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Thread: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

  1. #81
    Member luke peter's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Thanks Bongodrummer.

    The structure is pretty small all things considered, TSR will thus be reasonable. I did briefly consider diy VSR, but I dont have the time or energy for the R&D

    Its always tempting to keep adding to the machine in terms of stiffness and damping etc, trying to build a perfect machine on iteration 1, for me, it turns into analysis paralysis - and I never get anything done.

    Build thread: https://www.cnczone.com/forums/diy-cnc-router-table-machines/429232-forum.html#post2496634


  2. #82
    Member luke peter's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by ardenum View Post
    Love the boxy design, although all that grid on the spindle box is actually detrimental unless it's gonna involve some damping material later on. Only make cutouts where its necessary for things like visibility or cables etc.
    The edge cutouts are for weight, and draw bar spanner access, the non-triangulated cutouts are for bolt and belt drive inclusion for the servo spindle. the weakest part of the Z frame is the back plate - the 10mm steel bows more accross its width than the frame bends. It will probably be replaced at some point.

    Build thread: https://www.cnczone.com/forums/diy-cnc-router-table-machines/429232-forum.html#post2496634


  3. #83
    Member Bongodrummer's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by luke peter View Post
    Thanks Bongodrummer.

    The structure is pretty small all things considered, TSR will thus be reasonable. I did briefly consider diy VSR, but I dont have the time or energy for the R&D

    Its always tempting to keep adding to the machine in terms of stiffness and damping etc, trying to build a perfect machine on iteration 1, for me, it turns into analysis paralysis - and I never get anything done.
    If you see my concrete incorporated build you realise I have the opposite problem


    Bongo - https://www.youtube.com/flowering_elbow


  4. #84
    Member luke peter's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by Bongodrummer View Post
    If you see my concrete incorporated build you realise I have the opposite problem
    Ah, that's your machine

    I have watched a bunch of your videos already, impressively resourceful gantry build. I am seriously considering surface replication for my rail support beam to upright joints - how has that played out for you?

    I am also interested in how your machine is performing w.r.t. stiffness - I cant remember if you did any final compliance measurements with your spindle extended? what was the ultimate stiffness at your collet? Your machine performs really nicely, and it would be a good benchmark for what I can expect out of my mechanical assembly.

    Genuinely enjoyed your content.

    Build thread: https://www.cnczone.com/forums/diy-cnc-router-table-machines/429232-forum.html#post2496634


  5. #85
    Member Bongodrummer's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Hey thanks
    The surface replication worked perfectly for me. I didn't really know what to expect going into it, but yeah - no complaints on that front.

    w.r.t. stiffness: I don't think it's in the same league as yours, being a big router really. I hadn't actually measured this, despite testing it on steel etc. So I had a look today...
    By far the most flex is coming from the spindle plate, as it has a lot of z travel (400mm from the bed to the gantry, and it has a bit extra to reach things in the gap). I always thought that if I was going to be machining metals I would do them towards the top of the z's range....
    So fully extended out it's getting 0.14mm deflection at the tool when I put 30kg of sideways force on the tool holder... What surprised me is that deflection is roughly the same when I pull in both the x and y direction. I expected to see much more parallel to the long rails when it's trying to twist the gantry and bend the z spindle plate in the direction I assumed it would be weakest. Am I right in saying therefore a rather disappointing 2.1um/N
    Here was my setup for measuring in the other direction - the woodworking clamp made it easy to regulate the force:


    When near the top of z travel where I would have it (if I possibly could for metal), it's deflecting 0.04mm with 30kg force. Again both the x and y directions were the same. When I measure parallel to the gantry travel (what I call x), so not like the photo, I put the spindle in the middle of the 1.2m gantry, assuming that would give the most deflection... a bit better 7.5um/N if my calls are right?

    One last thing to note is that the ballscrews on this are 20mm pitch and with the servos unpowered I can push it by hand, so I did the tests with servos on, and I could hear them working as I cranked the force on.
    Ok hope that helps.

    Bongo - https://www.youtube.com/flowering_elbow


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    Member luke peter's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Your test methodology is good as far as I can tell, and the numbers I managed to find put 3000N/mm (3N/um) at a very comfortable place for ali milling. I don't think my machine as built will be anywhere near as stiff as the sims, since it assumes bonded joints that are 100% efficient, looking at how your machine is cutting, I will be more than happy to be in the same ball park.

    Your machine has a lot of really well executed stiffness fundamentals, its still really stiff for a router, and it has big levers. Its cool that your x and y stiffness have come out similar, it will translate into a more uniform surface finish (at least this makes sense to me - I have almost 0 actual CNC machining experience . Your bed frame is much more robust than mine, I am relying on the 20mm steel bed base plate to add a lot of stiffness for me.

    Do you have a video planned testing your machine in some steel (DOC and speeds/feeds ramping until you reach a stiffness roadblock with chatter)? So many people write off DIY routers for metal work, and I have a feeling your machine, and hopefully mine, will stand out as counterpoints to that narrative.

    Build thread: https://www.cnczone.com/forums/diy-cnc-router-table-machines/429232-forum.html#post2496634


  7. #87
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by Bongodrummer View Post
    Hey thanks
    The surface replication worked perfectly for me. I didn't really know what to expect going into it, but yeah - no complaints on that front.

    w.r.t. stiffness: I don't think it's in the same league as yours, being a big router really. I hadn't actually measured this, despite testing it on steel etc. So I had a look today...
    By far the most flex is coming from the spindle plate, as it has a lot of z travel (400mm from the bed to the gantry, and it has a bit extra to reach things in the gap). I always thought that if I was going to be machining metals I would do them towards the top of the z's range....
    So fully extended out it's getting 0.14mm deflection at the tool when I put 30kg of sideways force on the tool holder... What surprised me is that deflection is roughly the same when I pull in both the x and y direction. I expected to see much more parallel to the long rails when it's trying to twist the gantry and bend the z spindle plate in the direction I assumed it would be weakest. Am I right in saying therefore a rather disappointing 2.1um/N

    When near the top of z travel where I would have it (if I possibly could for metal), it's deflecting 0.04mm with 30kg force. Again both the x and y directions were the same. When I measure parallel to the gantry travel (what I call x), so not like the photo, I put the spindle in the middle of the 1.2m gantry, assuming that would give the most deflection... a bit better 7.5um/N if my calls are right?

    One last thing to note is that the ballscrews on this are 20mm pitch and with the servos unpowered I can push it by hand, so I did the tests with servos on, and I could hear them working as I cranked the force on.
    Ok hope that helps.
    how's the rotating nut coming along? I remember you had some speed issues/ bend ballscrew?...



  8. #88
    Member Bongodrummer's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Well, thanks for the encouragement! I must say I felt a bit down about the reading earlier today... But hay, I do know it can cut steel, it might not be amazing at it, but it works. I did always plan to box in the spindle with another aluminum casting, wich should add significantly to the rigidity, but since it was working, that dropped to the bottom of the jobs list.

    I actually think the bed of my machine could do with some kind of metal plate material (in a section at least) if I end up doing much metal with it. The 3/4" ply 3/4"mdf sandwich I have at the moment was just what I had to hand, but between the steel box the mdf can be deflected quite a bit. As well as the obvious stability issues - but that's not such a big thing as I'm just learning and cutting into it and doing different jobs on it day by day ATM - it's a spoil board after all.

    Yep, I am planning such a video - to talk a bit more about the spindle (which is ace but a bit fast for steel)... Am just making some tool changer rack things with it ATM and then will be trying it cutting stone, and then some surface grinding... Basically all the abuse... Anyway, this is about your build, and I'm looking forward to more...

    Bongo - https://www.youtube.com/flowering_elbow


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    Member Bongodrummer's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by ardenum View Post
    how's the rotating nut coming along? I remember you had some speed issues/ bend ballscrew?...
    Working great now. Changed up the ballscrews for something much lass bent, better quality and 20mm pitch. Which of course if I was to do over would be more like 15 or 10!

    Bongo - https://www.youtube.com/flowering_elbow


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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Hi Bongo - Thanks for doing the test. To do this test better you need to measure at least 3 load points. You start with a low preload say 2kgf, this takes out any mechanical play, then reset the dial guage. Then go 10,20 & 30 kgf . This will allow you to do a excel chart and regress the line. You may find the line stiffness to be quite a bit different to the single test figure as the single test includes the mechanical play. Then if you find play you need to get rid of it! The regressed line will not go thru "zero" and if you have a good correlation for the 3 load points then the "missed" zero value will be your play.... Peter



  11. #91
    Member luke peter's Avatar
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    Default Re: Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

    Quote Originally Posted by peteeng View Post
    Hi Bongo - Thanks for doing the test. To do this test better you need to measure at least 3 load points. You start with a low preload say 2kgf, this takes out any mechanical play, then reset the dial guage. Then go 10,20 & 30 kgf . This will allow you to do a excel chart and regress the line. You may find the line stiffness to be quite a bit different to the single test figure as the single test includes the mechanical play. Then if you find play you need to get rid of it! The regressed line will not go thru "zero" and if you have a good correlation for the 3 load points then the "missed" zero value will be your play.... Peter
    Thanks for this Peter. It makes sense and will help differentiate looseness vs flex.

    Quote Originally Posted by Bongodrummer View Post
    Well, thanks for the encouragement! I must say I felt a bit down about the reading earlier today... But hay, I do know it can cut steel, it might not be amazing at it, but it works. I did always plan to box in the spindle with another aluminum casting, wich should add significantly to the rigidity, but since it was working, that dropped to the bottom of the jobs list.

    I actually think the bed of my machine could do with some kind of metal plate material (in a section at least) if I end up doing much metal with it. The 3/4" ply 3/4"mdf sandwich I have at the moment was just what I had to hand, but between the steel box the mdf can be deflected quite a bit. As well as the obvious stability issues - but that's not such a big thing as I'm just learning and cutting into it and doing different jobs on it day by day ATM - it's a spoil board after all.

    Yep, I am planning such a video - to talk a bit more about the spindle (which is ace but a bit fast for steel)... Am just making some tool changer rack things with it ATM and then will be trying it cutting stone, and then some surface grinding... Basically all the abuse... Anyway, this is about your build, and I'm looking forward to more...
    A indicator reading cant take away from what your machine has done, or will do. This kind of thing is iterative, 80% of the fun for me is in the build and subsequent improvements. Looking forward to the next video

    I welcome comparisons and shared learning of other machines in this thread - it's the strong point of forum interaction, the shared experience of a bunch of people with a similar passion - and a history of dialog for everyone to see and process later.

    Build thread: https://www.cnczone.com/forums/diy-cnc-router-table-machines/429232-forum.html#post2496634


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Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.

Reasonably Rigid Router (RRR) - a cautionary tale (likely) in the making.