Just starting out.. 3,4,or 5 axis metal milling

[BadTad]

Hi Folks,

Well we all have to start somewhere right?!

I'm looking to build a 3 axis cnc mill ( upgradeable to 5 axis later on )

I want to focus on this project in 2 parts.

The mechanics and the electrics!

My first goal is to nail down the motor type , size and controller.

I've spent the last two weeks going over my options and simple can not make up my mind.

My Initial thoughts are to use 3x 200oz bipolar stepper motors, however finding a 3 or 4 axis controller kit ( to build myself ) has been some what daunting as most applications are set up for unipolar.

I've also run across parell port and usb options - I'm not which route to go with as I don't know each are limited to their own software programs.

Obviously USB would be more user friendly for me as it would work directly with my laptop, and I could connect it to my network, ect.

Aside from the above electrical decisions, I have the following mechanical concerns.

I would like to build a 3x3 ft mill , I'd like to be able to use this on metal projects, and would like to be able to upgrade to 5 axis at a later date.

I am not sure if a lead screw or ball screw set up would work the best, if I should use roller guide ways or linear guide ways.

I would like excellent accuracy from this set up.

Please also note that I have easy access to free or discounted parts for everything except the electrical items, so if anyone has a beefy recommendation for my set up, I am all ears.

I am tempted to start out with a 2x2ft set up, but would hate to just find myself building a 3x3ft set up at a later date.


Either way I am open to suggestions.

My first goal is to get the electrical out of the way, to do this I need help in picking components that will suit my needs the best, I would also like to run with limit switches, etc.. at anyrate if anyone can help me get my shopping list together I would appreciate it.. after I get the components on hand/ assembled and testing/running - then I'll worry about the mechanics

Thanks in advance for any input.

[Cartierusm]

What kind of metal do you want to cut and what kind of accuracy do you want? I.E. What kind of parts are you going to make?

[BadTad]

something simple like aluminum for now - the main goal for this mill is to learn cnc programming, I also have illusions of having a machine capable of 5-axis cutting an all aluminum engine block.

I'm not sure what accuracy would be required for the above?

I'd like to start with picking out the proper sized bipolar motors and finding a controller that will manage 5 axis's , preferably with usb and software rated for xp.

Of course I could just as well start off with a cheap 3-axis system and unipolar motors if thats how the $$ goes.

Either way I could use some educated advice.

I want to get the planning phase done quickly and move onto the building, and cutting part

[Cartierusm]

I hope I'm not disappointing you but, IN MY OPINION, there is no way you are going to build a machine able to do that for under $50,000. The ability to machine an engine would be building a machine of the highest level. I guarantee it would be cheaper to buy a machine made specifically for engine work. Most of the machine here are made for wood and light aluminum and are to a point very accurate but what you're talking about is beyond it's scope.

[jalessi]

Nothing wrong with thinking big!

You might get away with retrofiting a older full size 3 axis machine

and building the two additional axis.

Building one from scratch may have rigidity issues.

The trial and error you will go through might not be worth it.

This is the real deal>>>>

YouTube - V8 Engine Block Machined From Solid

YouTube - V8 Engine Block Machined From Solid

Welcome to the Zone

Jeff...

[ckm]

Cutting any kind of metal requires very rigid and heavy machines. It's easy to underestimate the forces in cutting metal, but the strength and stiffness required to hold both material and cutting tool are astounding.

That said, you can cut metal in not so stiff machines, but it requires very light passes. The net effect of this is that it takes forever to machine anything substantial. It once took me 6 hours to machine a NEMA23 stepper mount with a 1" pocket out of aluminum on my X1. That's one of the reasons I'm retrofiting the MUCH larger DM4400.

The other thing to keep in mind is that there are very few gantry-style machines that can machine metal. Enshu makes some, so does Tarus, but they are extremely rigid and heavy. Even then, they don't even come close to having a 3ft by 3ft machining envelope (except Tarus, but their machines are extreme in every way). You can see some pictures of CNC machine bases I've gathered here.

As far as 5-axis machining that could do an engine block, most machines capable of doing this weigh upwards of 20,000 lbs. It's not to say that a hobbyist could not build one, but it would take a lot of skill, knowledge and money. Just the spindle alone would probably weight more than 1000lbs, just think of what is involved in moving that up and down.

If you are REALLY intent on eventually machining anything the size of a block (even a small one), I would suggest you find an older used VMC with a broken control. Figure it's going to take you at least 3-6 months to retrofit and will probably have a total cost around $3-5k above the cost of the machine (you'll probably wind up in the $10-15k range). You'll also need a space with 3-phase industrial power and a floor capable of supporting 10-20k lbs. You can then shortcut getting to 5-axis by getting one of these: http://www.5-axis.com/index.html or use a trunnion.

One other thing to keep in mind is that having a machine capable of 5-axis is only 1/4 of what you need. You will also need a very, very good CAD program, and an even better CAM program. And you're going to need a lot of tooling.

OTOH, if your goal is simply to build a CNC machine so that you can machine some cool bits, then retrofitting a Chinese bed-mill is not a bad way to go. A Tormach would also be a good choice as a fully built, ready to go package.

Not trying to burst your bubble or anything, just want to bring some realism in to this as I have been down your path.....

HTH,

Chris.

[mc-motorsports]

Originally Posted by Cartierusm I hope I'm not disappointing you but, IN MY OPINION, there is no way you are going to build a machine able to do that for under $50,000. The ability to machine an engine would be building a machine of the highest level. I guarantee it would be cheaper to buy a machine made specifically for engine work. Most of the machine here are made for wood and light aluminum and are to a point very accurate but what you're talking about is beyond it's scope.

+1

Plus, you can fully machine an engine block on a 3 axis with enough travel, you'll need fixturing to complete all the operations. And the rough machining... IMO, isn't really all that accurate on older production engines. Finishing operations such as line bore and cylinder honing is a diffrent story.

MC

[BadTad]

Hey Guys,

Thanks for the input, I guess I should add that I do have regular cnc machines available to me, about 20 on the show room floor, from lathes, to mills to machine centers, double collumns, ect...

I can use them to make parts for my mill, but again my goal is to build something on my own, it would be a relatively simple matter to use one of the machines to make what I want my machine to make, but I'd consider that cheating

I am not quit resigned to limiting myself to a 3 axis just yet.. so with that out of the way.. I'm still looking on component advice

I don't mind starting with a 3-axis as long as an upgrade path is present. I would prefer a kit that I can make myself, and something that will power bipolar steppers of the 400-500oz range.

Once I can nail that down.. I'll be sourcing advice on the construction of the mill itself. I can always copy an existing example from one of the machines around.. I would like to keep it simple, accurate and rigid.

My main questions are with lead/ball screw, and the guides. What is more accurate, where can I get a good product, what examples have they been used in by members here.. etc.

Thanks for all the input so far, lets move forward, shall we?

[joeybagadonuts]

We can provide the brainfood for your project.

[BadTad]

How about we compare controllers?

I've seen this one;

http://www.hobbycnc.com/products/hob...er-board-kits/

( appears to be unipolar only, and only printer port )

http://www.xylotex.com/4AxSysKit.htm

( appears to be bipolar, but still only printer port )

http://www.stepperboard.com/prod09-BC4D15.htm

( usb based, bipolar? )

I also want to incorporate limit switches and possibly a probe later on.

my ideal package would be a usb based controller, with 3 or 4 axis capabilities ( upgradeable with add on cards for 5 axis in the future ), bipolar capable, and provisions for limit switch integrations.

Anyone see something out there that will do this?

[ckm]

Originally Posted by BadTad I do have regular cnc machines available to me, about 20 on the show room floor, from lathes, to mills to machine centers, double collumns, ect...

I think that part of the point people are making was not whether or not you currently have the ability to machine stuff (although that helps), but rather if you have the knowledge to design and access to large casting facilities. And, even if you have access to cast iron casting facilities, could you even machine something that large. The base on my small bed mill is around 5x2x1. Machining such a large casting would require a very, very large machine.

IMHO, the only way you could possibly do this without a huge operation (casting and very large component machining) is using a combination of welded components and epoxy-granite. Even then, it will be a huge operation, to say the least.

The electronics, quite frankly, are the least of your worries and possibly the easiest to do. You really should focus on the mechanicals first, since once you have that sorted, then the motors and electronics will be fairly easy.

Either way, be prepared to spend a LOT of money..... $50k is probably about right, given the price of steel and the size of the components you will need. Motors alone will be in the $8k range, not including the spindle.

Chris.

[BadTad]

My goals here are to decide upon the electrical and mechanical components.

I plan to start out with a simple 3 axis mill with 3x3ft workable space. (capable of milling aluminum.)

I am asking for help with this project for now.

Thanks