[metalworkz]

Hello guys,
I want to get started with a mid sized CNC router/mill and have done some sketching for the base using a concrete(or polymer concrete) as a building material. I was thinking the concrete base would ad some stability and vibration damping qualities while providing a solid foundation for the rest of the machine. Unlike a fabricated metal or wood framed base it seems the concrete would provide a very stable base that would not be subject to twisting, racking etc. like some fabricated frameworks might do? I think something the size I have drawn up would also be cheaper to do than some of the extruded aluminum frames or a steel frame and making the forms and pouring does not seem to require a lot of tools and equipment like some other methods of fabrication. I was hoping to get some of your expert opinions on what I have sketched and the pros and cons of a base made like this? I have attached a snip of what I have drawn so far for the base, so any suggestions or ideas will be very helpful for me to decide to continue or change things. Thanks!

[analogman]

By using concrete you are solving a problem that does not exist if you have an adequately constructed machine. With my datacut machine I have no twisting or racking problems. Vibration issues are not a problem either.

.001 +/- repeatability.

[metalworkz]

Hello,
Thanks for the reply. I realize that some of the things I stated in my first post are not things that the majority of the machines in use are experiencing. I was just trying to think of possible benefits from this idea. I am wondering what types of material you are cutting with your machine? I plan on milling metals along with routing of other materials, so I am trying to make the base a bit more substantial for that. Do you think I am overdoing it with this idea? I also thought the concrete would be a cheaper way to go compared to some other metal framework methods, but I honestly haven't done a cost comparison.
Thanks again for the input.

[ger21]

By using concrete you are solving a problem that does not exist if you have an adequately constructed machine.

That may depend on what you're cutting, and how fast you're cutting it.

[analogman]

I use mine for cutting .080 aluminum, baltic birch ply and engraving aluminum. If you want to mill metals, beyond aluminum sheet, consider a CNC milling machine.

Weight is a good thing for heavy metal work machines. My "small" lathe weighs in at 2000lbs. This seems heavy, but is a lightweight by professional standards. But it cuts with carbide and does a serious job of cutting steel. The option is poor a concrete floor that is 2 or 3 feet thick and bolt the machine to the floor. At one machine shop, they poored a 8' cube of concrete in the floor and bolted their large milling machine to the cube.

Take a look at what the Mechmate guys do. They are large steel machines.

Concrete as a permanent part of the machine would be a PIA the first time you reorganized your shop.

[metalworkz]

Hi,
Being a metal worker myself I would naturally prefer to do my machine with all metal construction, and that is exactly what I did with the small CNC router I finished earlier this year for my son.
http://www.cnczone.com/forums/showthread.php?t=101387
That machine was fairly small and I had most of the parts laser cut from both steel and aluminum along with machining some of it in my shop on my small Syil SX3. I also do aluminum casting and have made the Gingery series of machines from scratch, so I will probably be doing some of my parts with wooden patterns and aluminum castings. I have spending limitations as do most people, so I have opted to try and build this machine on the 'cheap' side to save up for motors and other things I can not make myself. Anything that does not fall into that category will have to be made by me, as cheap as possible and at the same time with some attempt at building it with strength and durability. Hopefully it all works out well.

[metalworkz]

Hello again,
I have 3 sides of a Newport table frame that I have assembled to see if it will work for my new build base frame. The 4" tube frames are heavy wall and the separator side is smaller in width but still thick wall tube. It is closer to 47" x 47" and I either need to make 2 smaller ends to get a 36" x 48" frame or maybe I should leave it the current size and revise my machine to a 48" x 48" material envelope? I have to think on it.

[CarveOne]

Hello again,
I have 3 sides of a Newport table frame that I have assembled to see if it will work for my new build base frame. The 4" tube frames are heavy wall and the separator side is smaller in width but still thick wall tube. It is closer to 47" x 47" and I either need to make 2 smaller ends to get a 36" x 48" frame or maybe I should leave it the current size and revise my machine to a 48" x 48" material envelope? I have to think on it.

Personally, I would go with a 4'x4' envelope just because a 1/2 sheet capacity is more convenient to work with. One cut across a sheet of material and you have a waste board, or a bunch of dinosaur parts. You will always find something to make that will exceed the size of the machine you have though.

CarveOne

[cxixer]

Personally, I would go with a 4'x4' envelope just because a 1/2 sheet capacity is more convenient to work with. One cut across a sheet of material and you have a waste board, or a bunch of dinosaur parts. You will always find something to make that will exceed the size of the machine you have though.

CarveOne

I tend to agree, when I built my router I didn't actually need the 49x49" cutting area, I maybe needed 30" or so, but I am very glad I went with a size to hold a half sheet. I ended up cutting bigger parts than I ever thought I would, not to mention cutting multiple small parts at once is a plus!

[CarveOne]

In the case of my recent expansion of 62" to 136" (12' machine) I have found that I also have a very useful 4' x 4' work table in the area near one end of the machine when it is not going to be running a job. Being excessively large and unused is not a problem in my work shop. Maybe I could add a second gantry.

CarveOne

[cxixer]

In the case of my recent expansion of 62" to 136" (12' machine) I have found that I also have a very useful 4' x 4' work table in the area near one end of the machine when it is not going to be running a job. Being excessively large and unused is not a problem in my work shop. Maybe I could add a second gantry.

CarveOne

I wish I had the room for 'excessively large' tools.

[metalworkz]

Hello guys,
I have a small Syil CNC SX3 mill on a 4' x 4' worktable in my garage already, and 3 Gingery machines I built from scratch with aluminum castings along half of the opposing wall so I don't have a lot of space left in my 2 car garage for a large machine. I got a shed so I can move a couple off-road motorcycles(grandsons) outside and make more room around my green sand molding bench, but I don't feel for me that going bigger than the 48" x 48" machine will be a good thing space wise.
I was thinking the 3' x 4' machine would not be too big if moved to one wall when not is use, but with the 4' x 4' machine I will probably just try to have a dedicated space for it. Right now while working on the frame I think casters will be great for moving it around as long as I devise a good locking device, so I will attempt to add them before building the machine base on top of the frame.
Thanks for the input on going with the 48" x 48" size and I think that is what I will do. I already revised my base drawing yesterday to the bigger size. Too bad the larger size will incur more costs for longer slides and ballscrews, but the payoff is when you can do larger parts with less grief or repositioning and wild setups that go with the smaller machine.

[CarveOne]

I wish I had the room for 'excessively large' tools.

I never had it either, until 2-1/2 years ago. I can assure you that I will outgrow it as fast as possible.

CarveOne

[metalworkz]

Hello,
I have pretty much decided to go with the 48" x 48" travel machine instead of my original 36" x 48" build. It will no doubt cost a bit more for the longer motion control and feed mechanisms but the extra envelope will be great to take advantage of. I have done a preliminary revision to the design to increase the size of the base, but have had thoughts of adding T-slots and/or other mounting hardware to the concrete base to add to the usable features. All comments or suggestions are appreciated!

[metalworkz]

Hello,
I added HRS flat bar to the mix to create the top sides for the T-slots on the mounting surface of the concrete base. I had several ideas of how to go about including T-slots and this is the first drawn design.
It appears that the slots will clear the threaded rod embedded in the base and I think the slots will provide fairly good mounting options.
I may see if I can include some threaded inserts in the areas that don't have good coverage with the slots to enable alternative clamping positions. I wonder if I should increase the thickness of the slab a bit?
For the gantry slide I have been looking at the Integral V bolt on units that seem like a good fit for the slides. Has anyone use these for their machine and would you recommend them for a gantry or other axis?

[metalworkz]

I changed the design to use 1"x 1.5" angle iron instead of .25" x 1.0 flat bar as this allows me to run the threaded rod through the vertical leg of the angle iron for a good locating feature. It will entail some drilling and tapping but should provide a well anchored T-slot table.
I felt that it would be easiest to fill the form with the top surface facing downwards so the top of the T-slots will be flush with the surface, but I will not be able to do any finishing on the surface of the concrete this way. Maybe it would be better to pour the concrete with the T-slots on the top and then finish the surface flush?

[metalworkz]

Hello again,
I guess I'm the only one posting and reading in this thread as there have not been any responses for a while? I had hoped I would get more input either Pro or Con for this idea but have not received much to that effect. I started to do some pricing for the items needed for the base alone today and after seeing the costs of the threaded rod and concrete without the angle iron I decided to do an alternative design idea with say .187" x 2" x 2" angle iron for the frame and this seems to be a little better cost wise although I have not included enough angle for T-slots. I may go with some HRS plate pieces bolted to the angle to form some slots for bolting along with tapped holes in those plates.
I figure I can always add the concrete if needed to the bottom of the base for vibration damping, but may not end up needing it? I have a small Hobart MIG welder and could weld the angle, but may just do a iron rivet or bolted construction. I prefer the bolted to the rivets as then the members can be removed and replaced or modified, but the iron rivets do make a more permanent construction like welding without the heat and related effects.

[metalworkz]

Hello,
I have been through several idea changes for the concrete base and am not really ready to start with the base at this time.(don't have the cash!)
I decided to move forward with finishing the frame instead and this probably makes more sense right now anyway. I have some casters on hand to use for it and had 2 alternatives. I have 4 very large heavy duty Faultless casters with a 1.25" dia. stud protruding from the top and 4 other lighter duty casters with a square bolt hole pattern for mounting them. I first thought I would use the lighter duty version for the simplicity of mounting them, but after a bit of thought I figured the bigger casters would be a better choice for the size and overall weight that may be rolling on these casters. I will have to drill the 1.25" holes in the bottom of the frame legs but I have the 1.25" dia nuts to lock them in place so once the holes are done it should be fairly easy to lock them in place. Here are some pictures of the caster options I had.

[osiervt]

Although you are using regular concrete most of the same design theorys would apply to you that apply to my build. I am currently experimenting with some different epoxy granite/quartz mixtures to build my machine with. If you havent already check out the thread on Epoxy granite, it is 300 some odd pages long but it is a great read. In particular a individual named ThomasZ posted a buch of pictures some where in that long thread that did a great job at depicting the best way to imbed inserts and mold tips.EG Thread

Here is a very good paper on design. If you are not MIT you can not print it but you are able to read it on your computer. Link

[metalworkz]

Hello osiervt,
Thanks for the information and links! It is really good to actually get a reply from another member pertaining to the concrete base build. Yes I have followed the EG thread for some time and although I have not been following it currently I am aware of the process and ideas they are working with. I just figured even a regular concrete and perhaps a post tensioned base would offer some benefits not found in the normal metal framework that is common to the CNC builds. I am not planning on making the concrete base very thick on mine so I guess this design might vary from some others in that respect. I have taken a brief look at the MIT file and there is an abundance of information there as well, and I will have to see if I can use some of that to improve my current design. You mentioned you are doing a similar build and I would like to check it out if you have a thread posted so please post a link if so. Thanks again!