Drive Methods

[Gary Thomason]

I understand that the original ShopBot was cable driven, and is now gear driven. Also, some routers are screw driven and others use a combination of methods for different axes. What are the advantages/disadvantages of one over the other?

[Wdyasq@yahoo.com]

Gary,

Yes indeed the original ShopBots had a sometimes slipping cable drive, a standard threaded rod for the 'Z' axis and screen-door rollers. It was difficult to decide which was the weakest link. If the cables were slipping was it??? the rollers binding or the cables stretching. OH, I forgot to add the encoders and the bead chain that ran them - did it stretch?

But, when working right, it would do things we had dreamed about. Then again, nightmares are a type of dream.

Gradually, the folks using ShopBots and the company put the bad dreams to sleep. The Uni-strut was first increased in dimension - then replaced. The cables gave way to gears, the threaded rod went to a ball-screw then a rack and pinion.

The ShopBot sold today resembles the one I bought in name only. The tool sold today is a VAST improvement over the early ones in both speed and accuracy. Not all of this is due to the drive system. There were many improvements in the control system.

In the cold cruel world, a ball-screw CAN be made more accurate than a rack and pinion. To achieve this kind of accuracy you sacrifice speed; spend money; or spend a BUNCH of money. My opinion is the ShopBot is a fine compromise. If one wants accuracy beyond practicality.............. It is a decision one takes.

I have seen few companies that stand behind their product like ShopBot does. The old machines really where a chore to keep 'tuned'. I have always found the advice and when necessary, the parts I needed from the kind folks in North Carolina. I am looking at a project where I might be able to employ another CNC router. ShopBot is on the top of my list.


Ron Brown - wdyasq@yahoo.com

If Stupidity got us into this mess,
then why can't it get us out? - Will Rogers