two rails on the same side will greatly simplify things, and allow me to focus on getting a solid frame and z plate mount set up before moving on. Thinking about it more putting the bearings on the same side will only move the head out another 30mm, and it would also provide support closer to the spindle. Having this weight slightly further out with such a large gantry member (200 x 200 x 6) probably wouldn't effect it too much. Glad I came on here as there's lots of good advice from people that have already been through designing and making.

With regards to spacing would it be better attaching another member (such as a 100 x 100mm) on top of the existing gantry beam to increase the X rail spacing (increase from approx 175mm spacing to 275mm).

Thanks john

[Geordie1996]

Your probably right with that haha, I do have a tendency to overcomplicate things sometimes. I think going back to your post of putting the two rails on the same side will greatly simplify things, and allow me to focus on getting a solid frame and z plate mount set up before moving on. Thinking about it more putting the bearings on the same side will only move the head out another 30mm, and it would also provide support closer to the spindle. Having this weight slightly further out with such a large gantry member (200 x 200 x 6) probably wouldn't effect it too much. Glad I came on here as there's lots of good advice from people that have already been through designing and making.

With regards to spacing would it be better attaching another member (such as a 100 x 100mm) on top of the existing gantry beam to increase the X rail spacing (increase from approx 175mm spacing to 275mm).

Thanks john

Never mind I think I'm being a massive overkill with that, and would be adding unnecessary weight the gantry. I just measured the spacing of a 3x2m 5.5kW router at work and it's 200mm, so mine would be only 25mm narrower with 1/4 of the weight.