Mark's EPOXY Granite 18"x20"x20" (700mmx780mmx780mm) vertical mill build

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Originally Posted by wizard

I'm not sure this machine will get you there. I think you are missing some important points. The number one point is that mass isn't everything. The first consideration is that you need securely mounted rails and frankly I'd be worried about the machine tearing out your rail mounting plates.

why not place the square column on the onside and machine it to mount the linear rails.

Again mass isn't everything. To function better the machine needs to be structurally stronger. In this regard I'm not getting good vibes about this machine.


Get a cement mixer!

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I am really not sure where you are coming from on some of your points. The base is stable massive and extremely strong. I reinforced the structure with rebar, 6" 3/8" bolts + the a2 tool steel is additionally embedded. I also added 2 steel pipes for lifting:

Attachment 279678

The a2 steel ground steel cast fine in alignment and the linear rails are through bolted to the steel via coupling nuts and 5" x 3/8" bolts embedded into the reinforced epoxy matrix every 80mm. You obviously don't understand the build if you are thinking the rails are going to be pulled out when they are cast in place this way.

The whole base is a 2ft by 4ft x 10" rock that is reinforced with steel throughout and is monolithic. I struck it with a sledge hammer like I did and it just bounced off. I look forward to continuing to the build after my move but I am quite satisfied that the base is meeting my design goals.

Strength rarely becomes an issue with building a good cnc machine.

Stiffness is the most important thing.
It is really hard to build a machine that is stiff enough but not strong enough.

CaptVee has it right.
CNC machines are lightly loaded structures, typically loaded to about 1-3% of strength. 10-50 N kgf /uM of movement.
Ie a 1-5 kg push must deflect only 1 micron.

Rigidity is everything.
Mass is usually everything.
Cannot think of a single example where its not.

All the best well-known lathes (ie Monarch10EE,Hardinge HLVH, Schaublin) are all heavy for their volume.
Mass absorbs vibrations (but may not improve strength. This does usually not matter, because the loads are so low vs ultimate strength).

Your build looks very good, ime, imo.

It will likely leave excellent finishes with finishing cuts, due to excellent vibration absorption.
Granite = 10x mild steel by mass.

Quote:

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Originally Posted by wizard

I'm not sure this machine will get you there. I think you are missing some important points....

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Have a look at your attitude 'wizard'. Mark is sharing his build with us, posting photos and inspiring others. Your post is not helping the project in any way. Perhaps you can link to some of your own, successful projects rather than criticise others?

Best regards
Frank

I just read through this EG CNC project and I am impressed by your ambition to tackle such a large machine project. I hope to read more on your project when you get fully moved in and organized at your new house. I'm particularly interested in your design for the vertical column.

Best wishes and success,

Paul H.

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Originally Posted by Hezz

I just read through this EG CNC project and I am impressed by your ambition to tackle such a large machine project. I hope to read more on your project when you get fully moved in and organized at your new house. I'm particularly interested in your design for the vertical column.

Best wishes and success,

Paul H.

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Thanks for the interest. I moved and am setting up the new shop. I will start work on casting the X axis and Z column after I finish upgrading electrical service in the new shop; Going with 200amp separate service for the shop and we need to run a new line from the transformer to the garage about 40 feet.

I will post a few pics but next week is the plan an then on to finishing the mill.

Great work! I'm also looking forward to the column build.

cheers, Ian

Awesome build! Wizard is simply not informed on epoxy granite, I have done as much researching as I'm sure you have done preparing for your build. I know there is no way your rails will come out short of throwing the base through a quarry rock crushing machine and even then I think it may break the rock crusher. Lol

One thing I have done differently in my design (also a large frame EG Design) was made both rails and the column mounting pad a single "U" shaped piece of plate steel 1/2" thick. And I will have it surface ground flat after casting along with the datum plane cut for rail mounting alignment and rail holes drilled at that time and the ballscrew mounting pads surfaced and drilled so everything is machined with one setup on the same machine for faster and easier final assembly. Same for the column base and column rails.

I am hoping that cuts down on on all of the alignment issues I may face. I don't know if you have considered it bit if you look at the Haas TM-2P, it uses a LONG table on a significantly less beefy base to achieve 40" of X travel and would eliminate having to make a ginormous Y saddle. I'm sure you could find a used knee mill table fairly reasonable and bolt linear rails to the bottom of it with a smaller Y saddle to save some time and money. Just a thought, one I have been going back and forth with between the vmc style a D longer table style with rails bolted to the table. Either would be fine I'm sure.

One other thing to consider, I don't know if you have already found a solution to it, but swarf build up in the ballscrew valley may be problematic. You might consider putting your main stage of rail and screw way covers between the trucks and Y saddle, this way you can run them as wide as the base so everything dumps over the base sides keeping everything under it clean and easy to hose off during clean up.

I am so glad I found your thread, it really is inspirational to see someone tackle a large DIY EG build. I will be following with great interest and likely picking your brain on a few details!

Chris



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This is a feat few of us would dare to take on. I'm sure it will be worth it in the end! A true manufacturing grade machine that fits in the corner of a garage! Subscribed thanks for taking the time to post this along with your prior builds I have learned a lot from your write ups and hope to try a retro myself in the near future.

Any updates on this?

Justin

Update:

I am back to work on this build following moving from CA to WA and setting up my shop. I also have been an instructor at the Bainbridge Barn- a 20000 square feet 11 studio non profit facility and have only recently got around to my personal stuff. The place is pretty awesome: Welcome to BARN (Bainbridge Artisan Resource Network) - BARN

I am nearly done with the base. It is ¼” thick 2” square tubing will have ¼” plate on the top and all sides. It is 23” by 44”. It seems pretty stout but I may cast epoxy granite into it to add mass as I am concerned the machine may move during rapids:

Attachment 393784

Here is rough draft of the design so far. I am still working on the head and tool changer mounting:

Attachment 393786

Attachment 393788


Over the past 2 years, I was able to purchase of all linear motion components for the machine. Even shopping for deals, this proved to be a significant investment with the large sizes being used:

THK SHS 35mm linear rails with 6 blocks for x axis 42"
NSK 35mm linear rails and blocks for y axis 36"
THK SHS 30mm linear rails and blocks for z axis 30"

Here is a pic. Keep in mind the base underneath is 44” long:

Attachment 393790

For ballscrews, I went with giant 36-45mm ground ball screws from THK or PMI(new replacement for a HAAS) all around.

Attachment 393792

Given the linear motion parts I ended up getting, the travels will be slightly different with the x axis being 25" in travel.

Next are the y axis bearing blocks and will post more after I make progress. FYI, I am using matched 3 bearing NSK Abec 7 sets for each axis on the ball screws. They should be arriving later this week.

Thanks for looking.

Update:

I was able to get a 300 lb scrap piece of steel to make the bearing blocks. It is 3" thick. Moving it and cutting was interesting!

Attachment 393944

Here is the design for the bearing blocks. It matches the 4" holes with coupling nuts I cast in place on the mill's base. 4" x 5" x 3" thick:

Attachment 393946

Angular contact bearing showed up while I was cutting. They are 3 bearing matched sets:

Attachment 393948

Attachment 393950

I hope to finish the bearing support blocks and mount the y axis ball screw and rails over the weekend.

Update:

I was able to partially finish the shear panels on the machine's sub-base and got the front and back one's welded on. Did a test fit of the base on the sub base and it is really solid. I am really happy with the height. By the time you add the saddle and table, It should be right. Hope to start work on the saddle mold next.

Here are a few pics of the test fit:

Attachment 394000

Attachment 394002

Looks great.

The ball screw location / pads seems a long way below the rail car tops?

Thanks! The ball screw track in the base is 6.5" wide by 7" deep. The ball screw is a 40 mm shaft and the nut is 4.75" diameter- 120 mm range. On the other hand, the 1.8 kw servos I am driving it with are 130mm frame size. With the servo mount, the track for the ball screw needed to be needed to be 6.1" in depth. I erred on the side of caution and made a little extra room, rounding it to 7". Anyway, It is easy to make a little larger ball nut mount.

Can't believe I missed this build, it really looks excellent. I'm actually planning on utilizing epoxy Granite and reinforcing my machine. I bought two PM-940's and came up with a design similar to yours. I'm especially interested in seeing what your going to do for machine head casting, as I'm contemplating that myself.

Looking forward to seeing any more updates.

Awesome build. Following!

I have not posted much since 2019 or so because of a lot going on, got married in 2021, moved out of my parents house, then my wife and I bought a house in late 2022...

Mark gave me this project when he moved out of state.

Not pictured is a 6K Hass 40 taper spindle he acquired.


back in 2017 and 2018 i started working on this project:
https://www.reddit.com/r/hobbycnc/co...mills_cheaply/