500W 12000RPM spindle not enough?

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This topic contains 34 replies, has 9 voices, and was last updated by  grishien 3 months, 3 weeks ago.

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  • #92312

    grishien
    Participant

    Hi everyone,

    I made a trial milling with 500W air cooled spindle (12000RPM). Did a roughing first with ok result. Then installed ball end bit (R=1mm, short one). feed rate was 1500mm/min on oak (also tried on pine). Z is lowered 100mm below the most upper state. Please check attachment for details of hardware.

    The vibrations were awful, like I needed to hold the bottom of router with hand, otherwise during passage the bit could do a 1mm circle movement due to kind of resonance vibration. Vibration seemingly comes from the bit interaction with material. Bit itself is centered well and it’s spinning perfectly on no load.

    On youtube I saw so smooth operation where bit is going easily along the material but here it’s absolutely not like not like that. I am even afraid to run one more time to take video for you to avoid possible damabe to bit or machine.

    So, is it not enough wattage on spindle? Not enough RPM?

    Thanks for possible suggestions.

    Attachments:
    #92350

    Guffy
    Participant

    1500 is too much. Use fswizard calculator

    #92354

    BT
    Participant

    I typically use 900mm/minute (15 mm/second) for milling.  Depending on the wood, it may get adjusted down.  Also, don’t forget a finishing pass as deep as your bit or workpiece supports and relatively slowly, like 450mm/minute

    #92361

    grishien
    Participant

    By finishing pass you mean making 3D milling again? Like a third pass after roughing and 3D?

    BTW, I changed feed rate to 860mm/min. Have a look at this. Pease pay attention to timeline 00:03, 00:16, 00:43, 00:57 – this is nowhere near to acceptable operation… Of course, all blame is on me but so far I don’t have a clue where I messed up.

    https://file.io/1bd32F

    #92363

    Barry
    Participant

    file not found

    My mpcnc is a 500w spindle, works just fine.  Throw some pictures up of your build.

    1 user thanked author for this post.
    #92365

    BT
    Participant

    Agree with Barry, some pictures would help.  The video you linked above gave me a file not found error.

    #92486

    grishien
    Participant

    1. Well, Barry, I must say that your machine is moving damn fast. Looks like a lot faster than 1500mm/min. Is it 12000 RPM? What kind of bit?

    I cannot imagine how would that be possible on my setup.

    2. Please check the video of resonance here (timeline 00:03, 00:16, 00:43, 00:57):

    https://www.dropbox.com/s/ksldqn3426xiuev/messup.mp4?dl=0

    Machine dimensions 1300*750, During operation Z axis is lowered 110mm down.

    3. Here is a short video to show you my setup overall:

    https://www.dropbox.com/s/qgzzudotg4z5nmm/setup.mp4?dl=0

    #92507

    Barry
    Participant

    50mm/s, 1mm depth of cut with the 1/8″ 2 flute ball endmill Ryan sells in the shop.  I have no idea how fast it’s spinning, I manually turn it up or down so it doesn’t chatter much and let it go.  You’ll always get some chatter cutting wood(with these spindles), just depends on the direction of the cut.

    1 user thanked author for this post.
    #92584

    grishien
    Participant

    50mm/s, 1mm depth of cut with the 1/8″ 2 flute ball endmill Ryan sells in the shop. I have no idea how fast it’s spinning, I manually turn it up or down so it doesn’t chatter much and let it go. You’ll always get some chatter cutting wood(with these spindles), just depends on the direction of the cut.

    Hi Barry, what about fine cutting with ball-end bit, also going smooth in your case?

    #92592

    Barry
    Participant

    50mm/s, 1mm depth of cut with the 1/8″ 2 flute ball endmill Ryan sells in the shop. I have no idea how fast it’s spinning, I manually turn it up or down so it doesn’t chatter much and let it go. You’ll always get some chatter cutting wood(with these spindles), just depends on the direction of the cut.

    Hi Barry, what about fine cutting with ball-end bit, also going smooth in your case?

    Yep, no issues that weren’t self inflicted.

    This is a 1/16″ ball.

    1 user thanked author for this post.
    #92723

    grishien
    Participant

    Looks like you don’t have problems that I do… I gotta investigate what can be done. I’ll report if I find.

    #92803

    Barry
    Participant

    Hey.  Just thought of something.   Look at this image, is your spindle sticking way down, or is the collet up close to the Z assembly like mine?  I had issues before moving it up.  Too much sticking out with no support before.

    #92817

    Mike Pensinger
    Participant

    In your video it looks like it only does it when it comes to a vertical wall cut. I cant tell for sure but is the bit plunged in past its cutting length? It looks good otherwise.

    #92887

    grishien
    Participant

    In your video it looks like it only does it when it comes to a vertical wall cut. I cant tell for sure but is the bit plunged in past its cutting length? It looks good otherwise.

    Actually yes, it was below the cutting allowance. You are totally right. However, resonance also happened in places where plunge depth was less than that.

    I will make sure that plunge is not more than allowance. Also will:

    • lower machine
    • install triangle supports to avoid X-Y vibration of frame
    • install middle supports for long rails

    Will report when done

    #93516

    grishien
    Participant

    Hi,

    So I did it. It took so long because I fell with machine in hands and broke half of fittings so needed to reprint )

    Ok I did the following:

    • designed and installed additional legs in corners and they are tilted at 45 degrees so that they’re forming triangle with main legs of machine. This way I avoid X-Y vibration of frame
    • installed vertical supports for long rails that ire advised in https://www.thingiverse.com/thing:1160962 (had to edit model though)
    • lowered machine and decreased Z axis traveling downwards to reach material.

    I did not try it on ball-end fine milling yet. But even on roughing operation with flat 6mm bit I clearly see that now it is performing much better.

     

    1 user thanked author for this post.
    #93579

    grishien
    Participant

    Yep, I tried on ball-end bit and it’s a lot better this time.

    I attach here pictures of upgrade.

    PS. I also installed 1.5kW water cooled spindle and it cuts a lot better because it’s 24000RPM vs 12000RPM in 500W spindle. However, not sure yet if MPCNC will be able to drag this heavy head all over the work piece with affordable speed.

    Attachments:
    #93586

    Eric H
    Participant

    I have run into similar problems with a 500W DC spindle. I spent months trying to get it to work correctly (discussed here), but invariably would run into the same problems with chatter and violent shaking. After moving back to other spindle options (DW660 and Makita RT0701C) I am pretty certain that the MPCNC frame is not the weak link. I believe that it is either a problem with excessive runout (I really need to buy some dial indicators) or a thin shaft with junk bearings that allows the endmill to get pulled into the material while climbing. I don’t want to say that the 500W spindles are all bad, but I think that there are a portion (mine and it sounds like yours too) where the manufacturing quality is too poor to work under anything but the lightest of cutting loads.

    #93631

    grishien
    Participant

    (DW660 and Makita RT0701C)

    Hi. I understand that DW660 and suchlike will work better just because they are higher in RPM with up to 30K. I would install such tool as well but since it’s a “collector type” I am afraid that it will run out it’s resource fast and I’ll need to buy new and so on.

    500W are ok and I have ensured that by inserting long 100mm bit. When you touch material only with flutes (not deeper) – it works fine. Of course I suggest that if area of contact will be large at some moment then problems may occur due to inability of spindle to push through so much of material effortlessly.

    MPCNC frame is not the weak link

    It is. I have ensured that when I saw difference “before” and “after” installation of supports.

    endmill to get pulled into the material while climbing

    Same, since it’s 500W and 12000RPM only, it may not have enough power at a moment to push through the material and therefore can not get in time with scheduled movement of gantry.

    #93649

    Ryan
    Keymaster

    It is. I have ensured that when I saw difference “before” and “after” installation of supports.

    You built a very very tall machine, most of us do not have room on the leg for supports. 3″ of Z is a lot, looks like you have 6+”?

    #93661

    grishien
    Participant

    Hi, yes I had.

    I reduced and now middle junction’s lower point is 5.9” above the bed. Z path can be up to 3” now.

    However, machine is still tall right now because of long bit (3.93”) and thick material (1.85”).

    #93684

    Tim
    Participant

    Hi, yes I had.

    I reduced and now middle junction’s lower point is 5.9” above the bed. Z path can be up to 3” now.

    However, machine is still tall right now because of long bit (3.93”) and thick material (1.85”).

    Holy cow, if you have a 3.93″ long bit you will not have good results. Even running a 4″ long 3/8″ diameter endmill in a WAY more rigid machine (Haas TM-2) you would get chatter.

    #93689

    Ryan
    Keymaster

    Sounds like a drill bit?

    #93707

    Eric H
    Participant

    I don’t mean to criticize the use of these 500W spindles, I have seen a lot of activity on the forums asking about or using them, and people have been able to do some fantastic work with these cheap tools. They are a quiet and economical option for light cutting, and are well suited to many applications.

    However, I have had a number of issues with mine (chatter, vibration, poor tolerance and finishes, etc), and as a researcher by trade I feel compelled to understand why it has been performing so poorly for me. I have seen documentation of other low power DC spindles (like in the Carbide3D Nomad that is only 70 Watts!) performing so much better, so I know that the power alone is not the culprit. I have also used the same MPCNC frame with the much larger Makita at 10K rpm, with no problems with no vibration, so I know that the frame should be able to handle cuts at those lower speeds. I tweaked CAM profiles for months and designed a set of extremely low-profile mounts to get the spindle as close as possible to the z-axis, but I would still run into issues with cuts that should not have posed any problems. Something has to be going on with the spindle itself, and I want to find out.

    A comment in another thread mentioned that the bearings in these spindles might be seated in rubber. This would allow it to feel stable and keep the runout low while idle, but as soon as you get cutting or the tool heats up everything can fall apart quickly (especially if you have a long tool or a less than rigid machine). I found a video where a guy takes apart and critiques a 300V Quiet-cut spindle (https://www.youtube.com/watch?v=7P5THNNjafU). He finds these rubber gaskets, as well as some other issues that he thinks explain the EMI issues. This was a slightly different model than the 500W spindles everyone seems to be using now, so I figured I would take mine apart and see what was in there.

    Dissassembled-Spindle

    After opening it up it was pretty clear this was just a slightly scaled up version of the spindle in that video, no significant improvements that I could see, and a couple of issues that weren’t mentioned.

    The bearings are the common 608z’s that we all used during he build process. These are not ideal for this application (they are not designed for simultaneous axial and radial loading), but I don’t think they are the major problem here. On definite plus is that we all probably have some of these bearings on hand if you ever need to swap them out.

    Unfortunately, the rubber seats mentioned in the comment and the video are present, and were much thicker and looser than I had anticipated. The bearings and rubber seats could easily slide out of the top and bottom plates, indicating that the rubber is not compressed in its natural state. The rubber sides are over 0.5mm thick, and I could easily compress it with my finger. The radial forces involved in cutting could definitely deform this rubber, and any deflection at the point of these bearings will be multiplied at the collet and even more at the tip of a long endmill. This will allow the cutter to be push away from or be pulled into the material, causing the violent chatter that has been reported.

    Shaft-with-upper-and-lower-plates

    Rubber-Thickness

    I also noticed these wave springs between the rubber seat and the front bearing. I believe the purpose of these is to provide an axial pre-load on the bearings. Ideally, the screws that connect the top and bottom plates would provide this preload, but the plates instead clamp the body of the spindle. The manufacturers needed some way to put some pre-load on the shaft, and I think this was there quick and easy solution. This seems questionable, because any tension on the shaft (e.g. cutting with an upcut endmill) can cause the entire shaft to be pulled down relative to the body of the spindle. This would cause deeper than expected cuts, exacerbating any other problems with vibration or chatter.

    Wave-spring

    I am not an electrical engineer, so I can’t comment on the design of the electronics inside, but if you are interested in more details I am happy to provide more images or measurements of those components.

    Again, I don’t want to say that you cannot have goods results with these spindles, clearly people can and have, but I think it is important for anybody considering them or currently using them to be aware of their capabilities and limitations.

    2 users thanked author for this post.
    #93795

    grishien
    Participant

    Holy cow, if you have a 3.93″ long bit you will not have good results. Even running a 4″ long 3/8″ diameter endmill in a WAY more rigid machine (Haas TM-2) you would get chatter.

    I understand that the longer the bit the more chatter. However it worked fine in a fine milling operation even on a 500W spindle, I cannot complain.

    Sounds like a drill bit?

    It’s R2xD6x60x100L from Aliexpress.

    exacerbating

    Eric H, that’s a valuable insight, thank you for that!

    #93897

    grishien
    Participant

    Hi. Today I tried to do a full cut with 1.5kw water cooled spindle. Which is around 3kg on it’s own plus some water mass running through.

    The piece gives 24000 RPM and I expected it to cut better than 500W air cooled one.

    However, I noticed that it:

    • makes a lot more burrs. Sometimes even chips off small parts on roughing 3D job
    • is very hard to move, MPCNC’s mena 17s move in jerked manner trying to move it
    • when RAMPS is turned off, the tool slides all the way down – resting friction cannot hold it in place
    • High mass makes it hard to stop and reverse on X-Y directions – little vibration happens there

    When you run such tool you expect it to feed faster but the mass multiplied by speed makes nema17 to miss steps at some time. But then if you have to feed slowly then why mess with it? I’ll better revert to 500W.

    On the upside I noticed that it spins perfectly without any clue of vibration on it’s own – nice to look and hear. The only benefit – to sit and watch it like a TV 🙂 I will use it when I grow into havier router design.

    #93934

    Ryan
    Keymaster

    1.5kW is a very strong spindle, we run a 600W and I have seen no reason to go larger. I bet it is a beauty though, maybe one day I will make a design for something that size!

    #93939

    Kostas
    Participant

    Sorry for being off topic.

    -snip-

    You really went above and beyond to figure this thing out. This is good info, good on you for sharing, maybe update your original post about the spindles or make a separate one to make it easier to find if someone is looking into it in the future.

     

    1 user thanked author for this post.
    #94026

    grishien
    Participant

    Hi,

    Today working with 500W again I noticed that machine’s steppers skip steps when it changes direction and has a lot of material to cut at the same time. By “a lot” I mean 6mm flat bit, 2.5mm stepdown, 900 mm/min feed and the bit touches material from 2 sides (like performing kind of round movement of very small radius fast).

    Skipping definitely comes from trying to change direction and accelerate fast still having to do some job on material.

    I have been thinking about possibility to gradually reduce/increase speed during changes of spindle movement direction. Is it possible to do in marlin itself or should I search for such possibility in artcam/estlcam?

    Thanks.

    #94030

    Tim
    Participant

    Hi,

    Today working with 500W again I noticed that machine’s steppers skip steps when it changes direction and has a lot of material to cut at the same time. By “a lot” I mean 6mm flat bit, 2.5mm stepdown, 90mm/min feed and the bit touches material from 2 sides (like performing kind of round movement of very small radius fast).

    Skipping definitely comes from trying to change direction and accelerate fast still having to do some job on material.

    I have been thinking about possibility to gradually reduce/increase speed during changes of spindle movement direction. Is it possible to do in marlin itself or should I search for such possibility in artcam/estlcam?

    Thanks.

    I don’t know about artcam/estlcam but maybe look for a setting called “trochoidal milling” in one of those softwares. It is a strategy designed to avoid spikes in tool engagement like you’re talking about.
    Surely you mean 900mm/min also?

    #94033

    grishien
    Participant

    Surely you mean 900mm/min also?

    Yes 900 )

    “trochoidal milling”

    Thanks, I ‘ll check that.

    Can it (the one that I was thinking of) be #define DEFAULT_ACCELERATION in Marlin?

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