Adding Linear Rails

[richards]

I just returned from the California Wood Expo where there were several CNC Router manufacturers running their equipment. None of the cuts on any of the machines had any "chatter". All of the machines used linear slides similar to the ones shown here:

http://www.automation4less.com/linhd.htm

The cost of retrofitting my 120-60 Alpha is about $2,500, which seems worth the investment - if it works. Has anyone retrofitted a Shopbot with linear slides? If so, did the linear slides eliminate the "chatter"?

[gerald_d]

Mike, here (http://www.mechmate.com/Forum/messages/329/646.html?1138275775) is a linear rail on the z-slide. But it can hardly be called a retrofit, nor has it cut wood yet. Plus it will run on Mach3/Gecko.

I have big doubts that changing only the rail system will eliminate the chitty chitty bang bangs.

[richards]

Gerald,

I should spend more time looking at your site. You've got some excellent ideas there.

If my tired eyes saw things correctly, it looks like you're using a single linear rail - which is probably sufficient. The machines that I looked at used two linear rails per axis, spaced as far apart as was mechanically possible.

If I understand the linear slides/rails design, since the bearing captures the rail on multiple sides, the only movement allowed, per axis, is parallel to the rail, which would eliminate all unintended up/down and side/side movement (within the specs for the linear slides/rails and assuming that the bearings and rails were installed to specifications). In contrast, the V-Rollers and rails seem to be able to allow a great deal of off-axis movement with the main restricting factor being the hold-down turnbuckle and spring.

Of course, as discussed before in other threads, the "chatter" could have many causes; however, allowing each axis to move only in its intended direction would probably eliminate any mechanical slop.