View Full Version : BUILD LOG: Advice sought on new Mill build

22-09-2014, 11:44 AM
Hi all,

I've posted the same thread on CNCzone but I would appreciate feedback from here too.

Soon I'll be undertaking a new project to replace my CNC'D BF20 which I've outgrown.

Proposed specs:

520x, 280y, 550z travels

X and Y motors will be 600W AC servos (Chinese)
Z motor is yet to be decided on.
Possibly a counterweight/gas spring to help lift the Z axis (the head alone will weigh over 80Kg)
2505 double-nut ballscrews on all axes
HIWIN 25 rails on all axes
2.2kW (3.7kW peak) Servo-spindle (10.5N.m from 0-2000RPM, top speed of 8000rpm, Chinese product)
BT30 spindle cartridge, 12000RPM max speed. (Chinese product)
Pneumatic/hydraulic tool release mechanism (comes with the spindle).
Table will be donated from an old RF45 - that will have the dovetails milled off for the linear rail bearing blocks.
Machine will be controlled by a KFLOP/Kanalog combo with Mach3/Kmotion

Machine will primarily be constructed of thick-wall tubular steel, welded together and stress relieved before being machined.
I'm thinking about epoxy-sand filling all the hollow sections to avoid the dreaded ringing that's almost certain to occur on a steel structure. Will see what the community says...
Solidworks estimates the weight to be about 400Kg at this stage.

Anyway, half of the components listed are already in my possession, so it's not so much of a fantasy.

You will notice a lot of detail in the photos is absent - namely how the axes are slaved together and other detail like that.

I'm looking for any input that could help.

Boyan Silyavski
22-09-2014, 05:52 PM
i am no expert but looking at your drawing common sense tells me that your Z is definitely weak, the bed also.

Interesting that last night i was contemplating the way i could do something similar.


-Forget about that fancy ribs on the Z. Use Triple profile welded together and reinforce it with say 60x10mm or even better 100x10mm ribs without undercutting them for "looking good" purposes . Or make it all from 100x10mm plate welded together, with ribs and so,, or why not even 20mm thick where needed.

-fill the bed with profile, don't leave empty spaces there. Only empty space should be for the ball screw to pass. Fill the empty spaces with short profiles perpendicular to the other.

23-09-2014, 09:10 AM
Thanks for the input silyavski.

I've changed the column to 250x250x9 hollow section for added strength. This will give me a LOT more volume for the epoxy sand formula to be poured into.
I still intend on keeping the bracing on either side of the column as I feel that it might help with the construction (and I also see all the VMC columns have flanged bases).

As for the bed, your suggestion is good. It will also allow me to put more of the epoxy sand mix in.

I've also added a way for my counterweight to go across the column. See the following pic:


Boyan Silyavski
24-09-2014, 08:11 AM
I still intend on keeping the bracing on either side of the column as I feel that it might help with the construction (and I also see all the VMC columns have flanged bases).

What i meant was not to remove it but to make it even stronger extending it to the top, at the back and interfacing it together. I meant not thinning it for visual design purposes.

Thats a big chink of steel. Instead of epoxy, i would use aluminum scrap, melt it and pour it in the column. Money wise it would be even cheaper. But whatever you have at hand.
Or some special cement /+ sand+stones/, that does not crack or shrink, for industrial flooring. It has epoxy in it.

So your will drive it 1:1? What motors and screws? I have always thought it wiser such a machine to be driven 1:3 or 1:2 at least,servo or stepper. Personally i don't like directly driven screws. I prefer pulleys and short belts

24-09-2014, 09:03 AM
You need a miny version of my recent aqusition.!! . . . .

The column won't be the weak link thou it could be made much stronger.! It will be the narrow head and weak base. Would look at making the Head have wider foot print by either using wide section or placing wide think plate on front of Section.

The base is far too Flimsy IMO and will require much more substance and bracing to avoid twist and stress from every thing above. You shouldn't rely on fastening the base to a frame for strength because this will introduce error in the frame by pulling and twisting. The base is the foundation and your starting with crumbling bed rock.!!
Look at the base of the machine above it's one Solid cast Iron lump with coolant tank built into it so it's very very heavy and dense to resist the forces from above.

From the outside the column looks like hollow box section but it's actually made up of 5 Thick steel plates welded and braced. If you look and zoom in you can see thru the lifting holes just how thick the material is. You can also just see the Red counter balance weight which is a Big lump of steel on round linear guide. That head is perfectly ballanced and I can lift it with one finger.!!

Personally I would forget using section and Epoxy Etc for the strong parts and make a weldment machine using thick steel plate and lots of bracing. If you do go down the Hollow section route just fill the Section with Sand it's much easier and dampens resonace good which is what your wanting. It's also easy to remove when moving.!

24-09-2014, 10:09 AM
Hi Jazz,

I can't see the attachment.

24-09-2014, 06:37 PM
pouring aluminium into the tube will just make a loose slug, the ally wont bind to the column

24-09-2014, 07:28 PM
pouring aluminium into the tube will just make a loose slug, the ally wont bind to the column

It could also distort the column with the heat coming from it.!!

24-09-2014, 08:13 PM
You want the X-axis rails attached directly to the bed, not the bearing blocks. It'll save material and keep the bearings (i.e the support) in the same place in relation to the spindle regardless of the X-axis position. The same goes for Y - orient the rails like on the machine Jazz posted.

You've mentioned using 25mm ballscrews, but it's a bit early to be deciding that yet. On a router we'd say use 16mm screws, as the critical speed isn't a limiting factor for this size machine. However on a milling machine it can be worth using bigger ballscrews if the increased stiffness is beneficial - but you can only know that when the frame (etc) is designed.

pouring aluminium into the tube will just make a loose slug, the ally wont bind to the column

Yep, and it won't do a lot for damping either, which is the purpose of the epoxy...

26-09-2014, 04:01 AM
Thanks for the advice everyone.

I will tackle the column design first.

So from the suggestions, I've moved from RHS (rolled hollow section) to a welded plate construction. the rear of the column has pockets to put the E/G mixture into, and to perhaps have another plate bolted on to seal the pockets and act as a torsion box.

Am I on the right track?

Boyan Silyavski
26-09-2014, 05:03 PM
What is the exact column length and what is the head height? Having in mind what Dean said that the head looks too narrow.

27-09-2014, 12:55 AM
Column width is 250mm at the narrow end, 500mm at the bottom end. length is 1100mm, and the depth is 250mm.

27-09-2014, 06:17 AM
Thickness of the plate used ?

27-09-2014, 06:20 AM
10mm thick. Solidworks estimates the weight to be 147kg in that render.

Boyan Silyavski
27-09-2014, 09:32 AM
So from the suggestions, I've moved from RHS (rolled hollow section) to a welded plate construction. the rear of the column has pockets to put the E/G mixture into, and to perhaps have another plate bolted on to seal the pockets and act as a torsion box.

Am I on the right track?

Bolted? Forget about bolted. Welded sounds better :pirate:. If you want to pour later E/G , just make pass holes prior to welding the pieces.

Making all braces same distance is not a good idea vibration wise. Introduce some progression or irregularity, in distance i mean.

What you call a torsion box will not function properly if braces are same thickness as the large plates. Plates should be thicker, or the side braces should extend more. Otherwise instead of torsion box you are creating weak spots.

Beware with that side braces cause they must be braced also between them IMO.

27-09-2014, 10:19 AM
The reason i'd like it to be bolted is so it can be disassembled and lifted without more equipment. It's also easier for me from a manufacturing standpoint.

Good suggestions on the irregularity. I'll do that.

I should mention that I'm more interested in HSM, not ploughing through plates with gigantic cutters - hence the 12000rpm spindle. I would put one of those high-speed ATC integrated spindles on it if they could measure up to the performance I would get out of the servo-spindle.

Boyan Silyavski
27-09-2014, 01:24 PM
I guessed so, about the HSM i mean. Your choice seems very good to me. Will it be 1:1 driven or variable puleys

So how you plan to move the counterweight? I mean could it be better that the counterweight slides on a cheap round rail or something, for the sake of perfection? Inside or outside?
Inside would be better, cause it would not be seen and at the same time you have to make the beam bigger, so that means stronger, tough also means heavier.

I believe that for a proper build you should forget your worry about moving the thing. I have made various mistakes thinking like that in the past. You will make it perfect, it will make money, so who cares. Any way making something more than 120kg needs special planning when moving and possibly a machine to lift it. It would cost you exactly the same if you move 200kg or 350kg or 800kg, so concentrate on the final characteristics you need.

27-09-2014, 01:43 PM
Good suggestion regarding the weight.

For the spindle, the motor I will be using has a max speed of 8000rpm. The spindle has a max speed of 12000rpm.
I will put a 60T HTD5M pulley on the motor and a 40T on the spindle. I will still get a large amount of torque on the bottom end - 15.7N.m. I don't really imagine I would need more than this, given that the BF20 I have only has 3.6N.m. with a 1.8kw servo - and I have not managed to make a cut using all the available power yet.

As for the counterweight, originally I was going to have the counterweight slide on a round or HIWIN rail at the back of the column. With the new changes on the column I am starting to think that I may be better with a gas spring next to the ballscrew to push the column up.


27-09-2014, 03:13 PM
If your using thick enough plate for the main structure braced correctly then you shouldn't need to mess around with epoxy etc. Esp if your mainly HSM as the cutting forces are much much lower.

I wouldn't use a Gas strut and would go with counter weigth down the column centre running along some cheap round rail. Every industrial machine I've ever seen use's this method inc 250,000 5 Axis machine I recently worked on.

I'm interestd to see the spinlde and motor your going to use can you post links to it.?

Boyan Silyavski
27-09-2014, 05:11 PM
I think he is talking about that (http://www.aliexpress.com/item/BEST-Spindle-with-synchronous-belt-for-CNC-milling-BT30-ATC-petal-clamp-disc-spring-drawbar/2012352744.html) , cause that's what i was looking at not long ago, when contemplating future mill build.

Boyan Silyavski
27-09-2014, 05:20 PM
Sorry, i have problem editing posts,

These bearings doesn't have to be conical roller bearings instead of angular contact ones?

They seem to be exactly the same bearings used on the water spindles.


Robin Hewitt
27-09-2014, 05:59 PM
And fix those rails to the table and the linear blocks to the saddle. No point in adding overhangs if you don't have to.

Boyan Silyavski
27-09-2014, 06:51 PM
Here is the Chinese solution (http://www.aliexpress.com/item/Milling009-cast-iron-frame-BT30-spindle-metal-vertical-Milling-CNC-machine-bed-metal-engraving-3-axis/2037578440.html), machine only, cast iron , without motors , smaller envelope, seems its quite worth to DIY it, price wise .

This below also should be taken in consideration when designing the head. In fact you will need the motor, the spindle and the air cylinder in your hands, before you continue further with your build after a certain point.

2Ton( 2000kg) air cylinder 13mm cnc piston cylinder for BT30 ATC Spindle of CNC milling booster cyliner FL003D (http://www.aliexpress.com/item/2Ton-2000kg-air-cylinder-13mm-cnc-piston-cylinder-for-BT30-ATC-Spindle-of-CNC-milling-booster/2039071754.html)

Boyan Silyavski
27-09-2014, 08:13 PM
Sorry for hijacking the thread :tan: , but its very interesting to me .

I gave it a lot of thought and believe i have the answer, at least for myself on my next build. My usual is "achieve maximum result with minimum materials" and easy to do it at home.

So here is what i have come with:

1. on the left is what i would do, on the right is the easier way, concerning soldering and so. Note that on the left side each cross is done separately and rotated 90 degree to the previous. The profile is 100x100x4, i don't believe bigger is needed.


2. The results in weight


3. So the final result , now taken in account the cut loss when cutting the 6m beam. Additional benefit is that can be used plates 100x10, for ease of soldering. So final size 300x300mm. Weight can slide at the back or additional extension of the plates could be made, without compromising the basic structure.

As you can see we are talking about 150kg total weight, easy to do and something like many many more times than the initial design. Also all the mixture of small stresses of soldering + the cellular structure will kill all vibrations at the same time the hollow place behind the rails will absorb the vibrations into the beam.

And as for the braces near the bottom, understand that if done correctly a structure needs only small braces to protect the soldering and the forces to go there smoothly. With the above design you will need only triangles with sides 100 and 100mm. if the base is done correctly i mean.


I don't know what you think, but i don't see how can be done better with less weight and easier. I am happy with the exercise.

27-09-2014, 08:23 PM
how are you going to weld the inner section "the +" to the outer square section ?

Boyan Silyavski
27-09-2014, 11:27 PM
how are you going to weld the inner section "the +" to the outer square section ?

very simple:

-if using big plates, first weld the core, then the 2 opposite plates, then drill every ...mm the plates and weld through the hole filling the hole with the mig. I have done it already on several occasions and works.


-but what actually i would do is use 100x10 plates, as together with the 100x100x4 profile they are available anywhere in the world and easy to cut with small band saws or dry circular saws. Which saves money. Say here in Spain steel is 0.95eur/kg if you buy from provider by the 6m, what i do. You go and buy it cut to size and they charge you 2eur/kg and some times even extra for the time they cut. Thats why i bought the circular saw, cause obviously on my build right now/ 500kg/ it saved me at least 500euro.

First weld the core, then form angle plates, then weld them to the core, then weld the final plates. Yeah, it would require some patience, careful welding and so, but a successfull build definitely requires these qualities.


depends from the method obviously the dimensions will vary a bit.


28-09-2014, 02:26 AM
Great contribution silyavski.

This is the spindle i'll be using: http://www.aliexpress.com/item/High-precision-CNC-machine-engraving-machine-BT30-unpowered-industrial-automatic-spindle-with-belt-5-Ceramic-bearings/2004506503.html

This is the spindle tool release mechanism i'll be using:

This is the motor i'll be using: http://www.aliexpress.com/item/Spindle-Servo-Driver-and-motor-1-5kw-Single-Phase-220V/1849189611.html

The motor has limited information on it, so i contacted the seller directly and got the following graph for it:

Not purchasing the items from the sellers listed (except for the motor).

Prices: Spindle is 755USD, tool release mechanism is 200USD
2.2Kw motor and driver is 1210USD.

Boyan Silyavski
28-09-2014, 09:35 AM
About the motor.
I don't know how realistic that could be. The data i mean and if it could serve well. Somebody has already tried it? For that purpose? Do your research there. Dont believe what chinese sellers say, cause mostly they don't know a sh*t about what they sell.

I would believe a similar Panasonic (http://www.aliexpress.com/item/MSME202G1G-2KW-Panasonic-AC-Servo-Motor/726104528.html) one/ what seemed the right one to me, look at the description/ would be jump in the known, not the unknown. Or just search more to find something more suitable for what you want, brand name.

Ask the seller of the spindle if he knows of a suitable motor. Ask linearmotionbearing , bstautomation and any other seller who seems credible and then decide.

28-09-2014, 09:41 AM
The seller is an OEM manufacturer for machines in China. They manufacture the motor. The same motor is used in many chinese VMC's.

It is not a normal servo anyway. it's an asynchronous servo with forced air cooling. All the real machines have these.
This type motor was recommended by the spindle supplier i might add.

The Panasonic servo you've linked is an axis servo. Not designed to power a spindle.

Also, linear & BST automation don't supply these motors. Their existence is not well known among hobbyists, and they're expensive to boot.

28-09-2014, 09:47 AM
This is the motor manufacturer's website.


I have contacted them on many occasions and they certainly do know what they're talking about. They were even able to tell me which EMC standards their drivers passed.

Boyan Silyavski
28-09-2014, 10:33 AM
That's good to know. Cause what i hate most is looking at manual in Chinese and nobody to ask for help in English.

Myself and believe others would be very grateful if you continue your build log here with details and so. i would especially appreciate if you share in the future the CAD drawing of the head assembly with the motor, spindle and tool release mechanism. This could save many hours of research and drawing.

28-09-2014, 10:46 AM
Yes, everything will be documented here.

I have found a VMC frame from China that seems to be around my specifications

The seller I have contacted (not the one above) will sell the frame my itself.
The 'Frame' includes the Spindle, HIWIN guides, P3 ballscrews, auto lubrication system and way covers for 7300USD. the ATC is a 1700USD option.

I have given some thought to either:

Making a fabricated steel clone of the machine above
Buying the frame and doing the electronics (not a creative project at all)
Sticking to my initial idea and doing the entire thing from scratch.

The first option is likely to be the cheapest.
The second option is definitely going to be the easiest and quickest, but the least satisfying.
The last option is one that has the least probability of success, but the most satisfying.


Boyan Silyavski
28-09-2014, 11:14 AM
rails and ball screws at the most will be 1500$
motor , spindle and so 2000$
500-700kg of steel 700$
mig wire, gas and so 200$
epoxy paint and so 200$
additional stuff 1000$
servo motors 1500$

That in worst case scenario, if you are careful with the design it will be more cheaper.

-the machine would be exactly as you want it
-better built than the Chinese frame.
-a lot of small things would be right, that makes a machine GREAT

Dont copy all,use it as guide lines only, build it from scratch and i assure you it will work. It seems you have done quite some research already. Plus one day next time you will like something like this (http://www.theinturn.com/) , which you can buy or make your self. So why not from now plan how will fit and be prepared. The Chinese frame will not allow it without sacrificing something.

28-09-2014, 11:38 AM
No brainer to me buy the frame.!!

You won't make it for less by the time you factor in machine time for grinding surfaces etc. Then you have all the time invested which will be many many weeks. With this you'll be up and working in fraction of time and making money.!

Then you have things like Class 3 ballscrews these shouldn't be confused with the cheap Class7 we buy. If indeed they are Class 3 then they will cost much more and $1500 would just about cover the screws and not rails as well like Boyan suggests.

BUT all this said if your going to this trouble have you thought about buying a second hand VMC. You can often find second hand VMC with dead or absolete Controllers that are perfect for conversion. Even with older ones that have many hours use and worn the structure is still perfectly fine and substantial.
Change the worn parts for new refit with new controller. Often you can reuse servo's and Scales etc even if they are analog drives etc.

You'll get a much better professinal machine for less or same money you'll spend doing this to this level and when done it will be worth double you invested.!!

Boyan Silyavski
28-09-2014, 11:45 AM
Unfortunately/or fortunately :-)/ Dean is darn right. Thats why we see so little mill builds from scratch and mostly they are in the smallish range. Moneywise that is Unbeatable, to buy something like Deans VMC and refurbish it. No way that you can do something even similar for the money.

01-10-2014, 09:14 AM
Well that revelation certainly changed my plans...

I had thought of getting a used machine and stripping retrofitting it, but the deals are so few that i would probably be searching forever.

I am strongly considering getting the VMC frame, toolchanger and enclosure (which is offered as a package) and extending the X and Y travels. Also replacing the existing spindle and motor with a single built-in motor spindle (http://www.alibaba.com/product-detail/BT30-spindle-atc-atc-spindle-milling_1534965688.html).

I feel that I really don't need the frame to be as rigid as it is given that i'm only doing HSM, and that extending the travels should not be at the machine's detriment.


01-10-2014, 09:53 AM
If they do a 40 taper either BT or ISO/CAT then I'd strongly suggest you go for that because you'll find toolholders cheaper and more available as there more common in industry and you'll also have more choice Ie: long nose, collet chuck, mini nose, high speed balance etc.

01-10-2014, 01:25 PM
Don't know if http://www.ebay.com.au/itm/Cnc-mill-Cincinnati-vmc-with-anca-2000-series-control-/121447873486?pt=LH_DefaultDomain_15&hash=item1c46db7bce would be of interest to you?

01-10-2014, 01:31 PM
I've been watching this one, but it's not quite what I am after. A bit too dilapidated for my taste.

Thanks for the suggestion though.

Boyan Silyavski
01-10-2014, 07:07 PM
I've been watching this one, but it's not quite what I am after. A bit too dilapidated for my taste.

Thanks for the suggestion though.

I know what you mean. I also like things that not only do the job but are just great even just looking at them.

So don't despair. If i were you i would go back to the drawing board, draw my best and once ready will start the build. At the end there would always be better choices, but there is nothing that brings more satisfaction than a custom build.

Now i said that you cant beat refurbishing old machine. But that's true that you can not easily waste so much metal in one machine for the same money. Not that you can not do better simpler machine. Look at that link above, 6 tons of a machine , 2.7m high, that's a monster. But imagine that you have to change the linear guides. That could be even more difficult than a new build. You will need a crane, just to see whats going on there and so on. I doubt that it could do HSM.

At the end its up to you, but when i decide to do something i do it. I am in the middle of a build. YES, i could have bought old CNC router and refurbished it and gained ATC and vacuum table.. No, i would not do it, now soon i would have a Ferrari i build to my taste. And i would be very happy every time i walk in the garage.

02-10-2014, 05:36 PM
By way of encouragement(ish) I'm also scratch building a mill (main frame from 180x180x16 steel box section) as shown in its very early stages on the final posts here:


In contrast to the thread title this has morphed into a stand alone CNC mill, approx travels 400X x 200Y x 200Z (yup I know more Z would be good) which is aiming for an accurate, good finish in steel. Linear rail all round and 25mm ballscrews. Will initially be stepper powered but I am building with a view to changing to servos later - have already scrounged some. Spindle probably to be ER32, driven by a 2HP AC motor with VFD, with pulleys to vary speeds if need be.

Note the dates on that thread... but I've been only getting small amounts of time (and money) to go at it. I have also temporarily lost my CAD facilities which is not helping (due to my Alibre version not liking Windows 7 - but I'll be freeing up an XP machine as an offline CAD-only computer in the next few days I hope).

So anyway, I decided not to post further updates until I have some serious progress to show in the metal. That should be soon :-)

Reasons for the scratch build rather than adapting or refurbing were for me:

- I only have a floorspace of approx 1m x 1m where it can go, and that has to include computer and control box. So I wanted to make maximum use of the space. So there will be a (very robust) stand with space under it for computer and electronics, and on top goes the machine, with the column barely clearing the ceiling.

- Refurb projects/machines tend to be a LOT bigger than that unless you're talking a Denford or the like, and even these are usually wider (so won't fit). Often the more serious machines also take more electrical supply than i have available.

- I have recently not had much money at all to spend on this project. DIY lets you scrounge bargains. For example, the metal for the frame and stand has been approx:
GBP 60 for the main beams (approx 2.7m long x 180mm square x 16mm wall) inc. cutting.
GBP 22 for beams for the stand (2 off approx 2.5m, 160x80x6mm rect. section, unfortunately galvanised)
GBP 40 for more beams for the stand (2 off approx 2.5m. 100x50x5mm rect. section)
GBP 15 for apprx 2m of 150x150x10mm steel angle
Plus some bolts, epoxy, welding rods, paint, sand etc. and petrol for collecting.
Still to buy are a few heavy steel plates. For mounting rails on and for closing tube ends.
So maybe GBP 250 for the main 350 kg+ (before sand filling) structure. Plus a lot of time of course, including grinding back that galv before welding the stand. And a few tools e.g. cutters knackered when cleaning up ends...
Still not bad. But it did take some time and luck to find those bargains. And when you count in linear rails, ballscrews, servos etc. gathered so far, even at ebay bargain prices I'm definitely into four figures for cost so far. One day I'll add it all up...

- But it's a challenge! And it will be very cool when finished :-) I'm really looking forward to the 'fun' bits - mounting linear rails and ballscrews, and seeing motion... But there seems to be a LOT of slow progress building the frame first...

As Jazz says further up the thread if you want to get up and running in a sensible time don't do what I'm doing - at least not unless you can dedicate a lot more time to it than I've been able to. Only really worth considering a scratch build if it's just a hobby and there's no real urgency (as in my case). You'll also want some reasonably large and rigid machines already to work on unless you plan on farming things out.

The results are not assured either - will my machine when eventually finished really work any better/faster/more accurately than e.g. a Denford Triac refurb? Could probably just about have bought one of those for all that's gone into it so far...