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my experience with MDF and EMI

Discussion in 'General Talk' started by Tom Bellfoy, Jun 22, 2021.

  1. Tom Bellfoy

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    first off I must say that I/m a hobbyist and still quite a noob when it comes down to the CNC learning curve, I have a busy retired lifestyle with many interests and take quite a few weeks or months off before coming back to my new lead 1010 with high Z. I built a 48 inch cube enclosure with all openbuilds products with two sets of doors and clear lexan with 1/4 inch plywood top, swing arm. I,ve carved out the Openbuilds logo twice out plywood and oak with no problems .

    I believe in the many benefits of forums such as the openbuilds forum and how with ones own guilt admissions and experience that can be shared to other guests and forum members that we can all gain something.

    The Openbuilds team have helped this noob out on many occasions with their very timely responses and with directions to move forward and I must say they should be commended for their help. I also love the Openbuilds products, very well thought out and designed.

    I have never been able to fully resurface my "MDF" spoilboard in all this time as my blackbox has either gone into alarm and quit the job or shut my computer port down and mostly all because of electrical interference. (EMI)

    I have to admit my guilt that I had not studied the blackbox documentation regarding issues with not suspending the USB port.

    I have come to the conclusion that the MDF dust or fine particles are the culprit

    my particulars :
    - adding the enclosure did not add to the EMI problems I have been experiencing
    - full 48 X 48 X 48 enclosure with two set of full doors open wide or closed
    -48 " LED light fixture inside roof mount on or off makes no difference with ferrit cores at both ends, unplugged or lit
    - harbor freight style one HP dust collector hooked up to grounded vacuum hose in enclosure always working during time CNC machine running G code.
    -- workshop router booster on or off no difference
    - laptop computer with 6 ft. USB cable with ferrite cores on each end no difference
    - ferrite wraps on two of three servor motors (so far)
    - ferrite wraps of three of six limit switches (so far)
    - ferrite wrap on XYZ probe wire
    - extra ferrite wrap on Dewalt router near Z area wire
    - ferrite wrap on Openbuilds relay module
    - trying to surface spoilboard with .5MM cut 40% overcut
    - with all above specs in play router shuts off after 25 or 27 minutes and quits the job.

    - disconnect router power, run program again = program runs to completion 65 minutes - all is good
    - remove 27MM surfacing cutter from Dewalt router, router powered up this time - program runs to completion - all is good

    so seems like there are no EMI issues when the dewalt router is not cutting MDF- shutdown only occurs when router is creating the fine dust from MDF

    Your thoughts ???

    I hope this summary will at least help other users.



    :


    When cutting just .5MM on MDF spoilboard at a 40 % overcut I can only get it to run for 18-24 minutes before closing the USB port
     
  2. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    Shielding and grounding are much better for EMI than ferrites. Make sure your motors including your router has an earth ground path.
    Also make sure your laptop is setup correctly, no sleep while plugged in, usb suspend off, get your router and dust collector on a different power circuit than your BB and laptop.
    I cut MDF all the time with my makita and now router11 with no issues also using a 2hp HF sucker (an never grounded the hose)..
    Get your usb cable away from any power wires, crossing at 90deg is ok parallel runs are bad.
    Why is your surfacing program taking 65min?
    Cheers
    Gary
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Much longer than our included cable
     
  4. rscamp

    rscamp Well-Known
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    Hi Tom. I think Gary lists some very good items to look at. It could be that some of Gary's points may have helped solve a similar issue that I had. But here's my experience FWIW.

    Fortunately I was able to solve a similar problem early on. In my case, aggressively addressing dust extraction grounding solved the problem while applying ferrites and such had no effect. Dust extraction can generate extreme static charge - particularly when large amounts of particulate are being extracted at a particular moment in time. You can literally feel this when holding an ungrounded hose. I also suspect that after a gradual charge buildup a threshold discharge can occur causing a delayed OB controller fault.

    You say you have a "grounded vacuum hose" which should help address the fault issue. But perhaps there is an issue with how it is grounded. Can you describe exactly what parts of the extraction pathway are grounded and how the hose and air stream are ensured to be in contact with a ground potential conductor? Do you have the machine frame tied to the same common or "star" ground used for the dust extractor?
     
    #4 rscamp, Jun 23, 2021
    Last edited: Jun 23, 2021
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  5. Tom Bellfoy

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    Gary, Mark and Rob:
    Thank you all for your input, In the next few days I hope to find the time to make the changes.
    From all your input I'm now certain poor grounding is the cause of the problem.
    My lead 1010 is in my workshop unattached 30 feet away from my house and I was relying on just an electrical ground.
    My Dewalt router, Openbuilds 01T relay, blackbox rely only on electrical ground all provided by a three prong extension cord.
    So (my bad)
    I will make sure I have an earth ground in my workshop and will also put my router and HF dust collector on a separate circuit.
    Mark: I think my kids borrowed my short USB cord supplied with my blackbox. I shall get another
    Rob: I did notice EMI buildup occurred faster when making heavier cuts
    Tom
     
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  6. rscamp

    rscamp Well-Known
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    I think this symptom points strongly to static discharge as the trigger of the fault. FWIW, the common ground point I used was a copper water pipe in the home. In addition to running bare copper wire along the hose and to a cyclone, the copper pipe was connected with another insulated wire routed directly to the extraction inlet on the machine which in turn was electrically connected to copper tape running along the inside. This additional wire actually runs in the cable track along with the other axis wiring. After this change, I noticed that dust no longer builds up on the inlet structure.
     
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  7. Rink

    Rink Well-Known
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    Good morning.
    May I ask for a clarification?...
    Isn't the ground on a three-prong outlet (here in the US anyway) grounded to the "earth"? Here at my house and shop, the electrical service is connected to an 8 foot copper rod, about 1 inch diameter, which was power-hammered into the ground. I've seen this advice about "earthing" on the forum before, and always wondered what the difference is.
    thx, rink.
     
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  8. rscamp

    rscamp Well-Known
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    Commercial machines are earthed using a rod similar to what you describe in order to provide the lowest possible resistance to ground. Your CNC machine frame and extraction grounding would all connect as directly as possible to a common point on this earthing rod.

    There are actually two things of concern here - bonding and grounding. Grounding is what we've been discussing. Good bonding is ensuring very low resistance connections. Among other things, this involves avoiding dissimilar metals, avoiding materials prone to corrosion, and sometimes employing hermetic joints. It is possible to have a good grounding strategy but also to have high resistance connections negating the benefits.
     
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  9. Tom Bellfoy

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    I've been busy with house chores and Friday morning I will inspect my electrical pony panel in my workshop
    (power from house main panel to workshop pony by underground wiring)
    Have to move some items to get to the workshop pony panel to make sure it has its own ground rod.
     
  10. Rink

    Rink Well-Known
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    Rs camp: thx for the explanation.
     
  11. TerjeB

    TerjeB New
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  12. Rink

    Rink Well-Known
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    Thank you.
     
  13. Tom Bellfoy

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    Gary:
    Sorry about the delay in responding regarding the 65 minutes it takes to run the spoilboard surfacing, maybe you can give me a hint as to how to shorten the time.
    Here is the specs I have entered on the Wizard for surfacing:
    router bit diameter = 27MM
    stepover = 40%
    feedrate = 800MM/min
    width (X) = 730MM
    length (Y) = 750MM
    skim depth = .5MM
    spindle RPM = 1000 MM
    router is dewalt set at 2.5 I think

    Finally today I installed a new ground rod with #6 bare copper ground wire and connected it to my cold water copper pipe in my workshop. To which I connected the vacuum hose copper wire running inside the 2.5 inch hose, also grounded the steel metal bench and the openbuilds enclosure to the copper pipe
    My pony panel in the garage does not have its own ground rod and according to our Ontario electrical code it does not require one as not recommended because it relies on the houses main supply ground rod. Good electrical bonding, clean pipe, low resistance

    My new earthed ground rod is only connected to copper pipe in my workshop which in turn provides an earth ground to my CNC setup.

    My Dewalt router and HF dust collector now runs on a different electrical circuit and is of course on a different circuit breaker.

    With all that said I just need the time to try it, Hopefully I will get the time by Monday and will report back

    TerejeB: thats a great article, thank you for that

    Tom
     
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  14. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    Should be able to do 1200mm/min and 60% step over but every machine is different.. I guess it doesn't matter that much as it's not something you should be running too often, as long as it runs!
    Cheers
    Gary
     
  15. Tom Bellfoy

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    UPDATE:
    better late than never I say:
    I finally made all the recommended changes to my CNC build with regard to eliminating EMI,
    new dedicated ground rod installed in ground, # 6 bare copper wire about 20 ft. to my CNC machine
    enclosure and steel frame grounded, everything that could be grounded was grounded.
    ran a .5 MM cut on my MDF spoilboard almost full size for my lead 1010. with my 1HP dust collector system.
    this time the program ran the complete job in about 20 minutes
    because I had many attempts which previously failed I had to make a 1MM cut to try to level off previous fails, machine, after about five minutes of
    slight cut, when it hit the 1 MM cut area it lasted about two minutes before it disconnected my computer, error code 31.
    frustrated, irritated, I just left the shop to deal with this next day.
    After a pause and dinner I went back out to shop, vacuumed up the MDF dust in the enclosure, disconnected the dust boot and its interior ground wire , ran the 1MM cut with no dust boot/vacuum, and used my original shop vac while leaning in to the enclosure, when it started cutting the 1MM, I was amazed, full of MDF dust, almost eating the dust for another 6-7 minutes, keeping the dust in the shop vac, the program ran its course with no shut down, no error code.

    With all that said I have to say the problem was with EMI build up through the vacuum hose, (Busy Bee Tools in Canada type clear plastic hose (2.3 inch)
    Maybe there is a static free hose product out there, but for now I'm just as happy to run my machine and periodically using my shop vacuum to manually vacuum up the dust.
    I hope this helps other users
     
  16. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Indeed. Foiled/metal coiled dust hoses exist. Earth the hose as well.
     

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