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IndustryArena Forum > MetalWorking Machines > CNC "do-it-yourself" > Need offers of advice please. Next level time with my router.
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  1. #1
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    Need offers of advice please. Next level time with my router.

    My build is version...... maybe 5? This machine started as a timber frame. One Nema 23 for the Y. Absolutely totally loose and gained nothing except for starting a hobby that has been awesome. Anyways I am at a point I need some help to get over some of the build hurdles and mistakes I must have made. Currently the machine is running a 4.5Kw 3 phase spindle. I bought a heap of linear rails years ago. Cost me about $1.5k all up. Including the SBR30.

    I use the machine for my small joinery business - this is the reason for the vices all in a long row. And I use it for alloy components. I was lucky enough to import a bunch of vices that are ok..... some needed shimming the manufacturing process they sit 0.5mm lower or higher. So needed setting up to align them.

    The frame is welded 6mm thick box section sizes 100*100, 152*76mm and some other pieces of box section I had. Nothing under a 4mm wall thickness. I have filled the main rails with sand and some of the verticle. I cross braced the nana out of the frame. Its level and dyna bolted into the floor.

    The T table is 1100*900*100mm solid cast. About 750kg (guess cant remember)

    The gantry sides are cut out of 25mm mild steel. And have the old alloy bracing screwed to it because I liked it. This was an upgrade. The rear of the gantry is timber in the centre. With 100/70/8mm unequal mild steel angle screwed deep into the timber. Also bolted to the side pieces. Gantry is sitting on several SBR30 blocks. The front of the gantry holding the X is 6mm alloy. Also screwed into the timber. The X is running on 2 x SBR20 linear rails.

    The Y is run by 2 closed loop Nema 34s on 2600mm 2510 screws. The X is also a Closed Nema 34 1400mm 2510 screw. The Z is a 1605 screw.

    The Z. Is made out of 16mm thick alloy rear, and spindle mount on front. The sides are braced with 6mm alloy screwed onto the sides. Using SBR20 linear rails. Has about a 280mm travel. This I think I need to rebuild.

    The machine is reasonably heavy. Level. And machines timber like butter. Alloy goes ok. Just ok but awesome results provided I program correctly. Ok. I am in total understanding that the round linear rails are ****e. I did think that by building the gantry that this would be minimilised.

    My problem and I have tried to address this before. If I use a 6mm endmill, or a 14mm endmill. I can climb or conventional mill cut alloy no problem. If I cut a large circle (or small) as the endmill travels around the circle, it will vibrate the whole gantry in a low resolution brrrrrp vibration. Only in certain directions and worst when both X and Y are running together (on a curve) Strange though, on a test today, the machine actually performed better when climb cutting. It is very apparent that there is something fundamentally wrong with my design if this even happens using a tiny 6mm endmill??? Now I can swing off the spindle and its tight. Real solid. Obviously if I put a dial indocator on it I can see movement. But nothing loose. I think the Z is not heavy enough. I think I need to get rid of the round rails. Dont get me wrong this machine is pretty good. I just cringe, everytime I hear the resonance. It will show in the cut too.

    So heres the thing. Do I rebuild a whole X axis assy. And a whole new Z axis assy. And bolt it onto the front of the gantry? I can also remove the round SBR30 rails the Y is sitting on too. But in all honestly? I am certain the main issue is in the Z. Resonating. I could do that. Build a new assembly. Take the time. And the change over would be rapid. But gee. I just dont want to waste my time. So. Please. Some help advice? Ive taken pics this time.
    Attached Thumbnails Attached Thumbnails 1.jpg   2.jpg   3.jpg   4.jpg  

    5.jpg   6.jpg   7.jpg   8.jpg  


  2. #2
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    Re: Need offers of advice please. Next level time with my router.

    Pants off now. This is all I have. Far out it would be awesome to sort this. I even thought about a super heavy Z with a counterweight.

  3. #3
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    Re: Need offers of advice please. Next level time with my router.

    there's so many elements here...redoing the Z is probably the cheapest to do, this time use proper rails. Then if the noise persists I'd move onto all the other rails

    did you try to locate this noise with a dB counter? can use a phone app for that. If the noise is localized, its a good sign that only one thing needs to be fixed...

  4. #4
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    Re: Need offers of advice please. Next level time with my router.

    You have to be heading in the right direction with the proposed changes.One further thing to check is that the nose of the spindle has a clean socket for the collet to seat in.A tiny piece of dust or corrosion can throw the path of the tool tip out of true.Cleaning the collets and collet nuts regularly is good practice.As I'm sure you know, a tiny amount of eccentricity in the rotation of the tool will very the loads as it rotates and can set up oscillations.

  5. #5
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    Re: Need offers of advice please. Next level time with my router.

    I have been a technician for a very long time in multiple trades. If I walked into my workshop, not knowing, I would say, "dude, there is something loose on that machine". Honestly it does my head in. And to clarify, the vibration is bad enough I almost think something will give one day. Just, its only on a certain direction or portion of a circle.

    Darn I had a Db meter in my hand today I should have brought it home. I would need to setup a large dia circle cut to catch it.

    I posted as much as I could so if it was possible, someone might spot a very apparent flaw in design.

    So the SBR type rails sit a lot higher than the HGR type. I was thinking I could get some steel milled as a packer to go under the HGR rails. drilled to match the HGH and also drilled to match the SBR mounting underneath. Then no need to modify the screw. That might stiffen the Z and be just an hour or so to install. Could almost do that to the X axis too.

    Next level is just build a new Z axis assy and mount it on some HGR rails for the X. So in the basic basic design methodology. And correct me if I am wrong. If I had a back piece of say 20mm mild steel cut out to shape for the rear of the Z axis. Installed a couple of HGR rails and then another mild steel say 20mm plate to mount the spindle too. Very simple and basic. Heavy. Or not heavy enough? I do know its cheap to get something cut out like this. Not sure if machining it flat is cheap. But as for the basic design - right direction? Will be heavy so will use a Nema 34 to lift it.

    I drew this up this evening. - mild steel plate because its a lot stiffer aye? Use 20mm alloy is no go because its not stiff enough correct? Although I did think of laminating alloy to some steel with bolts and then machining the alloy flat - that make sense?


    P.S - thanks and yes I do check my collet I am old school. Scotchbrite gets used a lot in my workshop. I have tried everything to sort this issue.

  6. #6
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    Re: Need offers of advice please. Next level time with my router.

    What are your cutting parameters with a 6mm end mill? Assuming when you say alloy you mean aluminum? Even with a 6mm end mill you can generate some pretty decent forces if you're running fast with a high DOC.

    Before jumping in, take some measurements. Get a fish scale and a dial indicator and see how much things are moving when you put a ~30lb load on them. You might find that you've got something loose in one direction or on one axis. Could also be a bearing thats shot or just out of spec.

    Your gantry doesn't look like it has alot of depth, particularly for the span length. That would mean its going to be flexing or twisting alot in your long axis (I think you call it Y). Could quick and easy bolt some big ole timbers to the back of it and see if that improves things.

  7. #7
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    Re: Need offers of advice please. Next level time with my router.

    Quote Originally Posted by jaguar36 View Post
    What are your cutting parameters with a 6mm end mill? Assuming when you say alloy you mean aluminum? Even with a 6mm end mill you can generate some pretty decent forces if you're running fast with a high DOC.

    Before jumping in, take some measurements. Get a fish scale and a dial indicator and see how much things are moving when you put a ~30lb load on them. You might find that you've got something loose in one direction or on one axis. Could also be a bearing thats shot or just out of spec.

    Your gantry doesn't look like it has alot of depth, particularly for the span length. That would mean its going to be flexing or twisting alot in your long axis (I think you call it Y). Could quick and easy bolt some big ole timbers to the back of it and see if that improves things.
    Aw Mr Jaguar it would be just fantastic to find a bearing - ive had them all out. Or to bolt a gnarly piece of Jarrah to the back of the gantry. Ive swung, heaved and hung off that spindle. I can locate a flex or slight movement but nothing that would point me to the easy loose sounding vibration I get. I am going to take a slow motion movie in the weekend. I am going to beat this. I take good decent full depth cuts out of aluminum with a 6mm endmill. I also find it happens on the less aggressive cuts - and its that, that gets me. In the real simple diagram attached. Imagine the endmill is travelling in the dotted line (either climb or conventional) the solid red section (from memory) is where it will vibrate. Thinking about it its almost when the load is starting to increase (or decrease) on the X axis.

    The two angle sections on the top and bottom of the gantry I now confirm are 100*75*8mm mild steel. Screwed into the beam with a whole lot of 8mm 70mm bolts. Bolted to the sides.

    Ok the weekend is a new set of days I can investigate with a DTI. Hey and I used to think it was my timber frame. That steel frame underneath? I welded that together over Xmas to beat this problem. Including purchasing the super heavy T Slot table ha

  8. #8
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    Re: Need offers of advice please. Next level time with my router.

    Hi Boydage - How is the circle programmed? circles in gcode consist of small lines. Depending on the line length and your acceleration settings will influence how your machine responds. If you send the profile to your machine from cad can you change the increment length of the lines? a 1mm increment will behave different to a 5mm increment? Also if you change the microstepping this may help. If its set to say 1000 change it to 2000 but remember to change the steps per unit as well. This will change the dynamics of the motion. Peter

  9. #9
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    Re: Need offers of advice please. Next level time with my router.

    Hi. Big week working away from home. I had an hour just before I left so decided to swing off my machine a bit. Wow. We build things and build them strong (as we consider strong) yet after a bit of shaking and twisting, I found a number of problems.

    Thanks I did look at my programming I use Fusion, and the vibration I am getting is definitely in time with the spindle. I did once set a tolerance of 0.0001mm to see exactly what Mr Peteng has mentioned. My poor machine slowed down, and made a ":dit dit dit dit dit....."as it travelled around an arc. Actually. I have found also if I model something with a spline curve in my CAD program it does this also. I guess its all the fine points a spline creates in the resolution of the CAD drawing. This is what you mean correct?

    But as for the mechanics of my machine I found:

    The end bearing support on the X axis ballscrew has become loose, click click back and forth laterally. The bearing is spinning inside the housing and has slightly flogged out the housing I made with not tight enough tolerance. Also, I can pull the top of the Z, forward and back in the Y direction, perpendicular to the SBR rails and hear a noticeable click with movement in the carriages. If I pull the gantry in the Y direction on one side, one of the screws is clicking longitudinally possibly from the angular pair of bearings having become loose somehow. There was something else that made me go "hmmm" too. But I almost missed my flight to work ha.

    Hey so I am going to sort these issues. I am confident they will fix an amount of my issue. I am still a bit bent towards getting those round rails off the machine. I know one of the guys on here doesn't like the chinese HG rails. But for cost over gain I think I will put some on perhaps go a bit oversize. I can handle the loose ballscrew stuff but I do know I have adjusted the SBR rail carriage that has become loose previously maybe 6 months ago.

    Example the Spindle/Z Axis assy is running side to side on the front of the gantry, on SBR20 rails that sit the back of the Z axis 50mm forward of the gantry. To replace them with a set of HGH30 rails and carriages I would only need to pack 5mm underneath and they would fit.

    Second example I fit some HGH30 rails in the same manner to my Z axis for not too much work either. And, while I am there have a new back plate cut out of mild steel for the Z as well. Too much? Attached is the Chinese catalogue I have for the HGH
    Attached Thumbnails Attached Thumbnails HG catalog (002).png  

  10. #10
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    Re: Need offers of advice please. Next level time with my router.

    Have a look at CGR rails, same price as HGR but stiffness of RGR(rollers).

  11. #11
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    Re: Need offers of advice please. Next level time with my router.

    Hi Boydage - Its not in the CAD model its in the export of that geometry that the spline or arc is changed. Then it also depends on your machine controller settings as some lines will be combined if they are within the "roadway" width of the controller setting tolerance. You have to look at each step of the way and figure out what setting or tolerance is the offending thing. I'm not familiar with Fusion. Does it directly export gcode? Peter what controller do you use?

  12. #12
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    Re: Need offers of advice please. Next level time with my router.

    Boydage, you are chasing your tail, most likely the chatter is coming from your spindle, I have not serviced the spindle you are using, but most of these spindles by design are not suitable for milling metal of any kind, there are some that have success just by chance and not by design, with means they have a tighter Bearing assembly, on most of these spindles the assembly of the front (2) Bearings, both face with the cup facing out, so when a milling cutter starts cutting, the cutter tries to pull down this unloads the preload and you then have a unsecure spindle that can vibrate and flop around in general

    So, if all your axis are tight, you only have some resonance in the Gantry and the Z axis, the rest of the problem will be coming from the spindle.
    Mactec54

  13. #13
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    Re: Need offers of advice please. Next level time with my router.

    Quote Originally Posted by mactec54 View Post
    Boydage, you are chasing your tail, most likely the chatter is coming from your spindle, I have not serviced the spindle you are using, but most of these spindles by design are not suitable for milling metal of any kind, there are some that have success just by chance and not by design, with means they have a tighter Bearing assembly, on most of these spindles the assembly of the front (2) Bearings, both face with the cup facing out, so when a milling cutter starts cutting, the cutter tries to pull down this unloads the preload and you then have a unsecure spindle that can vibrate and flop around in general

    So, if all your axis are tight, you only have some resonance in the Gantry and the Z axis, the rest of the problem will be coming from the spindle.
    Thats a really good point because its something I have thought about too. What made me scratch my head, was the fact this vibration is only in one direction or segment of an arc seemingly when both axiss' are unloaded it appears. No matter what size cutter. Ive decided to make a movie of it. All I need to do is create a round contour cut on a piece of aluminum. Its a G Penny 4.5kw I am using. Cheap. Mate. If I was able to nail it down to the spindle. I would kiss my cat.

    Mr Peteeng - what we are discussing I was actually going to raise in a different posting because it has only happened a few times and is different to this chatter - gee - might be related. I design a lot of curves in my work. Where I have seen this, at first I thought my pc ( or controller) was in need of some new RAM. Where I have seen it, cutter is racing around at 2000mm/min gets to a curve or radius, and almost hesitates before ditditditditdit....ing around a certain curve. Only to speed up again normal speed. This is rare though, I thought the pc (or controller) was having trouble processing so many lines at that speed. Also thought its where I have used the spline in my CAD program to create the curve. 95% of the time this machine will race around any circle or curve or radius. I am using Shark for CAD and import a STEP file into Fusion 360 which directly exports G Code for Mach. My PC is XP (I have a copy off Ebay) with a parallel port cable. All that make sense? Sorry been a massive week of late nights.

    Ok. Movie time. I have a home business. I am supposed to be working in my Joinery business but sooooo many times about lunchtime I look at my DIY CNC machine and go..... "well thats enough Joinery for one day" hahah

  14. #14
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    Re: Need offers of advice please. Next level time with my router.

    Hi Boydage- I'm not a mach user but you probably need to look at the tolerance settings in Mach. In UCCNC which I assume has similar settings see images attached. When the controller comes to a curve it looks ahead and makes several decisions:
    1) if straight within tolerance it combines the lines into one long line. This allows the machine time to accelerate to max speed or set speed (see linear error max setting and linear addition max length) in the image case its set to 1mm which is no good will always be slow. I picked this image from a desktop copy of UCCNC that I use for checking not running a machine also see linear unify length max
    2) if the lines are short the controller slows down the speed as it can't accelerate to Vmax before the next line starts ie if lines are short its always stopping and starting
    3) The linear error max setting also sets the "width" of the roadway the tool will travel down. The wider the roadway the faster the tool will go as the more points/lines can be combined to achieve the "curve" or pathway/toolpath

    All of this adds up to if your curves require a low tolerance don't set the machine at high tolerance as this will severally slow the machine.

    Also you must be able to set the polyline length export in Fusion? what controls does fusion have for creating the toolpath? Peter

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    Re: Need offers of advice please. Next level time with my router.

    Hi Boydage - I'll explain a couple of things as its hard to grasp first up. The controller looks ahead point by point. Extrapolating a line as it goes. If the extrapolated line fits the tolerance it goes to the next point and extrapolates that as a straight line from the starting point etc etc. This extrapolation continues until 1) The line gets to the specified unified line length. This is the max length allowable by the setting or 2) it goes out of the linear error max so the line stops there and a new look ahead begins. 3) When looking ahead, the look ahead is limited via the addition length. ie if the addition length is set at 10mm then thats the max it looks ahead past the interpolated line (unless this is greater then the unified length then the unified length overrides) Got that? Simples Peter

    The aim is to use the slackest tolerance that does not produce flat spots for your job or out of tolerance surface for your job. This allows the tool to run fastest around curves. Peter

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