To CNC or not to CNC – that is the question.

[Christopher KnightParticipant @christopherknight]

[Christopher KnightParticipant @christopherknight]

I have been an enthusiastic amateur cabinet maker for many years but an increasing sensitivity to allergens in wood is forcing me to do less. I am planning on switching my hobby to model engineering and wish to buy a milling machine. A question that is exercising me now is whether I should jump in at the deep end so to speak and go for a CNC machine.

I have had a Myford Super 7 (with a vertical slide) for a long time and have used it in support of my woodworking to make various metal fittings and the like so I can claim a small amount of machining experience albeit not to very fine tolerances. Whether this translates to useful experience in running a milling machine I don’t really know. I do know that I don’t wish to spend too many years becoming an accomplished manual machinist per se, I should like to see some end results before I get too old to do anything!

Practically every model engineering forum I have looked at has a section devoted to folk talking about CNC – usually converting various popular manual machines. This has caused me to worry that should I buy a manual machine, it wouldn’t be very long before I too wanted to convert it etc. and if this were the case, I would much rather simply get a CNC machine straight away. One machine I am looking at does have the possibility still to use manual control even when CNC equipped which I guess is the best of both worlds but it is an expensive machine and I am not sure whether such a facility would be really useful. (My Volvo car can be driven as a full automatic or with sequential gears but I always use it in auto..)

I’d appreciate any thoughts.

Chris

[mickParticipant @mick65121]

It’s proberly better to start off with a manual machine to establish a skill base, then if you still want to get envolved with CNC, then get a dedicated machine, so you’ll have a fully manual mill for the all the usual milling, plus a CNC for complicated profiles etc. In my experience a combo machine suffers if the the speed ranges have to be manualy altered at every tool change. Most modern cutting tools ( 2mm to 12mm diameter) will operate at speeds between 4500 and 7000 RPM no manual combo machine will give you this range of speeds.

I’ve got a mill/drill which cost under £500.0 that was five years ago, and its still doing every thing I ask of it. My CNC is a KX1 form Arc euro trade and is a great little machine, which is in virtually every day use. CNC even with conversational programing does take a while to come to grips with and enjoy the full potentional, a working knowledge of G codes and programme construction is usefull, especially when it comes to editing a wizard generated programe.

[TerrydParticipant @terryd72465]

Hi Chris,

 

I would agree with Mick. You can pick up small milling machines on the second hand market at reasonable prices or even an inexpensive Chinese model to begin with. You can cut your teeth on that, making mistakes won’t be too heartbreaking and really learn the ropes. If you decide to upgrade or even go to cnc in future you can always sell the machine as long as it is not in too bad a condition, there is a ready market out there,

 

In my opinion it can be a mistake to invest large sums in very expensive machinery when you are beginning. It is easy to make mistakes especially if you are learning from books rather than demonstrations. After all you wouldn’t expect a learner driver to drive a Ferrari. Many wonderful models have been made in the past on an old Myford with a vertical slide. My late, now sadly departed good friend Eric Whittle built a well known small Vee 8 aero engine on such a set up.

 

On CNC Stan Bray (first editor of MEW) had the following to say in his very first editorial in MEW 1:

 

“One of the biggest areas of change in engineering in general is the increasingly large part played by electronics with even the smallest of engineering works now having electronically controlled equipment. This does not mean that, even if they could afford it, all model makers will want to connect their machine to a drawing, put in a lump of metal and wait for the finished article to appear at the end. – there would not be a great deal of fun in that, the best part no doubt, being the book we were reading whilst waiting for it to happen.”

 

Of course I don’t agree with Stan now and there is a place for CNC in the modellers workshop, but as a woodworker you would know the importance of getting to know your materials, how they respond, how they cut, how to deal with interlocking grain etc. It is just the same with metals. A manual machine teaches you how to handle the materials you are using, the limitations and possibilities. I have used control systems since the days of my apprenticeship nearly 50 years ago. In the 1980s I was teaching CNC G codes in secondary school in teh 90s I had lathes, milling machine and injection moulder in my school workshop using CADCAM. I have a small cnc mill even now, but I much prefer the manual feel of manipulating materials. As I have said before, I enjoy the journey as well as the arrival.

 

Again if you are doing it on a commercial basis it is a different matter and other parameters come into play. Whatever you decide, I hope that you enjoy the hobby.

 

Best regards

 

Terry

[Christopher KnightParticipant @christopherknight]

Thank you very much Mick and Terry, for your thoughtful and very helpful replies.

 

To a large extent, you have confirmed what I was holding as reservations in my mind, especially getting to know the characteristics of machining different materials etc. Reflecting on my own journey as a woodworker and now that I am teaching my grandsons, I rely on a wealth of practical know-how regarding the behaviour and capabilities of hand tools and the different species of wood I use.

 

I think I shall be following your advice.

Chris

[Steve WithnellParticipant @stevewithnell34426]

One thing you might want to consider is what you take pleasure in, since it’s a hobby and why you do it.

 

I once carved a canoe paddle from a lamination of seven pieces of material, three different woods, using a spoke shave. I took great pleasure in manually shaping the paddle and a delight in the finished result. I could have used a CNC machine, it would have produce the same paddle, more accurately and in a very short space of time. I would have been delighted with the outcome. I would have lost the pleasure in the making though.

 

The other aspect to CNC is that you can produce components not possible with a manual mill.

 

Steve

[John Stevenson 1Participant @johnstevenson1]

OK I’m going to play devils advocate here and ask a simple question:-

 

If you need to learn to manual machine BEFORE you go on to CNC then how do they train modern CNC operators who have never seen a manual machine and their employers don’t have manual machines either ?

 

I know from experience they don’t just let a new guy loose on a 1/4 million pound machine.

 

As an aside when was the last time you saw an advert for a centre lathe turner in the local paper ?

 

I’d appreciate a quick answer as tomorrow I have to deliver a brand new CNC to a medical R&D lab in Harpendon and train three guys, this is assuming I get get thru passport control at Watford Gap.

 

John S.

Edited By John Stevenson on 11/01/2012 21:39:24

[Billy MillsParticipant @billymills]

I would go with the given advice, start milling – there is quite a bit to learn- and then decide what you want to make in the future. Many people on this forum are set against CNC for various reasons however it is the right tool for many jobs. CNC milling allows you to make complex curved shapes which would be impossible by hand and produces the same item every time.

 

There is quite a bit to learn with any CNC software package, some of which needs milling experience so I would suggest milling first then you are in a much better position to decide what you want in a CNC machine if you feel the need. CNC milling of wood and plastics can be very good too – you are not limited to metal. It can also be very creative at a level objectors don’t always understand.

 

One detail already mentioned is that mills sell for not much less than the buying price so even if milling looses it’s appeal little is lost on the price of the mill. You will find that cutters, vices, clamps and the other vital bits do add up however you can then make some fantastic things. Years of fun!

 

Billy.

[Tony MartyrParticipant @tonymartyr14488]

To answer John’s point.

You don’t need to learn to manually machine before learning to operate a CNC machine. But a CNC machine is about producing an end result repeatedly with the minimum human involvement in the cutting process. Model engineering, as I enjoy it, is about the process and the tactile involvement in shaping something.

Programming a CNC machine is about as interesting to me a filling in a tax return while working out how to mill exhaust ports is a happy way of getting to sleep and planning the next morning. If your interest is the end, go CNC, if your interest is the journey, craft things manually.

[Anonymous]

Well of course, as I’m sure John S is well aware, there’s a world of difference between a CNC operator, and a CNC programmer.

To respond to the OP, I mainly agree with the advice to get a manual machine first, if only because it’ll be cheaper, and you’ll break fewer tools during the learning process. A CNC mill is very unforgiving of mistakes. It is possible, however, to start off with CNC. I wonder if forum member ‘EtheAv8r’ will comment on this thread, as I believe he started off from day one with a CNC mill. It would be interesting to hear of his experiences.

 

It’s a funny thing, but there isn’t much difference in the process of making a part on a manual mill or a CNC mill. In both cases you need to decide the sequence of operations, how to hold the part, what jigs may be needed, what tools to use, and in what order, feeds and speeds, conventional or climb milling, roughing and finishing strategies. It’s just that for CNC some of it is done in front of the computer rather than the machine.

 

On the other hand, I do make extensive use of the power feeds on my manual mill so I don’t get much ‘tactile involvement’ with that either.

 

Regards,

 

Andrew

[blowlampParticipant @blowlamp]

Ultimately, you can make things with CNC that would be almost impossible to do with typical home workshop machines, so if awkward shapes are your thing then CNC could be considered a must. Conversely, simple but boringly repetetive stuff can be left to the machine (say a division plate), while you get on with something else.

 

Would you relish the thought of making a few of the parts in the above picture by hand methods?

 

I’ve got manual and CNC equipment and enjoy both disciplines, but for me, the appeal of CNC is because it’s a different way of working.

 

I like drawing the part that I want to make in CAD and then working out the machining strategy in CAM. It’s far more challenging (in an interesting way) than some would have you believe.

It is not just a case of loading a drawing into the machine and letting it get on with it – I would find that very dull compared to machining by hand.

 

Although it may seem that I’m trying to push you towards CNC to the exclusion of manual kit, I’m not. A lot of the time it’s quicker to mount the stock, skim the face and drill a few holes by hand than it would be to just draw it up.

 

I think I’m saying you might find a use for both!

 

 

Martin.

 

 

Edited By blowlamp on 12/01/2012 00:23:11

Edited By blowlamp on 12/01/2012 00:33:06

[Anonymous]

Ah, a Blue Peter moment; here’s one I made earlier! Well a couple of months ago, for a member on another forum.

 

Made in 1/2″ thick gauge plate. The holes were drilled and reamed on a manual mill and then used for jigging and referencing on a CNC mill for cutting the slot and outside profiling. The die block was programmed to be 0.02mm oversize and was then hand fitted to the slot.

 

Regards,

 

Andrew

[SpringbokParticipant @springbok]

Ah I dream on I wish I could afford a CNC machine and make what andrew has just done I have to purchase at a high cost these items.

Go for whatever you think will give you the most pleasure and enjoyment,, grandchildren will want to join in as they are now mostly computer orientated as for cutters etc; they are so cheap now if you do make a few bobo’s along the way so what. When I retired I took up a part time techy job in a local colledge to keep me out of mischieve that has CNC machinery and I was amazed how quick the kids learned G code and were making all sorts of things one made the shell of a jaguar e type..

A quick word on milling machines and from bitter experiance NEVER purchase one that has a round pillar it will whip no matter how you tighten it on anything other than small components. and this includes all of the chingaleese machines no matter what flavour.

Good luck and lots of enjoyment in whatever path you decide to take,

 

Bob

Edited By Springbok on 12/01/2012 05:22:47

[TerrydParticipant @terryd72465]

Posted by John Stevenson on 11/01/2012 21:38:10:

OK I’m going to play devils advocate here and ask a simple question:-

 

If you need to learn to manual machine BEFORE you go on to CNC then how do they train modern CNC operators who have never seen a manual machine and their employers don’t have manual machines either ?…………………………..

 

John S.

Edited By John Stevenson on 11/01/2012 21:39:24

Hi John,

 

I think that you have answered your own question here by using the word ‘train‘. I would assume that ‘they’ don’t just let a guy loose on a machine without training by a skilled and well experienced operator or trainer. and where did their employers get their knowledge? Off the back of a fag packet? I would prefer to think it to be the result of knowledgeable, skilled and experienced people working with an accumulated knowledge from previous generations.

 

Of course the operators you are discussing are just that I presume – operators. Surely there is a difference between an operator and a craftsman such as yourself who can design, program and operate the machine knowing it’s capabilities, understand ‘sequence of operations’ and the characteristics of various materials. Exactly what decisions do these ‘operators’ have to make in the performance of their duties? Not as many as a model engineer in his own workshop carrying out tasks from drawing to finished item on their own I would hazard to guess.

 

How did you learn? An apprenticeship? Did you just one day decide to do milling work and muddle your way through until you were skilled? Were you trained or or did you teach yourself milling? Did you learn manual before CNC? Only you know the answers to those questions.

 

Chris is not in the fortunate position of being trained in such a way. Of course if you could pop round to his place and give him a few sessions in you spare time he could learn to be an ‘operator’ under your skilled and knowledgeable tutelage. That would be a very different situation than being a complete beginner working in the relative dark and finding your own way.

 

All the best regards

 

Terry

[TerrydParticipant @terryd72465]

Posted by Andrew Johnston on 12/01/2012 01:57:34:

Ah, a Blue Peter moment; here’s one I made earlier! Well a couple of months ago, for a member on another forum.

 

Made in 1/2″ thick gauge plate. The holes were drilled and reamed on a manual mill and then used for jigging and referencing on a CNC mill for cutting the slot and outside profiling. The die block was programmed to be 0.02mm oversize and was then hand fitted to the slot.

 

Regards,

 

Andrew

 

Hi Andrew,

Just in contrast I have another ‘I made earlier’ – a couple of parts from a ‘Eureka’ device I made from ME articles a few years ago. Sorry about the finish being a bit rough but I am refurbishing the device as it was one of the very few things I managed to salvage last year, Originally they had a really nice finish.

 

All done by hand from 1/4 and 5/16 Gauge plate. Marked out, hacksawn and filed to dot marks (Dots cut in half just visible). Slots – chain drilled and filed (no milling machine then). Bored on faceplate 0.015mm oversize to give good running fit on shaft. Each one took about 1 hour not including setting up for boring.

 

However I could have made them on a cnc machine in the school workshop but I enjoyed the sheer pleasure of cutting the metal and them turning out really quite accurate, well within limits for it’s purpose.

 

Best regards

 

Terry

Edited By Terryd on 12/01/2012 06:35:21

[Christopher KnightParticipant @christopherknight]

OK- it’s all clear now, I need both a manual and a CNC machine, to
be 20 years younger with time for proper training and of course a
bigger workshop with space for the machinery.

Seriously, there is a lot of interesting and thought provoking stuff in these replies and I am very grateful for your advice. One thing is clear, looking at Terry’s hand made parts and that is that excellent work can be done purely by hand. In that regard, I hope that the hand tool skills developed for my cabinet making will translate in part to metal.

 

Chris

[TerrydParticipant @terryd72465]

Hi Chris,

 

I started on hand made stuff and developed good hand/eye coordination in woodworking classes at my Grammar school. I transferred to engineering when I took up an apprenticeship and the skills learned earlier were a massive help. The fine hand coordination and knowledge of materials needed to cut a good mitre joint is every bit as demanding as that for a part in metal and the accuracies involved are not that different really, and one has to design in allowances for movement of the materials.

 

You already know the importance of the ‘sequence of operations’, a tenon is always cut to fit the mortice, the interior sides of a box are given a finish before assembly etc. It is the same in metalwork, just different sequences. Those will be learned by working manually initially.

 

I am not saying no to CNC just that I believe that for a Master Craftsman (not me by any means) rather than ‘operator’ a good basic knowledge of processes and materials is essential.

 

I could go on about the lack of such skill learning in modern education but that is a sore point for this ‘grumpy old man’. By the way, I have been occasionally dubbed a Luddite. However a Luddite is one who futilely resists change. I welcome progress and change but only when necessary and when I see a need. By all means go for, and enjoy CNC but learn the essentials first.

 

Best regards

 

Terry

[David HaynesParticipant @davidhaynes53962]

After several years with a lathe and vertical slide, the need for a mill became evident and when looking at the choice between manual or CNC, I was tempted by the latter, but felt being familiar with first principles was, for me, the better initial step. The mill is now ordered and the delivery countdown clock is ticking. Looking this morning, only 109 days to go!

 

Dave

[TerrydParticipant @terryd72465]

Posted by John Stevenson on 11/01/2012 21:38:10:

OK I’m going to play devils advocate here and ask a simple question:-

………………As an aside when was the last time you saw an advert for a centre lathe turner in the local paper ?…………………………..

 

John S.

Edited By John Stevenson on 11/01/2012 21:39:24

Sorry John,

 

I missed that bit of the question which is a good one, and I quite agree that a person who wishes to work in manufacturing needs CNC skills. However it is irrelevant here. We are not addressing a guy who wants a career but one who is looking to change his hobby. Note the word ‘amateur’ in his post. This forum is essentially a forum for model engineers and they are generally home hobbyists, not production workers. We do like to discuss general engineering issues (out of interest or nostalgia ) But the main focus here is the amateur.

 

As an addition to your remarks about training, I see that you have a whole part of a day to train your three guys to use CNC after delivery and commissioning. Hmmm. I taught young children how to operate a cnc mill (they were very excited by the process) to make parts in a couple of hours, but very much longer to teach them how to use parametric CAD , then design the part and create the software solution for the machine to follow (as an amateur would). How you do that in one day I don’t know, I can only stand in admiration.

 

Very recently I was chatting to friend (I do have them) who is a cnc lathe ‘operator’ He’s not the brightest bulb in the candelabra and while discussing the process it was obvious he knew how to open the cabinet at the right time and how to change the blank, he also knew when to call the setter to replace the tool if he thought it blunt. But that was about it.

 

Best regards (again)

 

Terry

[TerrydParticipant @terryd72465]

Hi Again Chris,

 

As a light relief, for interest here’s a video of My friend Eric’s Vee 8 which I mentioned. There was a recent series of article in ME supposedly ‘updating’ the design.

 

However as Eric’s aim was to prove that such a small vee 8 could be built I think that he would dispute the ‘updating’ claim and were he alive and knowing he was even grumpier than me I think a few choice 4 letter words would have been flowing about the claim, but unfortunately he’s no longer with us.

 

Best regards

Terry

Edited By Terryd on 12/01/2012 09:34:57

[blowlampParticipant @blowlamp]

Chris.

 

Those are good examples of pieces that can be nicely hand machined, given by Andrew and Terry.

 

There is a difference though when compared to my example and that is the number of straight edges in each one.

 

Andrew’s looks to have five and Terry’s has six.

They would both be good jobs to do on a rotary table and fettle with a file.

 

The part I’ve shown has only one straight edge, the rest being blended curves and that makes it much harder to make by manual methods. It can obviously be done, but I thought was a fair example of using CNC to relieve you of some of the drudgery.

 

 

Martin.

[David Clark 13Participant @davidclark13]

Hi There

Posted by John Stevenson

If you need to learn to manual machine BEFORE you go on to CNC then how do they train modern CNC operators who have never seen a manual machine and their employers don’t have manual machines either ?

 

Hi John, you know as well as I do that they don’t train them on manual machines.

They don’t usually train them on CNC machines either.

They know how to operate and program the mill but have no idea how to mill.

 

I learnt CNC milling from the manual but it was Heidenhein rather than G code.

I broke one small drill in the first six weeks. I realised how I did this and did not do it again.

The particular company only had two CNC mills, no manual mills. They said the setter of the other CNC mill would teach me to program.

I started on the Monday, just operating.

Tuesday the chap who was going to train me was off ill with shingles.

6 weeks later he came book and was upset that I had taught myself from the book of words.

I never got on with him, he would never let me near the computer to write the more complex programs so I wrote them myself using Q parameters. This is a bit like algebra and formula. I wrote a program to mill hexagons, all you had to enter was the diameter of the cutter and the AF of the hexagon and it calculated the whole hexagon out.

Thi9s saved hours of programming once done.

 

I learnt G code from reading other peoples programs and made a cheat sheet with all the relevant codes on it.

Then I could just plug them into place in the program.

It is far easier to modify an existing Gcode program than to write one from scratch.

 

I had however, done five years horizontal and vertical milling before I went on to CNC and also programmed computers in the Basic language.

regards David

 

 

 

 

 

[David Clark 13Participant @davidclark13]

Hi Terry

I never thought Eric was grumpy.

He was fine with me, maybe it was just you he was grumpy with?

regards David

 

 

[Brian PriceParticipant @brianprice19431]

.

Hi Chris

 

I would go the manual route and then CNC. It is not that difficult to convert but bear in mind some of the techniques used on a CNC are bit different than the way you would manual machine something.

 

I converted an old Taylor Hobson machine to CNC and really enjoyed doing it.

http://www.youtube.com/watch?v=qpSji_Dqftw&context=C39ad477ADOEgsToPDskJaAcPw7a_SFVDGqr-1GWr6

 

I hope this helps

 

Brian

http://www.eBolt.co.uk

[Another JohnSParticipant @anotherjohns]

I now have both; both have their places.

 

Fortunately, I added a “game controller” to my CNC mill, meaning that I can easily “manually” mill with it.

 

I think, though that my older, larger, manual mill is of more use for building model locomotives. I like the feel/feedback of machining; much like driving full-sized locomotives, your feel and hearing is tres important.

 

 

Another JohnS.

[Author]

Posts