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  1. #1
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    Input on this new frame

    Ive gone the other direction as I needed my timber machine to be able to machine alloy to a component standard. Built a new Z with a 4.5kw spindle that was a great success, but then I rebuilt the gantry as it needed to be more rigid. Now the frame is up for a makeover as I have a resonance that goes through it when taking deep cuts. I want to use it for timber and alloy using some good vices on the T Slot table

    The frame, at present, is timber with steel rails running down the sides bracing it all. Funny really its doing so well for just timber.

    Anyway. The plan is to lift off the rails, complete with gantry and place them onto the new frame. The Nemas will sit alongside as they are independent on brackets alongside. They are driving 2510 screws. What is interesting is I used a machinist level to shim the linear rails at each attach point. By doing this, my machine currently is quite nicely accurate. I was surprised at just how much the 30mm linear rails bend with the attach screws. I will do the same when I lift it onto the new frame instead of trying to get the rails flat with epoxy (that idea looks not idea) or similar.

    The frame attached is in concept. The main rails are 152x76x6mm steel. The other sizes are 100x50x4mm and the feet are made out of 10mm mild steel. The T Slot table is 1100x900x100mm solid 680kg I bought it off a Chinese company.

    So bracing. No triangles because I thought the size of the steel might be enough? And I wont be machining steel only alloy.

    Have I gone for an overkill? I am also unsure how to attach the T slot table and make it perfect. I was thinking I would drill underneath something like a M18 and tap a thread into it. Also dont know how much support I need to give it.

    If I make this current design the steel is about NZ$1700.

    Always up for robust conversations on this. I am not an engineer of this type.

  2. #2
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    Re: Input on this new frame

    The T Slot table is 1100x900x100mm solid 680kg I bought it off a Chinese company.
    Can you post the link, I'd like to know the construction ? maybe bolting or dovetail ...

  3. #3
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    Re: Input on this new frame

    Sorry no link it was a custom one made to 0.1mm flat. I did try to talk about mounting options but there was a language difficulty so left it incase it went wrong. But. It's here. Its flat. Too heavy to lift and take a peek underneath until I grab my forklift.

    Sent from my SM-N970F using Tapatalk

  4. #4
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    Re: Input on this new frame

    I can't think of a good argument against incorporating some triangulation.It need not be massive if you add it so that an element will be in tension,rather than compression.Also,linking the table supports to the outer frame,at a level a little below any travelling parts,will only do good things.Perhaps moving the table supports so that the loads feed into the faces of the box sections instead of attaching to an unsupported face would improve things a bit too.There are some very capable structural analysis guys on this forum and one may be along with some detailed recommendations.My opinion is that a few well located lengths of steel box section would be a comparatively minor investment.

  5. #5
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    Re: Input on this new frame

    Hi Boydage - Why the "groove" in the machine base? The longer the loadpath the less stiff is the machine. Is something moving along this groove? Peter

  6. #6
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    Re: Input on this new frame

    Quote Originally Posted by boydage View Post
    Ive gone the other direction as I needed my timber machine to be able to machine alloy to a component standard. Built a new Z with a 4.5kw spindle that was a great success, but then I rebuilt the gantry as it needed to be more rigid. Now the frame is up for a makeover as I have a resonance that goes through it when taking deep cuts. I want to use it for timber and alloy using some good vices on the T Slot table

    The frame, at present, is timber with steel rails running down the sides bracing it all. Funny really its doing so well for just timber.

    Anyway. The plan is to lift off the rails, complete with gantry and place them onto the new frame. The Nemas will sit alongside as they are independent on brackets alongside. They are driving 2510 screws. What is interesting is I used a machinist level to shim the linear rails at each attach point. By doing this, my machine currently is quite nicely accurate. I was surprised at just how much the 30mm linear rails bend with the attach screws. I will do the same when I lift it onto the new frame instead of trying to get the rails flat with epoxy (that idea looks not idea) or similar.

    The frame attached is in concept. The main rails are 152x76x6mm steel. The other sizes are 100x50x4mm and the feet are made out of 10mm mild steel. The T Slot table is 1100x900x100mm solid 680kg I bought it off a Chinese company.

    So bracing. No triangles because I thought the size of the steel might be enough? And I wont be machining steel only alloy.

    Have I gone for an overkill? I am also unsure how to attach the T slot table and make it perfect. I was thinking I would drill underneath something like a M18 and tap a thread into it. Also dont know how much support I need to give it.

    If I make this current design the steel is about NZ$1700.

    Always up for robust conversations on this. I am not an engineer of this type.
    12mm bolts or 1/2" UNC will be enough to hold the table in place that is all I use for builds like this, add 3 100 x 16 flat plates in between each of the table supports, (or more depending on how wide the table is you may need more than 3) this will give you something to bolt the table too, and help with rigidity of that part of the frame.
    Mactec54

  7. #7
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    Re: Input on this new frame

    I found when I upsized my spindle, and rigidity was added to the gantry. That the new abilities in machining alloy can really quickly form a large pile of chips not as easy to evacuate as timber. The groove around the table is an entry to a steep angle chute that will hopefully accept and direct alloy chips down, onto a small conveyor belt running on each side in the Y direction.

    Ok good advice all of it. I will draw up some modifications and post again.

    The comment about tension and compression was understood but not completely sure how to execute into my design.

    I'm also thinking hard about accuracy. My machinists level was not expensive but a cigarette paper under one end is enough to move the bubble. I plan to use that but still, even just welding will move things. I take my hat off to all those who have succeeded prior.

    Ok time to continue with design.

    Sent from my SM-N970F using Tapatalk

  8. #8
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    Re: Input on this new frame

    Re resonance - do not break up the grillage in even spacings as this creates naturally resonant sections. Make the spacing uneven somehow and use small brace tubes to create triangles. Triangles are more difficult to get vibrating then square/rectangular grillages and they are stiffer. You will need every bit of stiffness you can create for this machine. Peter

    Plus stiffness first, swarf removal second, re think the "trench" if possible....

  9. #9
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    Re: Input on this new frame

    The comment about accurate levelling struck a chord with me as I once moved into a workshop where the 14 foot surface table had been set up with a small precision level.I had my suspicions about quite how level it was and checked it with a simple length of clear plastic tube,known in some circles as a water level,and found discrepancies.A few thin shims improved the situation and I think that only serious and expensive laser equipment would have improved it further.

    For a bit of inspiration about triangulating the structure you could do a lot worse than studying the wind braces in a steel framed building.You may not need to brace every single bay but if you can use a diagonal link on both sides of one of the central uprights then one diagonal will be in tension under most load conditions.

  10. #10
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    Re: Input on this new frame

    I knew it was the right move to post. Thanks. And I will take that advice using it to advantage. Far out it's going to be a heavy frame I will sell it with my house so I don't have to move it ha

    Just one question about resonance. The comment about avoiding evenly spaced components inside the frame. My background was aircraft although not airframe as much. But I have a habit, of making everything even like a line of rivets. Holes evenly spaced. Just about everything and if it's not it messes with my head. I had trouble infact installing the T table because I had to add an additional rib.

    But my question lies in the gantry. My very first build I balanced it perfectly in the Y direction so even though the spindle sits in front of the gantry, if I removed the linear rails it would still balance on the linear blocks or bearings. I wonder now if it should be "spindle/fwd heavy". Know what I mean?

    Sent from my SM-N970F using Tapatalk

  11. #11
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    Re: Input on this new frame

    Hi Boydage - That's always an interesting discussion. There is the argument that if its in "balance" then its easier to get vibrating. If its asymmetric then it will self dampen to a degree due to its weight bias. But it does come back to the maxim the machine has to be as stiff as possible, can't be too stiff. If you made two machines that had a Z and gantry stiffness the same but one was "balanced" around the bearings, the other was cantilevered I think you would find they work the same. For instance a std bridgeport mill is cantilevered but of adequate stiffness and they work fine.

    In regards to making things asymmetric to prevent vibration they still can be symmetric about the centreline so will please the eye.....Peter

  12. #12
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    Re: Input on this new frame

    Another question. I have currently 2 SBR30LUU linear blocks in line on each side of the gantry with approx 200mm gap between the forward and rear one making an approx 400mm long gantry runner on each side.

    Thinking rigidity. Is it worth adding another SBR30LUU on each side? I know they are not the best. I know they are inexpensive. Just is we work with what we have. Adding a third block on each side would be an advantage though? I have room.

    I just took delivery of 2 x 8m lengths of 152x76x5mm and 2 x 8m 102x76x5mm and a length of 10x200mm plate. Oh, and a length of 100x75x8mm angle. It's going to be heavy. Not easy to push around the workshop ha

    Sent from my SM-N970F using Tapatalk

  13. #13
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    Re: Input on this new frame

    I just found 6 x sbr30uu blocks in my workshop. That would be 2 x sbr30LUU and 3 x sbr30uu total length 490mm of linear block on each side holding my gantry.

    Is that silly? I have the length. May as well use them huh?

    Sent from my SM-N970F using Tapatalk

  14. #14
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    Re: Input on this new frame

    What do you have planned to run across the gantry?

  15. #15
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    Re: Input on this new frame

    Hi. The spindle is a 4.5kw unit. The gantry off memory is going to easily be 100-120kg I am using my original one but bracing it with some 100x75x8mm mild steel angles top and bottom. And I may add more as I am liking machining Alloy.

    Gantry is 1420mm in length.

    What do you think? Silly overkill with the linear blocks?

    Sent from my SM-N970F using Tapatalk

  16. #16
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    Re: Input on this new frame

    Hi Boydage - Re:: more cars question. If the cars are in a load path then more cars are good eg on a moving machine table where the part maybe in the middle of the table but the cars at at the corners so a central car makes sense. But at the saddle say where loads always travel in and out of the edge bearings then adding another car maybe useless unless the cars capacity is close to max then you are trying to share some load or increase life. If you are adding cars to the column bottom I think a central car is ineffective. If you add two cars and make the cars further apart that maybe worthwhile... Since they are round cars make sure the top of the column is well connected to the gantry as this connection can "roll". This is also relevant for the column base. The loading along the column will try to roll & flex these areas. With square cars they are stiff in roll so the structure does not need to be as stiff in this direction... Peter

  17. #17
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    Re: Input on this new frame

    Thanks for the detailed information about this. I would love to see more such awesome blog posts from you wuxiaworld

  18. #18
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    Re: Input on this new frame

    Thanks for the input. The material is all 5mm stock except for the feet being 200/10mm mild steel, and its too heavy until I cut it into lengths. The 152/76mm I cant lift alone ha.

    Drawing designs up and playing around with ideas I am in the middle of making this. I know it may well be overkill, but in all honesty spending a few additional hours cutting a bunch of triangles and welding them in this should be quite rigid. What is difficult to show, is in the center of the machine, I have also added 6 stringers at run at diagonals to the Y and Z, ie from the top corner across and down to a lower corner. It kind of ties it all together. I am a tad worried about introducing too much heat to the top rail so am going to tack it in say 20mm welds spaced out.

    I plan to manufacture each side piece separately. Then bring them together keeping everything as level and square as I can with what I have. The T Slot table is going to be bolted to the 100/16mm steel bars. Between the table and the bars, I am thinking about bolting some largish alloy washers down onto the steel bars, then milling them to height with the spindle. Not sure if that introduces implications or not? Its all about the rails that the gantry moves on huh? They need to be perfect in relation to each other correct? Once they are correct, then everything needs to be aligned with them as a central point of measure.

    I think, that this should be ok. What I dont think, is that I will have a damaged ego if someone spots an error or improvement. Thats what this is all about. I was looking at the timber frame I made in 2016 and think this will be much better lol. Thoughts?

    P.S: I plan to weld a cover over the ends of the open rectangulars if that makes sense. I think that will both look better and improve strength.

  19. #19
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    Re: Input on this new frame

    Hi Boyd - That's a lot of welding. More welding = more distortion. Use the size down tube for the brace so you are not welding on the radius. The radius creates a large weld puddle and gap and this creates more distortion. To minimise distortion the weld has to have zero gap and be a snug to tight fit and use the smallest weld possible. You don't even have to weld all round a 50% coverage would be fine. Are you mig welding? Peter

  20. #20
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    Re: Input on this new frame

    Quote Originally Posted by boydage View Post
    Thanks for the input. The material is all 5mm stock except for the feet being 200/10mm mild steel, and its too heavy until I cut it into lengths. The 152/76mm I cant lift alone ha.

    Drawing designs up and playing around with ideas I am in the middle of making this. I know it may well be overkill, but in all honesty spending a few additional hours cutting a bunch of triangles and welding them in this should be quite rigid. What is difficult to show, is in the center of the machine, I have also added 6 stringers at run at diagonals to the Y and Z, ie from the top corner across and down to a lower corner. It kind of ties it all together. I am a tad worried about introducing too much heat to the top rail so am going to tack it in say 20mm welds spaced out.

    I plan to manufacture each side piece separately. Then bring them together keeping everything as level and square as I can with what I have. The T Slot table is going to be bolted to the 100/16mm steel bars. Between the table and the bars, I am thinking about bolting some largish alloy washers down onto the steel bars, then milling them to height with the spindle. Not sure if that introduces implications or not? Its all about the rails that the gantry moves on huh? They need to be perfect in relation to each other correct? Once they are correct, then everything needs to be aligned with them as a central point of measure.

    I think, that this should be ok. What I dont think, is that I will have a damaged ego if someone spots an error or improvement. Thats what this is all about. I was looking at the timber frame I made in 2016 and think this will be much better lol. Thoughts?

    P.S: I plan to weld a cover over the ends of the open rectangulars if that makes sense. I think that will both look better and improve strength.
    I doubt that you need any of those side gussets, if your frame is fully welded

    At the ends where you have an overhang but nowhere else, a snip of a machine a friend makes around 1000 machines of this design a year, and has very few gussets, the frame is heavier than your frame though, this machine uses 1.3Kw servos on all axis, and they run at 2500 IPM. they can run faster with these motors; but are limit for safety reasons, this frame design is only one of what I have been involved with. over the years and most do not need any gussets by design.

    Your squares are not very big, so gussets like that would serve no purpose, the only thing the base frame has to do, is support the load on it, and to be able to overcome the inertia of the gantry and that is not much at all. with the speeds that you will run at. your current build without the side gussets would take much more than your Gantry inertia could ever be just the way it is.
    Mactec54

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