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    Default CNC Plasma Table Questions - Suppliers

    Hi All

    I've been considering building a CNC plasma table for some time now. I've finally got some funds together and am ready to pull the trigger.The problem is I don't know where to shoot. The research has just made me more confused as I learn more about ways to accomplish this.I'd like to collect the bits to get this built over my Christmas break from work.

    I'd like the table to be a 1200 x 1200. I will probably make it around 1300 x 1300. I'd love for it to be 2400 long, but just don't have the room.

    So some specs I've decided on and would like some input on are.....

    1. Nema34 motors to drive the carriage (I'll use one each side).
    2. 20mm x 5mm pitch ball screws for carriage. With 200step motors this gives about .001" per step mechanical resolution
    3. sbr20 slide rails for the carriage and sbr16 for the other axis's.
    4. 72V Power Supply.
    5. Gecko G203V stepper drivers

    So my initial questions come down to...

    1. Where can somebody get a reliable 72V 20A power supply from
    2. What Breakout Board would be recommended for the Gecko G203V.
    3. Is there a supplier somebody has had good luck with for Ball screws with machined ends?

    I'm sure I'll have plenty more questions.

    Damo.

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    Default Re: CNC Plasma Table Questions - Suppliers

    NEMA34 might well be overkill, given that a plasma torch doesn't weight much, and it won't be meeting any physical resistance.
    Would 60V supplies work for you? They should be sufficient for the motor drivers, adn they're far easier to fidn than 72V supplies are.
    As for machined ball screws, I have had no real problems with Chinese-supplied ones from AliExpress - sure, it's far from being a 100% consistent source, but for the money (and provided you don't go for the cheapest of the cheap) it's hard to go far wrong.



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    Default Re: CNC Plasma Table Questions - Suppliers

    Quote Originally Posted by GerryG View Post
    NEMA34 might well be overkill, given that a plasma torch doesn't weight much, and it won't be meeting any physical resistance.
    Would 60V supplies work for you? They should be sufficient for the motor drivers, adn they're far easier to fidn than 72V supplies are.
    As for machined ball screws, I have had no real problems with Chinese-supplied ones from AliExpress - sure, it's far from being a 100% consistent source, but for the money (and provided you don't go for the cheapest of the cheap) it's hard to go far wrong.
    I'm not set on anything. I am used to overbuilding things, so this will be a real test to focus on light weight. I had thought about making this dual purpose as a router but have decided to build this soly as a plasma table and then build a router. I'd like to use that for aluminium so the designs were at odds I think. I'm just starting to redesign. I'd really like that nailed down in the next week so I can order everything.

    From what I have learned, it seems volts equals speed. The gecko drivers have a max voltage of 80V so I decided 72V would be good. If 60V is common I could make that compromise. Not a hard thing to upgrade in the future. Maximum speed needed for 1.6mm plate. I cant see myself using anything less than 3mm.

    Do you have a supplier on aliexpress you have used before?

    cheers
    Damo



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    Default Re: CNC Plasma Table Questions - Suppliers

    Send me a PM if you like. I'm in Australia and have been there done that.


    Good luck putting a design together and finding the gear in a week!

    I kinda think you are starting at the wrong end. Start with the motors you need to move the weight of your gantry then decide on the stepper controllers to use. I use 269 Oz NEMA 23's on the Z and X. I was going to use the same size on the two Y axis motors but I found these cool 5:1 timing belt drive reduction drives to suit NEMA 34's so I went with the smallest ones I could find so as not to blow the power budget. I'm using a 10 amp 48V Meanwell power supply. 1600mm HGR25 rails on the table and HGR15 on the gantry with rack and pinion drive. The gantry weighs about 30 kg. This machine runs at 21 metres per minute and uses LinuxCNC and a Mesa 7i76e ethernet board with a Mesa THCAD-10 voltage input daughter board. Do your homework and don't just go with a Mach3 option. Likewise, look around at stepper controllers. There are other options outside of Gecko that are much cheaper and have not missed a beat for me and a lot of others I know.

    Look at Steppersonline, ocean controls, Homan Designs and Alibaba/AliExpress. Noulei on AliExpress is a good source. I got my gearboxes there but I bought my rails elswhere at a better price (but then they went up in price) https://www.aliexpress.com/store/437307 Stepperonline hold stock in Australia and are good for warranty with a Sydney return address but some stuff ships (quickly) from China.

    Rod Webster
    www.vmn.com.au


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    Default Re: CNC Plasma Table Questions - Suppliers

    Oh and also Power Supplies Australia for Meanwell power supplies..

    Rod Webster
    www.vmn.com.au


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    Default Re: CNC Plasma Table Questions - Suppliers

    Use low inductance NEMA23's. You want speed, not torque. Bigger steppers are generally poor at high speeds.

    Use 10mm pitch ball screws at the least, maybe higher. Mechanical resolution won't be your problem, slow speeds will if you use 5mm pitch screws.

    A rough rule of thumb for (low inductance NEMA23 anyway) is ~1000rpm is getting close to the limit. That's 5m/min max with 5mm pitch screws. (This is not a hard rule, but a good guide). 10mm pitch screws will double the speed.



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    Default Re: CNC Plasma Table Questions - Suppliers

    Hi,
    you haven't said anything about THC and if you want a professional cut then good THC is mandatory.

    What control software are you planning on and what will the hardware associated with that software support in terms of THC?

    Craig



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    Default Re: CNC Plasma Table Questions - Suppliers

    Quote Originally Posted by joeavaerage View Post
    Hi,
    you haven't said anything about THC and if you want a professional cut then good THC is mandatory.

    What control software are you planning on and what will the hardware associated with that software support in terms of THC?

    Craig
    Hi Craig
    I will definitely use THC. I've been considering the Compact 150 THC. I'm open to suggestions for software. I'm considering mach3 as there is a lot of online support for that, or maybe mach4. I'd prefer a windows compatible software as that is what I'm familiar with. So many choices. The more I investigate, the more things I have to consider. I was wanting to get the design done and built over the Christmas break. Now I'll just be happy to of come up with a design/system I'm happy with.

    I am also considering just doing this on the cheap with all chinese stuff and then swap out/upgrade as I go. Its getting a bit more costly than I imagined. I'll probably opt for a well known stepper controller though.

    cheers, Damo



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    Default Re: CNC Plasma Table Questions - Suppliers

    Hi,
    with Mach3 there are a number of motion controllers including the parallel port that support THC including the Ethernet SmoothStepper, UC300 or 57CNC

    https://www.homanndesigns.com/index....3cpr4pbvue2mi2.

    With Mach4, there is at this time only one motion controller that supports THC, the HiCon Integra by Vital Systems. It is not a cheap
    unit but is very capable and high quality.

    I am also considering just doing this on the cheap with all chinese stuff and then swap out/upgrade as I go
    DON'T DO IT!!! Most of the Chinese motion controllers do not support THC properly. What will happen is you buy a cheap controller only
    to find it doesn't work properly and then have to buy another one.....that's expensive even if the first one is dirt cheap.

    Craig



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    Default Re: CNC Plasma Table Questions - Suppliers

    Quote Originally Posted by joeavaerage View Post
    Hi,
    with Mach3 there are a number of motion controllers including the parallel port that support THC including the Ethernet SmoothStepper, UC300 or 57CNC

    https://www.homanndesigns.com/index....3cpr4pbvue2mi2.

    With Mach4, there is at this time only one motion controller that supports THC, the HiCon Integra by Vital Systems. It is not a cheap
    unit but is very capable and high quality.


    DON'T DO IT!!! Most of the Chinese motion controllers do not support THC properly. What will happen is you buy a cheap controller only
    to find it doesn't work properly and then have to buy another one.....that's expensive even if the first one is dirt cheap.

    Craig
    It's OK, If you read my post you will see I said I'll go for a quality motion controller. SO MUCH TO DECIDED. The more I learn, the more I realise I dont know much at all about this.



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    Default Re: CNC Plasma Table Questions - Suppliers

    Hi,
    if you want a quality and capable motion controller then:
    Mach4 Plasma Torch Height Controller, Ethernet Motion Control

    Its $1395USD but it includes the controller, a THC unit, the plasma screen software AND a Mach4Hobby licence. So its not cheap but is still good value.

    Craig



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    Default Re: CNC Plasma Table Questions - Suppliers

    Howdy Damo, How did you go with the plasma? I am following this thread as I am going to build or buy a table. I am planning to go and visit RodW in Archerfield - sounds like he is pretty experienced. Let us know please.



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    Default Re: CNC Plasma Table Questions - Suppliers

    Quote Originally Posted by Razzmeister View Post
    I am planning to go and visit RodW in Archerfield - sounds like he is pretty experienced. Let us know please.
    Happy for any of you guys to drop in at Acacia Ridge. Just contact me though the contact us page on my website in my signature.
    I won't say I'm experienced with plasma cutting but I've learnt a lot about the software side by building my own machine and building a THC in Linuxcnc.
    Perosnally, I'm not convinced there is any such thing as a quality external THC as there are things you can do in the motion controller that is impossible externally.
    So if you want quality, buy a table with a Hypertherm control that has fully integrated motion controller based THC control or try your luck with LinuxCNC and build something similar like I have.

    Rod Webster
    www.vmn.com.au


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    Default Re: CNC Plasma Table Questions - Suppliers

    @RAZZ

    I've got no where with this. Mainly because I have several designsa in my head and I need to flewsh them out and narrow it down to one. I have just downloaded Solidedge as I get a free license through work (like Solid works) to nut out the mechanical design.

    The electronics is still a puzzle to me. I'd like to do it cheap, but also want to do it well. Conflicting goals.

    @RODW

    Are you saying that THC works best when your plasma unit has a THC output, or is it more than that.

    This was a timely update as I've just cleared a bunch of projects and was ready to get back to this.

    cheers
    Damo



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    Default Re: CNC Plasma Table Questions - Suppliers

    Hi,
    since my first post in this thread there has been two new developments.

    WarpTD is days away from releasing its new plugin with THC support for Mach4. Warp9 don't charge an extra license fee like Vital Systems and their Ethernet
    SmoothStepper board is only $190US, you can get one from Homann Designs in Melbourne. Note this THC support is a genuine realtime solution, ie fast response.

    Mach4 has not officially released, but is available as a development version, a programed THC support. Because Windows, and therefore Mach, is not realtime
    the response may be a bit slow. In a non-demanding situation I think it will work OK, but with a really wavy piece of material you will need a realtime solution,
    ie the Hicon by Vital Systems which is ready to go OR the ESS from Warp9 due to be released within days.

    Craig



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    Default Re: CNC Plasma Table Questions - Suppliers

    @Razz, I hope you got value from your visit today. For the others we pulled up a small DXF file designed in Solid works, ran it into Sheetcam, had a quick look at the nesting features and then cut one of these parts in 2mm steel at 40 amps and about 1600mm/min from memory. Then we checked the 10mm hole for fit with a nutsert as that gets fitted. We decided (and I had proven previously) that it would be a good fit. The 6mm clearance hole was not 100% but we decided it was fit for purpose but not as nice as a similar laser cut part.

    I also told Raz that I had a fairly brutal learning about the importance of clean dry air which necessitate me spending about $3k on a refrigerated drier and a precooler due to our humid climate here in Brisbane



    I suggested to Razz that as he wanted a plasma cutter to do production paying work that he was probably better of buying a table and shared a recent quote that had options starting at $20k

    So now we get to @Damo

    If you follow some of Jim Colt of Hypertherm's posts on various forums, he says the best plasma CNC controllers do the THC internally where it is tightly linked to the trajectory planner. This is how Hypertherm do it. This is how I do it with Linuxcnc and I've written a lot of software to achieve it.

    Before we go on, its important to understand that in a Mach3/4 environment the motion controller is generally a smooth stepper or some other board but in the case of LinuxCNC it IS_THE_MOTION_CONTROLLER. This puts some added requirements on the hardware because LinuxCNC MUST service the Servo thread 1000 times a second and if it doesn't due to PC hardware latency, bad things can happen because the motion controller is late to the party on the next call. So while we use external hardware (like the Mesa 7i76e ethernet card I use) the step generation is pretty dumb as an external stepgen is told to generate a certain frequency until its told to change the frequency or stop. LinuxCNC can command those changes every millisecond. This is way cool but it does come at a cost. And that is you need to run a real time version of the Linux operating system, (Usually the PREMPT_RT kernel) But the good guys at LinuxCNC make available an ISO file that installs the right OS, the right kernel and the LinuxCNC program itself!

    The typical Mach 3/4 external THC has 2 signals. One that is enabled when the Z axis needs to go up and the other when the Z axis goes down. So Mach sees these signals and sends a fixed height adjustment either up or down until the external THC says its within range, much like moving with a MPG dial. This bit/bang approach is a fairly crude approach. And it usually involves a dead band either side of the commanded voltage where no adjustments are made. Further more, sampling torch voltage, disabling the THC function when the motion controller is unable to meet the commanded velocity (eg. when approaching a corner) or crosses a void (more frequent than you think if you cut a hole and the slug drops away), just can't be done becasue the external THC does not know what the commanded speed is.

    So compare that with what my internal THC does. First we read the torch arc voltage using a USD $69 voltage to frequency converter. The frequency is connected to the spindle encoder (which we don't need) and we decode it in software to a voltage. On my machine, 1.5 seconds after we start cutting, LinuxCNC waits until the current velocity is witihin 90% ofthe commanded voltage and samples the torch voltage in real time and then enables THC operation. It does not use a bit/bang approach, but instead uses a high performance PID based algorithm to control the torch height and makes adjustments 1000 times a second. We don't bother about defining a dead band as PID doesn't need it. Adjustments are done by applying an "external offset" that the trajectory planner knows nothing about (eg external to the trajectory planner). So now we are cutting, we check the current velocity against the programmed cut speed every millisecond and if it is say 90% below what it should be, we disable the THC until we are up to speed again (so called velocity anti-dive or corner lock). The next feature I need to finish implementing is to look for a void. We do this by monitoring the rate of change in torch voltage (in volts per second) and if it exceeds a threshold (which is several orders of magnitude higher than what is seen due to material warpage when cutting), we can disable the THC until its safe to enable it again.

    One final feature I have attempted to code is arc sensing using some advanced trig suggested by an engineer in the LinuxCNC movement. My hope was we would be able to calculate the arc radius in real time so that we could apply a limit to the velocity based on some algorithm similar to Hypertherm's true hole technology (which I think is dependent on the Post processor.) I tried one approach and it did not get a result but there is another method we want to try. But time is an issue for me.

    So thats the kind of thing you can achieve with an internal THC that has 100% complete access to the trajectory planner and a few hundred hours of research and coding. Compare that with the dumb bit bang approach most external THC's adopt and you tell me how they can be a quality THC?

    Rod Webster
    www.vmn.com.au


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    Default Re: CNC Plasma Table Questions - Suppliers

    @Joe. For the record, a Mesa 7i76e is USD $199 and the THCAD card is USD $69. The 7i76e has 32 inputs, 16 outputs, 2 MPG encoder input, spindle control and encoder and 5 stepgens capable of running at up to 10 MhZ and a few analog inputs. We are talking serious commercial quality hardware designed to use 24 volt circuits which is more immune to noise. I'm at a loss that somebody would choose an ESS board over this device.. You can buy from mesa direct but they are not really geared up to service the hobby market, so I got mine from BigJohnT here https://mesaus.com/

    @damo, plasma and cheap do not go hand in hand!

    Oh and I forgot, When Razz was there, I left a bit of 12mm steel on the table which jammed one side of the gantry so we racked it by about 30mm before I could stop it. This became a great example of LinuxCNC doing its automatic gantry squaring when we homed it.

    Rod Webster
    www.vmn.com.au


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    Default Re: CNC Plasma Table Questions - Suppliers

    Rodders, Thank you for your time today - I have to say your ability is impressive. The e-mail you sent me did not have the attachment to it. As for the metal cutting, I can lay my hands on a 150w CO2 laser with a 1300mm x 2500mm table in top condition. I know this will not do metal, but what if I convert it to a dual purpose by adding a Fibre laser head for thin guage metals up to 3mm thick? Is it possible without breaking the bank? or do I go fishing for the rest of my life?????



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    Default Re: CNC Plasma Table Questions - Suppliers

    Sorry mate, I resent it. reply to my email if its missing. Sorry but I have no idea about laser or how to control them. I just go to Laser Central, C-tech or Rockpress depending on the job if I need laser cutting.

    Rod Webster
    www.vmn.com.au


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