Thanks Chris
This is exactly the insight I was looking for now I understand why the
conventional mounting is always with the servo at the head stock end.
Linden
On 2023-12-25 22:35, Chris Albertson wrote:
When it comes to flexing and bending, think about the bed too. If the servo
motor and pullies are mounted at the tailstock end, then the bed will carry the
reaction forces and see exactly the same tension and “twist” force as the
screw. But if the motor is mounted at the headstock end the bed sees no net
forces.
The twist force on the bad will be the motor’s stall torque times the pulley
reduction. Would that be enough to warp a cast iron bad? That depends on the
detainees.
Also you. want the force of the motor applied to the fixed end near the
headstock because none of the mounting points will move as force is applied.
In short, think about what bends as force is applied, the motor pushes on the
screw one way and the motor mounts in an equal but opposite direction.
On Dec 25, 2023, at 3:37 PM, Linden via Emc-users
<emc-users@lists.sourceforge.net> wrote:
Hello All,
In the early stages of converting a 13 x 24 inch manual Chinese lathe to
run with Linux CNC.
I have 2 questions regarding replacing the Z axis lead screw with a 3205 ball
screw:
What I am thinking is mounting the fixed end in a pillow block at the head
stock end of the lathe and the floating end in a second pillow block at the
tail stock end of the bed. The question I have is there any reason I shouldn't
drive the ball screw from the floating end? My logic for driving at the
floating (tali stock) end is 1 I have more room for belt reduction at this end
and 2 with the fixed end of the ball screw at the head stock end is that the
ball screw will be in tension when it is pulling the carriage toward the head
stock during cutting and less likely to flex or bend.
The second question I have is what would be a realistic cutting speed range for
the ball screw in RPM? The servo motor I am using has a top speed of 3000rpm
and I am trying to figure out reduction ratio that is realistic.
Thanks in advance for any help or suggestions.
Linden
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