[CosmosK]

Spindle runout is basically wobble. As far as where it is measured, if you chuck up a perfectly straight 12" rod and spin it, there will be more wobble at 12" than at the collet. Just something to be aware of. For a machine over 1k, they should specify. .0005" should be fine, ideally measured both at the collet and some distance out. Nothing to do with Z travel, just an indicator of the quality of the spindle build.

Also, there's not necessarily anything wrong with an unsupported ballscrew. There are plenty of instances when you don't need the end support. It depends on diameter, length and rpm of the application. Could be the design doesn't require it or it could be they cheaped out.. hard to know.

[hanermo]

Ill give you some advice that may actually be useful ..
I have built a mill, and now a vmc, for milling steel.

Its modular, bolted together assemblies.
Its also about equal to a modern VMC in stiffness/power.

Otoh..
Its a bridge mill, with moving table. This is the most rigid design there is.

Bridge mass is == 700 kg.
Mill mass == 2000 kg.
Ballscrews = 32/4 mm.
Linear guides: 35 mm.

Servos, with 0.3 micron step size.

Its not all that hard.
But.. you need to increase your thinking about * rigidity * by about 100x.

I am now refinishing several pieces, as the spindle is going from a bridgeport to a modern, ISO30 spindle (I have) with ATC.
E.g.
Mill holder, similar to the ram on deckels and bridgeports, is 240x200 mm, 850 mm long, 2 cm thick tool steel, == 100 kg.

You can save money, yes.
But the costs you are comparing to are a Haas VF5/6, and the mass needs to be similar.
My design is larger (moving table), but more rigid (bridge mill), and lighter.
Its reasonably rigid, now.

Bridge is 220 cm wide, 20 cm tall, 2 cm thick tool steel, with 35 mm linear rails on top, for 235 mm total height.
Heavier is better.

[hanermo]

Further to my post;
My VMC is good for about 3kW spindle power - NOT the 40 hp on modern VMCs.
Thats why it can be so light, vs 4-6000 kg for equivalent machines.

And, a bridge mill == 4-8 times more rigid than a c-frame like typical VMCs today, for half the work area, due to fully supported moving table.

[victorofga]

the first one is a ""regular"" mill.. indeed for metal tan wood..

the second I just posted you, yes there are many type you can buy.. that has missing control and axis motors..

the 3rd one, what I was thinking the most suitable for you..
because it made of cast iron, and has a relatively large work area.. a lot larger than similar sized bed mills..

but, we all can only suggest you.. not to making decision instead you..

what I think everyone can agree, for your situation a ready built machine at this time better than entering in an endless journey to building..
reason I suggested you the aliexpress, because it too risky just go out for a 30-50K machine without real experience..

the 3rd type of machine really used for mold machining,, some small series of injection mold can be made of aluminum, or brass..
so it suitable for metal, yet enough flexible to handling wood projects..


also take gio adive, and ask about details.. most seller, or say manufacturer make you changes for no extra cost..
they can put in more bearings if you ask it..
heres another link more detail what inside in a machine..

SALE CNC Router Milling, CNC Laser, CNC plasma machine, China, Servo Motor Drive, UK, USA, Italy, Spain, Thailand

[oxi]

All right people, I think I'm learning...

CosmosK: Thank you for clearing things up.

hanermo: Woah, I think you're playing in a far different league! Now, I have to confess I had to Google quite a bit to grasp many of the technicalities you mentioned and I'm not sure I fully understood. But if you intended to teach me about the better stiffness of bridge mills sure enough you succeeded. I honestly believed these to be routers and I still can't see how this setup can be stiffer than a spindle on a single axis, but I don't need to understand as long as I can take this for a fact and it works for me I gotta ask, are you Spanish? Your English seems a bit out of reach for me

victorofga: Bearing hanermo's statements in mind, yes, you're probably right that I could benefit better from the last two models. Sorry, being the noob I am I was thinking these were just routers and they wouldn't be stiff enough for aluminum. I agree that I need something to get me going ASAP. victorofga: In my current financial status I could only dream of ever spending 30-50k on a milling machine! Thank you for all the support so far.

All right, people, do we all agree that I should go for a bridge mill? Guess I gotta search again... :tired:

[victorofga]

the bridge mill is (roughly) where the gantry standing, and table moving..

just don't hurry
take your time and digest everything you see here

[oxi]

Did I get this right?:

Engraver: Spindle moves along 3 axis, short Z travel, probably not very powerful spindle, usually bigger bed
Router: Spindle moves along 3 axis, longer Z travel, more powerful spindle, usually bigger bed
Vertical/C frame Mill: Spindle moves along 1 axis, bed moves along 2 axis, powerful spindle, smaller bed
Bridge Mill: Spindle moves along 2 axis, bed moves along 1 axis, powerful spindle, bigger bed

Please correct where needed.
Thanks

[gio666]

Spindle runout is basically wobble. As far as where it is measured, if you chuck up a perfectly straight 12" rod and spin it, there will be more wobble at 12" than at the collet. Just something to be aware of. For a machine over 1k, they should specify. .0005" should be fine, ideally measured both at the collet and some distance out. Nothing to do with Z travel, just an indicator of the quality of the spindle build.

Also, there's not necessarily anything wrong with an unsupported ballscrew. There are plenty of instances when you don't need the end support. It depends on diameter, length and rpm of the application. Could be the design doesn't require it or it could be they cheaped out.. hard to know.

Lots of cheap machines use motor shaft to hold ballscrew in place. Unsupported ballscrew will damage wiper and bearings in ballnut if motor side in not fixed to a bearing .Motors do not have axial support for weight and the bearings are not meant to take radial load for weight and vibration . If you look at lots of pictures of the lower cost machines you will see coupling going through upright straight to motor with no bearing. Most cases you will see the free end bearings is fixed to plate



XZero CNC Routers

[oxi]

Lots of cheap machines use motor shaft to hold ballscrew in place. Unsupported ballscrew will damage wiper and bearings in ballnut if motor side in not fixed to a bearing .Motors do not have axial support for weight and the bearings are not meant to take radial load for weight and vibration . If you look at lots of pictures of the lower cost machines you will see coupling going through upright straight to motor with no bearing. Most cases you will see the free end bearings is fixed to plate



XZero CNC Routers

Sorry CosmosK but I have to agree with gio666 on this. I know very little about bearings, but I do recall reading that there are different bearings for different applications depending on the forces they can take. If motor bearings aren't built to stand the vibration or other forces that go diagonally or perpendicularly against the axis (sorry I lack the technicalities) the motor bearings will wear off sooner and break. Just as in the difference between a spindle and a drill. And I have the feeling ballscrews get quite a bit of perpendicular forces due to the load and tool pressure.

I didn't give it much thought but now that I thought of it I feel this is intolerable so I'll definitely bear it in mind. Thanks. Obviously I'll also be bearing in mind that given my limited budget I might not be able to afford all the minimum specs recommended so far...

[ger21]

Sorry CosmosK but I have to agree with gio666 on this.

Cosmo is talking about a screw supported at one end only, which can be perfectly acceptable.
If you come across a machine with the screw supported by the motor, run as fast as you can. This should not happen, even on the cheapest machines.

[oxi]

I must not be understanding... Case #1 is acceptable?
Attachment 279516
Or you mean the other way around with the nut on the motor end and the other end supported where? by the frame?

I put case #2 because I think that's desirable, not to be confused by what I meant in the previous sentence.

[oxi]

Anyways, people I don't want to sound rude, but this is taking long and although I learnt some things I'm still frustrated. Can't you just tell me what to buy? That is, according to the kind of work I want to do. Just the closest I can get for a machine preferably under $5k. I'll live with that, it doesn't need to be the most perfect machine, it just needs to get me things done eventually.

victorofga: I tried searching in AliBaba but it won't let me sort by price! I think it could be done several years ago, or am I missing the option location? I just can't browse through aaaall the hits. Also I never bought through AliBaba and the FOB thing is a bit scary, although I guess sellers can arrange the whole shipping for me...

Also I read a bit more on the several types of milling machines and I got the impression there's no general agreement as to what the most rigid type is. Once again this whole thing is becoming increasingly confusing for me. That's why I'd appreciate some straight indications on what machine to buy and some confirmations from other members will really help. If I need to spend in the $10-5k to get things done properly, I will, if I can get things properly done in the under $5k range at the cost of time, all the better.

Thank you

[Tkamsker]

Hi oxi
no i meant get you an high quality router then you can cut Alu , POM, Plexi, Wood and source the steel parts to an company near you

i did the same later i got bigger demand then i bought an propper mill for steel ,..
but all i learned by the router helped me to decide what is good and necessary for me.
a sentence which is used in our region goes like who buys cheap buys in real world expensive

So in my case i made an decision excel to see really which machine i get

thomas

[wizard]

Anyways, people I don't want to sound rude, but this is taking long and although I learnt some things I'm still frustrated. Can't you just tell me what to buy?

Actually no, even after all of these posts no one has a clear idea of what you really want to do. Further to be perfectly honest I'm not sure you have the personality to run the machines if they where sitting in your shop. You would be far better off contracting with a local shop to do the work for you.

That is, according to the kind of work I want to do. Just the closest I can get for a machine preferably under $5k. I'll live with that, it doesn't need to be the most perfect machine, it just needs to get me things done eventually.

There isn't a milling machine in that price range ready to go! Further you are probably underestimating the value or cost tooling up any machine you buy.

victorofga: I tried searching in AliBaba but it won't let me sort by price! I think it could be done several years ago, or am I missing the option location? I just can't browse through aaaall the hits. Also I never bought through AliBaba and the FOB thing is a bit scary, although I guess sellers can arrange the whole shipping for me...

Then buy locally. It is pretty obvious you can't support yourself with this machinery so you will need a local support solution anyways.

Also I read a bit more on the several types of milling machines and I got the impression there's no general agreement as to what the most rigid type is. Once again this whole thing is becoming increasingly confusing for me.

This is why I strongly suggest dropping the DIY approach and finding a local shop to handle your machining needs. It should be pretty obvious that machines have different structural considerations and that those limitations impact the machines capacity or capability when it comes to machining different materials. A reasonably sized shop would take the work request you have and do the work on a machine that is proper for the job.

That's why I'd appreciate some straight indications on what machine to buy and some confirmations from other members will really help. If I need to spend in the $10-5k to get things done properly, I will, if I can get things properly done in the under $5k range at the cost of time, all the better.

Thank you

Not knowing what you want to do in detail it is difficult to suggest anything. Each time you come back to us with a desire to machine steel that indicates the need for a milling machine.

[Tkamsker]

You should not be desperate
you require input here you have :

Option 1)

As i wrote before here is a video https://www.youtube.com/watch?v=6dojAe7DKRc which shows steel milling is possible ( i have the 400 T version of that machine )
You are living in Europe i assume so go and buy european that is why i forward you that link.
Give them a call and ask them what you inter to do and you will find an solution ,..

Option 2) Get you an Wabeco or Klippfeld or Optimum with CNC Kit choose the size you need and go for it
But if your budget is 5k it will be hard. i guess this real steel machines are possible in europe for around 9-12k

Option 3) Find someone who does it for you or go to a Makerspaces where you can make your feet wet Like Happylab: Happylab i would recommend that anyway to learn cnc

Option 4) Get the china learning curve ,..

And if you choose Option 1,2 or 3 think of extra cost

Tools (i spent 500Euro on broken millers till i can master Alu !!!)
Vices
Software Cut2d till RhinoCam Sprutcam whatever suits you
Drill
Metal
Training ( books, etc )

So i hope now all is much clearer for you
thomas
if you would live in Canada i would go von Novakon ,..

[gio666]

I must not be understanding... Case #1 is acceptable?
Attachment 279516
Or you mean the other way around with the nut on the motor end and the other end supported where? by the frame?

I put case #2 because I think that's desirable, not to be confused by what I meant in the previous sentence.

You are right, Number 1 is not right. A stepper motor will stall easy with any vibration in ballscrew. Number 1 , if you put bearing on other side in front of motor it will work ok . It would depend on the length.

[gio666]

Any router will do what you need , square rails will be best to look for. Aluminum is very easy to machine. Steel also is not a problem , just takes a lot more time.

[CosmosK]

You guys are correct. There is a third case not pictured. One bearing support at motor end and NO bearing support at the free end. This is the acceptable case for some applications. Sorry for the confusion. Yes, #1 looks bad

[CosmosK]

Can't you just tell me what to buy?

Ha! This is your quest and your decision. The more research you do, the happier you will be with your decision.

[mcphill]

Anyways, people I don't want to sound rude, but this is taking long and although I learnt some things I'm still frustrated. Can't you just tell me what to buy?

I thought I pretty much did here: http://www.cnczone.com/forums/diy-cn...ml#post1696912 (Hint: Get the fireball, learn on it, and find out if this is even something you really want to do, transfer the skills you LEARN ON YOUR OWN to decide on your "real" machine purchase or build...)

But if we are confusing you, stop adding confusion to the answers!

I am done with this thread, there is more than enough advice here to get your started, and I think I agree with the response that maybe you aren't "cut out" for this type of work. If you are confused just picking a machine, I cannot imagine what you will do when it comes to setting up the machine controller and the CAM software...