Hello everyone,
This is my first post to this forum. I have been reading for awhile as an anynomous user. I am very impressed with the knowledge out here. Anyway, back to my question.

I am in the process of building a 4'6" X 10' Robotic plasma table. See attached photo's. I have built the table, and we are in the process of specifying the software / hardware to use to control it. I am leaning towards Camsoft with an Ethernet controlller card. (Camsoft Professional Software - 6 Axis DSP Ethernet Card).

But, I am still having trouble deciding whether to contunue the robotic process or scrap the robot idea all together and build a one sided gantry system to slide along the back instead. My concern is the accuracy of the slider.

Also, I am assuming that auto height control will be implemented with the robot.

Has anyone ever attempted something like this?

Does anyone have any concerns suggestions on camsoft or a replacement?

I can provide any additional data if needed (motor sizing, robot type, etc...)

I see you already have the robot, ASEA by the look of it. My spin on it would be that a Robots has its place, especially if you want to cut parts out of a preassembled shape for example and do all kind of vertical & horizontal cuts etc, but if you are doing all the cutting on a horizontal surface out of plain sheet, a robot is a bit of overkill, You will probabally need AHC whether a robot or gantry is used, were you thinking of designing that also? Why does it have to be a one sided gantry? Also would'nt 4ft6"x10" be stretching the work envelope of the robot? ( although I took a second look and it appears it also runs on rails!). Were you looking at implementing a teach function on the robot? I would say Camsoft professional should handle either robot or gantry, although with the rail function I can see the robot being pretty program design intensive . Do you have the amplifiers for the motors on the robot?
Al

Thanks for the reponse. I actually have two of the Asea L6/2 robots. One is on a 5' slider. This allows us to cut approx 42" out of an 48" X 8' sheet of metal. Hindsight, I would like a slightly longer reach on the robot, but it will handle all we need at this time.

I agree the robot is more than we need and I know this should not be a design factor..... but they look really cool running!

Yes I have the control cabinets as well, but I was not planning to use the existing amplifiers. I may change my mind after I get the costs for new ones.

As far as the one sided gantry (if we decide this would be better) goes, I would like to keep the front of the table open for loading / unloading parts.

As far as the one sided gantry (if we decide this would be better) goes, I would like to keep the front of the table open for loading / unloading parts.
Most plasma tables have the X axis travel mechanism below the top of the table.
With the gantry at one end this allows clear edge loading of material etc.
Also It looks like you have some kind of tilt mechanism on the table? Also with a plasma table in a production environment you need a practicle way to remove the scrap that falls to the bottom of the table, unless you have already thought of that.
Al

Are you sure you can control the robot via regular gcode? Most use propriatary software and need to be taught. Those robots are ABB no? Still parts available for them? If so they will be expensive.

An interesting project.

Eric

BTW, robots need very expensive cages and safety circuits around them to be legally run.

Eric

Thanks,

Actually, the table doesn't tilt, the table has ball transfers that will pop up to facilitate material handling (See photo). The angle of the table is configured to allow slag to "slide" to the front for easy cleaning.

Yes they are ABB Robots. And yes, I am sure the repair costs are high. I have found several vendors that sell replacement (or rebuilt) servo motors for this exact model.

I am told from Gary @ Camsoft, the programming is embedded in his software. additionally, Gary expressed that the professional version will allow importing of .DXF files (from autocad).

Obviously, I am new to CNC, but I enjoy unusual projects. I own a small business that manufacture's environmental equipment, and need to be able to cut parts projects. I could have just bought a CNC cutting table, but I wanted the challange. I am at a stage in my life where this is more fun.

BTW: The cost is not a real issue.

As for the safety issues, I am aware of the need for a laser curtain around the working area of the robot, but I was not planning to inclose it in a fence, maybe some of these issues will push me to a gantry instead.

EMC (www.linuxcnc.org) has the kinematics for a robot. I am sure there would be some work to be done to get it working again with the most recent revision, but I think the guys at NIST would probably help. The advantage would be that you could use G-code.

Someone recently was going to use Mach 2 on a cartesian robot by inverting the kinematics.

I have a GE robot which I took apart for parts. The amplifiers for all 5 motors were on one board. If your robot has discrete amps, I would try to use them. They would probably be analog command input which would mean either the Rutex step/dir to analog converter, or one of the many analog output options that works with EMC.

I would definately look at a Delta Tau controller before Camsoft. A lot more configurable, and a lot more features, and, I think, a better NC innerface.

To everyone, thanks for all the input. A question rwas brought up ecently in our office was the feed rate (ipm) of the robot movement ( I know... This should have been considered before now!),

We are looking for 300 ipm range.

I am thinking again about a cantilevered gantry (one sided), and based on this option, I am considering Rack & Pinion movement ( for the x axis ). What would be a good choice for the slide (example 3 or 4 thompson rods, roller bearings, etc) The x axis will need to traverse 10'

I would look at the plain linear bearing & track by Pacific Bearing for the outer rod and maybe an inner track with a cam follower style bearing that would have a front & rear sacraficial scraper for the track.
Plasma's put out a phenomenal amount of metal dust into the atmosphere, which brings up another subject of a dust extractor system of some kind.
Most of the commercial systems extract from under the work piece which means the table requires temporary covering around the sheet being cut.
300 ipm is usually the top end of the cutting speed (if that) with 1000 ipm for the rapid moves.
Al

It seems to me that the table you bought is asking for a conventional gantry to be put on it. Supported and driven from each side. Either by dual servos or a drive shaft.
Why reinvent the wheel and make it more complex than it has to be by introducing a robot into the equasion. The question you need to ask is, do you want a machine that works well, or an industrial peice of artwork? To go down the conventioanl path would be comparitivly cheap and easy by comparisom to using the robot. The thing is I know you can achive success using the conventional method, where Using the robot could cause all sorts of head aches.
Because I have a similar machine to what you could have, I can tell you that it shouldnt cost more that a few thousend bucks to get set up. Keep this in mind when comparing the cost of getting your robot setup up to scratch.
Keep in mind also that you could use cheaper off the shelf software with a conventional setup also.

Thanks everyone for the help in making this decision easier. I understand the complexity of the robot, not to mention the added issue of the gantry, the limited reach (cutting path), but the deal breaker was the movement speed. The Asea robot moves @ 1.3m/s Which (I Think I am right?, see below) is about 30 in/min. without varying the amperage of the plasma unit (which I haven't purchased yet), this would prevent thinner materials to cut cleanly.


Here is the specification on the robot:
( I don't really understand the second or third reading... is it millimeters, meters, and where is this measurement taken? I have no problem with the degrees per second.)

ASEA IRB6/2 Industrial Robot
1. Base rotation has a working range of ± 180° and a max axis speed of 114° /s
2. Radial arm motion has a working range of 80° and a max axis speed of 1.3 m/s
3. Vertical arm motion has a working range of 65° and a max axis speed of 1.3 m/s
4. Wrist rotation has a working range of ± 90° and a max axis speed of 138° /s
5. Wrist rotation has a working range of ± 180° and a max axis speed of 234° /s

So ..... Gantry it is then. Now, I have to design this, figure out what speed, ratio's, motor size, etc.... oh joy, at least I have a "great" resource in CNCzone.com!!!!


Thanks again everyone!


John....

the deal breaker was the movement speed. The Asea robot moves @ 1.3m/s Which (I Think I am right?, see below) is about 30 in/min. .

1.3m/s is more than 3000 in/min

The reason that these robots are so dangerous is that they can put a hole in a person because they are moving so fast. Speed would not be your problem, although you have probably made the right decision anyway.