Thank you Leonardo,
That makes me feel better 2 to 1 reduction will fit easily in the
space available.
I should have been a bit more clear both ends of the Z axis ball screw
will be supported by ball bearings in pillow blocks. The head stock end
will have two bearings back to back with a nut for preload against a
shoulder to hold the ball screw from moving in the Z direction. The
tail stock end will have a single row ball bearing riding on a journal
with no shoulder allowing the shaft to float along the Z axis only(allow
for heat expansion ect). All the ball screw installations I have ever
seen have always been driven from the fixed end with 2 bearings and a
nut. (Granted I have not seen that many ball screw installations)
In the morning I will measure up and order the ball screws pillow
blocks, bearings pulley wheels and belts hopefully I will have them in 2
weeks and be able to start moving forward.
Thanks again
Linden
On 2023-12-25 16:58, Leonardo Marsaglia wrote:
Hello Linden,
For your first question. I would mount the motor on a fixed end just to be
sure, so that would lead you to make both ends fixed. I guess you can mount
your servo on a non fixed end if the machine is not going to be used for
heavy cuts on hard materials but I would go the extra effort and make the
assembly fully supported.
Second question. I don't know what's your max rpm for the spindle or what's
the softer material you're planning to machine but with 3000 rpm of max
speed on your servo you can easily do a 2 to 1 reduction (if you have the
room for the pulleys). That would give you 7500 mm/min for rapids. I don't
know what power and torque your servo can provide but I assume 2 Nm at
least on continuous so with your 5 mm and the 2 to 1 on the pulleys you can
have 4000 N of linear force on the carriage and I think that's more than
enough.
Hope this helps!
El lun, 25 de dic. de 2023 21:08, Linden via Emc-users <
emc-users@lists.sourceforge.net> escribió:
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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