Whats Your Speed?

[islander261]

Hello

I am looking into a new table and or new electronics and drives. My question to the group is how fast does your equipment reliably cut? I am aware of what the various manufactures claim, I want real experiences. I am really interested in replies from those of you that have Arclight Dynamics or other tables that use the CandCNC electronics and drives. I cut mostly thin sheet, 18ga to 11ga. I am looking for reliable cutting too 300ipm (7.62/m/m). Most of my cutting needs to be around 250ipm (6.35m/m).

Any using the Neuron THC? Does it work well?

TIA

John

[acourtjester]

I may be wrong but the way I look at the speed issue is the spects sheet for the plasma cutter I use. I cut mostly 1/4" and run it at 48 ipm and with thinner metal it gets faster. Metal of 18 to 26 Ga. it shows 325 ipm with fine tip. And 11 ga would be about 110 ipm this is for a PM65 40 to 45 amps.
Some other plasma unit cannot do these speeds or the spects are different I had another plasma that the arc voltage did not very much with the thickness of material. Some companies do not offer a cut sheet and that is a bummer.

[Capstone]

It's really a question of proper pairing isn't it.

The overwhelming majority of folks seem to be using the PM45 (as I am) in your case so looking at the book for cut speeds I think is where John is testing the capabilities of the tables out there using C&CNC electronics.

We all know that A PM85 is overkill really for this scenario if you're never cutting anything thicker than 1/2in.

As far as the table, I'm very curious to hear real world results from others as well. My DIY homebuilt setup uses many of the same components, (see my siggy) and yet I have yet to reach "book speeds" that are dross free and don't have wagged out cuts for anything faster than 200IPM. I know most of my issues are related to the table/gantry weight ratios and the fact that I don't have pulley reduction installed yet. When it comes time to finally upgrade to a larger table, I would seriously consider spending the difference on a table (minus the electronics) that has proven and production level repeatable non-shuddering speeds at 325ipm or more too.

[islander261]

Ok

To make this clearer. The Hypertherm book specs for 45A FineCut consumables range from about 100ipm to 325ipm for the materials I usually cut. There are also the slow cut tables at 150ipm. My table will only go 130ipm max. reliably. The steppers intermittently go into mid band resonance and stutter when I try and go faster. So I am looking to the community for feedback on tables/drives that actually work at these speeds. I have read most of the manufactures sales information but I really want real world experiences.

John

[jimcolt]

When you buy the drives and electronics and build your own cnc /plasma machines....you must pay attention to the ability of the drives (motors, drive electronics) to overcome the mass (weight) and friction involved with your machine. Most high end industrial machine builders work hard to match their drives to their machine weights in order to ensure that acceleration and speeds are within the required ranges of the plasma cutting processes being used. Plasma is a very speed and height (distance between plate surface and the frontmost part of the torch) dependent process. Excellent acceleration at all speed ranges as well as very fluidic (not rough) motion and accurate height control are necessary in order to achieve the best cut quality and consumable parts life.

It is far easier to cut 1/8" through 1" steel plate.....as compared to materials thinner than 1/8". This is all due to speed and motion and acceleration characteristics of the cnc machine. What works for routers or thicker/slower metal cutting does not necessarily work on thin, high speed cutting applications.

Jim Colt Hypertherm

[islander261]

Jim

Thank you. Over the last three years I have come to appreciate how dependent cutting thin sheet is on table mechanics. I have improved the thin sheet cutting of my setup at least 500% with mechanical/electrical modifications, the Franken torch and AVHC hack. I now have a torch that will at least start out at the desired height and will usually stay pretty close as the longer segments are cut. I must be slow because it took me quite a while to not trust any aspect of the AVHC system and physically measure all heights and distances. This leads to why I am asking for feedback from the community as to what actually works for them. My present table was made by one of the larger players in the low end market. I admit that I bought the table second hand with no knowledge of plasma cutting other than a book basic understanding of the process, to be fair I have made the purchase price back a fair number of times over the last 3 years. The specifications for the table clearly include the ability to cut thin sheet. In reality the table is suitable for 3/16" (3.5mm) to about 5/8" (16mm) with the supplied torch and mechanics. I actually really like the control SW that came with it, the CAM was terrible and I have since switched to Inkscape and Sheetcam. In the original configuration the table struggled to even work consistently at 100ipm. I am now very wary of manufactures claims of suitably on systems that I can afford. I also live in a rather remote rural location that complicates travel to visit for demonstrations. So looking back I have the following advice for any newbies and maybe more experienced hands:

1. You will love this Jim, buy a Hypertherm torch and power supply. Don't even look at anything else. Get the full CNC interface package factory installed.
2. Don't buy until you have had an actual hands on demonstration using the material you usually or intend to use. Make sure the demo uses your own artwork or CAD files. Make sure you understand how your artwork or CAD file was used to produce the machine code. Have the vendor show you how well the cut parameters used fit the system specifications.
3. Have an independent 3rd party assess the cut quality on the parts if you are not sure what is good.
4. Carefully listen to successes and troubles forum members have with their systems. After all this is the real world no some manufactures laboratory.

John

[kingruar1]

Hey guys,

I am in the same boat, do you find a high speed table.

I have been looking at the bulltear table but i am concerned about the shuddering issue at high speed. I know the bulltear is a very good table but I want to see if there is anyone out there that is cutting 22a - 16a regulary with no problems and on what table.
I was even thinking of purchasing a well known brand (professional) table second hand as I know it would do it. only problem is, its twice the cost.

[Capstone]

Kingruar1,

Honestly, the PlasmaCAM set-up for really thin stuff seems like the way to go if that's all you have planned and want a turn-key set-up. Smooth servo motors and a light gantry make for very fast cut speeds, which can quickly change directions. There are drawbacks IMO though...
1. No watertable
2. Design Software is proprietary
3. Expensive compared to DIY
4. Can't expand/morph/upgrade into a wood/plastic routing capable table
5. May not do as well on super thick stuff at slower speeds.

[Thor]

My home built table with ac servos and candcnc mp3500 reliably cuts 14 ga at 220ipm, I have not cut anything complex out of any thinner material yet other than some 20 ga stainless, but that was just circles though it did handle them well. I am fairly confident it can handle 300ipm artwork fairly well. Rapids are 1200ipm.

[kingruar1]

Hey,

Yeah, will be noting intricate, the shapes will be mainly squares with circles in the around 4 inch diameter, do you reckon that will be ok? was thinking the servo route for sure!!

[BTA Plasma]

Servo is not always needed. A servo motor with CandCNC's electronics will yield a 1000 line encoder. This means with 5-1 reduction your running a 5000 line per revolution at any speed. Microstepping is 2000 lines per revolution up to a certain speed. But this is not enough info to make an informed decision. For CNC plasma cutting you can run at very very close to book speeds depending on the material and conditions like water bed, down draft, no draft with a stepper. A servo is nice because your rapids are much faster. Servo motors especially on the lower end of the market use an encoder cable that over time will fail as all cables will in a cable carrier. If the encoder looses signal with the drive the servo defaults to on and just takes off. Ever seen a machine that the servo motor on one side just takes off....you will be fixing the gantry and ensuring it is strait again. Not saying servos don't work, they work very well but are rarely needed.

That being said we have several customers that use 8 foot travel 109" long gantrys with 600oz steppers (With very specific reduction) and will get good cuts on thin material. We also have folks with NEMA 34 servos on smaller 4 and 5 foot gantrys that get good cuts on thin material. Within book speeds are the parameters that allow proper engineering of gantry components based on acceleration and weight. Both stepper and servo work well within those book speeds. Older book speed of 600 and 800ipm require servos due to the RPM they operate in. Whichever you choose you should be informed of the difference and possible issues that you will inevitably face with either components.

[kingruar1]

Thanks BTA,

Don't like the look of the plasma cam, doesn't look robust enough to me. I would be going along the down draught route as I don't like the idea of the water table with mess etc.
But it is good to know / be made aware of the benefits of a lightweight gantry.

BTA, would you recommend going for a servo package if i were to purchase a package from candcnc or stick with the steppers, I don't mind spending the extra if i will make a difference.

[BTA Plasma]

You can go servo and enjoy a faster rapid and smoother movement above a certain threshold but you will also have to deal with limits. A stepper will loose steps when it encounters an obstacle but a servo will go until the amp pops. A big deal on any axis including Z axis.

[hsolve]

Goodmorning to all
I have the MP3500 servo setup, the 5 motor 850in/oz. I started with the servo setup as wanted to do routing as well as plasma. One thing the above threads did not mention was that the servos require reduction. I have fitted 15:1 planetary reductions to the 'X' and 'Y' axis. I have no other reductions and use 29 tooth pinion for the rack and pinion. I had to use that size pinion as the shaft from the reduction gearbox is 1/2" (can't quite remember too long ago) you need the meat in the boss after you bore the pinion. I have routed at 4.5m/min without any problems. Just did some test cuts on thinner material 3mm but higher currents (I have a PM125 as most of my cutting is thicker materials) and found that my gantry as it is quite heavy will shake the shit out of the table. It can literally move the table around the floor. Don't know what my rapids are but don't run them at or near max speed. Even the jog in mach3 is not set above 50%. Initially when setting up I fiddled with high speeds (can't remember what they were ) but if was slow getting my finger off the jog button on the keyboard the X axis would smash into the end stops bending them, tripping out the control box on motor overload, not to mention the noisy crash. Since then I have dialed everything back, knowing that i have plenty of speed if required.

Just for your info just did the calculation for the possible rapids and got about 23m/min or about 900in/min, which is a lot. This speed I have for the X and Y axis, the Z is quite a bit slower. At those numbers above it starts to go out on motor overload, too fast anyway.

[kingruar1]

essentially, this is what i am after

https://www.youtube.com/watch?v=BFIREBlz9Og

These are the kind of shapes i would be cutting, that is a very nice table though in the video!!!

[jimcolt]

The table in the video (made by Esprit in the UK) is primarily designed for cutting thin galvanized ductwork......this you can tell by the plate rider height control....which keeps the torch at a fixed height. The problem is if you need to cut material thicker than about 1/8" (3mm)....you need a height control that can raise to the suggested (by the plasma torch manuafacturer) pierce height, then index down rapidly to cut height. Esprit can upgrade the table in the video to arc voltage height control....necessary for thicker materials.

Typical plasma cutting speed requirements are between about 5 inches per minute and about 300 ipm if you need to do very thin materials. Properly sized and geared steppers can handle this on lightweight machines. Typically when you get into larger machines with heavier gantries and requirements for cut quality that demand higher acceleration rates....then you will find servos. The statement by a poster on this thread made mention regarding servos running away at uncontrolled speed and direction....well that just does not happen with the technology used today. As soon as a feedback fault is sensed all motion on a servo machine will stop. My servo machine is 9 years old......have never had an issue as described!

Steppers and servos, properly configured have essentially the same accuracy. Servos have a wider torque vs RPM range than steppers....so better performance on heavier machines is the advantage. More costly and complex servos are the disadvantage, of course!

Someone on another site was interested in seeing 500 ipm cutting on a plasma machine yesterday.....so I went in my shop and filmed some 26 gauge being cut at 500 ipm on my Plasmacam machine using a Powermax85 plasma at 45 amps with Finecut consumables. The cut was very nice, though don't expect good cut quality on small holes and details at speeds like this! The Plasmacams are all servo driven.

Jim Colt Hypertherm

Here is the 500 ipm video! http://www.youtube.com/attribution_link ... load_owner

[BTA Plasma]

The statement by a poster on this thread made mention regarding servos running away at uncontrolled speed and direction....well that just does not happen with the technology used today.

That would depend on whos technology we are talking about in this thread. The poster was asking about CandCNCs servo versus stepper. The issue is also very prevalent with cheap drives. Those drives are all over ebay.

[jimcolt]

Sorry Matt, I guess I have not ever seen one of those! It has been probably 15 or more years since I have seen a "runaway machine" with servos....and steppers don't have this issue? I would fully expect the machine control software to detect the error and shut things down... Jim

[kingruar1]

Thanks Jim for the Video,
The thing I don't like about plasma cam machines is the way the gentry has the cables dropping onto it, i find it really irritating!! However you showed it can do the speed!!

So BTA plasma, are you saying that the candcnc servos have a habit of running away or it is possible to have them running away?

The machine in that video is essentially what i am looking for, although would be nice to be able to cut above 3mm but would be mainly cutting with .7mm and .9mm galvanised and .9mm and 1.2mm stainless.

Can i get a table combination that would site there and do that ok all day / being reliable by using the correct servo / stepper with weighted gantry work. I don't mind spending a bit more for the right system.

Jim, did you make your plasma cam downdraught?

[BTA Plasma]

Any servo drive that doesn't have a hook for turning off power when it doesn't see an encoder (like a tach, power monitoring or any other way to stop the servo from moving to hold position without encoder feedback) will run away. Cables in a cable carrier do not live forever. That being said you may never see a cable failure in a build and may never see a runaway condition. But eventually a cable will go out. Depending on the cable type some last longer than others. CandCNC servo systems are awesome and really open up a large envelope of capability. Can you imagine cutting at 800ipm or marking at 800ipm with DCC RS485 type interface all at 150 Milli Gs. 80-100Milli Gs are pretty much opening up the entry and mid level market customers to a whole new ball game of cut quality and you can pretty much thank CandCNC for that (since late 2008). Long gone are the days you had 2-3 choices of CNC plasma with 2 out of 3 really under powered.

Tables like the one shown use a large roller ball to hold the sheet down. This means you have to carefully watch what size material and features your using or you may slide your sheet around while cutting. The trick is in the set up. If they are set up very well that should not be an issue but those of us that have ran that style of head will tell you eventually you will fight it. With the small Z height you are limited to thin materials but if that's all your cutting maybe that wouldn't be such a bad candidate.

What we offer is a table with a huge Z clearance yet able to cut at books speeds. It takes careful constraints in design to get that kind of performance level. The extra Z axis is a huge plus if you want to mount a vise or cut large tubing or run some very thick material. But if none of that is something your looking to do and its thinner sheetmetal then there are a lot of other choices. Some better than others.

[jimcolt]

The downdraft on my 4 x 4 machine is simply skirting the sides of the table and ducting to a (high vacuum rated) 3200 cfm exhaust fan. I used 3 , 8' diameter galvanized pipes between the underside of the table....and a plenum box built on the inside of a wall mounted restaurant style fan...it is 32" diameter with louvers that close on the outside.

I have also built a few tables that we use at trades shows with hybrid water tray/ downdraft/ filtration units so we can demo plasma at trade shows without producing fumes / smoke.

I agree with BTA that some cables eventually can fail in a power track. If the cables are rated for power track use...and the power track meets the bend radius specs of the cable they typically will be good for 20 years or so of production use. Incorrect installation will cause them to fail much quicker! I have been involved in plasma/cnc machine installations for 38 years.....do it right and it will last just fine. On small machine cable carriers can have an effect on cut quality. When machines are designed you should take into account the drag caused by cable carriers as well as the mass of all of the moving components. Overhead cables are always in the way, however have less effect on the torch motion.

Jim Colt Hypertherm