[Erick Davidson]

Hello All!
I just wanted to post some pictures of my project thus far. This has been an on again – off again (mostly long periods of off) project for about 2 and a half years as I scrounged for materials and parts and refined my design. I asked some questions early, mostly regarding electrical questions and had little response. So I thought I would come back later when I had some progress to show before I asked anymore.
My design grew from ideas pulled from here (thanks guys!) and elsewhere, but was also driven by what I found on eBay and the local scrap yard.

























So far this project has influenced my day job as an R&D mechanical engineer, I have used ideas and components I first sourced for my personal project on new automated equipment and systems costing several hundred thousand dollars.
Feel free to comment and let me know what you think!
Cheers, Erick

[DanOSB]

nice build.. we have simlar design as yours

we are almost finished wtih that table.. few more days left on it

i know how it feels about not finishing as other things have came up

[millman52]

WOW!!!! I'm afaid your main frame isn't heavy enough.

Great job Now for the sparks.

[WSS]

Very clean! that puppy should move like oil on glass. Does the head have room for three torches? It's hard to tell, after some discussion the pics will make even more sense. How much room do you have under the gantry and /or including the Z lift? Ebay is a neat place to scrounge for hard to find items and rewarding when you make a good purchase.

Let's see it cut some stuff soon!

[Torchhead]

Have you been able to run the gantry under motor control? It's a beautiful build but those tall gantry arms with that much weight are going to present some flex and vibration problems. You can figure the forces involved. Consider with plasma you will be slinging that gantry around at up to 200 IPM and jackrabbit stops and starts. Your table won't vibrate but those columns might. Slight movement at the upper part will cause lots of movement down at the cutting tool/torch tip. you HAVE to have good acceleration at speeds to get sharp corners and tight arcs.

I think I saw a servo motor and gearbox. Hopefully that is your final drive to the belts. The gearing ratio of a direct drive with those pulleys and belt will leave you with blazing rapids but poor resolution and torque. A reduction between the motor and belt is needed to reverse the "PI" effect of the pulleys.

TOM CAUDLE
www.CandCNC.com
Totally Modular CNC Electronics

[Erick Davidson]

Greetings All!

Hope your Memorial Day weekend was enjoyable. I was out of town for four days so I was out of touch.

Thanks for the comments. Initially, I have it set up for three functions, plasma, oxy/fuel and a drill or router. The parts I first designed this for have around 200 3/16th holes per assembly in .090 sheet, both 304 stainless and CRS. I know plasma isn't the right process for that, so I intend to drill all the holes first with a pneumatically actuated drill (I plan to make a sleeve or collet to put a 3/16" bit in my 1/4" router).

The uprights are 4" x 4" x .25" aluminum gusseted, the gantry span itself is 5" x 5" x .25". I bought everything the local scrap yard had above 3" x 3" at the time. Eventually, I am adding a 6" tall water table on top of the 12" I beams and will have about 9" clear after that. I actually made the uprights as tall as my material on hand allowed. Thought that if it became an issue I could shorten it without too much effort.

The motors are 1100 oz 3200 rpm at 90V peak MCGID3304 servos through 100:1 gearboxes to 4" PD sprockets. Which as near as my newbie math tells me will give me 326 ipm at 75V (the rating of my power supply). Does that sound correct?

Mechanically, I still need to make adapters to mount my NEMA 34 motors to my Bayside gearboxes as well as put keyways on my jack shafts, before I can make it move on it's own.

Electrically (my weakest skill), I need to wire everything to the MP1000 and geckos. I asked earlier about suggestions as to wire gauge, and shielded vs. unshielded for the various components, motors, encoders, limits, etc. and did not get a response, so I am using what I have to get started. Any suggestions would still be appreciated.

Have to get back to work!
Cheers, Erick

[Torchhead]

Electrically (my weakest skill), I need to wire everything to the MP1000 and geckos. I asked earlier about suggestions as to wire gauge, and shielded vs. unshielded for the various components, motors, encoders, limits, etc. and did not get a response, so I am using what I have to get started. Any suggestions would still be appreciated.

If you are running single ended encoders they HAVE to be shielded and not run along side the motor power wires. If the drives have differential receivers, and the encoders are differential you can run them in unshielded wire (but still keet them sparated from the motor power wires. Limits to the MP1000 go to the Table I/O card that has noise suppression and then they feed internal opto isolators that provide isolation and added noise rejection. The current is small so you can use any wire (24, 22, 20 Ga). We recommend twisted pair unshielded. if you do use shielded connect the shields at one end only and a non-table ("dirty") ground

Motor cables need to be 16G or larger. Shielded is not required but if you do, don't make the shield one of the conductors and tie it on one end only.

Go back and read a few of my posts on grounding for plasma. Also there are some detailed posts on my Yahoo Support site (CandCNCSupport).

TOM Caudle
www.CandCNC.com

[Erick Davidson]

Thank you, Torchhead, that helps confirm I am at least going in the right direction.

Does anyone know if my estimation on performance is close? Would a servo rated at 3200 @ 90v put out 2600 @ 75v? Is voltage what determines RPM?

I am more familiar with using hertz to control RPM with a VFD in my AC industrial applications. I have been quite successful using an encoder for position control with a PLC and VFD controlled 480V 3ph AC motors. I am using them on a pick and place barrel handling system. Inspired by examples here! I will have to see if I can post a video.

Cheers, Erick

[millman52]

Erick, You mentioned earlier drilling 3/16" holes with your router. I'm assuming your router is variable speed? Are you going to incorporate a mist unit for cooling on the bit?

[Torchhead]

Thank you, Torchhead, that helps confirm I am at least going in the right direction.

Does anyone know if my estimation on performance is close? Would a servo rated at 3200 @ 90v put out 2600 @ 75v? Is voltage what determines RPM?

I am more familiar with using hertz to control RPM with a VFD in my AC industrial applications. I have been quite successful using an encoder for position control with a PLC and VFD controlled 480V 3ph AC motors. I am using them on a pick and place barrel handling system. Inspired by examples here! I will have to see if I can post a video.

Cheers, Erick

Brushed Servos are basically DC motors. Their RPM is linear with voltage. The torque comes from current so you don't loose torque with lower voltage just RPM. One of the nice things about DC motors. Your calculations are correct.

VFD's work well on 3P AC motors. It's harder to control the RPM of Universal motors because although speed drops with voltage, so does torque. A good control has some form of torque feedback but even with that the adjustment range is limit to about 60% of the upper range. It's not possible to control the speeds of normal induction type or capacitor start/run AC motors.

TOM Caudle
www.CandCNC.com

[Erick Davidson]

Well it has almost been a year since I first posted this build. I have gotten a lot done, I am about to 90% on the mechanical, with some small brackets to make for sensor flags, mounts for the e chain tray, mostly small odds and ends. The sort of stuff that eats up time seemingly disproportionate to your progress.

I haven't made the water table, but that isn't going to keep me from starting this up soon. I will try to take some new pics to put up by the weekend.

I have all my wiring routed and traced, terminated at the switches, encoders, servo motors, etc. I am almost finished bread boarding my power supply, MP-1000, BOBs and Geckos on a temporary table on one end of the frame where I plan to mount my MCC enclosure once all the start up trouble shooting is over and I tidy everything up in the box.

I have a couple (actually several, but I will ask these as I can act on them) questions about wiring. Perhaps not the specific forum to ask, but it is for a home built plasma.

1) the Gecko wiring, depending on who's build you look at have external capacitors(?) added and some suggest a dedicated external 5V dc power supply separate from the computer. Are these needed, do they help?

2) I have a Logitrol 72vdc power supply (from Aussie land) and it has the output with a blue and a brown wire, with the green/yellow ground clipped. The Geckos need the proper polarity brought in, correct? How do I determine which is + and -? Is it standard down there like red and black are here?

3) Grounding issues, I will need to read up once again. I started this project more than three years ago (boy, am I slow) and know I need a ground rod into the earth for some of it. Any highlights I should keep in mind? Plasma goes here, motors go there, sensors and encoders here, do or do not ground the enclosure to the table.

Thanks again to all the inspirational people and help here!

Cheers, Erick

[millman52]

Well it has almost been a year since I first posted this build. I have gotten a lot done, I am about to 90% on the mechanical, with some small brackets to make for sensor flags, mounts for the e chain tray, mostly small odds and ends. The sort of stuff that eats up time seemingly disproportionate to your progress.

I haven't made the water table, but that isn't going to keep me from starting this up soon. I will try to take some new pics to put up by the weekend.

I have all my wiring routed and traced, terminated at the switches, encoders, servo motors, etc. I am almost finished bread boarding my power supply, MP-1000, BOBs and Geckos on a temporary table on one end of the frame where I plan to mount my MCC enclosure once all the start up trouble shooting is over and I tidy everything up in the box.

I have a couple (actually several, but I will ask these as I can act on them) questions about wiring. Perhaps not the specific forum to ask, but it is for a home built plasma.

1) the Gecko wiring, depending on who's build you look at have external capacitors(?) added and some suggest a dedicated external 5V dc power supply separate from the computer. Are these needed, do they help?

2) I have a Logitrol 72vdc power supply (from Aussie land) and it has the output with a blue and a brown wire, with the green/yellow ground clipped. The Geckos need the proper polarity brought in, correct? How do I determine which is + and -? Is it standard down there like red and black are here?

3) Grounding issues, I will need to read up once again. I started this project more than three years ago (boy, am I slow) and know I need a ground rod into the earth for some of it. Any highlights I should keep in mind? Plasma goes here, motors go there, sensors and encoders here, do or do not ground the enclosure to the table.

Thanks again to all the inspirational people and help here!

Cheers, Erick

(1) Capacitors? I think you are referring to resistors. Refer to Gecko literature for the power supply & instructions about the resistors. Literature down loadable from Gecko.

(2) Color probably right but use a voltmeter on DC. At least my chepo digital will show + or - Example: red lead from meter to negative -72V Red lead to positive 72V.

(3) Lots of confusion on grounding...... Here is the short version as I understand it. Ground rod at or near table, hook case ground of plasma to that local rod. Shielding on your cables hook to ground on one end only & inside your enclosure best I remember. Your enclosure, Isolate it from your table & all grounds there go back to source.


I'm sure I missed something. & I am equally sure someone that understands more than I will add or correct me.

[Erick Davidson]

Thanks Millman52, this shows how weak my electrical skills are.

I am fairly decent at following simple schematics, but the schematics from CandCNC as well as Gecko don't seem very specific. I do best with a list of gauge sizes, component lists, etc. I guess they are so general because so many people mix and match components.

Most of the schematics I find seem to be for stepper systems, the one I am questioning shows a Gecko 320 with a jumper from encoder + to err res and something across the power ground and DC in labeled "100V-10000 uF CAP", is that a resistor? I see other schematics with something similar, but a different value, but those were stepper system schematics.

I don't know the why, so I don't know the purpose. I will check at my local Radio Shack and see if the kid there knows what this is.

I can see the finish line, so close!

Cheers, Erick

[millman52]

Thanks Millman52, this shows how weak my electrical skills are.

I am fairly decent at following simple schematics, but the schematics from CandCNC as well as Gecko don't seem very specific. I do best with a list of gauge sizes, component lists, etc. I guess they are so general because so many people mix and match components.

Most of the schematics I find seem to be for stepper systems, the one I am questioning shows a Gecko 320 with a jumper from encoder + to err res and something across the power ground and DC in labeled "100V-10000 uF CAP", is that a resistor? I see other schematics with something similar, but a different value, but those were stepper system schematics.

I don't know the why, so I don't know the purpose. I will check at my local Radio Shack and see if the kid there knows what this is.

I can see the finish line, so close!

Cheers, Erick

100V-10000 uF CAP = 100 Volt - 10000 microfarad. & yes that is a capacitor

I'm sorry I didn't re-read the entire post I assumed stepper system. My Bad.

I have to admit I know very little about electronics myself.

[Erick Davidson]

Well, Radio Shack didn't have capacitors rated that high. They don't really carry much DIY stuff anymore. Better than nothing, but they are really more of a cell phone store now. Guess I will need to search on the interwebs. Most of my parts have come from the online as it is.

My power supply, the 700 watt 75 vdc Logitrol, only has 14 gauge lead wires coming out of it. Is that sufficient? That is what it came with, so I would imagine yes. I guess being surrounded by 5 to 20 hp motors all day has me in overkill as to the necessary gauge for the little servos.

Thanks again for the help!

[nwrepair1]

Using a separate 5 volt power supply is the best method. If you get a short somewhere in that 5 volt system that blows out the power supply, you only have to fix the short and replace a power supply. Use a leg off your computer power and you may blow up your motherboard. The capacitor is used to smooth out the DC power. It removes the ripple that is created when you make DC from AC. Reduces hum in Servo and other more complicated things. You can use any cap at least 100 volt and at least 10,000uf. Check online: Digikey, Mauser, Allied. Buy new not EBay. Used caps lose their capacity like old zinc batteries. On that grounding rod: New electric codes use multiple ground rods in a horizontal bed. One vertical rod does not work well in soil that is sandy or not damp. Clamp onto the main water pipe and you will have a better ground. If you used shielded wire (you should to avoid noise problems), the shields and drain wires should be grounded at one point at the servo control, Do not attach shield or drain wire at other end. Best way to connect servo to power is to use twisted pair (shielded wire #14) not near the ground wire for the servo. Run all servo grounds directly to your main ground on machine. Do not combine these grounds with grounds from control wiring or servo control wiring. Any 120-240 volt wiring should be be at least 4 inches away from any low voltage wiring or put into some type of metal conduit. Those shields and drain wires I talked about should be connected to the ground wire connected to the water pipe (or ground rod). Use a terminal block near the servo control. Do not ground those wires or the terminal block to the machine frame. This particular ground point is a floating ground and prevents a ground loop with the main electric ground which by default is grounding the frame of the machine. All this is necessary to prevent electric noise from corrupting your control signals. (I do this for a living). It's 3 AM now and i need to sleep and work late today. Any more info will be after 11PM west coast time.

[Erick Davidson]

Wow, nwrepair1, thank you for the detailed explanation!

That is just the sort of thing I really need, not just what to do, but why. I have very sandy soil, that is hard packed and dry most of the year. I will pick up 2 or 3 ground rods this weekend.

I have a couple more electrical ground neophyte questions. Servo motor case grounds, which ground should I land those to? Also, off the power supply I have DC+ and DC-, correct? You don't ground anything to DC-, right?

I ran all my encoders with shielded 22ga., my homes, limits, and e-stops are unshielded 16ga. (inexpensive extension cords).

My servos are run with 14ga extension cords (it was less expensive to by extension cords than rolls of wire).When I strip the sheathing off the wire bundle, the three wires inside helix around each other for the whole distance. Is this wrapping of the wires around each other what people are referring to when they say "twisted pair"?

I will pick up or order a 5VDC power supply and the capacitors over the weekends as well.

I will snap a pic of my bread boarded controls to see if anyone can spot something I have done that would release the magic blue smoke when I power this up.

Thanks again, everyone!

[nwrepair1]

The use of extension cord to power the servo is going to give you lots of trouble. The DC power going through an extension cord will create 2 magnetic fields that will contaminate the signal going to and from the encoders. Your machine will lose it position and break something. I have seen gantry heads actually slam right off the gantry. Crashing into the table is another common result. Once you have that happen, You will wish you spent the money for twisted and shielded wire. Twisted pair wiring is 2 wires that are tightly cross wrapped throughout the length of the cord. Looks like two wire ends twisted together with a wire nut. Not like the helix wrap of an extension cord. Ground the servo with a separate 16 gauge wire directly to you main machine ground. Buy a grounding kit for an electric panel at Home Depot (looks like a terminal bar with a main screw to attach main ground). Attach your servo grounds to it and run as short a wire as possible to the main machine ground. Or connect the incoming main ground wire to the grounding bar. Even twisted pair without shielding would be better than electric cord. Go to a real electronics store for wire. They usually have wire on 500FT+ rolls and cut it by the foot.

[Erick Davidson]

Thanks for the insight, nwrepair1.

I am doing a search on 16ga twisted pair shielded and I seem to only be finding small gauge telephone wire. I have the encoders running about 4 inches away from the motors in the e-chain. I have the plasma lead in the same tray, as I have seen others do. I was most worried about that and thought the idea was to isolate and shield the encoder signal. I am using shielded on the encoder's cables themselves, will that be sufficient?

The rest of the switches aren't effected by RF are they?

I don't remember who I got the suggestion to utilize the extension cords from, but it was on one of the builds here. The rest of the spools at Lowe's didn't offer anything shielded.

Cheers, Erick

[millman52]

A quick google search turned up this place: http://www.surplussales.com/wire-cable/Wire1.html I didn't look to see if the cable was suitable for "tray", (flexable enough to use on CNC) but did notice twisted/shielded wire for about .90 per foot for quantities over 20'

If you can use 18 Ga. http://cgi.ebay.com/CNC-Stepper-Moto...item4cee49f9ad

It 4 strand shielded for .60 per foot.

I don't know enough about your needs, amperage draw of your motors etc to recomend sizes. It does make a difference. To small of wire is like trying to fight a house fire with a garden hose.

Will braided shield work, does it need to be foil?