--- In mach1mach2cnc@..., "scot" <scotxl@y...> wrote:
Hi Tom,i was wondering if i could ask you some questions on the THC
setup,i have decided to modify my machine and add a z-axis,can you
help me on how the z axis is driven and how much travel should i
give
it.Thank you
Scot
UK
The Z axis is normally a leadscrew type drive although you could use
other methods. The axis has to travel a short distance at relatively
slow rates so a stepper type drive direct coupled to a lead screw (5
or 10 TPI) works quite well. I built my large machine to handle a
2HP router as well as a torch sub-assembly (with floating head) so I
wanted torque rather than speed. I used a triple stack 23 frame
motor, a 16MM X 4MM ballscrew and nut, and two Thompson slides. The
motor is driven by a Gecko 201 microstepping motor drive module. The
rest of the table is all servo using Gecko 340's.
You need something that will give you the same basic precision as
your X and Y since you can use it with the THC circuit to get
accurate verticle positions above the work. The stroke need not be
but 3 or 4 inches total. I do most rapids with the head 1/2" above
the material but that can be dangerous if you are not watching
because loose pieces from an internal cut can start to fall out and
jam with one end sticking up, and a rapid over that spot (shear
chance) can cause an ugly situation. A safer rapid height is 1". I
like to raise my head 3" to more easily remove the torch handle and
replace the tip comsummables.
I added a special button to my THC screen layout that is marked "Load
Material" and it rapids the head up and out of the standard work area
so I can load/unload the machine. Since 90% of my cuts are on either
2ft square or 2 X 3 ft pieces I have the table "jigged" up so that
loading and clamping material is quick.
Having a controlled 3rd axis (4th in my case since I run a dual drive
Y axis) has distinct advantages over a fixed, manual adjust or
solinoid type design. Watch E-bay for short THK or Thompson type
linear slides. They typically go pretty cheap for the short ones.
Be sure to buy enough so you can build a spring loaded floating head
design like the one in the Master5 Photo's section under
THC_Project. It makes doing a surface find and Z axis zero a breeze
and it's saved my torch head on several occasions.
Good luck and have fun with your project. Ask any questions you
want. Someone on the list will usually give a quick answer.
Tom C
