From http://www.rszemeti.demon.co.uk/cnc.htm CNC Hobbyist
Posted by
Wilfrid Blais
on 2000-11-18 18:37:35 UTC
3 axis CNC Router
----------------------------------------------------------------------------
----
For some reason, as yet unclear, I got it into my head to build a 3 axis CNC
router. I'm not bad with metalwork, and seem to think in 3 dimensions quite
well, however, I'd be lying if I said it had all gone exactly to plan.
Anyway the first photo shows you a general layout of the machine.
You can see the 25mm steel rods that form the carriage slide, and the blocks
of aluminium Ive used as mounts for the linear bearings. The bearings and
shafts are from INA, a german firm who seem quite reasonably priced. You can
also see the 3 ballscrews ive used to drive it. It is necessary to have 2
ballscrews on the Y axis (thats towards and away from you in the photo) as
the gantry would twist and bend if driven only from one side. the flat metal
plate on the gantry will be used to support the other flat metalplate you
can see lying on the bed of the machine. This in turn will eventually carry
the Z axis. To give you some idea of the strength of the construction.. If
you place both axis in the middle of their travel, (so there is maximum flex
in the shafts) and then stand on the gantry, there is about 0.5 to 1mm of
deflection vertically...
The next 2 photos show the method of attachinf the roller nut under the
gantry. The main problem with this strength of construction is the very
tight tolerances that have to be followed. If the end mounts for the
ballscrew are just 0.5mm off centre from the nut it gets almost impossible
to move near then end of the travel as there is very little deflection in
the system to take account of misalignment. The ballscrews are HiWin 25mm
o.d. and 10mm pitch .. there is no measurable backlash and very little
rolling resistance.
The 3rd photo shows how the end of the ballscrew has been machined to mount
in to the endbearings, a large 12mm carrier plate caries a deep groove ball
bearing, and a nut and spacer clamp the bearing onto the ballscrew shaft .
the end of the shaft has been machined to take a coupling from the stepper
motor.
Update .. Well . I have just done a few more bits of machining for it and
bought some REALLY nice motors for the project. I've bought some Sanyo H
series from Alzanti Ltd. . they perform SO much better than my old Sanyo
motors its untrue. Anyway .. the long and short of it is that I now needed
new motor to leadscrew couplers as the old ones could not take the 5 Newton
Metres of torque they produce! And not only that theyre VERY quick .. I can
achieve rapid transit rates of 10 inches per second easily! .. and when
cutting I get about 2KN of thrust (thats 200Kg ..) Anyway .. heres a photo
of one of the couplings I made..
Well .. I now have two axes moving at the same time.. I have attached a
pencil to the carriage and made it draw patterns for me. I now have the
whole assembly mounted on a baseboard of 40mm MDF. The MDF is then supported
on a framework of boxsection steel tubing of 60mm*40mm cross section. This
is then mounted on a sturdy set of legs to provide a comfortable working
height. I have machined the aluminium plates to carry the router head and
just taken delivery of the linear bearings and shafts for the Z axis. Ive
used 20mm shafting and INA linear bearings in INA holders. I had originally
intended to drive the Y axis leadscrews on either side of the gantry using
two independent stepper motors, driven from the same set of pulses. It soon
became obvious that should the motors ever becom out of step, or that one
motor should fail, then the other motor would have more than enough force to
cause serious damage to the machine. For this reason I have now opted to use
a single steppe motor for the Y axis and linked the two leadscrews using a
HTD toothed belt and some taperlock pulleys.
In this photo you can clearly see the left hand end of the X axis assembly,
with the Sanyo stepper motor for the X axis. In the background with a blue
center is one of the taperlock pulleys and the toothed belt. From left to
right.. The motor drives a home made coupling, the couplling is mounted on
the end of the leadscrew which has been machined to 12mm at the end, then a
M16 thread and a spacer. The next piece is a vertical plate of 12mm H30
aluminium. This has a recess machined in it and a deep groove ball bearing.
An aluminium end cap is bolted over the bearing and you can just see 3 of
the 4 retaining bolts. All the endstop microswitches are now fitted, and the
machine zeroes itself quite nicely. The next step is to wire it all up with
its final wiring and chainlink trunking. Then fit the Z axis bearing parts
and mount the router. I dont yet have a leadscrew for the Z axis, but I have
a rather nice one in mind from the catalogue.
this page will be updated as the project progresses... Oh .. one last thing
.. throughout the project I have been using a demo version of some CNC
software by Microsystems of Buckhannon which is excellent .. I suppose I'll
have to buy it soon!
[Non-text portions of this message have been removed]
----------------------------------------------------------------------------
----
For some reason, as yet unclear, I got it into my head to build a 3 axis CNC
router. I'm not bad with metalwork, and seem to think in 3 dimensions quite
well, however, I'd be lying if I said it had all gone exactly to plan.
Anyway the first photo shows you a general layout of the machine.
You can see the 25mm steel rods that form the carriage slide, and the blocks
of aluminium Ive used as mounts for the linear bearings. The bearings and
shafts are from INA, a german firm who seem quite reasonably priced. You can
also see the 3 ballscrews ive used to drive it. It is necessary to have 2
ballscrews on the Y axis (thats towards and away from you in the photo) as
the gantry would twist and bend if driven only from one side. the flat metal
plate on the gantry will be used to support the other flat metalplate you
can see lying on the bed of the machine. This in turn will eventually carry
the Z axis. To give you some idea of the strength of the construction.. If
you place both axis in the middle of their travel, (so there is maximum flex
in the shafts) and then stand on the gantry, there is about 0.5 to 1mm of
deflection vertically...
The next 2 photos show the method of attachinf the roller nut under the
gantry. The main problem with this strength of construction is the very
tight tolerances that have to be followed. If the end mounts for the
ballscrew are just 0.5mm off centre from the nut it gets almost impossible
to move near then end of the travel as there is very little deflection in
the system to take account of misalignment. The ballscrews are HiWin 25mm
o.d. and 10mm pitch .. there is no measurable backlash and very little
rolling resistance.
The 3rd photo shows how the end of the ballscrew has been machined to mount
in to the endbearings, a large 12mm carrier plate caries a deep groove ball
bearing, and a nut and spacer clamp the bearing onto the ballscrew shaft .
the end of the shaft has been machined to take a coupling from the stepper
motor.
Update .. Well . I have just done a few more bits of machining for it and
bought some REALLY nice motors for the project. I've bought some Sanyo H
series from Alzanti Ltd. . they perform SO much better than my old Sanyo
motors its untrue. Anyway .. the long and short of it is that I now needed
new motor to leadscrew couplers as the old ones could not take the 5 Newton
Metres of torque they produce! And not only that theyre VERY quick .. I can
achieve rapid transit rates of 10 inches per second easily! .. and when
cutting I get about 2KN of thrust (thats 200Kg ..) Anyway .. heres a photo
of one of the couplings I made..
Well .. I now have two axes moving at the same time.. I have attached a
pencil to the carriage and made it draw patterns for me. I now have the
whole assembly mounted on a baseboard of 40mm MDF. The MDF is then supported
on a framework of boxsection steel tubing of 60mm*40mm cross section. This
is then mounted on a sturdy set of legs to provide a comfortable working
height. I have machined the aluminium plates to carry the router head and
just taken delivery of the linear bearings and shafts for the Z axis. Ive
used 20mm shafting and INA linear bearings in INA holders. I had originally
intended to drive the Y axis leadscrews on either side of the gantry using
two independent stepper motors, driven from the same set of pulses. It soon
became obvious that should the motors ever becom out of step, or that one
motor should fail, then the other motor would have more than enough force to
cause serious damage to the machine. For this reason I have now opted to use
a single steppe motor for the Y axis and linked the two leadscrews using a
HTD toothed belt and some taperlock pulleys.
In this photo you can clearly see the left hand end of the X axis assembly,
with the Sanyo stepper motor for the X axis. In the background with a blue
center is one of the taperlock pulleys and the toothed belt. From left to
right.. The motor drives a home made coupling, the couplling is mounted on
the end of the leadscrew which has been machined to 12mm at the end, then a
M16 thread and a spacer. The next piece is a vertical plate of 12mm H30
aluminium. This has a recess machined in it and a deep groove ball bearing.
An aluminium end cap is bolted over the bearing and you can just see 3 of
the 4 retaining bolts. All the endstop microswitches are now fitted, and the
machine zeroes itself quite nicely. The next step is to wire it all up with
its final wiring and chainlink trunking. Then fit the Z axis bearing parts
and mount the router. I dont yet have a leadscrew for the Z axis, but I have
a rather nice one in mind from the catalogue.
this page will be updated as the project progresses... Oh .. one last thing
.. throughout the project I have been using a demo version of some CNC
software by Microsystems of Buckhannon which is excellent .. I suppose I'll
have to buy it soon!
[Non-text portions of this message have been removed]