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  #1  
Old Sun 10 October 2010, 16:08
jwt
Just call me: John
 
Wexford
Ireland
Static and dynamic loads on the axes

I'm researching the pros and cons of the hand made rails and v-rollers, aluminium and pre-made steel v-rails and rollers and linear rails/guides.

Basically trying to offset price versus time/difficulty versus final accuracy.

I'm not asking for pros and cons, I've been reading the various threads and comments and realise it's been done to death. And yes, I'm going to slog through the whole "research it to death, evaluate all the permutations and probably end up going with the default answer of making the rails myself" routine, but I'm a glutton for punishment.


While trying to establish a cost I'm unsure of the size of guide-ways required due to the loads.

So if any existing mechmate users could offer an opinion or guesstimate on the following I would appreciate it.


As far as I can see the loads on the various axes breakout as follows

X-axis

Vertical
Weight of Y gantry plus weight of y-car Z-rail and spindle etc
Any decelerations or accelerations of the z-axis e.g dropping the spindle towards the floor and stopping it in 1ms
Possibly the spiral bit pulling down as it cuts?


Sideways (pushing and pulling in the Y direction)
Acceleration and deceleration of the Y car plus associated z-rail and spindle
Pushing the cutter against work e.g.cutting aluminium as an extreme

Y-Axis

Vertical
Weight of y-car, z-rail and spindle
deceleration of dropping spindle
Possibly the spiral bit pulling down as it cuts

Sideways (pushing and pulling in the X direction)
Pushing the tool head against the work

Z-axis

Vertical
Doesn't apply

Sideways (pushing and pulling in the X and Y directions)
Pushing the tool head against the work
Sudden start stops or speed changes of the tool head causing torsion


Any others?

So what are the typical weight s of the y gantry, y-car, z-rail and spindles?

Slapping the tool head into the work will max out at the motors stalling or jumping teeth, anyone care to guess at that figure?

Am I missing any other loads likely to be placed on the rails? I assume the table expands and contracts at roughly the same rate as the gantry so no mad sideways loads due to thermal stresses between day and night. Or does the board effect that?

Thanks




JOhn
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  #2  
Old Sun 10 October 2010, 17:11
jwt
Just call me: John
 
Wexford
Ireland
Update
http://www.houstonbearing.com/pdf/hiwin.pdf is a great resource for this sort of stuff to do with linear guides.
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