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View Full Version : VMC - Buy or Build? With Ramblings ;-)



magicniner
10-02-2018, 06:22 PM
I want a compact VMC that I can run on a good household 240V connection, I say it's a good connection because in addition to the house it has in the past happily dealt with a draughty garage where a 3hp compressor and enough convector heaters to get it warm enough for full 2k car resprays were in use.

I can't just buy a commercial VMC as they expect 3 Phase and more power draw than I suspect I could manage even through inverter drives, the Skyfire sounded ideal but recent discussions have knocked the shine off that a little as I will be working in Steel, Stainless Steel and Aluminium Alloys and expect a carousel tool changer to know where it is without intervention.

Do I go for a commercial compact VMC with a converter for all the motion and ancillaries and downgrade the spindle motor then run that from a VFD?
I think a diesel genny is out of the question from a noise and emissions standpoint.

Should I embark on an epic mill conversion journey or scratch build?
B*gger me, this has all just stepped a little sideways and well out of my comfort zone!

~Nick

JAZZCNC
10-02-2018, 09:18 PM
To me people are comparing apples with oranges when comes to VMC's and machines like Skyfire, Tormach etc.

Skyfire, Tormach etc are not VMC's they are Bench mounted Mills sat on a lightly built steel frame. True Vmc is floor mounted solid cast iron structure and column.
If you notice even Haas don't call there "Mini Mill's" VMC's because they are not. They are just heavily constructed base mounted machines. That is mounted on heavy constructed welded steel base frame. Unlike Skyfire or Tormach which in comparison are sat on light weight and bolted together benches.

To be fair were not even comparing apples to oranges when comparing to Haas "MiniMill" or other commercial MiniMill's like XYZ 2-OP because the difference is construction is night and day.

Skyfire, Tormach etc are just glorified Bench mills that come with all the weaknesses and traits associated with there manual cousins. Sticking servo's on them and wrapping in tin sheet doesn't make them VMC's or any stronger.

So to me, people need to start looking past all the eye candy sheet metal etc and pay attention to what they are truly buying with there "Starting from 16'950" lump of money, which in reality soon becomes 20K when they fall for few over priced extra's.!

Those are my ramblings anyway.!

m_c
10-02-2018, 10:08 PM
The problem is, this size of machine is always going to be a compromise.

I like my Triac for what it is, and it does the job I bought it for, but I can see something with more power and travel in the future.

A Tormach or Skyfire would fit that bill well enough, but for the same money, I could get a secondhand industrial machine. Somewhat ironically, I can get 3 phase installed for not that much money, but the current workshop isn't high enough for anything above 2.0m.
I could really do with a bigger lathe as well, but every enclosed slantbed I've looked at is also too high.

The big problem is with spindles. Without going to some kind of gear head, you're either looking at limited RPM to achieve reasonable torque, or high speed with limited torque. Although with a larger spindle, and with a suitable drive and/or controller, you could program it to operate in a power limited way.


At the moment, short of building a new workshop, I'm actually considering a solid router to handle aluminium work, and finally finishing the Matchmaker for steel work (every time I get back to actually working on it, some other retrofit comes along..).

magicniner
10-02-2018, 10:35 PM
So to me, people need to start looking past all the eye candy sheet metal etc and pay attention to what they are truly buying with there "Starting from 16'950" lump of money, which in reality soon becomes 20K when they fall for few over priced extra's.

You've carried me to that point but having looked beyond it's all a bit dark, at this point the best option I can put together is a new Bed Mill with a custom head incorporating a decent spindle cartridge and 3-4hp motor with ball screws and servos and a decent motion controller, PC and software.
More ramblings welcome ;-)

m_c
10-02-2018, 10:48 PM
That's just reminded me that Fadal's were weldments, and David Decaussin was making the UMC10 for a while, which was a welded steel.

magicniner
10-02-2018, 11:23 PM
I can see a whole raft of time with the MIG, TIG and MMA sets in my near future ;-)

JAZZCNC
10-02-2018, 11:30 PM
That's just reminded me that Fadal's were weldments, and David Decaussin was making the UMC10 for a while, which was a welded steel.

Exactly.!!. . . Weldment machine isn't beyond commited DIY builder. Steel is cheap and plasma/Waterjet cutting isn't that expensive. Out source some heat treatment/stress relief and grinding/machining services then you'll soon have strong base machine to start with. 15-20K gives you fare amount of room to play.

To be honest I'd even look towards EG or Concrete Fixed Gantry machine because could build a Very strong machine with larger cutting area in same footprint.

m_c
10-02-2018, 11:46 PM
My big worry with welding that kind of thing, is accuracy, and finishing the mounting surfaces. Unless you do it so things bolt together, access to finishing surfaces is going to be a challenge.

I've often wondered if there would be much price difference between welding and casting. By the time you factor in materials, machining them, welding them, stress relieving them, and finishing them, would it be more expensive than a set of patterns, getting them cast, and chucking the casting outside for year or so before machining/finishing them?
Plus spec the right grade of cast, and you get inbuilt damping, without having to worry that you're building a big resonator.

There are certainly lots of options. It just comes down to time and cost, as to what one suits.


If in your research, you happen to come across a Fadal with it's clothes of, I'd be interested in seeing how they've done the main construction.

magicniner
11-02-2018, 12:18 AM
would it be more expensive than a set of patterns, getting them cast, and chucking the casting outside for year or so before machining/finishing them?.

Pretty much yes, there is an element of "Time is Money" so I'm not really after a kit I can start to build in 18 months time or so, hence looking for a product and considering a conversion on a new Bed Mill or an adaptation of a second hand VMC.

m_c
11-02-2018, 12:41 AM
Pretty much yes, there is an element of "Time is Money" so I'm not really after a kit I can start to build in 18 months time or so, hence looking for a product and considering a conversion on a new Bed Mill or an adaptation of a second hand VMC.

That was more just me rambling :)

How about something like this? - https://www.ebay.co.uk/itm/Cincinnati-Milacron-CNC-Arrow-750-Vertical-Machining-Center-SPARE-REPAIR/162890979240
I'd want to know what exactly why it was non-running, but set of servos, new controller, and the basics are done. The hardest part is always the tool changer. Off course it depends just how much space you've got...

Attached are some plans that Dave Walsh (of BT15 spindle cartridge fame/saga) posted at some point.

And here's some notes I made about the UMC10 (IIRC I noted them down from his videos)-

6" x 6" x 1/2" wall thickness column
10" x 4" x 1/2" wall thickness base

6500rpm spindle = ~11000rpm motor speed
3hp spindle

table 1 1/2" x 8" crmo steel

JAZZCNC
11-02-2018, 12:42 AM
These are general questions to everyone, not just you Magic.?

#1 What travels would consider ideal.? . . . In X, Y & Z
#2 What's more important to you Bed size or Travel.? (Consider often you'll see 3ft+ tables with one or two 6" vices taking up only 18" space.)
#3 What would prefer to use Vice or Fixture plate.?
#4 What material cutting ability is most important Steel or Aluminium.?
#5 What's an ideal footprint.
#6 Bench mounted or Freestanding..?
#7 Fully Enclosed or Open.?

m_c
11-02-2018, 01:07 AM
#1 What travels would consider ideal.? . . . In X, Y & Z
X Probably a couple of feet. It's not that critical for me, as most of my parts are round, and those that aren't round aren't that big, but I wouldn't limit the X when it's relatively easy to make it longer.
Y Ideally minimum 250mm, possibly 300mm. This is where most small mills fail for me.
Z I'd want enough height so I can fit a decent (probably 8" or 12") 4th axis under it, so enough to probably get a good 400mm under the spindle nose, and still touch the table with a shortish tool
#2 What's more important to you Bed size or Travel.? (Consider often you'll see 3ft+ tables with one or two 6" vices taking up only 18" space.)
Neither really. As long as the bed has a bit room either end of travel, you work with what you've got.
#3 What would prefer to use Vice or Fixture plate.?
Both, although if I had the Z room, I'd probably get a Pierson pallet system, then mount what I need on pallets.
#4 What material cutting ability is most important Steel or Aluminium.?
Both for me. I need to hog lumps of steel down for repairing things, but most production bits are aluminium.
#5 What's an ideal footprint.
As compact as you can get the above with an enclosure, but still be able to overhang the table a bit when needed, or removable panels for the inevitable big bits (I do like the idea of the fixed table/sliding head setup used by Chiron, but it does complicate things)
#6 Bench mounted or Freestanding..?
Either as long it has a decent enclosure, and coolant tank.
#7 Fully Enclosed or Open.?
Enclosed. I've been soaked by coolant enough times to know enclosed is the only way.

magicniner
11-02-2018, 01:14 AM
Yeah, keeping an eye on all the usual second hand outlets, I think that Cincinnati might be just a little big but I might just squeeze that in.

BT30 is my ideal/minimum tooling, 6500rpm max spindle speed is NBG, that might do as a minimum though, he must have been a Model Engineer! ;-)

magicniner
11-02-2018, 01:27 AM
These are general questions to everyone, not just you Magic.?

#1 What travels would consider ideal.? . . . In X, Y & Z
#2 What's more important to you Bed size or Travel.? (Consider often you'll see 3ft+ tables with one or two 6" vices taking up only 18" space.)
#3 What would prefer to use Vice or Fixture plate.?
#4 What material cutting ability is most important Steel or Aluminium.?
#5 What's an ideal footprint.
#6 Bench mounted or Freestanding..?
#7 Fully Enclosed or Open.?

#1 X 800mm x Y 400mm x Z 500mm would be nice (has to have space for a decent 4th)
#2 I'll use all the travel I have, more is better, floor space limitations
#3 I can live with fixture plates, you can have one with vice mountings ;-)
#4 Sadly both Steel and Aluminium are a requirement, I have no objection to a belt/pulley change
#5 10' wide, 6' high and 5' deep would be in the ball park, could go 12' wide and 6' 6" deep
#6 Free standing
#7 Enclosure, flood needs to be an option

petesurrey
11-02-2018, 11:44 AM
I have had my mill for 6 years now it stared as a Cincinnati sabre 500 and it ran well for 2 years but then it was a pita. I have stripped all electronics out and replaced all drives with new AC servos and added VFD for spindle. It runs extremely well and all from a 240 1ph socket. Originally it had 500x500x500mm hence being a sabre 500 but as they 500 share the same castings as the 750 i fitted the X axis bearing from a 750 and due to the fact that i still have the 500 table i have a machine that now has 850x630x580mm. You couldn't ask for a stronger base they are extremely rigid. I also have a 4/5 axis that i use and tbh you need a machine this rigid to take the table weight.
The foot print of my machine is 2x2m and i built a 4x2m shed for it and it serves me well. ISO30 will limit you especially if you want run big fly cutters or boring heads. As well as bt40 or cat40 tooling is readily available.
I have another machine that is iso30 and i had to buy all my tooling new but rarely buy new tooling for my cat40 Cincinnati.

magicniner
11-02-2018, 04:43 PM
I have had my mill for 6 years now it stared as a Cincinnati sabre 500 and it ran well for 2 years but then it was a pita. I have stripped all electronics out and replaced all drives with new AC servos and added VFD for spindle. It runs extremely well and all from a 240 1ph socket. Originally it had 500x500x500mm hence being a sabre 500 but as they 500 share the same castings as the 750 i fitted the X axis bearing from a 750 and due to the fact that i still have the 500 table i have a machine that now has 850x630x580mm. You couldn't ask for a stronger base they are extremely rigid. I also have a 4/5 axis that i use and tbh you need a machine this rigid to take the table weight.
The foot print of my machine is 2x2m and i built a 4x2m shed for it and it serves me well. ISO30 will limit you especially if you want run big fly cutters or boring heads. As well as bt40 or cat40 tooling is readily available.
I have another machine that is iso30 and i had to buy all my tooling new but rarely buy new tooling for my cat40 Cincinnati.

Thanks Pete,
That kinda looks the direction I may have to go, buying new tooling will not be an issue.

Chaz
12-02-2018, 11:16 AM
Thor came about due to the same questions.

For me, its all about Alu. What could I build that I could run off 240V and give me as close to Datron's performance for 10% of the cost?

2 tons of concrete and a lot of labour, Thor exists.

Is it as good, no, very far from it. It does however give me reasonable results and does what I need.

Id certainly consider a retrofit machine like the Sabre 500 in future. My other limit was roof height, otherwise Id certainly have considered this too at the time.