I'm just an operator

[AnthonyDuarte]

Hi Everyone,

Before I begin, never in a million years would I sit here and suggest that CNC is better than manual machining, nor visa versa. I simply don't believe that to be true. I have a manual mill and a manual lathe, and I have no intention of getting rid of either one. They are invaluable tools and are used almost daily.

I already regret writing this post since I'm tired of seeing this topic, but I'm hoping I can clear up some misconceptions about CAM/CNC.
As someone who designs his own products, figures out how to manufacture them, and then makes them in production for our hobby using CNC, it's tiring seeing the attitude come up over and over that if you run CNC equipment, there's no way you posses the skill necessary to be a machinist.

I think we can all agree that pushing a button does not make you a machinist, in the same way that simply turning a dial does not make you a machinist.

CNC can absolutely be set up for people to operate that have no idea what they're doing, but other factors go into judging the skill of a machinist: ability to interpret a blueprint, think of the steps to make the part, build any necessary fixtures, and of course hold tolerance while maintaining the required surface finishes.

I have bad news. All these things apply just as equally to both manual and CNC machining.

Here's a comprehensive list of the things that programming software decides for the programmer:
1) Nothing

The programmer has to have an extensive knowledge of what tools are available, which ones are practical for the current job, and the best feeds/speeds to use for that particular tool given the material, machining strategies to be used, and of course limitations of the machine.
We still have to figure out order of operations, setups, fixtures, what methods of machining and work holding are going to provide the required finishes and tolerances, and all that fun 'operator' stuff.

Of course modern software offers suggestions for feeds and speeds, but they're never usable 'off the shelf'. Even the suggested feeds/speeds and chiploads from the tool manufacturers are only suggestions and often unpractical, especially when you start getting into tools smaller than 1/8".
There is a huge catalog of machining strategies, but you have to know which ones to pick for the job, and they're highly modifiable. If you know what you're doing, the biggest programming challenge is tricking the software into giving you the tool path you really want.
If working with material that's new to me, I like to take a cut out of it manually to get a feel for how the material likes to be machined. This informs my programming decisions. I don't have the luxury of picking a material to be greeted by a list of guaranteed machining strategies. No one does.

CNC is a tool just like any other piece of machining equipment and requires a machinist to properly utilize it. Whether it is practical for your average home shop hobbyist is an entirely separate issue.

Nothing will ever replace the art of manual machining, and I firmly believe it will always have a place in manufacturing.
But what do I know? I'm just an operator.

Raw material for link supports

Roughing operations on all 4 sides

More roughing operations

Bead blasted before cutting out (note thin holding tabs)

Finished part

[rwmorris]

Amen....

I find the Anti-CNC rhetoric nauseating.

1. Everything stated above is 100% true.

2. I have found my CNC machine full of more surprises and challenges then I care to discuss. It does an amazing job but only after I have put plenty of time into setting up the job and checking my work.

3. Sure, there’s some jobs that would be “just as easy” but who cares? I think it’s more important to keep making parts than spend countless hours poo pooing the advantages/disadvantages of the magic machine.

4. If you simply don’t know and like to argue about it then I guess that’s the way it will be. But, if you’re a true machinist and you still hammer on the idea of these machines, then shame on you. You all know darn well and good that it’s not just about pushing the cycle start button.

Popping some fresh corn for the entertainment surely to come from yet another discussion on the evil piece of technology.

-RM

[Pontiacguy1]

I think that a lot of people who are 'operators' actually call themselves machinists, and that may be where the disagreement is. For example, the person in the factory or job shop who puts a piece of material in a CNC mill, indicates it, bolts it down, Calls down the program, and then hits to go button may have the title of 'machinist' and may actually call himself or herself one if you ask them. But a lot of them could no more program the machine than I can, nor really tell you what the machine is trying to do and why. I've run across several people in that category before, and again a lot of them couldn't have made a slot in 1/4" thick piece of aluminum using a manual mill, nor on the CNC either. They were there to make sure the machine was constantly being fed.

I thought for most of us the objective here was to build working trains/models that we can enjoy and play with. Now the building may be more your thing than operating, but as long as you come out with a functional and safe model at the end, I really don't care if you went though the stone age or the space age to get there.

You must have used stress relieved material for it to come out like that. Very nice work. AND, you still have the program in case you ever want to make another one.

[thunderskunk]

I think that a lot of people who are 'operators' actually call themselves machinists, and that may be where the disagreement is. For example, the person in the factory or job shop who puts a piece of material in a CNC mill, indicates it, bolts it down, Calls down the program, and then hits to go button may have the title of 'machinist' and may actually call himself or herself one if you ask them. But a lot of them could no more program the machine than I can, nor really tell you what the machine is trying to do and why.

I’ll start with saying I agree to be real clear.

And yet, I still call our “operators” machinists. Yea, there is a difference between the guy that pushes the button, the guy that comes up with the feeds and speeds, and the toolmaker. Yet I used to work for a guy; he started out as a machinist for Pratt and Whitney. He put a part in a Bridgeport, cranked the handle until it reached the other side, took the part out of the Bridgeport and handed it to the next guy. A scrap rate of 30% was a good day, but that’s besides the point.

He performs a more monotonous and brainless task than an operator, more on par with a servo, but I still put him in the machinist bucket. I’ve been a horizontal engineer with the national guard, and the person we called an operator is a highly qualified, practiced tradesman who can do things very few others can with his equipment, be it a grader, dozer, or the like. I’m not trying to make up a name for the people who don’t have his skill set but still push dirt, and neither does anyone else I know.

The job description says ‘machinist’ and if you don’t learn something other than how to push the green button over 20 years, well, equal opportunity laws have got you covered.

[wbarbe]

As neither and operator or a machinist I am constantly amazed at the works of art produced by both manual and CNC machines. I believe there is a great deal of skill in both and most of it overlaps. I don’t think you can successfully produce parts with CNC unless you know how they would be made the old fashioned way.
I wish more shops offered CNC locomotive parts as they could reduce the price through mass production if you will. Many of us want to own and operate a steam locomotive but may not have the skill to make the parts themselves. I have posted about a company in England that sells a fully machined 0-4-0 and 0-6-0 that is mostly CNC. They sell for a reasonable price because they can produce batches of parts. Without CNC you couldn’t do that. Both have a place and both are necessary and we should recognize the skill in both. My 2 cents

[Harold_V]

You must have used stress relieved material for it to come out like that. Very nice work. AND, you still have the program in case you ever want to make another one.

Speaking from the position of one who worked as a commercial machinist/toolmaker for 26 years, no, using stress relieved material isn't a requirement, although it's not a bad idea.

When one is ****truly**** a machinist, one of the things that is understood is that materials are not static. Each and every one of them contain stresses---stresses that cause movement when any changes to the material occur. How much stress contained is the question.

Machined surfaces move, often in ways that may not make sense. Those with experience learn to deal with that problem, and the method by which it is dealt is called ***roughing***. Parts are machined oversized, which allows the material to relax the internal stresses. How much material must be left for finish is something that must be determined, as finish cuts, too, will relax stress, so enough material must be removed in roughing so that the finish cut won't make a significant change.

I have experienced one occasion where a roughing, semi-finishing and then a finishing operation were required in order for the resulting parts to remain stable.

My entire career was based on manual machining. Only in retirement have I acquired a CNC mill. It offers me the opportunity to do work that was previously beyond my ability (like engraving, as I never owned a pantograph). Having manual skills has been a considerable asset. Learning to operate the CNC was aided by my manual skills.

If a CNC operator is not able to make setups, to decipher prints, to determine what causes issues and be able to correct the machine so they are avoided, he is NOT a machinist, but an operator---he pushes buttons and feeds parts.

If one can not be handed a print, material, and pointed to a machine on which a given part can be made, and do it without supervision, he/she is not a machinist. Dues are paid to become a machinist--it isn't a title that is handed to everyone. No different from a musician, just a lot easier to learn (I tried music---it appears to be beyond my skill level).

H

[AnthonyDuarte]

Harold,

Working with internal stress is definitely a huge part of it, and something that unfortunately doesn’t go away with CNC.

I did not use stress relieved material. Might have been nice, but I planned my operations to work with it. The first order of business was to rough out all sides, leaving at least .01” on all surfaces. This relieved most of the internal stress before running finishing passes. The link support sprang open a little bit after cutting it out, but not much.

Some of my worst experiences with material stress was cutting .009 x .024 inspection gauges .150” long out of Elgiloy with wire EDM that needed to be +0, -.0001” on height and width over the whole length.
My wire path looked nothing like a rectangle to work with the material wiggling around.

[NP317]

Anthony said:
"If you know what you're doing, the biggest programming challenge is tricking the software into giving you the tool path you really want."
That made me laugh OUT LOUD! 'Totally describes my experience with CNC machining.
How I would like to have a CNC mill in my home shop!

Gorgeous work on the link supports. Especially the small cutters required to make all those radii.
~RN

[JTolan]

One thing that I would like to add on to. Anthony youve done a beautiful job.

Cnc has the same if not a multitude more of challenges when it comes to work holding. For parts that ive had to make ive used everything from hot glue, gravity clamps custom made soft jaws for vices ad infinitum. The challenge exists there in so many ways. Cnc allows more complex operations so the fixturing and tooling that can be used on a cnc are designed for that higher level of complexity and often speed.

The beauty of machining, manual and cnc, is problem solving. Whether its work holding, chatter, software, feeds and speeds, figuring out why the coolant randomly shuts off when you least expect it.

A machinist in the broadest sense is someone who uses the tools availible and develops the techniques need to make a part.

I believe that learning to utilize everything like shapers, waterjets, 3d printers, boring mills, laser cutters, robotic arms, remote sensing equipment, hand drafting and CAD software will make all of us better machinists, engineers, and fundamentally problem solvers. Solving problems is my favorite thing to do and its why I love modeling so much. It made me learn the techniques I needed to jumpstart my career as an Engineer, and not the train kind.

[Greg_Lewis]

I use DOC machining. Dumb Operator Control. I can mangle metal and ruin tooling on any machine that ever existed. Monty Python could make a great documentary in my shop.

[jcbrock]

Anthony, I'm just glad to see it looks like you are making time to work on your 0-6-0. It should be spectacular when it is done.

[AnthonyDuarte]

Anthony, I'm just glad to see it looks like you are making time to work on your 0-6-0. It should be spectacular when it is done.

It’s actually something else. A bit of a teaser for a later announcement.