[Aiman]

Hi, I need help determining the design for diy cnc mill that are capable of milling and engrave acrylic, wood, aluminum and steel. Hopes it capable of milling something like this:

[ame=http://www.youtube.com/watch?v=VaVr89FO_FE&feature=results_main&playnext= 1&list=PL5B7079D9B0020CFB]CNC Cutting a Face - YouTube[/ame]

Im a total newbie... Hope some easy to understand terms and languages.
AND i would like to have the highest precision possible for the machine... $ is not a factor... And please dont suggest i buy a commercial one because im doing it for the sake of satisfaction and learning.

[wizard]

I ask because it is fairly easy to build a nice mill/router to do acrylic, wood and aluminum. Build a mill completely DIY for steel though is much more involved. In fact I'd suggest that it would be better to build two, with one dedicated to Steel.

Hi, I need help determining the design for diy cnc mill that are capable of milling and engrave acrylic, wood, aluminum and steel. Hopes it capable of milling something like this:


Im a total newbie... Hope some easy to understand terms and languages.
AND i would like to have the highest precision possible for the machine... $ is not a factor... And please dont suggest i buy a commercial one because im doing it for the sake of satisfaction and learning.

I understand learning but I'm not sure you realize the big jump in construction effort to build a decent mill for steel from the ground up. It would be much easier to do a conversion to CNC of an existing mill.

[Aiman]

wizard,

yeah after much thought i would like to make a specialized mill for steel, and another for woods and the other one for plastic and acrylic.

the metal ones first and after that it will be the ones used to create the woods and the plastic ones.

i spend all night reading 27 pages of a thread of mill build of a experienced toolmaker

so i decide to sent the design to be fabricated (since i have totally 0 knowledge whatsoever in metalworking... intended to learn metal working from machining metal using the diy not from creating the cnc itself coz of lack of means and material) and here what i come up with in the internet, i found a company in my locality that does metal precision machining so i decide to have my cnc structure fabricated here, so anyone expert out there can give advise which material will be the best for my cnc mill (lightweight, strong, good vibration absorber, etc...)?

METALS
Aluminium Alloy
-2024
-5 Series
-6061
-7075

Stainless Steel
-2024
-5 Series
-6061
-7075

Carbon Steel
Tool Steel
Brass
Copper

EXOTIC METAL
Titanium
Carbide
Waspaloy
Nickel Alloy 718 (Inconel)
Stainless Steel 17-4
Monel K500
Stainless Steel 15-5

this i the kind of metal offered by the company... hope you can give list from the best to the bad...

[ger21]

Designing a machine can take hundreds of hours. No one is going to give design a machine for you, but if you post pictures of your own design, you'll get a lot of suggestions.

[Aiman]

What are the thing i should emphasize in my design? Coz i heard cnc mill have some issue of force exerting on the structure... so i want to plan ahead to minimize those issue in my design... what are the factors should i consider in my design? Any other factor apart from the issue?

thanks.

[wizard]

Seriously designing a mill to do a decent job on steel is a major engineering effort, that is why so many on this forum simply retro fit a manual mill to CNC. Beyond that, unless the mill and corresponding parts are very small the machine will be very heavy. To get a handle on what is involved make friends with a machine shop and ask to have a look at a Bridgeport or Deckle type milling machine. In industry these would be considered light weight manual milling machines. Then ask to have a look at a modern machining center from one of the big names, these machines are massive.

After all of that take a look at bench top and larger mill/drill machines. These sorts of machines have extremely limited work spaces and are still relatively heavy. Plus an argument could be made that they don't do steel well.

I like your enthusiasm but I don't think you grasp what is involved from the mechanical end of things. I'd strongly suggest an initial attempt at a wood & aluminum router just to get a feel for what is involved.

What are the thing i should emphasize in my design? Coz i heard cnc mill have some issue of force exerting on the structure... so i want to plan ahead to minimize those issue in my design... what are the factors should i consider in my design? Any other factor apart from the issue?

thanks.

[Aiman]

owh, ok... I get it... so aluminum then... does the issue on the mill for steel need to be addressed too in the aluminum one?

And one other thing... how do i start designing my cnc mill? Buy guide mechanical first and then design the mill according to the mechanical dimension or the other way around coz this thing starts to confuse me... coz design-it-first method need to have dimension of the mechanical and if i buy the mechanical first the design will be limited to the mechanism spec (max load, dimension, working area and etc)... I want to design the mill according to my spec n then later buy the mechanism according to the design specification requirement...

Hope you all understand what im trying to tell... Sorry if that question sound silly...

[ger21]

Precision machine design - Alexander H. Slocum - Google Books

[Bob La Londe]

What are the thing i should emphasize in my design?

RIGID - First and most important for good results in my opinion. Heavy can help, but if the machine can flex substantially under normal cutting loads nothing will help.

SMOOTH - All of your linear movement and drive mechanisms must be silky smooth with the least possible force necessary to do what they need to do,

PRECISE & ACCURATE - Of my 3 key items this is I believe the least important in my opinion for most hobby "machinists". Oh, don't get me wrong. Its very important, but if lower backlash comes at the expense of binding in movement then you learn to deal with greater backlash.

Just my opinions based on having dealt with flexing underpower binding machines for the last couple years. I am not a real machinist and I do not play one on TV.

[Aiman]

thanks gerry... thats really help... will buy one...

What?!! seriously?? That is something new... lower backlash means more movement binding?

[Bob La Londe]

thanks gerry... thats really help... will buy one...

What?!! seriously?? That is something new... lower backlash means more movement binding?

Nope. Nothing new.

However it might be more accurate to say that tighter fits in moving parts to eliminate slop and backlash may result in greater force required to move the machine.

Tighten down your way gibbs to prevent play, and crank down your pinch nuts (depending on design) to prevent backlash and it requires more force to move the machine.

Want a practical experiment?

Set a feather on the back of your hand and suddenly jerk your hand out from under the feather. Now repeat the experiment with a brick. Pretty simple.

There is a secondary observation you can make from this experiment. Assuming you used adequate force to jerk your hand out from under both objects at the same speed... which object moved further away from its starting point before falling back down into position.

I might also add that the feather is better designed to not damage the moving part (your hand) than the brick.

Just like a ball screw and a ball nut is a better design than an acme screw and an anti backlash nut for moving the parts, and an Acme screw is better than a V thread and a pinch nut. You will find a substantial difference in price though.

[Aiman]

Tighten down your way gibbs to prevent play, and crank down your pinch nuts (depending on design) to prevent backlash and it requires more force to move the machine.

Owh i get it! can you explain those statement in easiest dummy understandable language? what is way gibbs? play? pinch nut?

Anyway i am actually aiming to get precision ballscrew...

Thanks

[Bob La Londe]

Owh i get it! can you explain those statement in easiest dummy understandable language? what is way gibbs? play? pinch nut?

Anyway i am actually aiming to get precision ballscrew...

Thanks

Are you being facetious?

Gibbs are the adjustment on your ways. Play, slop, looseness. Pinch nut is one form of backlash control on a lead screw. It literally is designed so it can be cranked down to pinch the screw more to make up for wear in the nut or screw.

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

I was just looking at this machine. Down near the bottom they show pictures of the basic machine. Its an interesting design being semi router gantry and semi mill in its construction. Made out of such heavy cast iron its going to be very rigid.

[Aiman]

Sorry if that is inappropriate... I am from country that does not speak English... Although i am moderately fluent in English but when it comes to terms such as that, i dont know what it mean... For example i dont know what is the term play mean... And slop is some "not neat movement"? looseness i can understand... so that why i request for anyone to explain everything in the simplest language that i can understand in the 1st post... Sorry...

anyway, i have seen the mill... yeah.. the gantry is from router and the z axis is fashioned like a mill... Yes that one looks very rigid... About rigidity, does weight is one of the contributing factor for rigidity? coz that one looks very heavy... And one other thing, if lets say, i am able to design cnc that has less joint, does that reduce the stress, because from my shallow engineering knowledge, usually force acting on the joint will be the greatest, trying to tore the joint apart (correct me if im wrong)

[Bob La Londe]

In appropriate? Naw. You didn't swear at me. LOL. I just wasn't sure if you were poking fun at me for pointing out what you might think is obvious.


I am not sure about number of joins, but you could be correct. There is a term used in boat building that I have not seen used elsewhere that might apply. "Hard Point." A hard point is a sharp bend in the architecture as opposed to a more gradual change. Hard points if not properly reinforced and/or supported tend to break or crack more often than other areas.

I suspect if you could cast an entire fixed gantry and table support frame out of a single piece of iron and then machined to suit, it would be more rigid. Is that a practical solution? For me no. I do not have or plan to setup a foundry. For a commercial builder? Probably not since it would be an awkward and very tedious manufacturing process to do in house. Probably also more expensive than buying certain base items and then machining to fit.

[Aiman]

yeah i also think so... that is really unpractical, but it is nice if my will machine is built that way...

From what is can see from commercial cnc all have massive structure but relatively very small working space, that hint to me that the magnitude of force acting in the structure is more than what we thought it would be in our mind... Initially before learning anything i thought the force is barely bearable by hand but small matter for the machine, but boy i was wrong, it could even tear the joint of mill made of steel if the mill is not properly built...

What i can sum-up from my observation is that, in order to work on steel of certain size, the machine has to be way bigger than the workable space(maximum workable volume of the steel)... and Wizard(read post no 6) confirms my theory...

That why i took Wizard advice (credit to him/her) to first delve my self in aluminum first... And before starts designing i want to make sure every issues are overkilled (im a perfectionist, even smallest detail matter to me) and the first step is im gonna buy Precision Machine Design (thanks to Gerry), read it and design as i learn... Steel is only after i have some good grasp of diy cnc...

[Bob La Londe]

Well, yes and no.

After all of that I can tell you that people cut steel on Sherline and Taig CNC mills with light cuts and slow feeds. I happen to have a Taig. In order to get the most out of it I put it in an enclosure for coolant, and then I bolted it down through the bottom of the enclosure through the surface of a heavy work bench. If I have a heavy vise on the table and I am doing a lot of rapids or other fast movement everything shakes. I don't put anything heavy on the table. LOL.

In order to work it hard you do need a heavy machine, but you do not have to work it hard.

I'm not sure what a Sherline weighs, but it looks lighter than my Taig. I was able to carry my Taig complete from one side of the shop to the other when I moved it to the work bench and enclosure. I think I even saw a video of somebody milling titanium on a Taig once.

Depending on what you want to do you may find it as personally rewarding to get a mechanically decent used mill and go through it retrofitting as you go. I am currenty retrofitting an old Hurco to modern CNC controls for my heavy machine.

[ger21]

I'd recommend buying a small Chinese mill and using it to study and learn from.

[Aiman]

Although im a bit skeptical about anything made in china in terms of quality but i will give that a thought... Anyway if it is a China product, i think i can try to find it here in my country instead of buying it from US (much cheaper)... coz 1 usd dollar is equivalent to ~RM 3.1 (im from Malaysia). And that 3.1 ringgit here are equivalent as me in my country and u on usa spending 3.1 dollar... i doesnt sound much but for everything u usa people bought at x1 rate i have to bought it at three time the price...

Currently im targeting to made cnc mill for aluminum, but with mill for steel design and consideration... not that im gonna use it for milling steel, but i just want take the feel and learn how to create a good one for steel... That is as preparation for to embark on the higher level of steel... But yeah, any additional source of learning is better... Maybe ill try to learn from commercial steel mill also... just as Gerry suggest...

[Bob La Londe]

When I started out about 3.5 years ago I think in CNC machining I was intimidated by the whole process. Building a machine was beyond my wildest dreams. Heck even learning to adjust a machine to run decent was a challenge, but it was worth it.

I wouldn't hesitate to build a machine or buy parts and assemble one today. I've heavily modified my first machine, bought another one that was clapped out, and totally retrofit it so for light work its got backlash in the .0005 or less range. I currently am doing a retrofit on a large mill (Hurco) to modern control, and my next project is converting a midsize lathe to CNC control.

I'm not bragging. Ok, maybe a little bit, but my point is there is a lot to learn between starting out and building machines. I'm not an engineer so maybe I was slower at it than you will be, but it took me about 3 years to learn enough about available materials and controls to be comfortable with the idea of building a machine from scratch.

Ger's idea to buy a machine to start from is not a bad one. Besides. You can use it to make some of the parts for a better machine.

P.S. I work with a designer in Jakarta sometimes on some injection mold designs. Its getting to be a smaller world isn't it. (I'm in the USA)