Table requirements

[coldpenguin]

I am looking for the part of the forum for the really stupid questions, but I can't find it, this will have to do.

If I am planning to build/procure a CNC router, hopefully around 3'x4', is it important to have a steady and flat table /underneath/ the horizontal gantry? (i.e. underneath the XY plane, if I haven't managed to get the terminoligy right yet).

If the gantry itself is stable/non-flexible does it matter what is underneath it?

I.e. would there be a noticable difference between running it with the gantry placed firmly on top of the concrete ground, or with a plastic table underneath it?

[awerby]

Originally Posted by coldpenguin I am looking for the part of the forum for the really stupid questions, but I can't find it, this will have to do. If I am planning to build/procure a CNC router, hopefully around 3'x4', is it important to have a steady and flat table /underneath/ the horizontal gantry? (i.e. underneath the XY plane, if I haven't managed to get the terminoligy right yet). [When cutting materials with a tool, things always work better if the relationship between the tool and the thing being cut is stable; if everything's jumping around wildly, the tool will cut deeply one moment, and not at all the next.] If the gantry itself is stable/non-flexible does it matter what is underneath it? [Yes; if the workpiece is not mounted securely, you won't get a clean cut.] I.e. would there be a noticable difference between running it with the gantry placed firmly on top of the concrete ground, or with a plastic table underneath it?

[A plastic table? I think you've lost me here. Usually, CNC routers are made from metal, sometimes plywood or MDF, but I've never seen one made out of plastic. Any gantry needs to be supported firmly and leveled. The table that holds the workpiece is generally attached to it, and is built as rigidly as possible. Think of them as one unit, and try to minimize any vibration that might occur in the course of cutting.]

Andrew Werby
www.computersculpture.com

[coldpenguin]

Originally Posted by awerby [A plastic table? I think you've lost me here. Usually, CNC routers are made from metal, sometimes plywood or MDF, but I've never seen one made out of plastic. Any gantry needs to be supported firmly and leveled. The table that holds the workpiece is generally attached to it, and is built as rigidly as possible. Think of them as one unit, and try to minimize any vibration that might occur in the course of cutting.] Andrew Werby www.computersculpture.com

This is where my lack of terminology fails me I think.
So spindle is held by gantry, gantry runs on table.

I am talking about the object below the object upon which the table that the item to be machined is placed.

i.e.

0 object
______ table, which is mechanically attached to gantry
|-----| plastic table


?
Is the table upon which the CNC machine could be placed, important to be /solid/.
Does it need to be a nice solid wooden table, or could I re-use the plastic picnic table and pretend it is there for 'storge', and the CNC machine (all 3 axis) be placed on top of this 'for storage'

[ger21]

Depends how the machine is built, but basically, anything attached to anything that moves needs to be as rigid as possible.