Manual to CNC Conversion Questions

[UBeGon]

First off I am new to the forum, so PLEASE be patient with me. I am also new to CNC, and pretty new to MILL/Lathe work as well.
I own an old Enco Knee Mill/Drill, and a HF 36" Lathe. I am in the process of teaching myself how to use them for now. I am currently building 2x3' CNC Plasma Cutting Table, and should be done sometime after the holidays.

Anyway, I haven't really done much on the Mill at all, and I am thinking that if it was setup for CNC work I might get a little more use out of it. My main reason for not using it much is the time it takes to manually work almost anything. I know that running it as CNC is still going to require programming, but most of what I would make on it I already have the CAD Drawings for anyway.

So anyway, here is my questions:
1st off where do I start? I know I will need the servos, drivers, controller, software etc, but where do I start on the machine? Do I simply buy servos/stepper motors for each axis, then rig up a mount to attach them to the jackscrew, the hook it up to the pc and off I go?

If anyone has a link, or a book, or just about anything that can walk a beginner through what is needed to convert from manual to CNC I would love the link.

Down the road I might even consider doing the same conversion to my Lathe, but for now I mainly use it for Barrel Profiling, and chambering, both of which are pretty manual tasks anyway.

[Rick]

Anyway, I haven't really done much on the Mill at all, and I am thinking that if it was setup for CNC work I might get a little more use out of it. My main reason for not using it much is the time it takes to manually work almost anything. I know that running it as CNC is still going to require programming, but most of what I would make on it I already have the CAD Drawings for anyway.

I believe you will find it VERY beneficial to learn how to run the mill manually. Not only will you gain the basic machining fundamentals needed to set up and run a CNC you will find that doing it manual can sometimes be much more efficient than CNC especially for one off parts. You will not be successful with CNC without the fundamentals of machining, remember it’s the same process its just a matter of who or what is turning the handles. There is a “feel” in machining that you need to acquire, all speed feed charts and other published info is just a starting point every operation is very much an unique thing due to the numerous variables involved in each process. CNC's are great BUT they are dumb things that do exeactly what you tell them, and if you tell them wrong then they have a nasty habit of breaking things before you realize what you have told them to do is wrong.

1st off where do I start? I know I will need the servos, drivers, controller, software etc, but where do I start on the machine? Do I simply buy servos/stepper motors for each axis, then rig up a mount to attach them to the jackscrew, the hook it up to the pc and off I go?

There are guys here that have done these type of conversions that can provide tons of info and they will pipe in, I am not one of those guys. But I can tell you there is a little more to it than hooking it up to your PC and off you go

I am not trying to scare you away from your conversion only to realize that cnc is not that save all do all thing. You need to know what is required for the machining process for a cnc to be successful. Learning on a manual machine is a great benifit and path to this knowledge.

[UBeGon]

I have done a couple of small AL projects on the Mill, and my biggest complaint is the amount of time I sit there turning knobs. Most of the projects I have done had to be spread over several days due to time constraints so not only did I just sit twisting knobs, but I had to take pretty detailed notes about where I was, and what I had completed so that when I got time to get back to the job I could figure out exactly where I was.

Would it be possible to have a conversion that allowed me to work with either manual or CNC? This seems like it would be the ideal setup for me, it would allow me to do manual stuff as time permits, and then CNC for tedious stuff...

My most recent project was an AR15 lower receiver that I wanted to mill from zero to finish. By the time I got just a single side profile completed I felt like I had been working on it for a lifetime. I eventually ended up giving up because I completely ran out of time. I had previously completed an 80% lower, and spent maybe 4 hours total finishing it, I kinda assumed that 80%-100%=4hrs, 0-100% would be far less than a lifetime )

[Dave_C]

Ubegone,

I am working on a Lathe conversion but I have learned how to manually operate my machine first. There is a good reaason to do so! If you do not understand how to do manual machining you will not have success at CNC machining as you must understand proper feeds and speeds, approach angles and how to hold material. You will learn all that with hands on use of a manual machine.

There is a false impression that CNC is the answer to poor machining skills. NOT true!

CNC is the answer to doing the same tasks many times as it can repeat tool paths over and over with great accuracy. I supose if you have a very good CAM program it will do some of the feeds and speeds for you but most of us do not have those in our home shops. My complaint with most CAM programs is the time it takes to learn them.

With manual machine you just stop turning the handles and feed will stop. On CNC machine if you program the macine wrong it will break something. Mistakes are costly when you boo boo on a CNC machine. Not so much on a manual machine.

Just my two cents worth having been there done it and have the T-Shirt.

Dave C.

[RET]

Hi,

You are embarking on a long, but very interesting road. As the others say, you need to learn how to use the equipment manually first and to get pretty good with it so you know what works & what doesn't. I guess the first thing you need is patience. Remember, it takes as long as it takes! I got my first lathe and a home made bench shaper in the 1960's and I've been using the equipment & upgrading it ever since.

Now, I have a 13" South Bend lathe (made in 1942) and a Bridgeport mill (made by Adcock & Shipley in 1955) with a Sony 3 axis readout. With this and all the measuring tools I have, I can produce some pretty accurate work; the readout in particular really adds to my capability. About 2001, I bought a little Sherline CNC mill as a "turnkey" package and about 3 years ago I built a bigger, better machine (ballscrews, Thomson shafts etc.) to replace it. This new machine works quite well (see the picture which includes the CNC headstock I also made). I still use the original Sherline computer and stepper motors with the new machine. For someone starting out, you could do worse than buying their turnkey package; the software in particular is very good. The software has X,Y,Z & a rotary axis and if necessary, all 4 axes can be run at the same time.

Even although I have both manual & CNC capability, I don't use the little mill very often because many jobs are better done manually, but there are also jobs where the little mill is far superior. Some things that are very difficult to do accurately on traditional machines are very easy in CNC. For instance, I made two coupling rods for an English locomotive model and that called for a 60" radius. With traditional methods, that is very difficult and time consuming to do accurately. The little CNC mill doesn't care, it just does it! Not only will it do things that are difficult, but it machines to tenths while it is doing it. I also made number plates for the locomotive (raised letters with a raised border around the plate) and that's something you can't do with traditional machining.

Finally, it takes a lot of time and money to convert a manual machine to CNC, so don't start with just any machine. While it would cost more, a Bridgeport would be good, just remember, any manual machine you start with will have to be retrofitted with ball screws (because you have to have zero backlash) which are a significant expense in themselves. I don't know from personal experience, but you should be able to pick up a reasonably good used CNC mill for the same cost or less than converting a manual machine, but you need to know a lot about machine tools before you could select a good one or the right one for you.

Perhaps this might help a bit.

Richard Trounce.

[Michael_Moore]

To elaborate on what Richard says, you are probably better off starting with a dead control "made for CNC" machine and retrofitting the control. You'll save a lot of time and quite possibly money and have a more suitable machine. It will come with ballscrews, motors, mounts, an oiling system that is regulated by the controller and it is likely to be much stiffer than a manual machine.

I think there's something to be said for having both manual and CNC mills. Too often I've found myself wanting to put in one relatively precise drilled hole but I don't want to go to the bother of booting up the CNC mill to do it. I got tired of wrestling stuff on the floor with a hand drill and finally got a drill press for that kind of task. If I'd had room I would have been very happy to have kept my manual Bridgeport clone mill when I replaced it with a CNC mill (Tree 325 and later a Tree (TOS) 425.

I suspect that for many of us learning on manual mills is only a moderate amount of help. I had a Bridgeport clone mill and while I'd switch in and out of back gear that was usually about the extent of changing spindle speeds. I'd take what it was set at and try to feed by hand at what felt/sounded OK.

With CNC you need to tell the machine what spindle speed and feed speed to use, what tool you have in, where the axis 0 point is, etc. There's no "oh, I'll crank a little slower now it sounds right" option that is going to save your cutter.

CNC is wonderful as it expands your project horizons a great deal. But it is overkill on some simple jobs. If you can only have one machine than by all means go with CNC, but keep in mind that some tasks will be more tedious than with a manual machine.

If you are going to be doing a lot of small cutter work then CNC is way cool. Try engraving with a 1/16" EM on a manual mill for 4-5 hours and see how things go.

If you get a CNC mill going I'll recommend that you get a subscription to Bob Warfield's GWizard for calculating speeds and feeds (and many other handy things). I don't do anything on my CNC mill without referring to the program (or notes I've copied down from an earlier use of it).

cheers,
Michael

[oldvan]

With CNC you need to tell the machine what spindle speed and feed speed to use, what tool you have in, where the axis 0 point is, etc. There's no "oh, I'll crank a little slower now it sounds right" option that is going to save your cutter.

I feel so silly having used this.

[Bruce_Mowbray]

I was going to say that most CNC machines have an overide for speeds and feeds. It's quite handy to relieve chatter or reduce the amount of pretty blue chips that are accumulating under the cutter. I will admit there are times when the handles are easier and more convienient, but with the CNC, I can mill any size hole I want. I can make cool curves. I can change tools quickly to facilitate drill, bore then ream operations. I can make 8 parts that look exactly the same. I can even make fixtures to hold odd shaped parts in regular soft vise or chuck jaws and without taking the fixture or jaws out, machine that odd shaped piece.

[Rick]

I will have to pipe back in on "learning manual" again. I personally feel there is so much intangible knowledge that you pick up when you are cranking the handles. Sounds, vibrations of the machine, feedback thru the handles what the chips look like (and feel like when a hot one hits you ) are all part of the learning experience and knowledge that is part of machining. I have both CNC and manual mills at home and at work. Each have their place and strong points but I do not believe that with the type of work I do that I could get by with just one or the other. Actually I did for years as I only had a manual mill, then CNC opened up 3d surfacing, ease of making multiples of the same part. With the CNC my rotary table hasn't been used in a while. CNC can and do make life easier in some cases, and they can be aggravating monsters when they do not function correctly. There are things I can't do on my Home CNC ( a Hurco KM3P) that i can do on my manual and the other way around also. I can relate this to drafting /cad systems. I started my career back before CAD, learned to draw on a board when it was as much of a art form as a technical process. I now work with a bunch of young designers that have only used a CAD system, they can draw great 3d models etc but have trouble detailing them correctly so that the shop can produce the part correctly. So we have a bunch of cad operators but limited draftsmanship (draftspersonship for the PC).

Now we have people running cnc's at work that can't run manual machines BUT they are operators, they set tools and origins but are not responsible for tool selection, cutter paths/ programs, feeds and speeds. Before they do those specific items they go and make parts on the manual mills and lathes.

So if you are really wanting a CNC, a converted machine that had both handles and CNC would be a good choice, just my opinion.
Rambled enough, just my 2 cents and opinions.

[Michael_Moore]

I've got a feedrate overide knob on my control too -- but it doesn't provide any "feel" feedback as you'll get when cranking a handle manually. I think that a manual machinist is likely to depend on that type of feedback just as much as the visible/audible feedback, so if you take it away the operator will be at a comparative disadvantage to their normal practice.

On the other hand, the "feel" isn't terribly useful (probably for most people) when trying to mill with a 1/16" EM. For things like that CNC is much superior -- as long as you've selected the correct feeds and speeds.

CNC allows one to automate crashes as well as make good parts.

Since I've only got space for one mill, I'm quite happy having it be CNC instead of manual.

cheers,
Michael

[JimGlass]

You need to get good at manual machining before you try CNC machining. CNC is nothing more than a means of machine control. Speed, speeds and setups are the same for both manual and CNC.

Personally, I feel CNC is a wonderful tool for the manual machinist. CNC makes machining arcs and angles a breeze.

If I could only have one milling machine, it would be a manual mill.

Retrofitting and an old CNC mill with a burned out control is positively the best way to go. You will save money and have a better machine in the end and save time.
Jim

[Mid Day Machining]

You need to get good at manual machining before you try CNC machining. CNC is nothing more than a means of machine control. Speed, speeds and setups are the same for both manual and CNC.

Personally, I feel CNC is a wonderful tool for the manual machinist. CNC makes machining arcs and angles a breeze.

If I could only have one milling machine, it would be a manual mill.

Retrofitting and an old CNC mill with a burned out control is positively the best way to go. You will save money and have a better machine in the end and save time.
Jim

A CNC takes a good machinist and makes them an excellent producer.

I have always said "TO BE GOOD ON A CNC MILL, YOU NEED TO HAVE 10 YEARS EXPERIENCE ON A MANUAL MACHINE".

There are a lot of machinists out there with 10 years experience, but there are even more who have ONE year experience TEN times. There is a huge difference there.