Luttrell CNC Build

[jtluttrell]

Ok, so I thought I'd start a thread about my cnc adventure. I currently program / run 2 cnc routers at work and I thought it would be cool to build one of my own for woodworking. I started the base of my design from the CNC Shark Pro, but I was wanting to beat the price and gain table space at the same time. I've been obsessing and researching like crazy and here's what I'm currently thinking:

CNC Router Build

Cutting Area: Approx. 24” x 48”


Lead Screws: Acme ½ – 10, RH, Steel @ Roton.com (#59284)

Anti-Backlash Nuts: 1/2” – 10, RH @ Roton.com (#19660)

Linear Shaft: 20mm chrome-plated, hardened rod @ Vxb.com (#Kit1009)

X Axis Bearings: 20mm Open Twin Ball Bushing Pillow Block @ Vxb.com (#Kit8301)

Y Z Axis Bearings: 20mm Open Ball Bushing Pillow Block @ Vxb.com (#Kit989)

Motor Kit: 3 Axis Monster Stepper Motor Driver Kit @ Probotix.com

Router: Porter Cable 892 (2-1/4hp) or Porter Cable 690 (1-3/4hp)

Software: TBD, (Currently using Autocad)








I'm dying to start building!

[ger21]

You'll get very poor performance with that Monster kit and 1/2-10 acme. If you use that motor/drive setup, you should use a screw with between 2 and 4 turns per inch. #60404 or #60986

Even if you went with the 4 turn/inch, you might get more speed out of the Sidestep package, unless you upgrade the Monster package to 42V power supply.

[jtluttrell]

You'll get very poor performance with that Monster kit and 1/2-10 acme. If you use that motor/drive setup, you should use a screw with between 2 and 4 turns per inch. #60404 or #60986

Even if you went with the 4 turn/inch, you might get more speed out of the Sidestep package, unless you upgrade the Monster package to 42V power supply.

Ok, I'm all ears. Am I correct in thinking that by following your suggestions, I would be losing resolution and gaining speed? Have any good links to info on lead screw / motor relationship?

This is exactly why I posted this, to get suggestion/corrections! As a point of reference, I would like to say that as far as performance goes, I would like to be able to through cut 4/4 oak. Is this realistic?

[ger21]

Am I correct in thinking that by following your suggestions, I would be losing resolution and gaining speed?

Yep. Steppers lose torque as speed increases, so you are limited in the max usable rpm's you can get from as stepper. Also, steppers have a fixed resolution of 200 steps/rev. Because of this, when using steppers, increasing speed will always be at the expense of resolution. But, you'll still have far more resolution than you'll need.

This might help. http://www.pminmo.com/mechancial-power

Do you want to cut 4/4 oak in a single pass? If so, you'll need to build a much more rigid machine then I'm seeing. What are you building from?MDF? PLywood? Aluminum?

Also, it looks like you'll be spending quite a bit of money here. For an extra $200 or so, a Gecko G540 will give you at least double the performance of any of the probotix kits. The 381 oz motors are the preferred option.
http://kelinginc.net/CNCNEMA23G540Package.html
http://www.cncrouterparts.com/index....50ku52qrme6cj6

[jtluttrell]

So if what I'm reading is correct, 1/2 x .250 (#60404) or 1/2 x .500 (#60986) screw coupled with the G540 3 axis package (One G540 + Three KL23H284-35-4B (1/4” Dual shaft with a flat) 387 oz-in + one KL-350-48 48V/7.3A 115V /230V power supply) would make for a better set-up?

MDF seems to be a popular material, but I would actually prefer using 3/4" domestic core birch plywood and I intend to cut my parts out on the router at work so they'll be dead on, plus I can machine all neccessary holes, dados, etc.

As far as cutting 4/4" oak, I just wanted to establish a base point for the my expectations for this machine. I suppose that cutting in 2/3 passes would be perfectly acceptable considering the relatively low volume of work I'll be doing.

Again, thanks for the help.

[ger21]

So if what I'm reading is correct, 1/2 x .250 (#60404) or 1/2 x .500 (#60986) screw coupled with the G540 3 axis package (One G540 + Three KL23H284-35-4B (1/4” Dual shaft with a flat) 387 oz-in + one KL-350-48 48V/7.3A 115V /230V power supply) would make for a better set-up?

Yes, the G540 is the premier drive available in that price range.

Building the machine from single layers of 3/4" plywood will result in a lot of flex when cutting. Even the slightest amount of flex will show up when making heavier cuts. At a minimum, you 'd want to laminate two layers of 3/4" for additional stiffness. Using torsion boxes is even better.

[jtluttrell]

*Updated Setup*

CNC Router Build

Budget: $2400

Cutting Area: Approx. 24” x 48”

Structure: MDF or Plywood

Lead Screws: Acme ½ x .500, RH, Steel @ Roton.com (#60986)

Anti-Backlash Nuts: 1/2” x .500, RH @ Roton.com (#19664)

Linear Shaft: 20mm chrome-plated, hardened rod @ Vxb.com (#Kit1009)

X Axis Bearings: 20mm Open Twin Ball Bushing Pillow Block @ Vxb.com (#Kit8301)

Y Z Axis Bearings: 20mm Open Ball Bushing Pillow Block @ Vxb.com (#Kit989)

Motor Kit: G540 3 axis package (One G540 + Three KL23H284-35-4B 387 oz- in + one KL-350-48 48V/7.3A 115V /230V psu @ kelinginc.net

Router: Porter Cable 892 (2-1/4hp) or Porter Cable 690 (1-3/4hp)

Software: TBD, (Currently using Autocad)

[jtluttrell]

I wanted to post how I plan on mounting/supporting my 20mm linear shafts.

For my x axis (60" long), I plan on making my own shaft suppoort to make a rail:



On the z and y, I will probably use these from vxb.com (#kit7231)

[bitbanger]

Gerry,

The Gecko drivers are nice, but for an extra $200 they will NOT double the performance of the PROBOTIX drivers. Maybe 10-20% increase in top speed, but no more. You are right that the green motors are not the fastest motors on a gantry router - they are better suited for a mill conversion where you need the extra torque because of the additional friction of dovetail ways, and you don't care so much about rapid travel speed. The yellow motors scream though, on a mid or small sized gantry router, especially if you couple them with a 40V power supply.

>Len

[jtluttrell]

Looks as though I've still got some cyphering to do about the motors/drivers. I somehow feel that the probotix kit is going to be more user friendly to a beginner like myself especially if I order the kit "ready to run" in an enclosure and all.

Aside from that, to progress on my build, I would like some more info on the leadscrew/motor assembly. I plan on using lovejoy coupling to attach the motor and screw, but what about the other end of the lead screw? I've also seen thrust bearings used and drill rods. Do I need to have the screws end machined? Any help is appreciated. Perhaps if I had this assembly figured out, I could order my shafts, bearings, lead screws, etc. and get started.

Would something like this work for the opposite end of the lead screw? VXB.com (kit7494)


Thanks.
Tyler

[ger21]

The Gecko drivers are nice, but for an extra $200 they will NOT double the performance of the PROBOTIX drivers. Maybe 10-20% increase in top speed, but no more.

Here's a post from someone who went from a Xylotex to a G540, and tripled his speed. The Xylotex is basically the same as the Probotix Sidestep.
my experiance G540 VS Xylotex

Here's another:
G540 - WOW!

Not a Probotix, but another similar board.

Most of these inexpensive drives are based on the 3977 chip, and all offer similar performance.

There are quite a few posts here from people that have upgraded to a G540 and gotten dramatic performance increases.

[ger21]

Would something like this work for the opposite end of the lead screw? VXB.com (kit7494)

That will work, but you should really have one on both ends of the screw. The Lovejoy coupler alone will not support the screw on the motor end.

The Joe's 4x4 hybrid uses those bearings. The Z axis in this video uses two.
Joe's CNC 4x4 Hybrid