What is Binding and racking?

[JimmyL]

Hey all Ive heard this term over and over again but i cant figure out exactly what these two terms mean?


People say their rails bind?
Binding-

racking-

Thanks!

[P.Passuello]

Hi Jimmy,

Binding:
If you were to slide an carriage along it's axis by hand and were to feel a position on that axis where it is harder to push the carriage you would say that it is binding at that point. Binding may cause a carriage to stop moving thus loosing steps and upsetting your cut.

Racking:
Racking usually applies to the Y axis and is where one end of the axis moves while the other end stays still. Imagine that you have a stepper on each side of the Y axis and one motor stops turning for what ever reason ,(maybe binding ), but the other motor keeps going. The Y axis is now racked and will no longer be square to the X axis. A center drive Y axis can also rack if the router is cutting on the left side of the axis it will have a lot of resistance while the right hand side will have none. This will cause the axis to twist or rack.

Hope my long winded explanations make sense.

Cheers
Peter

[JimmyL]

Wow thanks for the quick response! I get it now! Ive always known these things might happen i just didnt know what they were called.

If i may, there were new questions that sprung up from your answers!

Binding: What are the most common causes of binding and how i can i prevent it from happening from my homebrew cnc router that i am plannign to build?

Racking: so if one side of the gantry binds, and the other is free, the entire setup is now racking correct? Are their other ways that one's machine could rack?

Losing steps: what does it mean to lose steps?

Thanks again!

[LeeWay]

Binding can be caused by a lot of things on different types of machines.
On a dovetailed way mill, you might see it as a result of wear, or improper gibb adjustment or a combination of those. Chips in the ways or screws can also cause binging. Improper alignment of the rails or screws can also result in binding. Racking can cause binding and vice versa.

Racking is when two side of the gantry or ways don't move in sync. Anything other than synced movement is racked or racking.


Loosing steps is when your motors isn't where the controller thinks it is due to stalling in a bind or rack or from having the motor tuning setup too high. There are other reasons for lost steps and the longer you stay here, some more of those will become apparent.

[Weldtutor]

Originally Posted by JimmyL Are their other ways that one's machine could rack?

Racking could result from;
- drive forces that are not equal on opposite sides such as a screw, belt, or chain on one side but not the other.
-structural materials that flex, move, or otherwise are not sufficiently rigid for the application.
-joint design that is not secure & requires more fasteners, brackets, gussets or welds.