[eloid]

which is better for wood working, looking for pro and cons of each
and trying to keep thing with in budget.. I know dust is a issue which is more accurate and better suited for woodworking applications.
Im guesing if your larger that 5 feet on y axis use rack and pinion ...cheaper?

[rustamd]

I think under mounted rack & pinion is perfect for router. my .002

[mxtras]

Ballscrews are typically more rigid and more accurate, but cost more money. Length is limited.

Racks are typically very well suited for most motion systems and can be accurate enough for a lot of applications - including wood routers. Rigidity is more than adequate for wood. Many, many commercial machines use racks - including some very expensive machines. They allow far greater distances to be covered than ballscrews.

I intend to build a 5'X10' router in the next 2-5 years. When I build this, I will be using a rack and pinion for the X and Y.

Scott

[coop2005]

Depending on the tools you have available to you, a rotating ball nut on a fixed ball screw can atain the high precision of the ball screw while avoiding whip problems associated with long ball screws. I just started work on a 4'x8' with this type of drive scheme. Here are some pictures if your intrested. The first picture is just a rough idea of how the ball screw is tensioned. The tensioning screws arent shown in the model but the circular hub is threaded allowing the ball screw to be put under tension.

Im using this site for ball screws not going to cost all that much more that rack and pinion.

http://www.roton.com/Recirculating_B...=Recirculating

Here is a thread discussing these same things

http://www.cnczone.com/forums/showthread.php?t=44452

[Greolt]

I have built routers with R&P and also with ballscrews and R&P would always be my first choice.

R&P really starts to make sense on larger machines too.

Whether using steppers or servos they really need a reduction method IMO.

Either belt and pulley or integral gear reduction. This has an impact on cost.

Having said that the Mechmate and, I believe, most of the Shopbots direct drive the pinions.

Recently I attended the major trade exhibition we have in Australia and I
went around and looked at all the routers and plasma cutters on show.

All but one of them were running R&P on the X and Y axis. These were all large and expensive machines.

Greg

[Gerald_D]

ShopBot no longer do direct-drive pinions - they only use geared motors from Oriental Motor now.

On the MechMate, the choice of motors/gearing is very much up to the individual. However, one can get a very profitable machine with Nema 34 direct driven pinions.