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  • Static Reduction for Dust Collection


    Recently, our Forum (and others) have had a high occurrence of static related issues. These "gremlins" pop up every year at this time when the weather gets cold and dry. Here are a few tips to help reduce static related issues:


    Static Reduction in CNC Dust Collection Systems


    Dust collection systems are one of the primary generators of static in woodshops. This static becomes very problematic when the dust collection system is connected to a CNC cutting tool. For those CAMaster owners that have experienced issues caused by static discharge, getting a reasonably priced solution is often difficult to come by. The following should give those users a viable option.

    Static is generated by air and dust movement in a non conductive hose. I have used metal ducting to solve a number of static related CNC control issues. The following instructions explain the use of light gauge home improvement store type galvanized 4" ducting in place of the often used flexible plastic dust hose. The advantages of metal ducting are as follows:

    • Metal ducting is installed grounded and "drains" any static charge carried inside by the particles
    • Increases flow due to less restriction than flexible hoses
    • Gives a reliable ground path out to the flex hose at the machine and allows it to be grounded well
    • Properly installed, forms an anchor point for the flex hose to attach to

    When you install a metal duct system to a CNC machine you should:
    • Use as large diameter pipe as can be connected to the dust collector housing, reducing diameter as distance increases.
    • Run the metal duct as far as possible, i.e., run it out to over the CNC table in the center 8 to 10' high
    • Screw the fittings to the collector housing and to each other
    • Tape the joints to reduce leakage
    • Verify that the dust collector itself is actually grounded to the electrical system ground
    • Make sure that the metal duct is grounded by adding a ground wire to the electrical system or collector housing (if needed)
    • Use a 4" flexible dust hose with an embedded wire. DO NOT USE AN ALL PLASTIC HOSE
    • Use the shortest length of flexible hose that allows full movement to table extremities
    • Make sure that the embedded wire from the flex hose is attached to the metal duct with a screw and crimp connector.
    • In high altitude, low humidity, or problematic locations an additional stranded wire run thru the hose may be required. This must also be connected to the ground screw along with the embedded wire from the flex hose
    • Do not allow the dust foot end of this wire to come in contact with the metal parts of the CNC machine

    Note: Along with the dust hose drain wires, it may also be beneficial to make sure that the dust hose itself has been insulated from any of the CNC components by at least 1/2". This can be done by providing a support near the top of the X or Z plates that work both as a strain relief AND an insulator. When cutting high static producing materials the charge inside the hose can build high enough to discharge thru the hose onto the frame. This problem most often comes to light when surfacing and an errant (charged) hose comes in contact with the machine.
    Last edited by Gary Campbell; 08-06-2014, 09:01 PM. Reason: ADDED ADDITIONAL INFO
    Gary Campbell
    Servo Control Upgrades
    GCnC411@gmail.com
    https://www.youtube.com/user/Islaww1/videos

    "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"
  • #2

    Gary, your last comment “Do not allow the dust foot end of this wire to come in contact with the metal parts of the CNC machine” is pretty cut & dry. I deliberately connected the ground wire to the machine thinking that is how it should be done.
    Attached Files
    Bruce Page
    Retired Hobbyist
    2013 Stinger 1 SR23
    FTC
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    • #3

      Bruce...
      The wire(s) inside and or outside of the flexible dust collector hose function only as a static drain. We want any build up of static charge to discharge AWAY from the machine (at the dust collector's electrical ground). This is the reason I recommend that no part of that wire comes in contact with the machine.

      There is a separate issue of creating ground loops, but I will not go into that.
      Gary Campbell
      Servo Control Upgrades
      GCnC411@gmail.com
      https://www.youtube.com/user/Islaww1/videos

      "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"

      Comment

      • #4

        Thanks. I'll disconnect it from the machine.
        I'm both high, (5,700') and dry! :)
        Bruce Page
        Retired Hobbyist
        2013 Stinger 1 SR23
        FTC
        Laser Pointer
        HSD 1.7kw Spindle
        KRS USB Keypad
        Mick Martin Table
        Aspire 10.512, WinCNC
        brucep128@gmail.com

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        • #5

          Thanks Jim for a timely article. I’m just setting up my machine and have the duct work grounded through metal duct and attached to the cyclone. I also installed a 4 foot copper ground rod outside the shop and was planning to attach this to the base of my machine. The new ground rod is located about 6 feet from the ground rod for the electrical service. Is this a good idea, can it cause additional problems, or is it totally unnecessary?
          Stinger II SR 44
          V Carve Pro
          1.7 KW Spindle on/off G Code

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          • #6

            Jerry....
            All that is required is to verify that the dust collector is properly grounded to the electrical system ground and have your ductwork bonded to it. Your shop electrical system (panel) should already have whatever ground rod(s) are required by local and/or national code.

            I personally have not seen where additions of driven ground rods have improved conditions as it pertains to CNC operations. In some cases they have created problems due to creation of ground loops and a change in the ground voltage potential. Maybe one of those scary smart EE type guys will chime in and tell us why.
            Gary Campbell
            Servo Control Upgrades
            GCnC411@gmail.com
            https://www.youtube.com/user/Islaww1/videos

            "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"

            Comment

            • #7

              Static reduction

              Gary. Like others, I too have been concerned about static discharge in my shop. I have a metal dust collection system for all my major machines but also a few short runs of 2 1/2" - 4" flex hose for mobile machines. I've experienced the occasional static jolt as perhaps others have. I recently replaced my shop floor with solid PVC interlocking 1/4" X 19" tiles as a result of a 1/2" - 1" minor flood which ruined my "Dricore" (read "Wetcore" when it gets wet) subfloor. The Dricore was my finished floor. At any rate, the increase in static discharge with the PVC flooring is considerable, especially when vacuuming the floor with my shop vac. I began to worry about this until I came across the following article on the web-
              http://home.comcast.net/~rodec/woodw.../DC_myths.html
              "Grounding PVC and Other Dust Collection Myths". It's an exhaustive, no pun intended, treatise on the subject of static discharge in dust collection systems. I'm still not comfortable with the odd jolt I get but this article allowed me to sleep a little better. Ian Bernard
              Ian Bernard
              Stinger 1,
              1.7kw spindle
              WIN-CNC
              V-Carve Pro
              Home made vacuum

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              • #8

                Ian...
                Rod Coles work is good, he echos the work of Sandor Nagyszalanczy who has published a few books on dust control with attention paid to static. However, unless I missed it, neither of them have any advice as it pertains to connecting these static generators known as dust collection to a computer controlled CNC machine where we expect 30-50K bits of data to flow both ways between them without an error.

                What is important here is that we operators know that he dust collection requirements for a small or home woodshop can drastically change when a CNC machine is installed. Not so much with the equipment that is required, but in the attention that is paid to the section(s) near the CNC. WinCNC's I/O boards are better than most, but not immune to static discharge.
                Last edited by Gary Campbell; 11-22-2013, 09:16 AM.
                Gary Campbell
                Servo Control Upgrades
                GCnC411@gmail.com
                https://www.youtube.com/user/Islaww1/videos

                "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"

                Comment

                • #9

                  Gary. My apologies for not reading your post more carefully. I was thinking along the lines of a dust explosion which is what Rod Coles article was addressing. Put this down to a senior moment on my part! I had run a bare copper wire from the dust collector through the flex hose (approx. 5') and then to the CNC. Obviously I will do as Bruce Page did and disconnect it from the CNC. That said, should I just terminate the bare copper wire at the top of the dust boot or do you feel I'd be better off with a flex hose with the embedded wire? Thanks again for your wisdom. Ian Bernard
                  Ian Bernard
                  Stinger 1,
                  1.7kw spindle
                  WIN-CNC
                  V-Carve Pro
                  Home made vacuum

                  Comment

                  • #10

                    Ian..
                    No apology needed. I have seen a number of solutions. From "poked "out the side of the flex hose and tied in a knot to a terminal installed and bolted to the inside of a rigid pipe. As long as it doesn't get sucked up the hose with the debris or have a chance to discharge against the machine, it doesn't matter.
                    Gary Campbell
                    Servo Control Upgrades
                    GCnC411@gmail.com
                    https://www.youtube.com/user/Islaww1/videos

                    "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"

                    Comment

                    • #11

                      "poked "out the side of the flex hose and tied in a knot'

                      Glad to see my machine left a lasting impression!

                      Nat
                      GCMF

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                      • #12

                        Nat...
                        I was not using any names, nor was I evaluating the quality of any installation.

                        MMF
                        GCMF
                        Gary Campbell
                        Servo Control Upgrades
                        GCnC411@gmail.com
                        https://www.youtube.com/user/Islaww1/videos

                        "There are 10 kinds of people in the world. Those that understand binary logic, and those who don't"

                        Comment

                        • #13

                          So, the static interferes with the stepper motors and makes them skip? I don't see a ground wire in my cable track. Is there a reason the head of the machine is not tied to ground through the cabletrack? Seems it would make sense. Thanks
                          2014 Stinger II (SR-44)
                          1.7 kW Spindle w/ speed control, Performance kit, VCarve Pro
                          www.cosmos-industrial.com
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                          • #14

                            Not clear on how to terminate the ground wire.

                            Can anyone post a pic of how the ground wire needs to be terminated?
                            "Knot or screw but not touching the CNC"?? Also, what about the other end?
                            How does that ground wire get terminated.

                            Thanks
                            Stinger I newbie.
                            abesau
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                            • #15

                              I drilled a small hole near the dust boot but not touching machine metals, I then pulled the copper thru and made a knot so it would not retract into the hose
                              James McGrew
                              CAMaster ATC 508
                              The principle of Measure twice cut once has not been replaced by a CNC

                              www.mcgrewwoodwork.com

                              https://www.facebook.com/pg/Mcgrew-W...=page_internal

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                              fixed 4-27-2020

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