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Thread: GME's New 80/20 CNC Build - My Design

  1. #385
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    Default Re: GME's New 80/20 CNC Build - My Design

    The saga continues . . .

    To get to the numbers I needed, I started by leveling a 3/4 glass plate on the spoilboard. I used 2 setups, one on the extreme left, and another on the extreme right. This was important, because the gantry beam has some twist. I can tell before measuring, because I have ridges in one direction on the left, and in the opposite direction on the right. At the midpoint, there are no ridges. That means that as the Z axis moves from left to right, it is tilting one way at one end, has a neutral position at the center , and then tilts the other way as it continues it's travel.

    I used my Edge Technology Pro Tram System to take measurements. Here's a picture of it:

    GME's New 80/20 CNC Build - My Design-pro_tram_by_edge_technology_bridgeport_milling_spindle_square_front__47776-1390781111-100-100-png

    I oriented it so the dials faced the sides of the CNC. Using only one of the dials, I got the glass plate leveled. I zeroed the dials according to the instructions that came with the Pro Tram using the supplied magnate, and lowered the gauge until the plungers were depressed about .050". Then, it was a simple matter of reading the differences between the 2 indicators.

    Here's what I found (fractions rounded):

    GME's New 80/20 CNC Build - My Design-left-side-measure-jpg

    GME's New 80/20 CNC Build - My Design-right-side-jpg
    Correction to the right side drawing. The .015" measure is wrong. It should read .0015".

    The angle errors (.054 and .017 degrees) seem fairly small. However, when projected out over distance, t#he amount of error in thousands of an inch can increase rapidly over distance. My interface plates are 9.25". Assuming I shim between the horizontal lower interface plate and the gantry mounting plate, on the left side, it will take about .009" to correct the error. The right is much better. It will only take about .003" on the right over 9.25".

    As noted in post #384 above, I used an online calculator to crunch the numbers. It saved a huge amount of time, and I could select how many decimal places up to 9. I highly recommend it.

    Okay, let's look at what it all means in day-to-day operation. Aside from my 60mm surfacing bit, I limit my cutter to 1/2" diameter and under. I use 1/8" and 1/4" most often. On the left side, .054 degrees translates to a deviation of only .000471" for a 1/2" cutter, .000236" for 1/4" and .000118" for 1/8". Not much deviation. The right is much better: .000148" for 1/2", .0000742" for 1/4" and .0000371" for 1/8" - a minuscule amount. All of this is at 100% stepover. With a reduced stepover, the error should be even less.

    Unfortunately, while the calcs provide the theoretical amount of shimming to correct for the deviation, the practical may not comport with theory. That's because the aluminum gantry beam not behave like the theory suggests it should. There will also be issues when it comes to re-squaring the gantry. Making adjustments means loosing mounting screws. Once loosened, the gantry will predictably try to return to its original shape. That will throw off measurements when trying to make adjustments. What should be a quick and easy setup process may turn into an exercise in trial and error. Seems like a long and frustrating process.

    ger21 suggested in his post #381 that I might not notice the error during normal cutting operations. I tend to agree. If start a project requiring a higher level of precision, I can always make the adjustments at that time. I'll just hold onto the data I collected, so I don't have to reinvent the wheel.

    Conclusion: For now, I believe I will leave things as they are. If I find the need for higher precision, I will make the changes at that time. In some cases, I can also mitigate the issue somewhat by cutting parts using a raster cut running with the Y axis.

    If anyone would like additional detail, just ask.

    Gary


    Attached Thumbnails Attached Thumbnails GME's New 80/20 CNC Build - My Design-right-side-jpg   GME's New 80/20 CNC Build - My Design-left-side-measure-jpg   GME's New 80/20 CNC Build - My Design-pro_tram_by_edge_technology_bridgeport_milling_spindle_square_front__47776-1390781111-100-100-png  
    The Old Man and the C -----NC


  2. #386
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    Default Re: GME's New 80/20 CNC Build - My Design

    A wise decision, Now get started making things!

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


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    Default Re: GME's New 80/20 CNC Build - My Design

    Overdue for an update.

    Call it a touch of OCD, or whatever, but I just couldn't let go of the gantry issue. So, I fixed it. I first trammed the gantry (front to back) with the Z axis to the extreme right. Then, I moved the gantry to the extreme left and recalculated the amount of error. The gantry is held in place by 5 pairs of bolts. So, I calculated the amount of shimming required to attain the correct angle at each bolt - maximum shimming at one end and tapering to zero at the other. I guess I did the calculations correctly, because I got it right on the first try. Tramming looks good in both directions all the way across. I ran my 60mm surfacing cutter, taking off .010" and the surface smooth - no ridges.

    For my first project, I decided to cut some new hard maple hold downs. The t-track spacing is closer together than my previous machine and the hold downs from back when weren't optimal. Here's a Vectric Aspire rendering:

    GME's New 80/20 CNC Build - My Design-hold-downs-2-jpg

    Cutting the hold downs revealed a new problem to address. I was cutting them with the length of the wood oriented from front to back, so that the slot was cut parallel to the Y axis. I was cutting 7 pieces at a time from one stick. The first 3 slots cut as expected, but the last 4 were off. The X axis went negative about 1/8" and held that position for the remaining pieces. The second stick was fine. The 3rd stick went off for the last 2 pieces.

    My first thought was noise. Mechanical didn't make sense, because I used roughly the same positioning for each stick I cut. I also knew I hadn't made a positioning error, like at an angle to Y, because all 7 pieces would have had their slots cut at an angle. Not the case.

    Previously, I tried using an AM radio tuned off station to try to get a read on noise. There was definitely noise there, but unless it was giving me problems, I was going to live with it. Turns out living with it wasn't an option after all.

    mactech54 suggested specific line filter (a TDK Lambda) in another thread. I ordered and installed one. Cleaned the noise right up, or at least as far as I could tell with an AM radio. I could detect no change in the AM static, which was very different than before, without a filter. Without the filter, there was no question about noise. As soon as spun up the router, the noise was obvious. With the filter, no noise at all. Can't beat that. Still need to cut some parts to ensure the problem is solved, but I'm confident.

    More to follow. . . .

    Gary


    Attached Thumbnails Attached Thumbnails GME's New 80/20 CNC Build - My Design-hold-downs-2-jpg  
    The Old Man and the C -----NC


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    Default Re: GME's New 80/20 CNC Build - My Design

    Good news Gary. It seems like SOP to add a line filter when using those Chinese drives.

    Last edited by wmgeorge; 10-05-2019 at 10:00 PM.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP


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    Default Re: GME's New 80/20 CNC Build - My Design

    Good work compensating for the twist Gary.
    It sounded like a daunting task to me....lol

    I missed Mactecs comment about the noise filter. Which one did you end up buying?

    Steve



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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by Sterob View Post
    Good work compensating for the twist Gary.
    It sounded like a daunting task to me....lol

    I missed Mactecs comment about the noise filter. Which one did you end up buying?

    Steve

    Thanks, Steve. It was a bit scary taking on the twist. I worked on it in my head for days, before putting my hands on. Lot's of preparation paid off.

    The noise filter is a TDK-Lambda (manufacturer), model: RSEN-230L. It's good to 250VAC; 30 amps. I have no idea where you would get one in Australia. I got mine from Mouser Electronics here in the U.S. They sell globally. I took a quick look at their global locations. The closest to you appears to be Singapore. Here's the address I found:

    3 Changi North Street 2
    LogisTech Building #03-01B
    Singapore 498827

    Here is a link to the Mouser page containing the filter I bought: https://www.mouser.com/ProductDetail...rrencycode=USD

    Here's a link to the thread where mactec made the recommendation. It's on the 2nd page, post #21. https://www.cnczone.com/forums/diy-c...metimes-2.html

    Gary


    The Old Man and the C -----NC


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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by wmgeorge View Post
    Good news Gary. It seems like SOP to add a line filter when using those Chinese drives.
    Thanks, Bill. Funny, but I didn't have problems with my first machine, which ran on the same electronics. I'm guessing that it had to do with physical separation. With my first machine, the VFD and control boxes were separated by more distance, and the cable to my spindle was separated from all of the other control cables. With this build, the boxes are very close together, and the Spindle cable is in the same cable tracks as all the other cabling.

    I'm with you. A line filter is a must for anyone using HY VFDs. Fortunately, they are a relatively inexpensive solution.

    Gary


    The Old Man and the C -----NC


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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by wmgeorge View Post
    Good news Gary. It seems like SOP to add a line filter when using those Chinese drives.
    There is no difference between any VFD Drives it does not matter where they are manufactured or by who they all put out the same EMI, if they don't then they are not
    power up

    How cables are placed shields are Grounded play a big part of a noise free system

    Placement of the VFD Drives in a separate cabinet can sometimes give a false impression that you don't have a noise problem

    Mactec54


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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by GME View Post
    Thanks, Steve. It was a bit scary taking on the twist. I worked on it in my head for days, before putting my hands on. Lot's of preparation paid off.

    The noise filter is a TDK-Lambda (manufacturer), model: RSEN-230L. It's good to 250VAC; 30 amps. I have no idea where you would get one in Australia. I got mine from Mouser Electronics here in the U.S. They sell globally. I took a quick look at their global locations. The closest to you appears to be Singapore. Here's the address I found:

    3 Changi North Street 2
    LogisTech Building #03-01B
    Singapore 498827

    Here is a link to the Mouser page containing the filter I bought: https://www.mouser.com/ProductDetail...US¤cycode=USD

    Here's a link to the thread where mactec made the recommendation. It's on the 2nd page, post #21. https://www.cnczone.com/forums/diy-c...metimes-2.html

    Gary
    Thanks Gary,
    I think TDK have a presence in Australia. If not, Mouser is a possibility.



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    Default Re: GME's New 80/20 CNC Build - My Design

    Quote Originally Posted by mactec54 View Post
    There is no difference between any VFD Drives it does not matter where they are manufactured or by who they all put out the same EMI, if they don't then they are not
    power up

    How cables are placed shields are Grounded play a big part of a noise free system

    Placement of the VFD Drives in a separate cabinet can sometimes give a false impression that you don't have a noise problem

    I know what you mean about putting the VFD in a separate cabinet can give a false sense of security re EMI. I put mine in a separate cabinet mistakenly believing it would make a huge difference. It didn't. What made the difference was proper grounding, and a good line filter. On my first machine, where the spindle cable was not properly grounded (grounded at only one end), noise didn't interfere with operation, probably because I put the spindle cable in a separate cable chain running in the opposite direction and physically separated from the other cabling. I'm guessing that the physical separation and distance kept me from suffering from noise induced issues, despite the fact there was still a lot of noise.

    On my current machine, I have the spindle cable running in the same cable chain as stepper and proximity switch cables, which seems to be the more conventional setup. Proper grounding and filtering lets me get away with it.

    Thank you so much for your willingness to help us get our systems working properly. I got my VFD settings from your various posts (2.2 kw HY), and learned the proper grounding and filtering methods from the information you have so often provided. Your specific product suggestions were also very helpful. You are a valuable resource and much appreciated.

    Gary


    The Old Man and the C -----NC


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