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georgebarr
06-30-2003, 10:24 AM
Here is a picture of my plans I drew up using Solidworks. It is for my future CNC machine which uses aluminum extrusion for the frame. It is not yet complete. If anyone has any suggestions for additions or changes to this plan then let me know. I will post the rest of the designs as they are completed.

The frame measures about 4.5 feet x 5 feet. This is an all purpose cnc machine used for metal and wood projects. Wood projects needs more space than metal hence the large size of this cnc machine. It also has to be sturdy for those metal projects.

wjbzone
06-30-2003, 02:41 PM
George,

When I designed my CNC, I tried to keep under a 2:1 ratio between by bearing spread on the X guide rail and the height of my Z axis. It turned out to be very rigid.

I would be interested in what ratio other machines use and how it worked.

Just something to keep in mind.

Bill.

HomeCNC
06-30-2003, 02:51 PM
Hey! That might be a pretty good rule of thumb. I just measured my router design and it was 12.22 base X 23.6 high which is just under your 2:1 idea. Mine also seems rigid.

georgebarr
07-01-2003, 02:24 AM
Here is the update to my cnc design. Take a look at the dimensions (in inches). This is a pretty big cnc. I want to use it for wood and metal projects and should be sturdy. I do not want to build more than one cnc machine (usually one for metal (small) and another for wood (big)) since I want to cut the cost of everything. Do you think this design using aluminum extrusions will work. That is do you think it will be sturdy.
Thanks,

anoel
07-01-2003, 11:42 AM
Is there a particular reason that your gantry is 4 feet tall? That's enormous! The gantry being that tall will certainly lessen the rigidity of the machine and make the gantry unstable with the z and x axis weight that high in the air with the skinny base.

HuFlungDung
07-01-2003, 01:51 PM
Don't overlook the possible benefits of adding pure mass to your machine. Part of the battle is not only rigidity, but also to kill resonance. For example, concrete is great stuff for this. Choose larger extrusions so you can fill up the interior void with something that will help dampen resonant frequencies. Fasten the machine to a concrete base when its done.

georgebarr
07-01-2003, 06:40 PM
Some of my projects for this cnc design will include lathe turning which requires some z height. Also, I plan on putting together a 5th axis assembly which will take up some z height. Since this is my first cnc machine, I want it to be versatile. The z height is a rough approximation. I can decide later to mount the y-axis lower or higher on the z-axis. The z-axis is that high so I can adjust the height when needed.

Thanks,