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  • Home shop CNC plasma....

    Hi all,

    Thinking of a project for the shop. I have a small plasma cutter, up to 12mm cut.

    What would I be looking at to build an x-y table and CNC control system for it?

    I have looked at plasmacam but while it is pretty superb, I don't have £10k for the project, I'm looking at home build, low cost, speed is not a requirement.

    Manual height control should be ok and I'm guessing it's a. Pretty basic system as micron precision is not really required.

    Looking to cut shapes and designs in steel sheet etc.

    Bear in mind I have never used anything CNC before but and pretty good with electronics and welding etc. I have built an attachment for a machine at work that used a 4 axis card for a PC, but that was used only for linear feed and I wrote the program in VB.

    This would need software etc that I have no idea of.

    I have a massive amount of Flexlink structural aluminium which would be good for the chassis and table support frame and maybe a few stepper motors soon but not sure if it needs feedback or not?

    Any ideas or links?
    Last edited by Davek0974; 01-11-2014, 11:55 AM.
    If it does'nt fit, hit it.
    https://ddmetalproducts.co.uk
    http://www.davekearley.co.uk

  • #2
    Ignoring the cnc part for the moment (there are MANY reasonably simple and cost effective options...), one thing to watch out for with the plasma cutter is duty cycle. While you may be able to cut continuously in 16 gauge, at 1/2 inch it's probably quite limited. Recently I've been running into this with my small welder.

    You won't need "feedback". The stepper counts are maintained by the system so it "knows" where it is. As there are no tool pressures, with the correct sized sized motors skipping counts due to overload isn't a problem.

    Comment


    • #3
      Make a down draft table, if you can do a wet bed all the better, there is a lot of fumes and dust from a plasma cutter. For what it's worth a friend of mine bought a system and after getting it assembled and building a table and wet bed with a suction fan found it was VERY SLOPPY, so he went about fixing it, he now has less than .001 backlash in both X & Y. He was one of my better employees.

      Comment


      • #4
        I think CNC forums has links for CNC Plasma Table kits using Mach III and Gecko Drives and a whole forum dedicated towards them

        Comment


        • #5
          Thanks for that, just checked and it's a smallish unit but well built, 35% at 30A and will easily cut 7-8mm steel. I am only looking to cut 1-5mm on it.

          Good regarding the feedback, much cheaper.

          I'm only looking to make the table around 1m square, guessing so far would say I could get away with a one sided drive on the gantry?
          If it does'nt fit, hit it.
          https://ddmetalproducts.co.uk
          http://www.davekearley.co.uk

          Comment


          • #6
            Downdraft would be easy, I have a large extract duct system that I can connect into, will look into water bed as well, thanks.

            What sort of software am I looking at to generate paths from pictures etc?
            If it does'nt fit, hit it.
            https://ddmetalproducts.co.uk
            http://www.davekearley.co.uk

            Comment


            • #7
              I second duckman's advice about provisions for ventilation.

              I was on the sidelines nearly 3 decades ago when a local firm installed
              a Linde plasma machine. This had a downdraft table and for it to be
              effective at exhausting cutting smoke, not only was a fairly substantial
              fan required, it was also necessary to beef up the provision for make-up
              air to supply and heat air to replace what the plasma's exhaust fan was
              pulling out of the building. Not a trivial consideration where winter
              temperatures drop to -40F and below as they regularly do here.

              That first unit had no provision for filtration. Whatever particulate matter
              was light enough to remain in suspension went up the spout and into the
              sky. The machine was used for HR, CR, SS and lots of galv. The following
              machine had a filtration system that trapped a lot more material.

              I believe the firm is on its third or fourth machine these days but I don't think
              they are using a waterbed system. I looked at a small one of those on display
              at Praxair a few years ago. IIRC, the water eliminated or at least greatly
              reduced the ventilation/filtration requirements. However, there were some
              downsides.

              Incidently. Back in the 80's, the Linde used proprietary control systems. Users
              could cut basic patterns provided with the machine, buy additional canned functionality
              from Linde or set about piecing together their own patterns very laboriously using
              G-Code (and a lot of trial/error). It was a hair-pulling time for tradesmen who
              had taken the vocational route through school and then found themselves being
              called upon by mgmnt to learn to operate computers so that the big new investment
              would begin to pay for itself. (That wasn't my role but it happens that I played a
              prominent part in freeing that first Linde machine from the shackles of its
              proprietary patterns.)

              Anyway, consider how fumes will be dealt with.

              .

              Comment


              • #8
                About the intended table size.

                My vote is that if the room is available, larger is better from
                the perspective of being able to start with bigger, preferably
                full-sized sheets. More economic to purchase, less handling,
                the potential for a lower scrap-to-finished part ratio.

                Mind, handling larger sheets brings its own considerations.

                .

                Comment


                • #9
                  Hi, sorry but space is tight and intended ideas don't call for a massive table, cost is most important factor here.
                  If it does'nt fit, hit it.
                  https://ddmetalproducts.co.uk
                  http://www.davekearley.co.uk

                  Comment


                  • #10
                    Originally posted by Davek0974 View Post

                    What sort of software am I looking at to generate paths from pictures etc?
                    Sheetcam from Les Newell was designed from day 1 for plasma cutters.

                    www.sheetcam.com
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                    Comment


                    • #11
                      Ok thanks, what other software would be needed?

                      I guess there is something to control the driver boards, is that mach3 or similar?

                      The software part seems harder to grasp than the hardware

                      Dave
                      If it does'nt fit, hit it.
                      https://ddmetalproducts.co.uk
                      http://www.davekearley.co.uk

                      Comment


                      • #12
                        I am doing the exact same thing. I already have an oxy/plasma table which I made and use a magnetic tracer. Now I am in the process of changing it to cnc plasma only. I have purchased BobCAD/CAM software for the drawing package and also Mach 3 the the plasma setup. I have just received a quote from Camcutcnc on a price and kit for my table including all controllers etc. They have quoted me $1100 US (I live in Australia) and have asked for more details. Maybe give them a try.

                        Mtw fdu.

                        Comment


                        • #13
                          these can literally be as cheap or expensive as you want to make them. i've looked into it myself a few times, but space, time, and necessity aren't high enough on the priority list to even think about the cost factor. for one looking to make it as cheap as possible, there are linux based software packages (open source = free) that can save you $1000+. there are numerous builds to be found on the internet based on many types of track systems, so you can go with what is easiest or cheapest. i think you are pretty much in line as far as my knowledge goes, but here's what i think of your ideas so far:

                          table size of 1m x 1m: probably reasonable if size dictates. i'm sure you considered this already, but i'd also see what size sheets i can get the cheapest from my local supplier that suit the parts i would cut, and work around that. since things here are in feet, i can't say what you are likely to have available there.

                          one drive for each axis: probably ok for a smaller table like you are planning. since there is no resistance with a plasma or fuel torch system you don't have the forces to deal with that you would with a cutter (router, mill, etc). i'd do some research to see what people think is acceptable for a single drive unit, then figure out how heavy you are. considering aluminum for the gantry material might be good.

                          manual height control: this is a way to cut costs, but it might not be a good idea. sheet steel isn't perfectly flat, especially thinner materials, and especially after a thermal cut has heated part of it. the digital height controls will take feedback from your plasma unit and adjust the height of the torch to match any curve in the metal as it moves along. if you do decide to go manual, see if there are any contingencies you would want to plan for if you were to want to add height control later.

                          material thickness: with a plasma table you are dealing with a pierce operation to initiate your cut. most all plasma units are rated to pierce at 1/2 the normal rated cut, so if you have a 12mm rated machine, 6mm is the rated pierce thickness. this will vary by brand, but it sounds like you are ok if you want to do 6mm and under. i have a 1/2" rated machine and there are numerous videos of that machine cutting 1" plus, so it could probably pierce 1/2" if i were trying to push it.
                          Last edited by lost_cause; 01-11-2014, 06:23 PM.

                          Comment


                          • #14
                            Thanks for that, very helpful.

                            I have been scanning eBay and where there once was very little of any good, I am now seeing thousands of control boards, motor drivers, hand controllers, motors etc, brilliant.

                            I have seen a combined 3axis board that connects to a PC via parallel port, drives 3.5A steppers directly, will take a manual jog unit and will talk to mach3 all for about £70, it also has a demo version of mach3 but I'm not sure what the demo version does.

                            I think I can create DXF files in Photoshop which I use a lot, so maybe the only missing link I have is DXF file - mach3??? As I said, CNC is pretty new to me so maybe I am oversimplifying things?

                            Stuff like limit stops, home stops, e-stops, power supplies etc are easy, it's mostly the control side that is difficult it seems. I have found a UK CNC forum and will register today, but reading so far seems to be that tool height control is an ultimate luxury and not generally needed, so something else to consider.

                            This project is partly for fun and education and partly for a small money making idea I have so I'm not too worried about chucking a couple of hundred quid at it either way. I have a PC waiting, tons of aluminium structural beams, and itchy fingers
                            If it does'nt fit, hit it.
                            https://ddmetalproducts.co.uk
                            http://www.davekearley.co.uk

                            Comment


                            • #15
                              Keep away from those cheap 3 axis combined boards, they are utter rubbish, one chip goes, and they do very regularly, and the whole board is toast.

                              Demo version of Mach will only run a file 500 lines long then bails out.

                              Sheet cam will import a DXF from Photoshop and convert it into code for mach3 to understand will also send signals to fire the plasma when needed. It can also handle torch hight control [ THC ] but you will need an addon board for this. As you say you don't need THC from day one

                              http://www.candcnc.com/

                              I run my plasma by bolting a length of 40mm box section to the bed of the mill sticking out one side and the torch clamps to this.
                              I use a spare set on contacts on the coolant pump rely to switch the plasma on and off. That bit needs manually editing but for the limited amount I do, it's a get John out the $hit setup, it works.
                              material is supported on a metal milk crate at the side.
                              .

                              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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