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mcArch
11-26-2007, 10:47 AM
I've posted some of this project in another thread, but I think I may have maybe hijacked Lamicron's "Plasma table construction in progress" thread a little, Sorry lamicron, did not intend that, Pete Stenebaugh has been very helpful with this too. These last few photos did not make it into the last post in that thread.

Issues I'm thinking about are thc, how important is it?, extreme accuracy of parts is not critical, cutting like 14ga. to 3/8" material with plasma Miller 625.
The machine is also meant to mount a router to & use to cut wood, foam, & plastics.

Still working on the low cost end bearing mount for the threaded rods & the ball screw on the z-axis. I am thinking of adapting a tapered bearing set for the thrust bearing for the one end mount of the ball screw (Z-axis) & for the 3/4"10 acme threaded rod on the X & Y axes. Also, the synchronization of the Xaxis drive rods I have not nailed down, thinking of using a chain & sprockets. Would a bicycle chain & sprockets have too much play in it for this use? how about a chain from like a garage door opener? I suppose that if the tolerance is +/- .003" or so, or the added backlash between this chain/sprocket plus the threaded rod/nut is +/- .004 or .005" it would be ok. ??


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scrambled
11-26-2007, 11:44 AM
now that is a big piece of round stock to use for the x axis!!! I love it. Bigger is always better.


Keep up the good work



Steve

mcArch
11-26-2007, 12:45 PM
Well, I figured I could not go wrong, & I has those columns sitting in my stock racks here for about 7 years, so, they'll work, nice & stiff, & keep it simple.
thanks.

mcArch
11-27-2007, 12:37 AM
The X gantry is rolling on the 3 1/2" pipe rails today. The y rails at the top of the x gantry are deflecting about .030" (with feeler guages) under the preload of the tensioners, see pics. You can see a little light between there.

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I will have to fabricate a tension rod truss piece for underneath these 2-1/2" pipe rails to take that out. Other than that, it is rolling very smoothly. I wanted to make the end connections adjustable so the checking & wracking due to moving the table around & welding could be calibrated & it's trussed to keep the weight down.

At first I located both adjustment bolts (both the compression pipe & the two 1/2 threaded rods) on the lower end where the rollers are, this allowed the roller bracket to twist under its own weight ever so slightly.
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I realized I should have welded the compression pipe at the lower end to take out the moment stress & put the adjustment bolt at the top. It is much stiffer this way.

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More next week

Cheers.

mcArch
02-27-2008, 12:32 AM
We've got the machine running now, the x only chugs along at like 12ipm cutting with the 3/4" dia router bit, have not turned the plasma on yet, next couple days will tell that. We had to do some fine tuning with our low cost bike chain drive, the sprockets are really too thin for alignment, but we were able to make the vinly lined guides & use a spring loaded tensioner underneath that just lets the chain ride on a small section of 1" pipe. It seems to work ok for now. We got another 400ozin motor to slave the x with on the other rod, but we didn't get the mount bolts aligned well enough yet, then the keyboard or something must have hit the y motor drive & it got toast, so we unhooked the x-slave motor that we got & used that driver for the y & was able to get it back up & running at the slower speed at least. We still have to make an enclosure for the electronics, a better table surface for the monitor/keyboard, & a cover for the plasma while it's in router/dust mode. The threaded rods could use dust covers too.

We have a problem with the limit switches falsely tripping in Mach though, we could not get it to stay reset, so I just turned it off at the switch & it's working ok, just have to watch it like a hawk in case something goes wrong. I'd like to get that resolved, but have no idea what else to try, have tried all the stuff the mach manual & FAQ's suggest, nothing helps. We have all the switches set up where the circuit is closed until tripped, maybe that's backward? I cannot figure it out.

Working well overall, cannot complain for what we have into it . . . still lots to do, but I think it can produce at least.

I have a couple short videos (.mov's) about 1mb or so, but I cannot figure out how do knock the size down to post them here in the zone, I can email if anyone is interested.

mcArch
03-01-2008, 10:27 PM
Much thanks once again too everyone on CNCzone, the info here in the zone is really great & has been a tremendous help in our building this table. Here are some of the first pieces done with the plasma setup, I'm still switching the plasma on by hand with a remote switch I mounted by the computer . . . still trying to figure out how to control it w/ Mach3.

Is anyone using Probotix drivers & controller? I am trying to figure out if I can use one of the pins to control the torch on/off on a plasma setup. I will have 3 axes with 2-motors on the x axis. Motor A will be slaved to the x. Anyone know if there's a way to use one of the home/limit switches(typically an input pin) for an output to control the plasma on/off? Also, how would I do it? with a relay, & how do I figure what specs I need the relay, amps/volts?

On another note, I think I don't quite have enough torque on the x drive with just one motor. When you lose steps, does it sound like a toruqe limiter in a cordless drill? and the motor keeps trying to turn but the rod does not? My solution is to add another motor to the other drive rod & slave it to the x motor. You can see in the one photo if the circle where I lost X-steps, I have to listen to it & when I hear it start "grinding" I give the chain a little pull, I think it's just not enough torque on that axis. Really bites to have to try to re-align it & re-run the program.

Motors: 400oz/in steppers, bipolar parallel, 4 wire.

millman52
03-02-2008, 07:54 PM
Much thanks once again too everyone on CNCzone, the info here in the zone is really great & has been a tremendous help in our building this table. Here are some of the first pieces done with the plasma setup, I'm still switching the plasma on by hand with a remote switch I mounted by the computer . . . still trying to figure out how to control it w/ Mach3.

Is anyone using Probotix drivers & controller? I am trying to figure out if I can use one of the pins to control the torch on/off on a plasma setup. I will have 3 axes with 2-motors on the x axis. Motor A will be slaved to the x. Anyone know if there's a way to use one of the home/limit switches(typically an input pin) for an output to control the plasma on/off? Also, how would I do it? with a relay, & how do I figure what specs I need the relay, amps/volts?

On another note, I think I don't quite have enough torque on the x drive with just one motor. When you lose steps, does it sound like a toruqe limiter in a cordless drill? and the motor keeps trying to turn but the rod does not? My solution is to add another motor to the other drive rod & slave it to the x motor. You can see in the one photo if the circle where I lost X-steps, I have to listen to it & when I hear it start "grinding" I give the chain a little pull, I think it's just not enough torque on that axis. Really bites to have to try to re-align it & re-run the program.

Motors: 400oz/in steppers, bipolar parallel, 4 wire.

I know nothing about Probotix drivers & controller & haven't heard of them.

Typically if you are going to slave a second motor to the same axis, In Mach there is a simple setup to slave the 2 motors together. you need a seperate driver to control the slaved motor & the chain from side to side isn't needed (& probably not desired as it only adds friction to overcome).

Yes if a motor is stalled from not being able to overcome weight/friction it will sound like it's wanting to come apart.

My on off controls are worked through a remote relay (table imput output) card. Mach turns on then off the relay to operate your torch with a MO3 & MO5 command respectively

mcArch
03-03-2008, 11:41 AM
Millman, what is the relay driven from? Does the relay card run from the breakout board?

millman52
03-03-2008, 06:39 PM
In my case I have a THC from www.candcnc.com the relay card is mounted at the table & hooked to the back of the THC using a 25 pin straight through parallel cable. The THC box sits beside my computer.

Since I know nothing at all about your system maybe a look at this relay card. Then look at the pdf wiring diagram for the card, might help get you started in the right direction. http://www.cnc4pc.com/Store/osc/product_info.php?products_id=148

I'm not saying this is what you should buy merely that it is similar to most relay cards. Almost every manufacturer has some sort of solution for switching optioinal equipment on & off.

Can you post a link to the probotix drivers break out board etc. It would help if I knew what you have to work with.

mcArch
03-04-2008, 12:56 AM
Here's the link to the breakout board I'm using:

http://www.probotix.com/breakout_boards/pbx-2/

Len is the guy who designed them & owns Probotix, he designed it to work with Mach3.

& here's the driver board that I'm using for all 4 motors:

http://www.probotix.com/stepper_motor_drivers/SideStep/

I'll take a look at the links you sent, thanks.

I got the X-axis working, you can see the "A" motor on the left side under the monitor, it's slaved to the X, I had found the slave setup in Mach3. I just took the chain off. "A" lost a few steps a couple times but I finally got it working pretty well, lots of adjustments on that left side (bearing preload & motor/shaft alignment). I have gotten 15ipm so far, haven't tried it faster yet, probably will step it up a little tomorrow.

Len also has a relay board there,
http://www.probotix.com/relay_boards/rbx-1_isolated_3_channel_relay_board/

I'm just not sure where it would connect to the computer system, since I am using the A-axis motor where that rbx-1 relay board would normally connect, plus that Miller Spectrum 625 trigger signal is I think a 5v signal, not sure the amperage in the signal. Right now, I just have a remote wire run to a switch just like my limit switches (rated at 5A/125VAC) so I can switch the plasma on/off by hand.

Overall I can't complain, I do have nearly 48x96 cutting area & a full 16" in the z. My X is at 94.25" right now, but I can move the limit switches a little & get it to about 96.5".

millman52
03-04-2008, 06:20 PM
Your best bet is to contact probotics tech help on this one. At a quick overview of the wiring schematics for the Probotics boards I can't really advise you what to do. I would think there would be a way to connect the relay board in addition to running 4 drivers.

millman52
03-12-2008, 09:48 PM
Upon further research on installing a relay bord with your system. You'll have to install a second parallel port & additional break out card + the relay board. all together less than $100.00.

bekx
03-13-2008, 05:42 AM
i think millman is right , i just looked at your wiring diagram, couldn't see any spindle/plasma relays ont the breakout board , so u need a relay board and a way to use it (could hack in the unused wires of the printer cable not the most elegant option)


i'm in the same position right now, the table is moving but i can't control the torch from mach, my problem is i don't know what wires to hack from the plasma... opened it up , opened the torch too, but one wire changes the color somwhere in the cable and confuses me. I also have the torch cable too small.

mcArch
03-13-2008, 10:26 AM
That's what I've come up with, thanks. I called Miller plasma support & the guy there told me which wire to cut (the purple one in my machine). I just ran 14ga wire to a switch by the controls/computer station & I watch for my M03 code line & the pause then I switch it on, then off again when it goes to the M05 code, then on, etc. I also can hit pause, then raise the z with the hotkey(page up in my case) then restart. It's working for now, or I can just loosen the clamp for the torch head & raise it a little for that section.

Bekx, you should call the mfr. of your plasma machine & ask the techs what wire to tap into so you can at least put a remote switch in.

I'm looking at doing a separate relay board that can provide on/off & thc - the links you sent earlier are a great start Millman, thanks.

mcArch
03-13-2008, 10:28 AM
I have lots of router work to do for now, making forms for concrete panels. The Plasma is ok for the simple stuff I'm doing right now (& not alot yet), it's thicker plate(3/16 & up) so it stays pretty flat, plus I can turn down the amps to reduce it.

millman52
03-13-2008, 04:14 PM
Installing a 2nd PCI parallel card is easily done. I bought a couple cards from ebay $10.00 each. http://cgi.ebay.com/High-Speed-Parallel-Port-PCI-Card-Adapter-PC-25-pins_W0QQitemZ320225425368QQihZ011QQcategoryZ31534QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

They install just like a modem card In fact I have high speed internet & removed the modem & installed the #2 parallel card in that slot.

After that it is a simple matter of the second Breakout board & an inexpensive relay board. Go into Mach & map the M03 & M05 command lines to port 2 pin XX & you have it The relay card & possibly BO board will have to be powered for the relay(s)(usually 12V) same source you are using on your other boards probably will work.

What I am using is different from your setup but as I understand what instructions on the Probotix boards, That's what you need to do. Hopefully someone with more experience with Probotics can help. I am merely giving the probotics instructions my interpretation.

Neil

mcArch
03-17-2008, 12:42 AM
Here's a video of the plasma as it stands, cutting 12ga at 12 ipm (should have had it at 15ipm)

YouTube - CNCtableOperation05

It cut 1/4" aluminum plate fine, about a 6' long cut along the x-axis, no problem, pretty clean. The Plasma machine is a Miller Spectrum625.

The motors do not want to push this thing faster than 15ipm, that works well enough for now. - lots of ideas for improvement later, thanks to many on the Zone.

-Mike

millman52
03-22-2008, 01:26 PM
You need a good bit more speed for plasma on 12 Ga. steel. But Hey!! it works much better than the other one you have . Right!!?? :cheers:

mcArch
03-22-2008, 01:49 PM
Thanks Millman,
Yep, works a little better than the manual one with my eyecrometer. My motors on the X are just too small (400oz-in), &/or my gantry design has a little too much friction, (the 3/4" allthread w/ coupling nuts are not the greatest, but hey, the price was right!) I already have plenty of ideas of how I'd change it all, but I have to cut with it like this for awhile . . . time, time.

What size steppers did you end up w/ on your X/A?

:cheers:

millman52
03-22-2008, 02:12 PM
Thanks Millman,


What size steppers did you end up w/ on your X/A?

:cheers:

Your gantry is pretty heavy too. Hey I'm not knocking it. I followed your build & know you are running & don't have a big bundle of cash wrapped up in it.

If you decide to build another later you have gained most of the needed knowledge to streamline your build. The do's & don'ts if you want to look at it that way.

I have 740s on X,A & Y 4:1 belt reduction & rack & pinion. I have a 500 oz in on my Z with a screw drive there. Mine will achieve around 200 IPM & swap directions without beginning to loose steps.

I am using O/A so most of my speeds on 3/8" - 1" steel are from 18 IPM to 26IPM. It's really nice having the speed for rapids & returning home.

mcArch
03-22-2008, 03:11 PM
That's the way I'm looking at it, it was a good practice run, I already have a guy who will buy this one if I build another, so it'll get worked into the plan.

I'm just turning down the amps to run it slower where the table likes to be.

On another note, I have a little slag on the bottom side of the cuts, even with thicker plate: 1/4". It chips off easily enough with a chipping hammer, but sure would be nice if there was not any to chip off. Is that a result of the speed?, or will I always have a little to chip off from the underside?

:cheers:

--Mike

millman52
03-23-2008, 04:41 PM
I'm just turning down the amps to run it slower where the table likes to be.

On another note, I have a little slag on the bottom side of the cuts, even with thicker plate: 1/4". It chips off easily enough with a chipping hammer, but sure would be nice if there was not any to chip off. Is that a result of the speed?, or will I always have a little to chip off from the underside?

:cheers:

--Mike

Mike It is my understanding there is almost always a bit to have to deal with. There are just so many variables. Air pressure, quality of air, having all consumables matched, speed being exactly correct as well as earth venus jupiter & mars being in perfect alignment to get "dross free" cuts.

I use O/A & it's the same thing. I was cutting a sheet of 3/8" steel last night. I usually can get it clean enough a wire wheel on a 4" angle grinder is all that's needed for clean up. I was getting mere dross than normal. Cleaned tip, changed tip, finally came down to needing about 1/2 # more on the Acet. & about 3# more on the pierce Ox & picked the speed up 1.5" IPM from where I normally cut 3/8. I think even the relative humidity comes into play. I can always get good clean cuts across the edge but the amount of dross varies like the weather.

mcArch
05-02-2008, 11:19 PM
On another note, does anyone know if Mach3 can handle a setup with a swiveling router head in 2 directions along with the typ. X,Y & Z axes? Axis B = rotate about the Z axis, Axis C = rotate about the X/Y axis. Check out this sketch of what I'm thinking. In reading the Mach manual, it seems that it (Mach3) cannot control the tool when set up like this, but maybe I read that incorrectly. If Mach cannot do it, does anyone know of another controller that can do it (& not break the bank for the license)? I am pretty sure that mach can control a fourth stepper axis that rotates about the X and is essentially like a lathe spindle to hold a part & control how the part is rotated to be machined while the router head mills x,y,&z, but what about the rotating milling head (as well)?

Just thinking here . . .

mcArch
06-04-2008, 08:58 AM
I have a motor, the literature of which lists the rotor inertia as 4.4oz/in^2. The motor sizing/system calculating software I'm using has the rotor inertia in units of in-lb-s^2. and shows a reflected inertia to motor of 0.011222939in-lb-s^2. It indicates that rotor inertia of the motor must be at least 1/6 the reflected inertia. Does anyone know what the relationship of those units are, or how to get from the oz/in^2 to in-lb-s^2?

Thanks in advance for any help

--Mike

cobree
05-27-2009, 12:00 PM
Hi this is my first visit at this forum, and I really like your idea how to build your table, I will try to make an simular but smaller.
I have a some tubes diam 45mm, Is it something I should think about? Did you have some adjustments on the base, and the adjustment for the boom you had an comment to make the smaller welded down and adjustable in top, and this should be more stable, why?

I will do a drawing and put up here it is more easy to discuss an picture...

Really nice work...

//Conny

mcArch
05-29-2009, 11:09 PM
You just have to make sure the 45mm tubes don't bend too much with the load. I built a digital model of the structure of mine & put a lateral load of 50lbs. at the machine tip, then held the deflection to 0.005". Designed the connections & structure according to that. Also, I would make the bearings differently if I were to do it again, make it so there's a set above and a set below the pipe so that you don't have to clamp them laterally against the table to get it stable (pre-loads the bearings too much I think). I made that gantry so that I could adjust it to fine tune the tolerance. I'd also use rack & pinion to drive the X & Y axes - it's about the same, price wise, as the lead screws I ended up with. You can get the rack & pinion at www.mcmaster.com (McMaster Carr). Also, try to make it so you can shield the bearings & pipes from dust/debris & enclose them if possible, use like a brush seal or something. Try to get the Z-axis ball screw inside of something too to protect it from dust & debris. millman52 has a great build and some great ideas, check out his build log too. Post a pic or sketch or something & we can talk more about it.

millman52
05-30-2009, 10:18 AM
You just have to make sure the 45mm tubes don't bend too much with the load.

Also, I would make the bearings differently if I were to do it again, make it so there's a set above and a set below the pipe so that you don't have to clamp them laterally against the table to get it stable (pre-loads the bearings too much I think).

I made that gantry so that I could adjust it to fine tune the tolerance. I'd also use rack & pinion to drive the X & Y axes - it's about the same, price wise, as the lead screws I ended up with. You can get the rack & pinion at www.mcmaster.com (McMaster Carr).

Also, try to make it so you can shield the bearings & pipes from dust/debris & enclose them if possible, use like a brush seal or something.

Try to get the Z-axis ball screw inside of something too to protect it from dust & debris. millman52 has a great build and some great ideas, check out his build log too. Post a pic or sketch or something & we can talk more about it.


"if I were to do it again, make it so there's a set above and a set below the pipe"

Probably very good advice for a plasma table. However in your case using a router the way you have them designed preloads the gantry from side to side, as you stated. This would help stabilise cutting froces from a router.

"I made that gantry so that I could adjust it to fine tune the tolerance."

I think also a very good idea.


"Try to get the Z-axis ball screw inside of something too to protect it from dust & debris."

Also with rack gears be sure to either position the teeth out to the side or teeth down. This will prevent dust from accumulating in the gullet of the teeth.