I am looking to get some input on the trade offs between selecting a moving gantry or a moving table for the X-direction.

If I am targeting about a 3 foot X direction, which seems to be the consensus for an open CNC design. the moving gantry would result in a smaller machine. The lenght of the machine would roughly be the length of the gantry travel plus the width of the gantry. A moving table would be roughly twice the length of the table ( 6 feet) as both ends of the table need to be positioned underneath the table.

The other considerations are the stability of the moving componenet. The moving table seems to be the best from a predicatable platform as it would be easiser to create a stable platform for several reasons: 1.) the rollers would be farther apart, say at the four corners of the moving table. This would result in a less movement at the router head given a fixed movement at a bearing on track movement. 2.) The primary force of the router would be down and be the same direction as gravity driving the table onto its track instead of lifting it off the track as in a moving gantry version.

The moving gantry version has the advantage of being smaller and thus costs less as the cost is directly proportional to the size and amount of materials used. The question is can the performance disadvantages be minimized or eliminated to the point to make this the best choice.

Any thoughts?

Greg