New Machine Build- Ridgid mill/router

[louieatienza]

OK I'm finally going to start building this! After collecting parts for the last year and a half, I'm ready!

I will be building a gantry-style mill, though I haven't yet decided if I will make a moving gantry or moving table. I'm looking for a work envelope of about 24" x 8" x 8" (i x w x h). Depending on how I configure everything I could get 24" x 12" x 8". But being that my y axis is relatively wide, I wasn't sure if I could make the z carriage sturdy enough if I built in the traditional mill shape.

I have THK 30 series profile rail for the y, 25 for the x and 20 for the z. I plan to use mic-6 tooling plate and phenolic (1-1/4" garolite) for my structure. Eveything is drawn on scrap paper and fast-food napkins, though most of the parts will be cut on my CNC router. All are SHS series, so I'll have some flexibility as to their configuration. I have 15-15 ground ballscrews for the x and y axis and 15-2 for the z axis. I also plan to allow different drive configurations, but for now I will be using timing belts and pulleys for gear reduction. With 15 teeth on the motor and 36 on the drive shaft, I'm looking for an effective 4:1 reduction, which should give me decent rapids and a mechanical resolution of .0013"...

Will be using the Geckodrive G540 setup from Deepgroove1, which comes pre-wired in a nice enclosure, with a 48v power supply, and other stuff, and worked out cheaper than buying all the parts separate. Will be using 2.8 N*m steppers (I believe...), but they're 2A, so does anyone know what size resistor I need? And it should be at the Gecko side? I also have some 4A steppers, but according to Geckodrive I'll only have 7/8 of the available torque if I use them? Eventually, I will upgrade this machine to servo, and put these steppers and controller in my CNC router...

So anyways, I've been going through different designs, and was hoping to get some opinions (pros/cons)

1- Fixed z column, moving x-y
2- Fixed z column, table rides on x in an actuator-style configuration, sitting on y
3- Fixed x gantry, table moves on y axis
4- Fixed y gantry, table moves on x axis
5- Moving gantry (router style) long on y axis
6- Moving gantry (router style) short on x axis

I'm probably going to use a Sherline or Taig spindle as well, but hope to upgrade to a direct-drive spindle in the future. Since I already get decent feeds and speeds on my CNC router now, I hope to improve a bit more on resolution and surface finish with the sturdier design...

Anyways, I hope to have my mind made up on final design this weekend, and will be starting next week. Wish me luck!

[zool]

I thought you would have learned by now!

[microcarve]

My own personal opinion is, that's an excellent size to
use this machine as the model.

There are all kinds of benefits to this sort of dirt simple
design. It's easier to build, account for error, adjust. It's
extremely strong and rigid....of course depending on how well
it's built to begin with....

But, it's really easy to work on and modify. The bridge can easily
be made to be adjustable up/down by changing a few bolt positions.

I made mine from thick 1-1/8" MDF stair treads from Lowes. they
come in pieces about 11 x 48" long and are easily transported and
cut and worked....and are very strong.

I just wouldn't go through all the problems a moving gantry machine
can present, when something like this is so much easier and more rigidly
built.

This will easily handle any full sized router with the rails you mentioned.
It's a matter of opinion, but I really like the sheer practicality of these
type designs.

It's a breeze to keep clean as well...


John

[louieatienza]

zool, I'm always learning, that's what makes this fun!

John, that's more the direction I think I'm going to go. Though I'm not sure of whether to make the x bridge the long axis or the table in y. I've seen that Thermwood design, as well as Onsrud HD series... I believe Vibra-Free makes their VMCs with a fixed bridge as well. I also plan on letting the rails run well past my table, to make it easier to surface and edge stock, as well as remove the z carriage for service. It would also allow me to possibly add ATC...

As this will be mainly for soft metals and composites/plastics I want as much sturdiness bang for the buck. I think I feel more confident moving the table with one screw than the entire gantry, even with these linear guides. I do need the z height because I plan to add a rotary axis in the future. It will also allow me to use clamps on my table to mill blocks and other such parts.

I did even think about making the bridge adjustable. I even remember a build, I think in Germany, of a guy who made a raising and lowering bridge for the Z axis!

[microcarve]

Here's mine...and you can see how easily...and cheap! it is
to make. I've decided to make it my main machine for awhile
as most of the parts I cut are within it's 26 x 15 cutting area.

It's a lot more rigid than my moving table machine. This one was
just a 2 day experiment to do something with some 30" 30mm rails
I had on hand, but it's turned out to be a gem.

Not a pretty gem like a fine Ruby or Emerald...looks wise...but that
can be fixed easily enough with some paint....


John

[louieatienza]

Originally Posted by microcarve Here's mine...and you can see how easily...and cheap! it is to make. I've decided to make it my main machine for awhile as most of the parts I cut are within it's 26 x 15 cutting area. It's a lot more rigid than my moving table machine. This one was just a 2 day experiment to do something with some 30" 30mm rails I had on hand, but it's turned out to be a gem. Not a pretty gem like a fine Ruby or Emerald...looks wise...but that can be fixed easily enough with some paint.... John

That was pretty much what I though of at first. I then thought a column style mill would be better, but making the head cantilever out 10" was I think asking way too much, even with my linear guides. So I'd have to make my y shorter to make it practical. I saw this guy's stuff, and wished I had the machinery to make what he makes...

ZealCNC » News

The small router looks like a Minitech copy, but it really performs well.

But since I will be working mostly with plate stock, I think a gantry style mill would be most convenient, and easier to build ridgidly.

Still waiting on some parts, but I might have enough to start this weekend...

[microcarve]

Originally Posted by louieatienza That was pretty much what I though of at first. I then thought a column style mill would be better, but making the head cantilever out 10" was I think asking way too much, even with my linear guides. So I'd have to make my y shorter to make it practical. I saw this guy's stuff, and wished I had the machinery to make what he makes... ZealCNC » News The small router looks like a Minitech copy, but it really performs well. But since I will be working mostly with plate stock, I think a gantry style mill would be most convenient, and easier to build ridgidly. Still waiting on some parts, but I might have enough to start this weekend...

Wow..that's some machine that guy built! Yeah, I wish I had the tools
to do that too...

One thing I did just by 'incident' on my cheap machine that turned
out to be a pretty good decision was to make the table an entirely
separate assembly. That makes getting it as square with the bridge
as possible a very easy thing to do.

Then if it's not dead level...it's easy to use some thin material...foil,
plastic, even cardstock...underneath the table assembly to bring
it to level.

Mine's a little tall, but it's not a problem so far. It'd be easy to lower
the bridge if need be.

The vise holds the table fixture very well in place.

Just a really good and simple thing to make....


John

[tjskcnc]

Originally Posted by louieatienza but they're 2A, so does anyone know what size resistor I need? And it should be at the Gecko side?

All info is on the Gecko website - they are excellent on documenting their products, as well as support. You can actually call them directly and ask for help.

In a nutshell, use 1K for each amp, so a 2amp motor will require a 2k resistor. The resistor goes on the G540 end. Fine Line Automation has been installing them in their cables/kits on the motor end for some time with no problems, but Gecko says to put them on the G540 end.

Will you be starting a build thread?

[zool]

Originally Posted by louieatienza I saw this guy's stuff, and wished I had the machinery to make what he makes... ZealCNC » News

WOW!! This guys stuff is not only well designed, its art by the time he gets done.

[louieatienza]

Originally Posted by zool WOW!! This guys stuff is not only well designed, its art by the time he gets done.

Yeah, he does have the eye. and apparantly, some cash to fork over for raw materials...

tjskcnc thanks for the gecko info... I will start a thread in the proper spot once everything's in..

[RomanLini]

Louie, that 24x12x8 envelope would be quite suited to my "L-shaped plate fixed gantry" design as you can cut and drill the aluminium L-shaped gantry and base plate using your existing router;



http://www.cnczone.com/forums/cnc_wo...ll_router.html

[louieatienza]

Originally Posted by RomanLini Louie, that 24x12x8 envelope would be quite suited to my "L-shaped plate fixed gantry" design as you can cut and drill the aluminium L-shaped gantry and base plate using your existing router; http://www.cnczone.com/forums/cnc_wo...ll_router.html

Yes, this is pretty much the way I want to go. Only thing is, I was wondering if I should make 24" along the bridge, or make the table movve 24". Also, I was wondering if I should mount the rails on the base and put the carriages under the table (stronger but need more table space) or mount the carriages on the base and put the rails under the table (more compact, need less rail, but maybe not as sturdy?) I do plan to use 30 series profile rails for the moving table, if I decide to have it move the short way...