# Cnc plasma



## Traian (Dec 13, 2020)

Hi guys i would like some advice for building my cnc plasma
My idea is to use steel L unequal profile 150x90mm, 1700x1250mm size frame with downdraft,
rails hgr25 in the side of base with direct drive motor with helically rack and pinion,
gantry i was think to use rectangular box section with one rail in front bottom and second top gantry hgr25 with hgr20 and same helically rack and pinion. I know the gantry has to be as light as possible but in same time I want to be stable, as many projects see it many of them are aluminium extruded box section but not reali sure about it 
Now my questions are:
what closed loop motor should i choose because there on the market are plenty like nema 23,34,hibrid motor servo, servo motor.... because of direct drive i understand is better but probably with planetary gearbox low backslash ? i presume you won't put gear on motor shaft and drive?
Rack and pinion is any particular module to use ,i was think to use 1.5 M but how many tooth to chose helically gear, or how to calculate with this idea i want direct drive,
reason telling you guys i want to make a stable gantry, is in the future I'm planning to found information for bevel head to attached, i think they have servo motor inside the head to angle head when plasma cutting.
i will be happy you could help me please or any anything I left behind unmentioned 
Thanks


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## Traian (Dec 13, 2020)

They seems affordable but not sure if are right or good


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## JimDawson (Dec 13, 2020)

You might look here for some ideas https://www.hobby-machinist.com/threads/cnc-plasma.86436/

Regarding motors, Delta servos look to be pretty good.  Like anything else, you get what you pay for.

1.5 Mod is OK for the rack & pinion drive. most machines use a straight cut gear.  You need about a 4:1 reduction, this can be a planetary gear box or a belt reduction.


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## Traian (Dec 13, 2020)

I’ve been searching for delta servo, different watt speed,any specific?  they are priceless 
Looking on Alibaba.com found cheaper but I think freight will kill
Any trusted suppliers around Europe? 
or any other option on motors? Does have to be left right about helically rac? Thanks


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## Traian (Dec 13, 2020)

If I look for delta what NM, kw,speed ....or how do i determine what motor power using by you determine with reduction 4:1 ?


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## JimDawson (Dec 13, 2020)

750W seems about right for that machine.  Should have enough power and speed. Most of those small servos are rated at 5000 RPM, more than enough.

I don't know of any suppliers in Europe.  I like DMM Technologies servos, but they are in Canada.


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## Traian (Dec 15, 2020)

Right im looking around to buy servos delta or dmm but far way for my budget now, what about china one like this
Should i be aware about anything about cheap servos or china one . What i mean like mybe not be compatible with any software i will use or with thc.... ??? Don’t know what exactly to look for, as a beginner


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## spumco (Dec 15, 2020)

If I could make a few suggestions for you to consider as this is your first time build...

1. Don't use HGR25 linear rails.  Unless you have some way to straighten and machine the L-profile steel angles, the linear guide bearings will bind.  You need a guide system that is much more forgiving of misalignment.  The round-shaft rails with built-in supports (SBR-20?) are more forgiving of misalignment than the high-precision type profile rails, and wheels/bearings rolling on plates is even more so.

2. Stick with closed-loop stepper motors for your first build.  Plasma tables do need reasonably high speed, but very aggressive acelleration is key.  Stepper motors have lots of torque at low RPM, which means a 3:1 or 4:1 belt reduction is usually sufficient (assuming similar size stepper vs servo).  You will lose top speed as the steppers cant spin as fast as the servos, but how fast do you need to cut?  400ipm maybe for thin stuff?

The nice thing about closed-loop steppers is that virtually all of the ones I've seen have an alarm output when they lose steps.  That's critical for a dual-motor gantry system to keep it from racking.

3. Drive system...  Getting a rack system aligned can be tricky, especially a helical-tooth version.  I suggest you consider a belt-drive system.  For a short table, a moving belt system works fine (<1m length).  For longer (>1m) I would use a stationary belt and mount the motors on the gantry.

I've built a few tables - huge and small - and a belt drive has worked exceptionally well in all cases.  You just need to use a very wide belt to make sure it's stiff, and stick with a polyurethane/steel cord belt.

The easiest and cheapest linear guide system I've seen is one for a smaller table I built.  Flat steel plate, bolted vertically to a box tube forms the guide.  V-profile roller bearings run on the top and bottom plate edge.  If you use plenty of bearings the uneven plate edge gets averaged and there's no binding and essentially no 'slop'.  Or at least not enough to care about on a plasma cutter.

The V-bearings are hardened and will eventually wear out the plate edge, but if you have lots of wheels the load is low per bearing.  The first table I built is in daily use, over 100k pierces, and hasn't required adjustment yet.  And neither has the belt drive - still on the original belt & pulleys.  Lightweight gantry, and NEMA23 closed-loop steppers drive it to 1000ipm no problem.  Cuts like a dream.

If I did another one like it I would have used steel tube for the stationary rails and a simple aluminum tube for the gantry to save some money over the 80/20 extrusions.  But it worked out fine and the cost difference wasn't a big deal in the overall budget.

_(ignore the fiddly lightening holes on all the motor mounts/drive assemblies.  That was me just having fun on the CNC mill trying to 'hot-rod' the thing to save weight.  It helped, but wasn't strictly necessary.)_

My most recent build runs on profile rails, has DMM servos, is gigantic, and unbelievelably precise... but it was expensive and fussy to get aligned well.

The really important parts of a plasma table are the torch height control, and the downdraft (or water) system.  Building a plasma table is fairly easy, but having it cut nice and not turn your shop in to a disgusting cavern of soot and filth means a happy long-term relationship with it.

Keep it simple for your first build.  Steppers, rollers (of some sort), and belt drive.

-Ralph


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## JimDawson (Dec 15, 2020)

Traian said:


> Right im looking around to buy servos delta or dmm but far way for my budget now, what about china one like this
> Should i be aware about anything about cheap servos or china one . What i mean like mybe not be compatible with any software i will use or with thc.... ??? Don’t know what exactly to look for, as a beginner



The China servos will work OK with your software, but normally have poor documentation and no tech support if you have problems.

What @spumco said above is good, closed loop steppers are a good option.  I'm going to start with steppers on my build to see how well they work, and I have them on the shelf.  If they don't perform the way I want I will install DMM servos.


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## pontiac428 (Dec 16, 2020)

I think you'll be happy with steppers.  There is no cutting load for plasma, so all the movements are just tracing without contact.  Steppers have to work much harder on a router.


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## Traian (Dec 16, 2020)

Hi all
Thanks for all suggestions really a helpful  already i have this type of rails, i have chance to machine the side of L profile to fit rails straight, L profile is 150x90x10.
I have home a large cast iron t slot table, 
Idea was to cutt this L shape 45 degree, mount on the big table when welding to cheep straight and after that give to my friend to machine in the side to fit the rails and rack, I wasn’t so confident with belt drive for 1.7m but if you guys used with no problem i think will reconsider( in case i still want to use helically rack what size of pinion shell i chose?  20x20 will be rack 18toth?
 Im planing to cut from thin to thick no more than 25mm 
Another things about THC , as I understand well better is better cutting witch one shell looking 
For plasma machine i was thinking for hypertherm and the are really expensive bit for my resorce I understand they are good !
I will go first for stepper motor save some money for other things ! Thank you all ,nice machine by the way spumco


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## spumco (Dec 16, 2020)

Thank you.  That's the small one I did a couple years ago.

I understand you want to re-use some existing rails...  but I think you'd still be better off with a different guide system.  The L-profile will not be straight in any direction - including twist - and machining it after welding isn't going to result in a perfectly flat/straight mounting surface for profile bearing rails.

You want 1.7m of travel... you have access to a milling machine that has that much travel to machine the L-channel?  That is a rather large machine.

Finally, if you make the gantry out of the steel L-profile you mention it will be way heavier than necessary.  Stick with aluminum or much thinner steel box tube.  There are no cutting forces in a plasma table and the gantry only has to withstand inertia and the weight of the head assembly.  Make it as light as possible.

I'm not an expert on torch height controllers.  I've used UCCNC controls with a Proma THC as well as a Neuron Lite.  And am about to do another table with a PriceCNC (now defunct) AVHC-10 THC.  They all work well.  You should join the PlasmaSpider forum and start researching THC's - that place is a wealth of info on all things plasma.

Before you go much further, I suggest you decide on the CNC control system.  The main control (software & hardware) will determine many things - maximum step rate, number of inputs/outputs available, etc.  This will drive many other decisions down the road.

Yes, a belt drive will be fine for a 1.7m table.  If you use a 25mm wide stationary belt it will be plenty stiff enough not to 'bounce' and the settling time during aggressive direction changes should be adequate.  If your gantry or head wind up being heavy, move up to a 32mm (or wider) belt.

Photo of the drive system from the earlier table.  The basic layout is fairly easy to make/copy and doesn't require extremely precise machining to function well as the bottom V-bearings are in slots for adjustability. (sorry for the blurry photo, you get the idea)




The important feature is that the drive pulley and idler rollers are supported at both ends - they are much stronger that way and the bearings last longer.  Permits tensioning the belt significantly higher to reduce backlash and system compliance.  The motor belts are not tensioned as much, and divorcing the motor from the main drive with a reduction belt helps the motor bearing live longer.

-Ralph


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## Traian (Dec 16, 2020)

Ok thanks to come back , L profile was think to use just for base frame and gantry thin steel box or heavy duty aluminium extruded, sorry my bad if I didn’t explain that,
Yes you are right about L shape for twisting, and was thinking but didn’t specify thicker rectangular for base frame,
About software, if i will chase linux or SheetCAM what possible look for , i mean more explicitbor a link where to read because nothing come in mi mind as question
Thanks for your time


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## Traian (Dec 16, 2020)

This was examplu of L


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## Traian (Dec 16, 2020)

Olso could you point me about closed loop motor you got and happy with?
There are hybrid servo drive closed loop or closed loop motor 
Thanks again


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## Traian (Dec 16, 2020)

What about this type, have too look for brake board ? thanks for patience with me, I don’t want to be pain in the ass but I want to learn  thanks


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## Traian (Dec 16, 2020)

Probably this helps later





						PriceCNC THC System — Kronos Robotics
					

CNC Construction Set   PriceCNC THC System




					www.kronosrobotics.com


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## Traian (Dec 16, 2020)

I have been reading your post again ,about stationary belt I think i will use 30mm, but have to decide what material i will use for gantry,what pitch choose for belt ? Bu the way for what software you guys recommend, not really impressed with mach3 for plasma


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## JimDawson (Dec 16, 2020)

Either of those motors will work.  Mach3 isn't the best, but it's cheap and there is a lot of support.  I have run a plasma on Mach3 and it works.  I think


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## spumco (Dec 16, 2020)

*Steppers - *I'm using the StepperOnline NEMA34's to retrofit my mill.  I've not run them yet, but, they appear to be rather good quality.  I'm not impressed with the cable connections - those will be replaced - but otherwise I'm satisfied.  More importantly, they have alarm outputs (for the E-stop circuit), and you can change the encoder count deviation alarm in the drives using their free software.  Both of these features were mandatory (for me).

It really depends on what's easily available to you, but I'd shy away from the no-name Ebay stuff.  The StepperOnline offerings are probably about the same as most Chinese ebay things, but at least they've paid to have different color drives and they have an actual web site with actual tech support.  Small but meanful reasurrance (for me, anyway).

StepperOnline also offer a higher-specification series of steppers/drives that I suspect are genuine Leadshines (rebranded) if you want to spend more money.  Those are creeping up on cheap servo prices and their Y-series (from your post) appear hit the sweet spot for performance vs. cost.

*Belts - *For the stationary belts I'd suggest AT5-30mm.  It really depends on local (to you) availability, but the AT belt profile is better than common HTD for backlash.  Real Gates GT2/3 belts 30mm wide are very expensive but are also good for positioning applications.  If all you can get are HTD belts, fine.  You can always have the drive pulleys hard-anodized for a few dollars to decrease the tooth to belt gap and reduce backlash.

3mm pitch belts are going to be very hard to find in 30mm wide, and 8mm pitch are too coarse.  The drive pulley will be very large, which will require a greater than 5:1 primary reduction ratio - not practical with a compact belt drive.  So the 5mm pitch hits the sweet spot using a 16T drive pulley and a 3:1 or 3.5:1 primary reduction.  The 5mm-16T pulley is the smallest pitch diameter recommended by a few belt manufacturers for decent belt life.  And use the largest possible idler pulleys to reduce back-bending stress - think 35-40mm.

For the primary drive HTD5M or AT5M, 20mm are plenty stiff.  Get whatever your bank account can support - the AT pulleys are a bit pricy.

*Gantry - *depending on your desired cutting area (1.7m, right?), I'd get a 2m long, 75mm square aluminum tube, maybe 4-5mm wall thickness and use that as my primary gantry tube.  The rails will be hot-rolled steel strips, 100mm wide x 3mm thick.

Don't get a big plate and have them cut out - you want the rolled/rounded edges that strip steel generally has.  Drill & tap 6mm holes every 100mm near the top and bottom of the tube sides and bolt the steel strips on.  The strips should have generously oversized holes to permit alignment/adjustment.  This combination will be lighter and stiffer than using extrusions, and probably cheaper too.  Just a bit more work drilling the holes.

*Software -* you can't go wrong with LinuxCNC, and the new(ish) THCAD torch height system looks spectacular. I don't have much personal experience with LinuxCNC, but I was very, very close to swapping to it for my mill rebuild. THCAD appears to be on par with high-dollar OEM THC's and the Neuron system.

I'm very happy with UCCNC for plasma (and milling) control.  Very stable, and it has many built-in features specifically for plasma systems.  I'm not a fan of Mach3, but it mostly works.

*THC - *The PriceCNC AVHC-10 is only available through Xtreme Plasma now.  I believe they bought out PriceCNC earlier this year and while they will sell you an AVHC-10, Xtreme will not support the THC unless you purchase their machines.  That said, I think it's the best stand-alone THC short of the Neuron.

The Neuron Lite is, quite frankly, awesome.  Spectacular control of the torch, tons of features, extremely well integrated with UCCNC software.  The downside is it's expensive.  And you can't control the Z-axis except through the Neuron 'box' - UCCNC (or Mach3) is not connected to the Z-axis at all.  Neuron 'owns' the Z-axis, so to speak.  Makes for a very responsive torch height control, but you cannot use the Z-axis for anything else (router motor, laser, whatever).  That was why the Neron didn't get used on the last build as we want to add a quick-change router spindle to the Z-axis.

The Proma is functional.  It works, it's fairly cheap, it's better than nothing, and so far it's behaved properly on the machine I just finished.

Those are the ones I have personal experience with.  There are other stand-alone THC's available, particularly in Europe, but you'll have to research those yourself.

*Bottom line - *For someone who wants to save some money and doesn't mind working a bunch of stuff out, I'd suggest LinuxCNC/THCAD.

For someone who wants it running as quickly as possible with as little fuss as possible, I'd suggest UCCNC/Neuron or UCCNC/Proma (if you need the Z-axis).

LinuxCNC is more capable than UCCNC (and UCCNC is more capable than Mach3), but LinuxCNC has a steeper learning curve.

Ok, that's enough.  Go do some research and CAD modeling!

-Ralph


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## Traian (Dec 17, 2020)

Hi there.
Wow this is so informational i have everything i need to know yes is enough, much appreciated you there for your time spending writing Jim,Ralph 
Regardless Traian


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## koenbro (Dec 18, 2020)

My own plasma table runs on Mach4 and uses a Texas Micro Circuits 3in1 THC on a Warp9 ESS. 


WORKS VERY WELL


Sent from my iPhone using Tapatalk Pro


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## Traian (Dec 18, 2020)

spumco said:


> *Steppers - *I'm using the StepperOnline NEMA34's to retrofit my mill.  I've not run them yet, but, they appear to be rather good quality.  I'm not impressed with the cable connections - those will be replaced - but otherwise I'm satisfied.  More importantly, they have alarm outputs (for the E-stop circuit), and you can change the encoder count deviation alarm in the drives using their free software.  Both of these features were mandatory (for me).
> 
> It really depends on what's easily available to you, but I'd shy away from the no-name Ebay stuff.  The StepperOnline offerings are probably about the same as most Chinese ebay things, but at least they've paid to have different color drives and they have an actual web site with actual tech support.  Small but meanful reasurrance (for me, anyway).
> 
> ...


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## macardoso (Dec 18, 2020)

Did not read the whole thread but wanted to write quickly, be very careful about buying servos from AliExpress. I spent two months helping a guy on another forum who bought some. We never go them working. The manual was 50% Chinese, 30% Russian, and 20% bad English (completely intermixed for no good reason). There was no software interface so everything needed to be done from the front panel buttons (ugh!). To top it off, the motor tuning was unstable out of the box and did not have an autotune. Tried hard to help him manually tune them and we never got it to work.

If you want servos, buy some with good manuals, good support, and a software interface. Delta, AB, DMM Tech, Clearpath, etc. are examples that come to mind.


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## macardoso (Dec 18, 2020)

I run a CNC using Mach 4 + ESS + Allen Bradley Ultra 3000 servo drives. I love Mach 4 and the ESS.

Plasma creates a lot of EMI. Plan on spending extra for shielded cables and be very diligent about your electrical grounding or you probably will have issues.

If you buy the ESS, Warp9TD has absolutely excellent tech support for free on their forum. There is one guy, Andy, who answers on behalf of the company. He really knows his stuff and is often willing to help with the setup of Mach 4. 

Don't go with Mach 3, it is no longer in development and nobody wants to help you if you are using it.


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## koenbro (Dec 18, 2020)

macardoso said:


> Don't go with Mach 3, it is no longer in development and nobody wants to help you if you are using it.



Strongly agree with the recommendation for Mach 4 vs Mach3. Although you hear on the forums about many people who have sorted out the system with Mach 3 and it works for them [very happy for them] when you START you should start with Mach 4 which is in development and is being currently supported.


Sent from my iPhone using Tapatalk Pro


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## Traian (Dec 18, 2020)

Ok thanks guy something new to get searched, really appreciate your effort 
At the moment I didn’t bought any drive motor servos or stepper, I scraped the idea about Chinese servos


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## Traian (Dec 20, 2020)

Hi All
As a beginner and my first build, i have been search about everything i could find about what was pointed about all of you, probably will take long way to all information i need to understand,
mechanical part i never was scared to manufactured or understand even reading and watch, i can learn quick if i see and practice, maybe not relevant here, but the most scare things most the time was electrical and electronic staff, 
Does out there is any  book/online web where is posted all in,of cnc controller build component contain{parts}
when start to search for wire up ,what part list do i need to make all drive controlling
 limit switch, home switch where to positioning them .
I will stick to nema34 8 NM kit including servo drive, but from there I'm kind of stack,
i know will use linuxcnc software but about hardware ?
PlasmaC, The integrated THC from using a Mesa THCAD10  this is for torch control.
when i looked in controller box been scare maybe asking wrong question and maybe in same time stupid,
I've seen some filters relays circuit board more than other driver control, power supplier etc.... hope understand the point
thanks


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## spumco (Dec 20, 2020)

There's no one 'book' about this hobby-level CNC stuff - that book would be out-of-date as soon as it was written.

If you are set on LinuxCNC, then you'll likely want to use a Mesa card - but there are other options like Pico systems.

*Your best bet - and the Mesa options are pretty intimidating - is to head over to the LinuxCNC forum and ask there what PC/Mesa card you want to go with the THCAD.*

Have a list of all inputs & outputs you want to use (limit switches, drives, etc.  All the 'stuff' you want to control or need information/signals from) and then count how many of these things you need.  Also make sure to let the LinuxCNC folks know what drives you want to use because the signal 'type' used for those stepper drives  - while pretty common - is not the _only _type of signal used to control other types of drives.

Here are the _major_ components in the scary electrical box you have to build:

Mains power stuff (_disconnect switch, breakers, distribution blocks, noise filter (maybe optional), line reactor (maybe optional), contactors (big relays for the drives_).

DC power supply for stepper motors (_big toroidal thing, converts mains AC to 48/60/72/whatever DC volts your drives need_)

Drives (_powered by big DC toroid_)

DC Power supply for control system (_generally 24vdc, but you may need additional voltages like 5v, or 12v depending on other components)_

Relays (_turn on/off AC or DC stuff.  Like lights, pumps, etc.  Usually uses 24vdc on the control side, and can switch AC or DC depending on the component you're turning on/off._)  Relays are _(hopefully)_ also part of the E-stop circuit so when you press the big red button you aren't relying on the computer to stop everything.

Control Board (_Mesa thing. _ _PC connects to this thing as well as the drives, limit switches, torch height switch(es), and other signal items)._

Terminal blocks & other stuff.  _(terminal blocks help connect stuff outside the box to things inside the box, as well as combine signals/power wires)._

That's all there is to it.  Plus some wires, and maybe labels. 

In the first photo below there is no control card/board, but all the other bits are there.  This build has the controller mounted remote near the operator station (and away from the plasma noise and mains AC components.  Note that not everything is connected - this was before it was installed on the machine so no external components have been connected yet.

The second photo is for a stepper-driven plasma system.  Note that there are no servo drives, but there is a big transformer for the steppers.  This one has the control board (UCCNC UC300ETH + UB1 BOB) and a Neuron THC in the same box.

See if you can spot all the items I listed above.


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## Traian (Dec 20, 2020)

in special wires and labels.
Thanks for explain again.  your control locks really detailed and you have Ac servo drive


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## Traian (Dec 20, 2020)

maybe this help later ?


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## spumco (Dec 20, 2020)

Traian said:


> you have Ac servo drive


AC servos were for the huge plasma.  The owner (and I) didn't want steppers on a 12' x 6' industrial machine.  It's a big machine and he wanted it _FAST_.

The other enclosure is for the stepper-driven smaller table I mentioned earlier in the thread.  Works great - aside from one loose drive pulley (set screw), there have been zero issues since it was commissioned.  Not one!


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## spumco (Dec 20, 2020)

That diagram is an excellent starting point.  I would change/add quite a lot, but the basic connections are there.

I don't do ladder diagrams - I'm just self-taught - but a diagram for that big plasma looks like this:


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## Traian (Dec 21, 2020)

You are a start thanks again for your time have good point to search now and go ahead.


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## Traian (Dec 22, 2020)

Hi Ralphi found in  europe something about integrate servo motor with low inductance, witch i understand is better 








						JMC servo motor with integrated driver 400 Watt and software version 6
					

Integrated servomotor with 400W from JMC ✓3000 rpm ✓Latest software 604 ✓NEMA24 ✓for CNC and automation ✚ Immediate delivery ✚ 30 days return policy ➨Order now!




					www.rocketronics.de
				



and other https://www.rocketronics.de/shop/en/hybridservodriver-es-d808.html 
i can found 8 nm nema 34 closed loop, least can provide data sheet and support
trying to go away from eBay as said. thanks


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## spumco (Dec 22, 2020)

I tend to shy away from integrated drive/motor combinations.  If one of the two components (usually the drive) has issues you have to scrap both items.  Motors rarely die.

I think you'd be happier with some Nema 23 or 34 closed loop steppers like you posted earlier.  When I suggested "stay away from ebay" I was referring to the no-name vendors.  StepperOnline is not a 'no-name' vendor.

The steppers will have much more torque at low RPM than similar-sized 48v servos.  This means you don't need a complicated and expensive drive reduction system.  A simple 3:1 belt reduction will be sufficient for speed and acceleration using steppers.  A small servo will likely need a 5:1 or greater reduction to get the same torque.

I think this would be perfect for a small table.  It's essentially what's on the first one I built:

https://www.omc-stepperonline.com/c...4-motor-and-driver.html?mfp=16o-ship-from[61]


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## Traian (Dec 26, 2020)

hi 
i know i have few idea been told to not use hgr rails but i was thing to use existing one because instant to buy other rails,buy something else don't have.
i have been drawing a section of gantry and my intention is to fit stepper inside the gantry, I don't know if will affect change direction in acceleration, the belt i will using will be AT5 32mm wide. sorry for my drawing is beginner.
or shell i fit the motor in the bottom? thanks


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## spumco (Dec 26, 2020)

Put it behind or on top of the gantry.  Fitting it inside will be a pain, it will not get as much cooling, and maintenance on the motors will be impossible without significant disassembly.

The HRD (or other profile) rails are fine, but they require quite a bit more care during the frame construction.  If everything isn't extremely flat/straight, they bind up or wear out much more quickly.  That's why I suggested bearing rollers - they're more tolerant of misalignment.


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## Traian (Dec 26, 2020)

Ok understood, instead to asking many questions already answered to all my questions.
Enjoy rest of the Christmas and hope have a good new year


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