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CNC- the new religion?

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  • CNC- the new religion?

    I guess the old fogey in me is showing, but this CNC thing is getting to me.

    I am not going to argue the merits of CNC- they are fantastic machines and can do work in minutes that I can remember taking days to do. However, speaking from the standpoint of one who started this trade before CNC was widely available (and if it was, it was called NC with punched paper tape) there is an attitude about it these days that it is superior to all other types of machining.

    Yes, it can do things precise, and repeatable, but what if that is not necessary? What if your tolerance was such that you didn't require that kind of precision? I am thinking set ups with mill stops, that you could drill holes or make quick bores or tap holes. You can run a pile of parts with all the same hole size/ location, then change position, drill, tap, etc. and run them all back through. To me, your accuracy is there, and you save the time of programming. In addition, your CNC cycle time would probably be greater because it (assuming a machining center) has to stop for tool changes and so forth. Not talking willy nilly careless set ups here, just some old time common sense stuff.

    Have had a couple of situations recently where the attitude is that it can't be done right without CNC! My point is precise is precise, no matter how it is achieved, but that is getting hard to sell!

    Yep, I can run CNC mills and lathes (and even EDM machines). It just amazes me that people (customers) are getting to believe that it is the only way that work can be done right! Just had to bark a bit!

  • #2
    I know exactly what your saying toolmaker. I started on manual machines and never did get training for CNC. Several shops I worked in had them and I did all the manual machine work. I never have been interested in learning CNC or buying one.

    I have to admit that there are things they can do easier than a manual machine but they are not the end all to machining. There is plenty of things the manual machines outshine CNC at. Making a one off complicated part is one thing for sure.

    There are still thousands of screw machines pumping out parts as well. Turret lathes still do a good job. Anyone that thinks CNC is the only way to go has a closed mind and may have no exposure to manual machines so they have no concept of what a manual machine and a good machinist can do.
    It's only ink and paper

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    • #3
      HTML Code:
      Have had a couple of situations recently where the attitude is that it can't be done right without CNC! My point is precise is precise, no matter how it is achieved, but that is getting hard to sell!
      That, unfortunately, is so dern true. We won WW2 with manual machines. Today, I doub't it possible to get a gov't contract w/o CNC machines. Yes, they are great, and yes, they will do complex shapes, and yes, I even plan to but a VMC and ta urning center, but still, I have to agree with you. Seems CNC has become a religion. Seems most of the Chicom crap we get here is like +/- 1/8". The last two factories I worked in rarely required tighter than +/- .005". This was usually for interchangeability of replacement parts and/or automated assembly of mass produced consumer goods (door locks). I was just ran an automatic punch press.

      Of course, our tool and die men worked to very tight tolerances, and that was strictly on manual machines. I left 25 years ago and already there was a lack of qualified American T&D men as nearly all of our guys were from the UK or Europe.

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      • #4
        At my day job we have 4 cnc mills and 2 cnc lathes, we just got the 2nd
        lathe. Not sure what the new lathe will do but with the old Cincinnati
        most of the bearing tolerance stuff is still done on the manual lathes.

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        • #5
          I've seen that,I've also seen where people automatically assume CNC is cheaper for they're particular part.

          Lately I have seen a trend toward people who don't know how to make the part,don't know what to make it out of and don't know what tolerance they need.They also don't believe the machinist/engineer when they give them an answer????? They don't know,so they ask and then argue WTF?

          I was asked for a quote on a bunch of plate burnouts(I don't do them I farm them out normally)I got a quote from the plasma cutter,added my commission in on it and faxed them a quote mentioning the plasma cutter had a 3 day leadtime.
          I got a question back from them asking why I wasn't personally doing them(I have a fan base apparently)I told them the gospel truth,CNC plasma was cheaper and faster in this case and it would cost them more if I did them the old way.
          The next question I got was "well,can we deal with them direct?"

          My answer-"Yes,certainly,but since I am offering you the parts I would have charged $750 for ,in less time,in better quality for $560 I figure they're phone number and my contact is worth $200 at least"

          Lesson for the week,some customers are better off as Mushrooms,kept in the dark and fed s---.
          I just need one more tool,just one!

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          • #6
            WS, I have been reluctant to tell a customer I was farming them out for just the reason you mentioned.

            The one time I did tell my customer I told him to call them, gave him the number and name and he said he didn't want to fool with it, he had more important things to do and for me to be the middle man. I was kind of surprised because I really didn't want to be the middle man. I didn't make much on it because I did all the disign, drawings, part gathering and farming out the CNC work.

            On the other hand, he is a very good customer and I do all his machine work at the main shop so I couldn't refuse to help him on it. They have several branches around the East.
            It's only ink and paper

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            • #7
              I have two good friends that run pretty successful shops.

              They both have cnc's and manual machines. The manual machines are rarely used. Although one of them uses his manual lathe because he has no cnc lathe.

              Bottom line is that they use the cnc's so much that they can program for single piece jobs faster than they can do the job manually.

              The tools are setup in tool changers so there is little measuring of the part, edge finding etc.

              I still think that sometimes the manual machines would be a better choice for some of the jobs they do. They just don't use them.

              I am just breaking into cnc's for my home shop. There are some things such as profiling that the cnc's easily do that are almost impossible to do on a manual machine.

              I am told that the buggie makers said the same thing about those new things called automobiles. Don't see a lot of buggies out there except in Amish country.

              Come to think of it, the Amish seem to do pretty good without cars.

              Brian
              OPEN EYES, OPEN EARS, OPEN MIND

              THINK HARDER

              BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

              MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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              • #8
                Originally posted by Carld
                WS, I have been reluctant to tell a customer I was farming them out for just the reason you mentioned.

                The one time I did tell my customer I told him to call them, gave him the number and name and he said he didn't want to fool with it, he had more important things to do and for me to be the middle man. I was kind of surprised because I really didn't want to be the middle man. I didn't make much on it because I did all the disign, drawings, part gathering and farming out the CNC work.

                On the other hand, he is a very good customer and I do all his machine work at the main shop so I couldn't refuse to help him on it. They have several branches around the East.
                The smart customers I have figure the shops I am doing business with don't do walkin work and they are right.I find it's easier if I tell them what I'm farming out ahead of time rather than having a glitch with delivery and them finding out the hard way.

                The example I gave seems to be a growing trend in new customers.They have not a clue about anything,but they think they do.The ones that don't come back I'm better off without and the ones that are humble enough to admit they don't know and come back are keepers.
                I just need one more tool,just one!

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                • #9
                  The only commercial shop that I am familiar with is the one in town where I buy my supplies. I know the owners and the staff including tha machinists and fabricators. There are about a dozen main machines, mills and lathes of various sizes range from medium to big (40" swing). They are all manual and there isn't likely to be a CNC machine in there any time soon. It won't do they job that they need to do which is most one off repair parts that are needed now and not a month from now when it finally arrives from the manufacturer for the faller/buncher XYZ 3000.

                  I built my self a CNC mill for a several of reasons. I needed a milling machine. My hands are weak.

                  But the big reason is that I can and do use it to make things that cannot be made without CNC or would be very difficult to make any other way. I do a lot of fancy engraving and I make oddball parts like a ten inch sector gear with 20 teeth per inch. I use it to sharpen end mill flutes and to cut aspherical mirrors from solid aluminum. I have used it to generate metallic surface holograms, engrave photographs and even to play music.

                  It also does a good job of agitating the etch tank when making circuit boards.
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    Originally posted by Evan
                    I do a lot of fancy engraving and I make oddball parts like a ten inch sector gear with 20 teeth per inch. I use it to sharpen end mill flutes and to cut aspherical mirrors from solid aluminum. I have used it to generate metallic surface holograms, engrave photographs and even to play music. .
                    And jewelry!

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                    • #11
                      Ever since I started using the CNC, I think that they are the greatest thing ever, and only use the manual mill for the most menial and imprecise tasks.

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                      • #12
                        Originally posted by beanbag
                        Ever since I started using the CNC, I think that they are the greatest thing ever, and only use the manual mill for the most menial and imprecise tasks.
                        How has that affected job turn-around time? I've wondered if CNC can keep up with non-trivial but low yield jobs - say less than 10 parts in a one-off batch, vs manual.

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                        • #13
                          With a machine that has decent conversational programming its way faster than a mill. For example the base plate on my vacuum system. Put it in the VMC, had it mill out a hole 5.5" in diameter through 1.25" thick aluminum then drill 8 holes concentric to the hole on a 5" radius and then tap those holes. Took about 1/2 hr. There is no way I could have done this on a manual mill in one setting. Even drawing the part in cam real quick would have only added 20 to 30 minutes to the job. Still faster than doing it manually.

                          Even for one off parts I have found the CNC mill to be faster. You can operate it like a standard mill with power feeds if you use the handwheel. Lathes are a different story. I prefer to use a manual machine for most ops. Maybe its just because I really havnt used my CNC lathe much.

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                          • #14
                            Originally posted by dp
                            How has that affected job turn-around time? I've wondered if CNC can keep up with non-trivial but low yield jobs - say less than 10 parts in a one-off batch, vs manual.
                            Unless it's a one-off of a menial and imprecise task, the CNC is generally faster. There are a bunch of other benefits too, like:

                            If you get the first part right, you WILL NOT screw up on any of the rest. This is very helpful if you've been working continuously for 6 hrs and are starting to get pretty tired.

                            Your tools last longer because you can do things like climb cut, don't dwell while you are alternating between the x and y axis, have more efficient and expeditious toolpaths, etc

                            You can be busy doing other things like planning for the next part while the machine is busy churning on the current batch

                            Even for doing something rote like drilling a series of holes in 1/2" steel, I prefer to do on the CNC because you can just turn on the flood coolant and let it go. It will use a continuous feed rate and won't work harden the material.

                            The only tool I haven't used on the CNC is the slitting saw, because I can't turn it off fast enough if something goes wrong.
                            Last edited by beanbag; 02-02-2010, 02:58 AM.

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                            • #15
                              You have to differentiate here between home shop and work, then split that up into one off's and production, so basically you have four different groups all requiring a different method of doing a job.

                              Then throw into the equation that two people, doing the same job, with the same machinery won't do it the same way.

                              That gives you the correct answer

                              I'm a big believer in CNC as many know but my main machine often stands idle for a couple of weeks at a time or just ticks over making division plates for Gert to sell.

                              Guy up the road, one man band, lives on his Hurco and would be lost without it.

                              .
                              .

                              Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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