CNC Bragging rights

[kohned1]

Just want to put in a few words on one of my pet peeves.
Everywhere you go you see folks bragging that their parts are made by CNC.
I am a machinist by trade so I feel qualified to put out a little information on
this. CNC machines produce parts with very good finish because they can cut
at optimum speeds and feeds. To turn a part on a manual lathe at high RPM
with a feed rate that will produce a good finish will make your digital readout a
blur. You generally have to compromise to be able to cut up to a shoulder and
be able to stop the cut at the correct point. A CNC lathe can use the correct
speed and feed at all times. They don't use eyeballs to control the tool and
have really good reaction times.
A CNC mill can cut a straight slot for X distance then cut a radius followed by
an angle. Manually this would have to be done is several successive set ups.
In my job I make one off parts using a manual lathe and a low-end CNC mill.
The mill has no automatic tool changer so cannot be left unattended to cut a
complex part. If we need 10 pieces i crank 'em out. If we need 250 pieces we
job them out to a commercial shop with better equipment.
Bottom line- CNC parts generally have better surface finish. Dimensional
accuracy is mostly a function of the machinists skill in setting up and running
the job. CNC work is expensive on a onesie-twosie scale but for quantity
production it offers accurate high quality parts at the lowest cost. So ads
that brag about CNC parts are really saying " our parts are made efficiently at
the lowest possible cost". Actually it is an example of redundancy in print
because virtually all machine work is now CNC produced.

[Rad Racer]

I am not sure what point you are trying to make, but people DO use CNC's to produce their products....if they didn't this hobby would be cost prohibitive to all those but a select few.

Also, there are many items used in this hobby that can't be made by twisting the handles of a manual mill......take the 3-axis work required to produce a mold for example.

[birdofplay]

Unfortunately THEY are bragging CNC to UP the "Value To You"
and therefore substantiate their High Price - IMHO

However the other take is ...
If they were not using CNC then costs would even be Higher. right ?

I agree with the redundancy comment.
How else would you do anything these days besides CNC ?

In another discussion Brushless Vs Discbrake
I was making a similar commentary.

They ( whom ever that is - pick your favorite player )
are simply trying to justify high prices by either ...

Dazzling us with brilliance
or
Baffeling us with BS

your milage may vary - nuf said

[dogon1013]

......
How else would you do anything these days besides CNC ?
....


You could cast the parts, or even MIM them (Metal Injection Molding). But i don't think the quantities are up high enough (yet) to MIM them. I wouldn't be surprised if some "eastern" country's are casting them.

Another point to add to this thread is that even CNC machines can make (s)crap. The operator, programer, and part designer need to know what they are doing too. At least if it is done on a manual machine, you know the operator has some skills. Anyone can simply hit the go button on a CNC machine.

[ryanl2006]

I am not sure what anyone is trying to argue here. Are you saying that advertising "cnc milled parts" is a load of BS? Someone please explain...

A cnc mill is faster, more precise, and easier for the machinist once the program is written, why would anyone use anything else?

I think the point motor manufactures are trying to make is not that it was done on a CNC mill specifically, but more so that the parts are customed milled as opposed to pressed or stamped or however they make stock can cd-rom cans for example.

[sp1nm0nkey]

"A cnc mill is faster, more precise, and easier for the machinist once the program is written, why would anyone use anything else?"

Parts machined by hand I guess have more heart to them. There's so much work that goes into machining a part by hand, it's just a beautiful thing. I'm being tutored by a local machinist (who wouldn't be caught dead in front of a CNC machine), and the guy has been in the trade forever, and he's devoted so much time to helping me. It's so sad to see that go. Machining is a dying trade.

But the first post... urh... I don't quite get the point.

[Keith43221]

I dont get the point and I think you dont either. People are bragging, because it looks good. And because other people dont have it. And because it is quicker than hand cutting.

[ryanl2006]

"A cnc mill is faster, more precise, and easier for the machinist once the program is written, why would anyone use anything else?"

Parts machined by hand I guess have more heart to them. There's so much work that goes into machining a part by hand, it's just a beautiful thing. I'm being tutored by a local machinist (who wouldn't be caught dead in front of a CNC machine), and the guy has been in the trade forever, and he's devoted so much time to helping me. It's so sad to see that go. Machining is a dying trade.

But the first post... urh... I don't quite get the point.


Well yes there are many people that do hand work for the 'art' of it or because they do not want to learn cnc or whatever their reasoning is, but for large scale manufacturing it is simply not realistic.

[sp1nm0nkey]

Never said it was. Hand machining is much slower. The point is, the trade has been in my mentor's family forever, and mine as well to a certain extent. I'll never just give up hand machining, even if it is much slower and labor intensive than CNC. Never said the results were better, just that I'm sad to see it go.

You just can't beat watching chips fly on an old Hardinge lathe.

[westfw]

I think part of the point of claiming CNC is "repeatability"; the fact that
the next part made should be exactly like the last one made (and measured,
and reported on.) A hand-machined gadget is a work of art. A CNC machined
gadget is muc more potentially a volume-produced product... If I'm buying
something remotely, I don't think I want to rely on the seller having N generations
of accumulated experience...

[lensrc]

I see the use of the term "CNC machined" in product decriptions as a way to impart the products consistant quality. I agree, it is redundant to even mention it, but I dont believe doing so is being a bad thing.

Len

[ScubaSteve]

my own 2 sents...
a lot of the time esp with smaller shops the "CNC made" is kinda implied to separate them from the home-grown lathe-in-the-garage outfits. it's almost there to make the mfr feel better:)

truth be told, while i've seen gorgeous CNC parts at great prices, i've also seen work done by hand (DadHav on the GB forum for example) that is so intricate and amazing that it can ONLY be done by hand.

[DadHav]

Hi Steve, I just stumbled across this string. Thanks again for the compliment. I'm proud to be part of all this fun. I think after reading through the comments, that we're taking an opportunity to mention what we think about CNC machining. I'd like to add a few thoughts of my own. CNC is a wonderful technology. There is, unfortunately, some very negative sides to the story. First let me introduce myself so that you know where I'm coming from: I started a Tool & Die making apprenticeship one week after I graduated from High School in 1964. Prier to that though, I had been running my Grandfathers small shop equipment since I was 12 or 13 years old. Through the years I've taught several apprentices who all have become very successful. In later years I moved into engineering and worked in mold design, downstream automaton, CNC programing and machining. After that I decided I would have my own business. Well enough of that, but what I wanted to say was: A CNC lathe or mill has the capability of making hundreds or thousand of parts all nearly identical. That is of course if you can find an operator that knows enough about tooling techniques. This also means that poor quality and mistakes can also be duplicated over thousands of parts. The thing that makes me so sad isn't that though, and it's not the fact so much that the CNC cuts peoples jobs out. After all no young person wants to even get started into an apprenticeship anyway. Heaven forbid that they might get their hands dirty and even worse have to work his way into a good wage gradually. Does anyone even remember what a Master Tool and Die Maker is?
I'm very sad to say it, but I thing a great era of proud highly skilled craftsmen is all but come to an end. So at least try to find the few that are left, treat them with some respect, let them work, pay for their insurance even though it's expensive because they are old. Maybe they can still teach a few interested youngsters how to do more than push a button and hope the part passes inspection.
Oh: Long live the old South Bend Bench Lathe.
At least the few if them that are still left also. I still use the one I inherited from my Grandfather, along with a drill press and hand full of rifler files.
Kindest Regards.
John

[ecologito]

Hi Steve, I just stumbled across this string. Thanks again for the compliment. I'm proud to be part of all this fun. I think after reading through the comments, that we're taking an opportunity to mention what we think about CNC machining. I'd like to add a few thoughts of my own. CNC is a wonderful technology. There is, unfortunately, some very negative sides to the story. First let me introduce myself so that you know where I'm coming from: I started a Tool & Die making apprenticeship one week after I graduated from High School in 1964. Prier to that though, I had been running my Grandfathers small shop equipment since I was 12 or 13 years old. Through the years I've taught several apprentices who all have become very successful. In later years I moved into engineering and worked in mold design, downstream automaton, CNC programing and machining. After that I decided I would have my own business. Well enough of that, but what I wanted to say was: A CNC lathe or mill has the capability of making hundreds or thousand of parts all nearly identical. That is of course if you can find an operator that knows enough about tooling techniques. This also means that poor quality and mistakes can also be duplicated over thousands of parts. The thing that makes me so sad isn't that though, and it's not the fact so much that the CNC cuts peoples jobs out. After all no young person wants to even get started into an apprenticeship anyway. Heaven forbid that they might get their hands dirty and even worse have to work his way into a good wage gradually. Does anyone even remember what a Master Tool and Die Maker is?
I'm very sad to say it, but I thing a great era of proud highly skilled craftsmen is all but come to an end. So at least try to find the few that are left, treat them with some respect, let them work, pay for their insurance even though it's expensive because they are old. Maybe they can still teach a few interested youngsters how to do more than push a button and hope the part passes inspection.
Oh: Long live the old South Bend Bench Lathe.
At least the few if them that are still left also. I still use the one I inherited from my Grandfather, along with a drill press and hand full of rifler files.
Kindest Regards.
John


I like your comments a lot, it is true we can all buy CNC machined pieces for our motors but I am trying to learn how to use a lathe ( not very new one) and turn my own parts. It is not easy and sometimes frustrating when you mess up a 3 hr. session part and bend or break it, but is part of the learning curve. I am hoping I can buy my own lathe sometime soon and turn my own parts.

It is pretty to go and but a nice motor, but it feels great when you make it yourself.

[DadHav]

Yep, That's a cool old baby. I can hear her now. I bet she sings a real song when you crank it up to it's highest speeds for making small aluminum parts. I put a few links on the other string where people are showing their motors. One of them shows my machining steps using the old South Bend. Maybe you could get a few ideas from there.
And you're right. It's a lot more fun to make them yourself. Look at all the good friends you have here too.
Dad

[latrans]

Hi Steve, I just stumbled across this string. Thanks again for the compliment. I'm proud to be part of all this fun. I think after reading through the comments, that we're taking an opportunity to mention what we think about CNC machining. I'd like to add a few thoughts of my own. CNC is a wonderful technology. There is, unfortunately, some very negative sides to the story. First let me introduce myself so that you know where I'm coming from: I started a Tool & Die making apprenticeship one week after I graduated from High School in 1964. Prier to that though, I had been running my Grandfathers small shop equipment since I was 12 or 13 years old. Through the years I've taught several apprentices who all have become very successful. In later years I moved into engineering and worked in mold design, downstream automaton, CNC programing and machining. After that I decided I would have my own business. Well enough of that, but what I wanted to say was: A CNC lathe or mill has the capability of making hundreds or thousand of parts all nearly identical. That is of course if you can find an operator that knows enough about tooling techniques. This also means that poor quality and mistakes can also be duplicated over thousands of parts. The thing that makes me so sad isn't that though, and it's not the fact so much that the CNC cuts peoples jobs out. After all no young person wants to even get started into an apprenticeship anyway. Heaven forbid that they might get their hands dirty and even worse have to work his way into a good wage gradually. Does anyone even remember what a Master Tool and Die Maker is?
I'm very sad to say it, but I thing a great era of proud highly skilled craftsmen is all but come to an end. So at least try to find the few that are left, treat them with some respect, let them work, pay for their insurance even though it's expensive because they are old. Maybe they can still teach a few interested youngsters how to do more than push a button and hope the part passes inspection.
Oh: Long live the old South Bend Bench Lathe.
At least the few if them that are still left also. I still use the one I inherited from my Grandfather, along with a drill press and hand full of rifler files.
Kindest Regards.
John


Thanks for sharing your story, thoughts, and work with us John. I couldn't agree more.

Adam

[PerfectStranger]

When I was younger, my neighbor was a tool and die guy. I graduated ('89) and tried to get into a shop but it wasn't happening. They were good paying jobs and you pretty much had to be blood to get your foot in the door. Now I'm glad I didn't get in as I'd probably be in the unemployment line.

matt

[DadHav]

When I was younger, my neighbor was a tool and die guy. I graduated ('89) and tried to get into a shop but it wasn't happening. They were good paying jobs and you pretty much had to be blood to get your foot in the door. Now I'm glad I didn't get in as I'd probably be in the unemployment line.

Matt
You have that right Matt, I'm in Akron Ohio. Akron existed one time on the rubber industry and the plastic injection mold industry. Every thing is in China now. There are a few shops existing because they picked up the slack left behind from others closing. I almost went to the line myself because I refused to continue working for a large company that had shut down in the USA and now had me coordinating engineering in 9 other countries. Your right about another thing also. The trade never paid what it should have for the skill level.
Enough already. Lets be happy and build motors.
John.

[GavinBLDC]

I converted my micromill over xmas to cnc
This post just made it obvious to me that I may now be able to cnc my stators for some BLDC motors I am building for modeltrain motors. Unlike airplanes heavy is better. Got my magnets from George, who else:)

CNCing on a home mill is great for prototyping but for production the big machines are great. The stators was the tricky bit apart from the windings of course. Model trains don't need high speed or high power so I am trying 2 and 3 phase designs, have 12 designs in the works but until now had no idea to use the cnc mill for stators. I guess I have been having too much fun cncing to remember why I cnced in the 1st place.

My smallest rotor so far is 1/4"OD with 10 magnets, no idea yet how to make a stator for it but I suspect for the low freq and lower power a solid stator may work.

Anybody got an idea how to wind them for production, unlike you guys I am looking at hundreds of turns of 40-42 gauge wire. I keep snapping the wires winding on hand jigs.

Gavin