Chris,
Do you have a link for these "new style ball screws" ??
Thanks, Dave
On 10/4/2018 3:33 PM, Chris Albertson wrote:
Have you seen the new style ball screws? They are now cheaper then belts
and have pretty "over kill" specs.
The problem with a 30mm wide belt drive is the need to resist the belt
tension and a way to adjust it. Not only the tension between the two
pulleys but there is side load on the motor shaft unless you use a flexible
coupler and ball bearings on both sides of the drive pulley. The lead
screw is mechanically simpler because the motor can be directly coupled to
the screw and for $70 you get all the end blocks and mounting hardware.
These have made router design nearly a "screw driver only" project. No
design to even much thinking needed. I bought one for the vertical axis
of a CNC milling machine and I can set there is zero backlash and not
adjust needed or the life of the machine. Cost me about $35.
A screw give the drive motor a larger mechanical deduction and you can
likely skip the need for a reduction stage. A screw might advance the axis
4mm per revolution but a belt drive moves maybe 30 to 36mm per rev.
You get more force the resolution with a 4mm pitch ball screw.
You can make a one meter square X,Y router base or laser cutter today using
two pair of supported rails and two screws for under $250 plus the motors
and your z-axis.
On Thu, Oct 4, 2018 at 11:41 AM Roland Jollivet <roland.jolli...@gmail.com>
wrote:
The idea of using belts, and gearboxes, and rack and pinions, sounds like a
bad recipe.
While I did suggest a bar across the gantry, the problem is that you're
carrying all those gears, and the motor.
I drew a quick concept sketch of how I would do it. Buy cut-to-length belt,
probably HTD M5 x 30mm wide for your application.
I think this would be quite adequate for a wood router. At the far end of
the table, connect the two idler pulleys with a shaft too. Obviously all
the pulleys and motors will be below the table height.
And;
- motor is no longer on the gantry
- no skew can happen
- easy to get your drive ratio
- single motor
http://imgbox.com/ccZJF5nH
On Thu, 4 Oct 2018 at 17:41, Leonardo Marsaglia <ldmarsag...@gmail.com>
wrote:
Hello Les,
No, I plan to support 50 mm bars every 600 mm more or less. I'm attaching
some pictures of the design I'm working on. (The adjustable stands for
levelling are not in the assembly because I'm saving resources on this
laptop)
I like the idea of using the rectangular ways but unfortunately they are
quite expensive for this project and also there's the aligning problem.
With the setup I'm trying to do I can adjust the parallelism on every
corner of the machine and also individually adjust every suport to level
the guides perfectly. I'm sending pictures of everything to clarify what
I'm intending to do. Please note this is under development and some
things
are going to change a little bit.
The idea of welding the frame is out of discussion because I plan to move
and set up this thing in place. Also, I don't have the means to
guarantee a
clean and squared welding for the frame. Instead I decided to do what you
can see in the pictures, having an enormous amount of bolts to keep the
parts rigid and firm.
No problem about using tubing to lower the inertia. I also thought about
reducing the 3000 max RPM with the worm and gear to 100 RPM on the shaft
and then increase the size of the pinions to have the linear speed I
want.
This way the long shaft doesn't have to withstand the high RPMs.
I uploaded the pictures because the list doesn't allow me to attach them.
Here's the link:
https://imgur.com/a/7kLUWsq
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