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Thread: Concrete VMC

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  1. #81
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    Finally its done it took 4,5 hours of mixing stamping and vibrating to complete the mold. In it there is now 265kg of silimix and 29,5 kg of epoxy separated in 11 mixing batches.
    Now its time to wait and let the epoxy cure. Im so curious how the casting is gone look like.

    Stef



























  2. #82
    Join Date
    Aug 2009
    Posts
    291

    Re: Concrete VMC

    Looking forward to seeing those forms stripped!! Fingers crossed!!

  3. #83
    Join Date
    May 2008
    Posts
    1185

    Re: Concrete VMC

    I'm looking forward to seeing it set up too.

    It is really nice to see someone step up and do something that has not been done too many times before.

    I hope the results prove good.
    youtube videos of the G0704 under the name arizonavideo99

  4. #84
    Join Date
    Jan 2008
    Posts
    1523

    Re: Concrete VMC

    Looking forward to seeing the results!!!
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  5. #85
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    This afternoon i carefully try'd to brake away the mold, Im super surprised how easy it went The release agent did a super good job.
    The thread inserts came out super nice, cant wait to turn this monster around an get the rest of the mold off.

    Stef











  6. #86
    Join Date
    Dec 2015
    Posts
    46

    Re: Concrete VMC

    Wow it came out really good.... Next part is going to be the column?

  7. #87
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    This weekend i want to build the frame where it gone stand on.
    Im still struggling with column design mostly because im not sure how i want to do the head. After this casting i really think i can do my head also with EG.
    But Im not sure how i gone mound my carriages and still be able to adjust the tram of the mill.

  8. #88
    Join Date
    Dec 2015
    Posts
    46

    Re: Concrete VMC

    Quote Originally Posted by stef110 View Post
    This weekend i want to build the frame where it gone stand on.
    Im still struggling with column design mostly because im not sure how i want to do the head. After this casting i really think i can do my head also with EG.
    But Im not sure how i gone mound my carriages and still be able to adjust the tram of the mill.
    I'm actually taking on a project with epoxy granite as well, I'm about to order the materials for me to make my mold soon. Your project has given me the inspiration I need to get back to my designing.

    I too want to design my head to be EG but the difference with my machine is I will be casting the EG around the original cast iron casting (I have a PM-940 Mill).

    Could you design the column and head in the similar manner as you did the base, by putting steel for the rails of the column which can be machined after and put steel squares on the back of the EG head for your linear blocks to attach to after being machined? That way you can square all of your components and only if absolutely necessary you can put shims between the mounting points of the linear blocks for any further adjustment.

    How I envision building my EG head is in two separate pieces. One piece will be the moving head and the next will be a mount for the spindle which will get bolted to the moving head. Similar to a configuration on a CNC router. That way I can adjust the tram of the moving head to ensure it is perpendicular to the X & Y axis, then adjust the tram of the spindle to ensure it is perpendicular to the Z.

    Hope the above helps, if not I can post post pictures of my idea with your permission, as I have not created a thread yet.

    I have been meaning to ask, what's the reason for all the threaded inserts on the sides? I get the ones on the bottom are for your alignment pads but what about the ones on the sides?

    Also what did you use to vibrate the mold?

  9. #89
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    This evening we flipt this 350kg beast. And pulled off rest of the mold. Amazing how it all turned out i never expected to be this smooth.
    Next thing to do is the frame, then lift this beast on the frame and then do a post cure with a heater underneath it.

    @ AutomatedIngen
    All those side screws are there for mounting the enclosure there are probably more bolts in there then necessary but who cares.
    I get your idea about the head made from 2 pieces but i like to make mine out off one single piece i think.
    I would like to see your head design to get some inspiration
    For the vibration i just hired a concrete vibrating needle and putted it in the EG.








  10. #90
    Join Date
    Dec 2015
    Posts
    46

    Re: Concrete VMC

    Quote Originally Posted by stef110 View Post
    This evening we flipt this 350kg beast. And pulled off rest of the mold. Amazing how it all turned out i never expected to be this smooth.
    Next thing to do is the frame, then lift this beast on the frame and then do a post cure with a heater underneath it.

    @ AutomatedIngen
    All those side screws are there for mounting the enclosure there are probably more bolts in there then necessary but who cares.
    I get your idea about the head made from 2 pieces but i like to make mine out off one single piece i think.
    I would like to see your head design to get some inspiration
    For the vibration i just hired a concrete vibrating needle and putted it in the EG.
    Wow 350KG that thing is a beast. The casting looks absolutely beautiful, you have really done an excellent job here.

    I was thinking that the side screws we're for the enclosure but was not totally sure. The concrete vibrating needle makes sense, I was definitely overthinking things by researching vibrating tables.

    Here are some pictures of my design. I'm uncertain if the two piece design like I made it will be strong enough. I still regardless would go with a two piece configuration but have another idea to box the spindle in. Please ignore the fact that I haven't drawn in the bolt holes or put the steel plate on the back of the head for the linear guides.

  11. #91
    Join Date
    Aug 2009
    Posts
    291

    Re: Concrete VMC

    Quote Originally Posted by AutomatedIngen View Post
    Wow 350KG that thing is a beast. The casting looks absolutely beautiful, you have really done an excellent job here.
    I was thinking that the side screws we're for the enclosure but was not totally sure. The concrete vibrating needle makes sense, I was definitely overthinking things by researching vibrating tables.
    Yeah, 350KG is something you don't want hitting the ground, let alone your foot.

    I've seen some designs that have pvc through the base for sliding through lifting rods or straps. Indents under the bottom edge for forklift forks for larger bases. I think I would install deeply embedded welded brackets with couplers/nuts for lifting eyes. Not something you'd want to have pull out (that's what she said).

    For vibration tables, you often see vibrators which are simply motors with enclosed, offset weights on either end. I've seen DIYers use cheap (HF) bench grinders with offset weights instead of wheels.

    But I ran across a concrete paver video (south american I think) where they showed a concrete vibration table that had 2 bearings, pulley and shaft mounted underneath the table top which held the offset weights, and a long belt to a motor mounted on the table's frame. Great idea, the motor isn't subject to the offset weight forces nor the vibration.

    Pickup a free craigslist treadmill for the variable speed motor and much of the frame.

  12. #92
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    This week we finished building the base frame. Today give it a little paint job and put base on top of it. To make the picture complete also put the X axis on top of the base and damm it looks impressive.
    Now i build a wooden box around it with an electric heater to do a post cure to give the epoxy its final strength.

    Did some designing this week on the head an column, and i think im able to mount the carriage and still make the head out of EG.

    Stef

















  13. #93
    Join Date
    Aug 2013
    Posts
    189

    Re: Concrete VMC

    looking great mate, keep us posted! I should receive my missing motors tomorrow (5.5kw spindle servo and a 400W absolute servo for the 4th axis), hopefully I will have my castings done by the end of the month!!! have lots of work in hands at the moment but all the funds available for the rest of the build...

  14. #94
    Join Date
    Jan 2008
    Posts
    1523

    Re: Concrete VMC

    Great work!

    Are you going to fill in the steel X axis with epoxy granite for damping?
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  15. #95
    Join Date
    Aug 2009
    Posts
    291

    Re: Concrete VMC

    Quote Originally Posted by pippin88 View Post
    Great work!

    Are you going to fill in the steel X axis with epoxy granite for damping?
    Placement of the holes suggest no, but you could drill from the side and fill with sand.

  16. #96
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    No the X saddle will be just steel like it is now.

    The base now have been baked for 26 hours at a max temp of 55 degrees in the end. Now it will be waiting on some measuring devices and epoxy to try to make the steel plates flat so i can mount the rail.
    In the mean time im working on the Column design.
    Im in contact with some Chinese sellers for a big servo for driving the spindle. currently im doubting what to do my BT30 spindle has a max rpm of 6000 but maybe in the future i will update it to higher rpm.
    Now the servo i can buy will be or 8000 rpm or 12000 rpm but it comes with a 390 dollar higher price. On my current mill i also have a 6000 rpm spindle which seems enough but more is always better.
    Would it be smart to already buy a high rpm spindle or just stick to an 8000 rpm max and use that money for something else.

    stef

  17. #97
    Join Date
    Dec 2015
    Posts
    46

    Re: Concrete VMC

    Quote Originally Posted by stef110 View Post
    No the X saddle will be just steel like it is now.

    The base now have been baked for 26 hours at a max temp of 55 degrees in the end. Now it will be waiting on some measuring devices and epoxy to try to make the steel plates flat so i can mount the rail.
    In the mean time im working on the Column design.
    Im in contact with some Chinese sellers for a big servo for driving the spindle. currently im doubting what to do my BT30 spindle has a max rpm of 6000 but maybe in the future i will update it to higher rpm.
    Now the servo i can buy will be or 8000 rpm or 12000 rpm but it comes with a 390 dollar higher price. On my current mill i also have a 6000 rpm spindle which seems enough but more is always better.
    Would it be smart to already buy a high rpm spindle or just stick to an 8000 rpm max and use that money for something else.

    stef
    I've always tried living by the principal of buying the best of what you can afford at the time because it increases the longevity of you using that item and not having to purchase the same or similar item again.

    Having said that my suggestion would be to buy a high rpm spindle.

  18. #98
    Join Date
    Jan 2005
    Posts
    15362

    Re: Concrete VMC

    Quote Originally Posted by stef110 View Post
    No the X saddle will be just steel like it is now.

    The base now have been baked for 26 hours at a max temp of 55 degrees in the end. Now it will be waiting on some measuring devices and epoxy to try to make the steel plates flat so i can mount the rail.
    In the mean time im working on the Column design.
    Im in contact with some Chinese sellers for a big servo for driving the spindle. currently im doubting what to do my BT30 spindle has a max rpm of 6000 but maybe in the future i will update it to higher rpm.
    Now the servo i can buy will be or 8000 rpm or 12000 rpm but it comes with a 390 dollar higher price. On my current mill i also have a 6000 rpm spindle which seems enough but more is always better.
    Would it be smart to already buy a high rpm spindle or just stick to an 8000 rpm max and use that money for something else.

    stef
    After doing a great job of the base and you are not having the rail mounting surfaces machine, mounting them on epoxy is not a good idea, all your rail and mounting areas need to be machined
    Mactec54

  19. #99
    Join Date
    May 2013
    Posts
    480

    Re: Concrete VMC

    i recommend just lapping the top of the X axis rails flat. epoxy a strip of steel just as wide as the rails so you don't need to remove any more metal than necessary.

    to get the twist out of it, you need a straight edge, 4 referance points at the ends of the rails, and a dial indicator in the center. the indicator should read the same across both diagonals. --you do not need a precision straight edge, you can use a 2x4 block of wood with 3 mostly flat gauge blocks epoxied on the surface.. mark the locations of where the referance points on the straight edge touch the ends of the rail mounting surfaces and the dial indicator needs to be located exactly where the two diagonals cross... it doesn't have to be perfect but if the location of the dial indicator is off then imperfections in the straight edge begin to matter.

    all the straight edge has to do is compare the three points with the other two points, it doesn't have to be straight. you can also use the center point where the diagonals cross as a pivot point and measure twist with feeler gauges at the corners.

    getting the convex or concavity out of the rails is a bit more work, but if you can get it to .0005" across 18" (comparing with a 100$ 12x18 surface plate) then you can get it to .002" over 36 inches.. may be good enough.


    one of the problems with pouring epoxy is the bolt holes are too far apart (unless you drill and tap a bolt every 30mm. for 15 and 20mm profile rails they are too flexible for 60mm bolt spacing for sure and you will probably see .0005" disappear into the epoxy under each bolt. ) but since you are using 25mm rails iirc you may not have a problem with 60mm bolt spacing.

  20. #100
    Join Date
    May 2016
    Posts
    108

    Re: Concrete VMC

    @ Mactec54
    If you gone pay the transport and the machining i would really like to do it that way...

    I know machining will be the easiest way and the best way but those parts are to heavy to move around easily for me. Let me first try i with epoxy and if that fails or not giving the right result i can always consider machining.

    I have ordered a straight edge and epoxy few days ago. My plan is to use the way
    Markus Müller did on his huge EG milling machine.
    He pressed his straight edge in the epoxy to get an almost flat surface an from there he scraped and sand the surface to get it perfect flat.
    I ordered the same epoxy as him, that one is special designed for this applications in machine building environments.

    https://www.youtube.com/watch?v=xtFzb6r6Np8

    Stef

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