very first cnc

[vfcnc]

hello. i was wondering if someone can help me. i don't know much about cnc machines so i thought i'd post here. i usually use a standard mill to machine my parts but now i need 100% accuracy. So can anyone suggest an entry level machine to cut alloy parts such a motorcycle yokes (they are about 250mm x 50mm) but must be perfect to hold the forks.

i can use autocad to design parts but i've heard some machines come with their own software. please help!

[tai42]

This is a bit of a loaded question. There is no such thing as a 100% accurate machine, there are only varying degrees of inaccuracy. If you have something specific you are trying to make, then you should sit down and figure out what tolerance is reasonable, how many you need to produce in a given period of time, and how much you expect the per-part cost to be. (I'm not a business major, so there are probably other things in there as well.)

The tolerance will tell you what type of process you will need. For example, you may find that you need to be looking at EDM machines, as a mill won't give you the required accuracy. How many parts per given time period will also factor into the process. If you want to make them quickly, then EDM is probably ruled out unless you have parallel machines running. If you want to go really fast, then you might consider a waterjet machine, but this would have to fit within your tolerances.

Finally, if you can get a handle on how much per part you expect the cost to be, then you can figure out how much you are willing to spend on a machine. This can get a little tricky, but if you're planning on putting a large amount of money up front, or leasing a machine then it's worth the effort.

Now, all that said, if you just want to play around with CNC and maybe make some stuff in the process, then you have a whole different set of questions to answer. For example, how big is the largest piece you expect to work on, do you want to buy an "off-the-shelf" system or "roll-your-own" conversion, and again how much money do you want to spend.

You will find that all machines have their pro's and con's, and that there is no such thing as the perfect machine. However, once you start defining your needs, then you can narrow down the choices.

[vfcnc]

hi Tai42.. thanks for your response.
i'll start by explaining the purpose of the machine. i design & mill my own racing components like camshafts, gears etc. i've attached a few pictures to show what sort of stuff i mean.

the key in racing is light weight.. where ever i can reduce the weight i have to and by 100% accuracy i meant more accurate than me. i waste too much material and even slight damage or fracture is not tolerable. i've been told and i've seen many pro shop using cncs now so i'm guessing its the way forward.

i would prefer an "off the shelf" system as it won't take time away from my racing work (with a full time job i only get limited time to do that!!

i don't intend to produce many numbers of the same parts.. just lots of different parts (maybe in quantities of 2-3) to work as spares.

budget would have to be limited i'd say not more than $15k.. the cheaper the better.

thanks for your time!!

[philbur]

I'd be very surprise if your are making those components with just a manual mill.

If you are then there's not much the people on here can teach you, rather you can teach us.

Regards
Phil

Originally Posted by vfcnc hi Tai42.. thanks for your response. i'll start by explaining the purpose of the machine. i design & mill my own racing components like camshafts, gears etc. i've attached a few pictures to show what sort of stuff i mean. the key in racing is light weight.. where ever i can reduce the weight i have to and by 100% accuracy i meant more accurate than me. i waste too much material and even slight damage or fracture is not tolerable. i've been told and i've seen many pro shop using cncs now so i'm guessing its the way forward. i would prefer an "off the shelf" system as it won't take time away from my racing work (with a full time job i only get limited time to do that!! i don't intend to produce many numbers of the same parts.. just lots of different parts (maybe in quantities of 2-3) to work as spares. budget would have to be limited i'd say not more than $15k.. the cheaper the better. thanks for your time!!

[sdopp]

I agree with philbur, If your doing those parts on a manual machine, do a cnc retrofit and keep on truckin.

[vfcnc]

Originally Posted by philbur I'd be very surprise if your are making those components with just a manual mill. If you are then there's not much the people on here can teach you, rather you can teach us.

hi Phil.. i cannot make the cams on my mill.. once i've made the design or modified an existing one i get a pro shop to do it for me. As it is only a 1 time thing the costs are really high. The bikes are all from the late fifties so the engines are not as complex as modern bike.

on the other hand the yokes i can make easily.. as well as rear sets etc. These are all non engine components and perhaps require less accuracy. i will try to post pictures soon. (the earlier pictures are from the net, i wanted to post them to show what i meant to do)

so any suggestions?

[vfcnc]

Originally Posted by sdopp I agree with philbur, If your doing those parts on a manual machine, do a cnc retrofit and keep on truckin.

Ok this sounds interesting.. probably i can keep my existing setup and costs low?? right?

[philbur]

Yes but that will not meet your requirement for an "off the self" system. You could also consider selling your current manual and buying a ready to run CNC.

You should look at:
IH
Tormach
SmithyCNC

What's your current manual mill.

Also I am interested to know how you do the radiused edges around those profiles on a manual machine. Particularly on the none symetrical hole in the top yoke.

Regards
Phil

Originally Posted by vfcnc Ok this sounds interesting.. probably i can keep my existing setup and costs low?? right?

[vfcnc]

Originally Posted by philbur You should look at: IH Tormach SmithyCNC

thanks for this.. i'll check them out.

Originally Posted by philbur Also I am interested to know how you do the radiused edges around those profiles on a manual machine. Particularly on the none symetrical hole in the top yoke.

i'll try to do one better and take pictures of the entire process when i get working this weekend.

[tai42]

Originally Posted by vfcnc Ok this sounds interesting.. probably i can keep my existing setup and costs low?? right?

The answer is a definite maybe. (And it all depends on how you look at it.) Again you are faced with a myriad of options. One thing to consider is that if you live in the UK, and already have a mill, then you will save on shipping! (I don't know about the UK, but in the US the import tax on a CNC mill is MUCH higher than a manual mill.)

Depending on the type of mill you have (RF45 & clones, or a Bridgeport & clones, etc.) there are many places offering retrofit kits. (With varying degrees of complexity on installing them.) So if you tell us what kind of mill you currently have, then someone could probably recommend a compatible kit.

If you were buying a mill and retrofit kit, then you might save a little money over an off-the-shelf system. Most people then say when you factor your time to install it, the savings are a wash (or you actually "spend" more!) However, I like retrofits as they give you valuable "hands-on" experience with the system you will be using. Consider the cost of taking a class that would teach you the same thing you learn from installing the kit and I think you still come out ahead. Of course, you already have the mill, so the "additional" cost is going to be lower regardless.

The one caveat I have is that you should go into a retrofit with the idea that it is a learning experience, and NOT with the idea that it will save you money. I get worried when people take on these things thinking they will save money and wind up skimping, cutting corners, and in the end just get frustrated. (Talk to someone who has built an airplane from a kit to "save money," if you can find one who actually finished it. ) Also, it's a good idea to ask to see the installation manual before you order something so you are prepared.

The other consideration you should make is that when a mill is converted to CNC, it becomes a little less convenient to use for "quick" jobs as a manual mill. If your retrofit kit keeps the acme screws on the mill, then you have a chance to keep the handles for use as a manual mill. (This is NOT recommended. I would stay away from any kit that does not put on ball screws!) However, once you put ball screws on then you need the motors to prevent things from moving as much as to move them. With that in mind, you may decide that it's worth keeping the mill you have as a manual mill and buying a separate CNC mill.

As for the "off-the-shelf" mills, I concur with Philbur's list as an excellent place to start.

-Bob

[vfcnc]

Thanks Tai42 & Philbur.. your advice is greatly appreciated!!!
i'm reading up on the websites of the names mentioned to see which will be most suitable for me.