Milli a new composite mill kit

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    Default Milli a new composite mill kit

    Hi All - This maybe a bit early to start but here goes. I'm building a CNC router to build the parts and moulds for this Mill. The parts will be made from infused fibreglass, steel fibre reinforced epoxy or aluminium grit epoxy. I make these materials using a vacuum casting method, look up Tetrium-S. Choosing the best material as we go. The router build can be found by searching for Brevis-HD build. I shall build Milli using MDF for the proto parts and use those parts to make the moulds for the actual parts. The aim of the first round of design is to determine major flaws in geometry or function. The mill will be a lifting gantry design to remove the usual issues with bearings and geometry being crammed into the saddle. Other work has been done (in another thread) on using twin rails or single rails per side to improve rigidity with the single rail seeming to be OK. The lifting gantry is required to allow high Z axis for mould work and other high Z applications. It also removes the saddle from the design, so the tool plate can be very stiff as it only moves across the gantry not also in the Z. There are a couple of lifting gantry designs in the forums... 500x500x500mm as a round figure envelope is the starting target. It aims to be as stiff as a standard benchtop machine being able to cut steel and aluminium, It will use a BT-30 spindle... The BT-30 maybe a bit big, opinions on the spindle would be appreciated as its my first mill build...

    I have started by using YaGs parts as they exist and morphing the sub assemblies into Millis geometry. Having many years experience with testing laminates means I have a very good data base of mechanical properties for the fibreglass and carbon fibre. Generally its stiffer and stronger then the quoted values of epoxy granite so will be a very good material to use. I can also use carbon fibre if more stiffness is needed. For example a general fibreglass laminate will have E=25GPa a bending optimised laminate will be E=35GPa and a carbon fibre laminate will be 50GPa general and 80GPa optimised for bending. Both carbon and fibreglass test well over 500MPa in tension/compression and flexure so are stronger than mild steel and high strength aluminiums. Moulding the parts allows for geometric optimisation and combining parts into less parts. It get me away from using standard size tubing and sheet metal bending as I have done in the past. The CNC thread journey begins... Peter

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    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no1-jpg   Milli a new composite mill kit-milli-no2-jpg  


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    Default Re: Milli a new composite mill kit

    Hi All you Lurkers - G'Day... The first thing to do is to create lands on the walls to even out the drive nut and car stack height. This will then give a good platform for the columns to sit on... Peter

    In YaG (formerly Brevis-HD) I built the drives on sub boards to allow some wiggle and levelling room, these will now go. Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no3-jpg   Milli a new composite mill kit-milli-jpg  


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    Default Re: Milli a new composite mill kit

    Good Morning - I've built the small 15mm high land to even out the nut and cars, I may go to 25mm rails for the mill but for now 20mm will do. Next is the columns. Round 1 model will be basic to get the main features sorted no fancy shapes yet....Keep Making - Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-1-jpg   Milli a new composite mill kit-milli-2-jpg  


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    Default Re: Milli a new composite mill kit

    G'Day - I thought having the nut connection to the column would be integrated but this would mean the columns are mirrored. Would be good to have one mould that did LHS and RHS. Hmmm maybe the nut connection is a separate part.... Peter



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    Default Re: Milli a new composite mill kit

    Hi All - A machine especially a mill has to be pyramidal in nature. Huge base and stiffness all supporting the tool at the "top". My columns are clunky sitting on two bearings. The 4 bearing foundation seems to be the way. But this also reminds me of the moving column designs I have worked on and they were really stiff. But let's work on it a little further.... Peter

    My gut is going back to my mill design called P2P. For 500x500x500 this is probably better.... conceptually stuck

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-columns-jpg   Milli a new composite mill kit-p2p-jpg  
    Last edited by peteeng; 10-18-2020 at 08:24 PM.


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    Default Re: Milli a new composite mill kit

    Peter,

    Why not moving table?
    Stiffer
    Single ballscrew - don't have to deal with different ballscrew errors
    Single servo - much easier to tune


    I am very slowly designing a lifting gantry mill but with moving table. ~700x700x500 travels.

    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)


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    Default Re: Milli a new composite mill kit

    Hi Pippin,
    Can't argue with your bullets but People ask for high Z, minimal footprint, cut metal. Moving table, fixed columns is the stiffest for "wide" table but has more footprint. It will be interesting to see what the footprint of Milli is vs P2P. I think the lifting gantry, fixed columns has lots of merit may end up there....Peter

    I like the idea that the job stays still so maybe the Mazak config is the go? stuck again.. Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-mazak-vtc-200-jpg  
    Last edited by peteeng; 10-18-2020 at 11:42 PM.


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    Default Re: Milli a new composite mill kit

    Hi All - Conceptually the lifting & moving gantry/bridge design seems to be doubling up on various parts. The Mazak moving column design is much better I think for a 500x500x500 size machine. The X axis could be longer with no negatives.... The P2P design is good but I like the solid fixed table idea. The stiffness of the bed then can be maximised. Seems I've taking a left turn... Peter



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    Default Re: Milli a new composite mill kit

    Hi All- VEAR RIGHT! The Mazak config uses a saddle and I've tried to get away from saddles forever! So Milli No2 has stalled as well.... The mill image shows were I'm headed now except will be a vertical spindle. Notice the drives are off centre. There's no reason for them to be on centre with profile rails and cars. With bushes the drive has to go through the centre of friction of the bearings otherwise stick slip will occur. I've covered this in other threads. So drag out P2P or work some more on the moving gantry design... Peter

    may review envelope to 600x300x500Z Hmmm 500x500x500??

    Keep going with Mill No2 but its overhanging heaps to get the 500mm Y, so its back to tweeking P2P !!!

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no2-jpg   Milli a new composite mill kit-mill-jpg   Milli a new composite mill kit-milli-no2-1-jpg  
    Last edited by peteeng; 10-19-2020 at 07:34 AM.


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    Default Re: Milli a new composite mill kit

    Hi All - Here's Milli No4 a moving column design with moving table. The proportions are scalable and the bearing arrangement is solid. I've worked from the base up now its time to figure the spindle end and proportion from the spindle backwards and see how that goes. I came across a "combo" mill that uses subtables at the bearings. Good idea as then each axis can be set up on a bench then installed and trammed on the machine as a whole. My complaint about this config is the table drive is down in the crud. That's why I tried to do a fixed table and keep everything high. Now I think I'll revisit the lifting gantry design and see if I can unstall it or revisit the Mazak config... Peter

    Objectives for Milli:
    1) Make as many parts as possible (AMPAP) from composite. Fibreglass, carbon fibre, Tetrium-S or Tetrium-A
    2) make AMPAP in house
    3) General purpose mill so can machine AL and Steel, as usual max out the rigidity &
    4) max footprint 1000x1000.

    These models are quick geometric blocks for visualisation purposes. Mainly to get the envelope and bearing arrangement to a happy place... once I decide on the real direction then more detailed models will be rebuilt...

    I adjusted its envelope Milli No4-1 is 650X 300Y and 450mmZ so needs some more Y?

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no4-jpg   Milli a new composite mill kit-milli-no4-1-jpg   Milli a new composite mill kit-combo-mill-jpg  
    Last edited by peteeng; 10-19-2020 at 06:58 PM.


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    Default Re: Milli a new composite mill kit

    Hi All and Sundry - I've pinched parts from P2P so its config is complete. So now I think I'll look at the lifting gantry again and see if there are any inspirational moments. Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no4-config-jpg   Milli a new composite mill kit-milli-no4-3-jpg  


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    Default Re: Milli a new composite mill kit

    Hi All you gcoders out there - I revisited the lifting gantry machine with the idea of the subplates at the bearings. Using these means that the bolt pattern of the cars is not as critical as the bit bolting to it. It's always a juggle to have car bolt holes not in the way of structure or vice versa. Also with the subplate it can be used to align the motion bits before you mount the big structures on it. the drawback is that you can't re-tension the car or drive nut bolts without pulling the structure down so you will have to be 200% certain when you do this. Pull it down loctite it up before you bury it forever.... now to get the gantry & Z axis on and then we can compare No2 to No3 to see which one wins.... I maybe able to have thru holes for some access but probably not...

    No2 is a moving lifting gantry, No3 is a moving column, C frame design. Pippin how's yours looking? Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-mil-no3-jpg   Milli a new composite mill kit-mill-no2-jpg  


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    Default Re: Milli a new composite mill kit

    Evening all - I have brought both concepts up to the same level. Now I'll have a quick review and then decide on which one to detail. Any ideas out there? Lets call the lifting gantry LG and the moving column MC.

    LG
    Can be scaled to nearly any size, gets the important bits up and out of the way. Clearly more complex with two slave axis to deal with. Can have very high Z & X&Y Can be very stiff. Complex... but looks like fun.

    MC suitable for conventional 2:1 table size. Can be very stiff. Simple one control, to one axis. No mirrored parts so mould count is low. Good starter mill. Simpler...

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-lifting-gantry-mill-jpg   Milli a new composite mill kit-moving-column-mill-jpg  


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    Default Re: Milli a new composite mill kit

    I always learn so much from your posts.
    Thank you very much for sharing Peter!


    Sent from my iPhone using Tapatalk Pro

    Avid CNCRP Pro 4824 ? Hypertherm Powermax 45XP ? 2.2kW spindle


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    Default Re: Milli a new composite mill kit

    Hi All - Thanks Keon, "Sharing" the term was invented by the alcoholics anonymous organisation and it has filtered out into the community. So after a restless night thinking through these machines... I've decided to go with the lifting gantry. The C frame machine would be simpler but the lifting gantry is scalable to large machines which I'm interested in and I want a lifting router and a lifting mill in the fleet. The size of the current machine is driven by the package size of the bearings so I'm going to drop to 15mm bearings. I also don't like the look of these monster columns sitting on two bearings so I'll do the twin rails in 15mm for the columns but single rails for the gantry. I'll also drop back to 12mm for the ballscrews...So I'll go through my CAD library and check what I have in this suite of parts and start rebuilding... Keep making Peter



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    Default Re: Milli a new composite mill kit

    Hi All and Sundry - I've started the 15mm version its called Milli No4. I have to research the motor mounts and bearings for the 12mm ballscrews. I don't have them in my CAD system so will have to build them. The 500mm Z looks a little tall so may cut that back to 400mm. The model Z is currently 450mm. The footprint is 1000x1000mm. X footprint may stretch to 1200mm. The subplate idea is making things much easier plus I can include grub screws allowing adjustment then use epoxy bedding to set the connection. The design is moving well. I put twin rails on the Z. The column would then be a LHS or RHS so only one mould needed. If one rail works the second can be dropped off. Or I can start with one and be able to upgrade to 2 if needed. But the twins looks great...

    The BT-30 maybe too big but I don't know what the alternatives are. So I'll research spindles (suggestions welcomed) and ballscrews... Keep making Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no4-1-jpg   Milli a new composite mill kit-milli-no4-2-jpg   Milli a new composite mill kit-milli-no4-3-jpg   Milli a new composite mill kit-milli-no4-4-jpg  

    Milli a new composite mill kit-milli-no4-5-jpg  


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    Default Re: Milli a new composite mill kit

    Hi - Couldnt resist getting it into FE. The main parts are MDF as would the prototype be and as expected the columns are the main flexing element. The machine stiffness is 6.5N/um so reality would be 4 tops so not really stiff. Would like to get to double digits but unlikely with mdf... So get a bit more done and we will see how it goes. Maybe for the proto I'll use mdf / aluminium laminates Hmmmm Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no4-mdf-jpg   Milli a new composite mill kit-milli-transverse-jpg  
    Last edited by peteeng; 10-21-2020 at 06:48 AM.


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    Default Re: Milli a new composite mill kit

    GOOOOD MORNING CNC World - The rebuilds going well but I'm having some de ja vu moments with 15mm cars. I picked the flanged type and now I realise they are the same width as 20mm sq type so no width lost. I also decided to go with 16mm ballscrews for their stiffness and buckling vs the 12mm so stuck the 16mm drives in. The current envelope is 600x600x450mm. I have concerns I'll never get to my stiffness target and the C frame maybe better. I can get 600x300x450 easily out of the moving column design and it will probably be stiffer and less complex.... So do I need the 600mm sq XY envelope? Probably not.... router and mill parts are long so the C frame maybe the G - O.... More detailing needed. Keep struggling... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-milli-no4-jpg   Milli a new composite mill kit-milli-no4-b-jpg  


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    Default Re: Milli a new composite mill kit

    decisions decisions etc - I opened the column model and in simsolid converted everything to steel . The model then weighed 998kg I placed a 1000N push load on it and it deflected 16um (62N/um). I did the same for Milli No4 and it weight just over 1000kg so same mass coincedently. The 1000N deflected it 37um so maybe the moving column is the G-O. I realise its early days and I can fiddle with geometry and stuff. But I'm up for heaps of time to get this to the point of making swarf so want to maximise the success/time ratio. So I think the moving column is the go and I can make it a little longer with no losing stiffness. Plus being my first mill it needs to be simple... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-column-steel-jpg   Milli a new composite mill kit-gantry-jpg  


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    Default Re: Milli a new composite mill kit

    Hi All - I dislike the screw under the moving table. Its the place all the crud goes to. Plus there is excess X width due to the column width. So I extended the table in X and will put two outside drives on the table. The drives can sit up on walls so the fluids drain in the middle. I also like this as we always set up jobs in the middle of the table so now there is a bearing directly under it every time...

    A few details to sort but it gives a bigger table, more room for clamps etc. So I'm now into Mill No5... Better decide on the real envelope needed and start tuning up some dims... Peter

    Attached Thumbnails Attached Thumbnails Milli a new composite mill kit-mill-no5-jpg  
    Last edited by peteeng; 10-21-2020 at 11:28 PM.


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