Simple Machine (help and advice needed)

[Gregor]

Hi
When you talk about the gantry rails are they the rails on the x axis,Heres a few new pics ,I have done all the metal work to scale on sketchup and the dimension's off the base are 860mmx720mm not including the end plates on the base. The gantry was made 730mm to allow for clearance for the plates for the ballscrews. As I say I want to try and make it as simple and easy to make with most off it made by welding so let me know if this design is a load off Cr@P
Cheers

[EddyCurrent]

Hi
When you talk about the gantry rails are they the rails on the x axis,

Well I assumed mekanik was talking about the Y rails, those actually on the top and bottom of the gantry cross beams.
Are you putting the Y ball screw between the two cross beams ? if you are it's been suggested to add a plate to the front to keep crap away from the screw. This means putting a slot in the plate to allow the bracket where the ball nut attaches to the Z axis to move across. like here; http://www.mycncuk.com/threads/6418-...8048#post48048
It also adds strength to the two cross beams.

[mekanik]

Yes the Gantry rails, top one can be leveled as per the X axis ie with epoxy but you then need to align the bottom gantry rail to the top one.

[Gregor]

Good point Mekanik I don't have an answer to that I hope someone will read this and know how to do it. EddyCurrent I don't have anything to cut a slut but I could weld some 3 or 4mm plate on like in the sketch

[Ross77]

If you get the 4way loading bearings then it is best to mount the rails on the front face of the gantry and means the z axis mount is simple plate as well.

You only need to mount the rails top and bottom if they are the supported rail type due to the unequal load capacity of the open bearing.

Your triangulation needs to go from one node to another node (connection) or else to will place a bending moment in the middle of the beam. :0)

[Gregor]

Hi Ross thanks for the advice
Could you explain what you mean when you say triangulation needs to go from one node to another node please
Cheers

[EddyCurrent]

You only need to mount the rails top and bottom if they are the supported rail type due to the unequal load capacity of the open bearing.

One advantage of the top and bottom mounting is that the Z axis can be closer to the gantry, i.e. less overhang of the spindle.

[Gregor]

HI
I have been looking at designing the z axis and I have notice that on my gantry design the bottom off the cross section is only 110mm above the base and building the z axis will lower it by another 20mm if I use aluminium plate to attach to the Hiwin linear rails, My goal was to be able to cut up to 75mm hard wood,Do I need to raise that bottom beam up to achieve that ? I have put the measurement's in the sketch
Cheers

[Ross77]

The top and bottom mounting does pull the z axis closer but not by much and you still need to get a ball screw in there any way. Horses for courses i suppose, easy build or extra strengh.

With regard to the diagonal bracing I meant the node as is in the connection point of all the beams. As you have shown them at 45 degrees then they start at a node a go to the midspan of a beam.

If you think of it as a wire frame then where ever the main beams meet there is a junction then this is the node.

[Gregor]

Hi Ross Thanks for explaining that,I have changed the side rails in the pics what do you think