[Jason3]

Hi everybody,

I've started a new project, and wanted to share it for anybody interested. It's a larger mill than all my previous builds, and is nearly as big as I think I can practically make in my workshop :drowning:

I originally called this a Benchtop machine, but realistically it's a little bigger than that so I don't really know how to classify it. I'll have some wheels underneath so it can be moved around readily when necessary, so maybe it can be called the MobileVMC™

In contrast to my other CNC projects, this one is to be pretty much all steel. It'll use NSK ball screws, THK caged ball linear bearings, and brushless servo axis drives. I'd like to enclose it so I can use flood coolant when necessary and to keep the noise down as well.

Hopefully it'll be a decently capable machine when it's done. I'm certainly looking forward to a larger work envelope than my current baby CNC mills

Cheers,

Jason

Here's the first few parts:

[MrBean]

Very cool project. I shall certainly be following along.
What size work envelope would you say the mobile VMC will have, roughly?
I'm sure I won't be offering you advice during your build, but I'll make sure to shout Yeeeeee Haaaa!!!! and other such noises of encouragement, now and again from the sidelines

Really looking forward to this one. Thanks Jason.

Regards Terry.

[hesham morsy]

:banana::banana::banana::wee::wee::wee:

[henrikw]

I'll just add myself to the YeeeHaaa! choir

Always looking forward to your posts, very nice work!

Henrik

[LeeWay]

Have you got any video of it running yet?
I would love to have another mill myself.
I am looking for a used one to retrofit, but those are few and far between around here. I may wind up doing one in concrete or epoxy, though I really like the 80/20 for it's versatility.

I will stay tuned for a video even if I have to wait until tomorrow.

[sergizmo]

Yesss! That looks solid. What is the bar, 2.5" by 2.5"?

What do you have in mind for the spindle Jason?

[Starleper1]

Looks good so far. It looks like your choosing the path i did with my mill, as far as the table goes.

[Jason3]

Hi guys,

Terry, Hesham & Henrik - thank you for the encouragement! Cheering is always welcome and gladly received The work envelope will be 750 x 400 x 400 mm or so (30 x 16 x 16" roughly), just a bit more than my knee mill.

Lee - Oh no, no video! I better pick up the pace An Epoxy granite machine would be good - there's pretty few nice examples of scratch built EG machines here. I started a retrofit too, on my knee mill, but it's on hold waiting for some ball screws. Somehow I can't help myself, I always end up with another machine I simply must build, usually before the last one is finished

Sergizmo - close! That's 3" x 3" bar, except the servo/ball screw mount which is ex 4" square stock. For the spindle I'm ultimately looking for a BT30 taper, around maybe 4-5 Kw. 10Krpm would do, but more would be nice. I'd like to try making my own, so it may be that I'll put my Kavo spindle on this machine to get me started.

Starleper - there's some definite similarities to your mill! When you refer to the table, do you mean the work table or the machine stand?

Best regards,

Jason

[Starleper1]

I meant the way the table will be mounted.

[Teyber12]

Great luck! i have followed your lathe thread and am amazed at your talent to just make it come together so well... Keep up the good work, i was excited to see this thread title

[the4thseal]

teyber whats up with the avatar pic? curious.

[Jason3]

I'm telling myself: progress is progress, however small it may seem

This part (the longer one, on top in the photo) itself didn't take long, but I spent some time confirming that the big mill was staying flat throughout it's travel - I didn't want any dips in the rebates that the linear rails will mate with, for obvious reasons. The part is quite a bit longer than the travel of my knee mill, so I felt it was worth some care to get it as good as possible. I think it went ok.

Starleper - right, I see. Actually, I was a little concerned about rigidity with the linear bearing blocks being closer together on the X - on an industrial machine they would usually be further apart. However, this machine isn't going to have to handle hogging out 4340 steel with a 20 Hp spindle, so I think it will be ok - I'll take the extra travel for now. I will do some measurements though, and if I find it is deflecting more than I expect, I will have an extra set of holes spaced further apart in the table carrier - I can just shift the bearings out and increase the stiffness at the cost of some X axis travel with no other changes.

Teyber - thank you for the encouragement!

Best regards,

Jason

[HRW-MASTER]

Even if it takes a year to finish it sure beats baby sitting.

What kind of servo drives are you going to use?

Hank

[Jason3]

Hank,

After a day lifting and turning these big steel parts on the mill, baby sitting is not so bad. Having said that though, I spent Wednesday & Thursday last week minding the kids, and caught a cold for my trouble

As to the servo drives, I very much like Granite's VSD-E drives - and my company is a regional distributor for Granite Devices so it wasn't a hard choice. I will have to decide whether to wait for the upcoming high voltage version though :violin:

Best regards,

Jason

[Cornchip]

Hi Jason. I followed you Part's Bin Mircro Lathe build and plan to follow this thread. What I'm personally curious about is the panel building side using the Granite drive's (I have zero experience with DIY CNC components). When you get that far, I'd like to see that end of the build. I'm more than a little intimidated buying the component's and having a less than positive outcome. Keep up the good work.

Cornchip.

[asuratman]

Jason,
This mill is big, its alot bigger than IH mill. It looks very stiff, all steel. I'd like to build one like this. If you have 30" travel, it means you have table of 30" X 2 + half length between base bar. Maybe 66", just curious. For this size of mill, its good to have VSD-E 160 with big motor. I always follow your thread, good to build one in near future.

[Arquibaldo]

Dear Jason:

Absolutely astonishing workmanship - Congratulations.

I will also follow this thread closely... Now for some questions:

-3" square solid steel!! This thing will be real heavy! do you have an estimate for the final weight?

-I assume you'll need quite big servos to move this monster - have you sized them?

-You must have quite a workshop to be able to build this big and this good - could you tell us what are your main machines?

-One of the most interesting parts, for me, will be the spindle - a spindle this big rotating at 10000plus will certainly need liquid-cooled bearings. As far as I could find, this will be the first artisan-built spindle of this kind. Lots to see & learn...

Keep up the good work

[Jason3]

Hi Jason. I followed you Part's Bin Mircro Lathe build and plan to follow this thread. What I'm personally curious about is the panel building side using the Granite drive's (I have zero experience with DIY CNC components). When you get that far, I'd like to see that end of the build. I'm more than a little intimidated buying the component's and having a less than positive outcome. Keep up the good work.

Cornchip.

Hi Cornchip,

Sure thing, I'll try to take plenty of photos of the electronics assembly. Feel free to send me a PM if I can be any help picking components

Jason,
This mill is big, its alot bigger than IH mill. It looks very stiff, all steel. I'd like to build one like this. If you have 30" travel, it means you have table of 30" X 2 + half length between base bar. Maybe 66", just curious. For this size of mill, its good to have VSD-E 160 with big motor. I always follow your thread, good to build one in near future.

Thank you for your comment - yes, this is a big mill, compared to my previous builds. The X axis rails are actually only about 44" long - the blocks will be spaced 14" apart over the outside ends. That does mean the table will cantilever each end, and the force of the spindle will sometimes be acting outside the bearing envelope too, which is not ideal. However as usual I've selected oversized linear bearings, and the load ratings are well beyond what the servos and spindle will generate. It is possible there will be some deflection under heavy cuts and as I said earlier I have allowed for a remedy should this become necessary, at the cost of reducing the X axis travel.

The servos will be higher voltage models, and if the new VSD-E isn't here by the time I'm ready I will just run them slower and swap the drives in the future. Even at the 80v max for the current VSD-E, I expect feed rates to 550 ipm which is quite respectable.

Dear Jason:

Absolutely astonishing workmanship - Congratulations.

I will also follow this thread closely... Now for some questions:

-3" square solid steel!! This thing will be real heavy! do you have an estimate for the final weight?

-I assume you'll need quite big servos to move this monster - have you sized them?

-You must have quite a workshop to be able to build this big and this good - could you tell us what are your main machines?

-One of the most interesting parts, for me, will be the spindle - a spindle this big rotating at 10000plus will certainly need liquid-cooled bearings. As far as I could find, this will be the first artisan-built spindle of this kind. Lots to see & learn...

Keep up the good work

Thank you very much I keep revising the estimated weight, every other day it goes up a little! I'm guessing about 1100 Lb or so with the stand and enclosure.

I have done the calcs for the servos, yes. Big, but not huge (Nema 34) - the torque requirement is not that high, the main reason for the big servos in this case is to get a very low inertia ratio.

Actually, my workshop is very modest. All I have used so far is a horizontal bandsaw and my manual mill, a 10 x 50 Chevalier FM3-VK turret mill. I could have even avoided using the bandsaw by ordering the stock cut to size. For the stand I'll go to my Dad's 'shop and use the big mig welder there.

The spindle will be interesting for me too Yes, I agree - it will need cooling!

Best regards,

Jason

[LeeWay]

Looking good, Jason.
I was thinking about the way you are setting up your table. I don't think you will have much of an issue, but I was also considering my newest brain storm.
I intend to build a bigger mill myself. Probably using standard concrete for the base. It would have threaded steel plates where needed and would have a welded steel skeleton within. The concrete mainly for weight to help with dampening. This one would be a bridge type mill. Y and Z similar to my router, but with a non moving gantry.
On the X table, I was considering using HSR25's like my mill and lathe. Perhaps 35's even.
Mount them rigid to the base and let the rails travel. Similar to what you are doing. The key feature on this though would be outrigger rollers. Solid steel rollers with bearings mounted hard to each side where the table rails would travel. Cold rolled steel is much softer than the rails, so I don't see any issue with peening the rails. Maybe even use stainless or brass rollers. These don't have to be placed at the end of travel, but just outside the trucks so that the rails are supported for any cut.
I think this would make the setup more rigid on my bridgemill design and you might be able to use something like this as well.
Just brainstorming really.
I'll get a design started one of these days.
Keep up the good work.

[Jason3]

Lee, that's an interesting idea - with the rollers acting on the flat top of the HSR type rails, I doubt they'd affect the ball tracks even if they did mark it, there's a slight chamfer on the corners anyway.

On this machine the rails are all 'right way up' - the blocks are attached to the table and the saddle carries the X axis rails. Your idea would still work with the rollers mounted to the ends of the table, though that would make my way covers plan somewhat more complex!

I'll take some measurements and see what deflection I get once it's all assembled. I did a similar exercise with my other mills, and found that with just one block on the X the table would move relatively easily, but with two blocks it was very much stiffer. Since this machine will have four higher rated blocks spaced further apart, I'm not particularly concerned at this point.

Does anyone know what size linear bearings the smaller industrial machines use - like the Haas Minimills/Officemill etc.? I'd be very interested to know, I would go and look for myself but such machines are very thin on the ground way down here!

Best regards,

Jason