5'x 9' CNC ground up.

[gurvy]

G'day to everyone, Well looks like a couple of weeks reading your posts, gave me the itch, So as usual, after lots of reading Im in, Hands on style.
After a trip to the steel recycling yard, Im on my way.
What do you guys have for recomendations on servo's, steppers and encoders, for a heavy gantry 150 lbs +/-

[ger21]

Don't be surprised if your gantry is closer to 300lbs+ complete. My 40" wood gantry is close to 100.

[Coogrrr]

Well it seems your starting where I started a nice steel frame and a nice chunk of aluminum for a gantry. I am nearly completed with the build process and need only to get off my butt and get it done.

My all aluminum gantry is close to 150lbs and is only 40" wide with everything on it except the router. I guess the key is in making the most smooth movement possible as wieght is only relevant to taking off from a stop and slowing to a stop for direction change. Of course the larger the stepper/servo used the less of an issue this is anyway. As to that (motors) i would suggest you calculate how much you need and then double it. So I knew I needed at least 200oz/in and I placed 464oz/in on it instead.

I have zero issue moving this around at 300+ IPM with the router attached not that I would go along anything near this speed while in the wood or plastic anyway it just shows that over built is better IMHO.

Good Luck and have FUN above all else! This is a real addictive hobby/job so be careful you don't make it your mistress! LOL

Coog

[gurvy]

Firstly, Hats off Coogrr,
You seem very close to finishing, I have definetly appreciated reading all your documentation, posts and posted videos. I do intend on following along in your footsteps with alot of the hardware / layout. So definetly post anything that was a show stopper, or any after thoughts you may have had. *compliment*
I've read alot on the Servo / Stepper dilema, and for this app I think Im going to stick with steppers. Im sure I'll kick myself later for this stepper decision (less computer play-ability). There is still the posibility of being talked out of the steppers.
comments anyone?
As for the frame above in the first post, Sheeesh. I hurt already, and I just got going. I hope to have the frame done being welded up and primed by the weekend. Maybe get my rails ordered up this week. Im leaning toward 25mm Y axis an 20mm for the X and Z
*PS, my wife already dislikes like my mistress,

[gurvy]

Im having a hard time sourcing some good linear rails / bearings for my x and y axis. Does anyone have some expertise to share regarding these units. What is the best product for the job on a larger gantry style unit. $$ vs performance. I'd like to hear of some some hands on experiences as well.
TIA.

Progress... I located smaller 13" linear screw / bearing for z axis (2 reverse steppers and screw). probably will be too small, but we'll see each motor was approx 200 oz-in. has not arrived yet
Found some servo's by electrocraft. model E3622 w/Hall and encoders, Im having some trouble finding specs on theses servos (anyone??) and hopefully have an amplifier to drive them being a mitsubishi MR-J2S-20A1.. Does anyone here know if the amplifier above is only good for 1 servo or will it drive 3? it would seem simple enough to find out, but the literature out there is deceptive.
The 5x9 frame is all buffed up, & primed, ready for rails.

[gurvy]

I've picked up a couple of these Servo's, these seem large enough on the surface. Can anyone tell me whether these brusless servo's will be appropriate for driving my X-Y axis ?? I assume from what I read, that I'll have to gear these somewhere near 10 to 1 to achive 480 oz in torque, (or is my thinking off)
Gantry apprx 200lbs, Im having a hard time understanding this. TIA.
Specs are..
Continuous Stall Torque 3 lb-in. (conv. 48 oz-in)
Peak Torque 7.5 lb-in (conv. 120 oz-in)
Max Continuous Operating Speed 5000 RPM
Inertia lb-in-sq2 0.00012
Weitht 2.8 lbs
Damping oz-in/kRPM .66
Frcition Torque lb-in 0.07
Ke Voltage Constant V/kRPM 8.4

[gurvy]

I now have some servo's (2) and some steppers (2). some linear rails (ouch on the pocketbook) and a single servo amp, I'll need to hunt down another. hopefully I can make these things all work together. I am really hoping the servo amp will run at least my x axis. I'll hopefully have those rails next week.
Anyone have any suggestions / experiences on mounting the gantry for height and base width?

[gurvy]

Progress. Gantry made while our 18 month old was chatting online , he colored my flat panel with crayon and pen, little eaten crayon bitties all over my desk and cola in my keyboard, (no.. it doesnt work anymore) and yes my honey was upstairs the whole time. ... The servo amp I picked up turned out to be an AC servo amp, apparently I have Dc Servo's, (learning curve), so now I need to source some DC servo amps. I think next week I'll be taking those hardened steel rails in to have some linear support pegs machined in..
here's some more pics.

[gurvy]

Shopping.... ebaying... electronics... power supplies...servo amps....hardware.... shipping.... parts.... parts.... parts..
I gotta go mow my lawn pretty soon before my wife kills me.

Well, Im currently building the electronics to drive a couple of high resolution servos X&Y and a couple of steppers for my Z axis. I ended up using PIC-SERVO SC IC's to interface to the PC and build the boards to save some $$ ... we'll see... . I successfully converted a test computer ATX power supply to drive one servo. (seems amperage is low though), so I'll probably daisy chain 3 or 4 P/S's together to achieve a 48V supply for all of them, Hooked up to my servos and servo amps, I have a single running on the bench, I believe this unit will hum once connected. I am really happly with the servo settings, being that the speeds voltages are all adjustable by input voltage, (slow precision) or (fast transitions). Electronics sure take alot of time testing and research, but well worth it. I'll post up some more progress pics for anyone who is following this build.

[mxtras]

Are you planning to support the rails? It appears you have open bottom bearings, is that correct? - -edit - after re-reading things, I see that is your plan. I can't read at night - I never went to night school.

Nice job so far, by the way. Keep the updates coming!

Scott

[dz1]

how are you planning on having the support pegs made?

only thing i could think of was to grind flats on the bottom of the rail, drill a partial hole up from the bottom with a carbide bit and then press fit a stud in?

i used unsupported rods for mine and had to compensate by adding bearings that ride on frame elements to support the extra weight

my tools werent up to the task of trying to machine teh hardened rods (i could barely cut them to length with an angle grinder..tough stuff)

let us know what the machine shop comes up with

[gurvy]

I did end up taking the rails into the machine shop, it cost me 80 bucks, but well worth it seeing as how I couldn't even grind the end of these rails. I had them drill and tap 1/4 inch holes for me 1/2 way into the 1" rails. I then used ready rod and threaded it in, I used nuts and lock washers top and bottom on my frame to support the threaded rod. This worked out nicely because now I can adjust height along the length of the rail. My maximum run is about 30" unsupported but it seems to be plenty. I will post some more pics once I find some batteries for my digital camera. I had to steal the double AA's from my camera to power up the lights on my little ones toy truck, sheesh.