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Buying a CNC Lathe & CNC Mill - Need Advice

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  • #46
    Originally posted by Sparky_NY View Post

    Does not matter where to tool probe sets so long as it remains in the same spot for the job ( or its location is repeatable). What you are setting is the tool offset, the DIFFERENCE in length between the various tools, the part and its location has nothing to do with that difference. Your confusion lies with the difference in tool length offset and part zero.

    Its not uncommon for the operator to set all his tool length offsets before the stock is even put in place. When the stock is mounted, then all that is required is to set part zero with ANY tool and ALL tools will be calibrated due to their DIFFERENCES in length previously being stored earlier.

    Another example: Lets assume you have 10 tools, all entered in the tool table along with their offsets. You do job#1 and touch off for part zero and run. Job#2 comes along, it is NOT necessary to touch each tool, you only part zero touch off with ANY of the tools in the tool table and all tools are not in calibration. The tool length offsets in the tool table never change so long as the same tools remain in each holder (tool number), what does change job to job is the part zero.

    All of the above is in reference to the Z height only. X and Y are handled in almost the same manner though via the tool diameter in the tool table for each tool.

    Worth noting also, that some operators set all their tool length offsets using a special fixture OFF the machine on the bench. The values obtained from that fixture are then entered into the tool table. When it is time to run a part, the part offset Z is set ON the machine with the stock in place using ANY of the tools in the table.

    Bottom line, tool length offset is a OFFSET, the difference in length of the various tools measured from "some" constant Z reference. That reference can be anything, a fixture, the mill table, the part, does not matter, we are just looking for the DIFFERENCE in length between the various tools. PART ZERO is only done once and gives the control the location of the STOCK , the control then does some simple math each time a tool is changed to maintain zero at the same place on the part for every tool.

    Kinda like your altimeter, you only need set it once (part zero) then it is calibrated at every altitude (different Z heights) because the DIFFERENCE in pressures vs altitudes has been previously saved (permanently) in the inner workings of the altimeter (tool length offsets in tool table). Theory is pretty much the same.

    Not having repeatable length tooling is probably the reason for your confusion, you need to touch off every tool every time. Tool length offsets require repeatable Z capability. You have not been able to use tool length offsets thus far. Rather than using offsets, you just reset part zero every time you change a tool.
    I'm speaking from the mindset that I currently don't have tools with known lengths because the Taig mill has an ER16 collet spindle.
    Once I install my new spindle with TTS tooling, the confusion goes away.

    Comment


    • #47
      Unfortunately I'm getting to this a little late, I'm just a hobbiest, and I only have a Taig Manual mill. I love the little thing and as far as I can tell, it'll handle anything that fits on the table.

      I'm seeing a lot of comments on how you will need to zero the z-axis again if you change tooling... ok that's something I would just live with. It isn't worth the cost to me if we're talking about paying the price of the machine to get it, and we're only going to be milling a few small parts.

      If your choice is between trying to "learn" milling without a mill, and trying to "learn" with a Taig, I wouldn't even think twice. Get the Taig and learn by actually milling things. You don't need to run out and buy a bunch of things for it, either. Use the little vise it comes with to make a clamping set for the t-slots. It already comes with a few ER collets and a couple end-mills, so just use those in the beginning and buy more endmills one at a time as you need them. For measuring just use a cheap pair of calipers from the hardware store until you think you actually need the accuracy of more expensive tools.

      I hate to see people get turned away because they think they need to drop lots of money on a fancy machine. Imagine someone telling you to put off learning to drive until you could afford a Porsche.

      Comment


      • #48
        Originally posted by AssertiveWall View Post
        Unfortunately I'm getting to this a little late, I'm just a hobbiest, and I only have a Taig Manual mill. I love the little thing and as far as I can tell, it'll handle anything that fits on the table.

        I'm seeing a lot of comments on how you will need to zero the z-axis again if you change tooling... ok that's something I would just live with. It isn't worth the cost to me if we're talking about paying the price of the machine to get it, and we're only going to be milling a few small parts.

        If your choice is between trying to "learn" milling without a mill, and trying to "learn" with a Taig, I wouldn't even think twice. Get the Taig and learn by actually milling things. You don't need to run out and buy a bunch of things for it, either. Use the little vise it comes with to make a clamping set for the t-slots. It already comes with a few ER collets and a couple end-mills, so just use those in the beginning and buy more endmills one at a time as you need them. For measuring just use a cheap pair of calipers from the hardware store until you think you actually need the accuracy of more expensive tools.

        I hate to see people get turned away because they think they need to drop lots of money on a fancy machine. Imagine someone telling you to put off learning to drive until you could afford a Porsche.
        Apples and oranges.

        Comment


        • #49
          Originally posted by Bented View Post

          Tool Offsets, some controls offset the difference in size between tool #1 and all other tools in the library.
          Work Shift moves the Zero position of tool #1 therefore all other tools as well.

          A perfect example is the length of a part held in a lathe spindle, you can move the Z Axis 0.000 the usable length of the lathe using the #1 tool and all other following tools used have the same zero position.

          Do not confuse tool offsets and work shift.
          Wrong term used in my post. I get it.

          Comment


          • #50
            Right. You are missing it.

            You have a tool length sensor on the machine (probably table)
            You install your first tool and touch off to the surface of your stock.

            Run program and the first thing the program does is touch the first tool to the tool sensor. Now the program knows the stock height and the reference to the table.

            every tool after that (that isn't known because they are not repeatable) touches the tool length sensor.

            Gcode program has all it needs to automatically set the tool length based on the part and first tool.


            Originally posted by RB211 View Post
            I'm speaking from the mindset that I currently don't have tools with known lengths because the Taig mill has an ER16 collet spindle.
            Once I install my new spindle with TTS tooling, the confusion goes away.
            Rt

            Comment


            • #51
              Originally posted by reggie_obe View Post

              Wrong term used in my post. I get it.
              Some controls will work shift from any tool and some will only work shift from a reference tool (often tool #1). The reference tool has no offset, it is absolute 0-0-0

              Comment


              • #52
                Originally posted by skunkworks View Post
                Right. You are missing it.

                You have a tool length sensor on the machine (probably table)
                You install your first tool and touch off to the surface of your stock.

                Run program and the first thing the program does is touch the first tool to the tool sensor. Now the program knows the stock height and the reference to the table.

                every tool after that (that isn't known because they are not repeatable) touches the tool length sensor.

                Gcode program has all it needs to automatically set the tool length based on the part and first tool.



                Rt
                Tried a script to do that, gave an error that said I went outside of Z envelope. I had a feeling this was the way to do it. I'll have to ask on the Centroid forum, but again, will be using TTS now.

                Comment


                • #53
                  Well, thought I should post pictures of the new Taig R8 spindle with pneumatic drawbar.
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                  • #54
                    After a lot of thinking, I'm planning to go with :

                    MicroMill DSLS 3000AB System

                    Info on it can be found here :
                    http://www.microproto.com/vss_micromill_dsls_3000ab.htm

                    Its an upgraded Taig with :

                    - ballscrews
                    - closed feedback loop servos (i.e. no slippage or missing steps which even Tormach 440 does not have)
                    - 3/4 hp motor (i.e. looks like the famous sewing machine motor)
                    - 4th axis rotary table and tail stock (i.e. i won't use it as a make shift lathe for fear of damaging the mill, only gentle cuts)

                    Might cut out the 4th axis if the price is too high.

                    I'm wondering if I should order the above without the standard ER16 headstock supplied and instead replace it with a GlockCNC R8 or ISO-20 headstock for the Taig instead.
                    I'm not quite clear on what the pros and cons would be between ER16 vs R8 vs ISO-20 other than I would not have to re-calibrate the Z axis during tool changes for the latter 2.

                    As most of the parts I machine will be small and in aluminum, I don't need anything bigger than this machine.
                    Its size makes it portable should I need to pack it up and move which is harder to do with a Tormach 440.
                    Getting it in the basement itself would be a challenge.


                    I looked into other options like getting a G0704 type machine and re-fitting it with ballscrews, steppers, stepper controllers... etc. and realized I didn't want to bite off more than I can chew as a newbie. There's a lot of meddling and tinkering with stuff to get it working well even after the conversion has been completed.

                    The Tormach 440 seems out of my budget range.

                    Comment


                    • #55
                      I've just read this entire thread and wonder if you've followed up on a suggestion that has been made here - taking your parts to a job shop, or at least an experienced CNC machinist.

                      You say that you are behind, that you need to be cranking out parts. Buying a CNC mill today, without any machining experience, will not have you cranking out perfect parts tomorrow. There is no magic bullet, and a lot of frustration, in CNC. You need to have machining knowledge first. The computer control doesn't make up for a lack of machine tool knowledge, it just lets you make parts while you are doing something else. As someone else said here, and like all things computer, it will do exactly what you tell it to do, even something stupid. Except, of course, when it's not calibrated or something else is amiss, and how would you know that unless you had some knowledge and experience? CNC tools don't care whether they are making parts or scrap, they just do it quickly and efficiently.

                      Even if you had a CNC mill right now, if you are looking at producing many copies of actual parts of a machine, without years of experience you still need an expert opinion before proceeding. If you don't have a friend who has the knowledge or the experience take your CAD files to a job shop, ask for a quote for 10, 100, 1000 of each. You'll also need 2D drawings with dimensions and tolerances on your parts, have you done this? You'll need these even if you do it yourself, so that you can run your own quality-control as you crank out parts.

                      You say that your parts are complicated, and that you've verified them by 3D printing. However, many things that can be easily 3D printed cannot be made at all on machine tools, or would be insanely expensive in terms of tooling and/or time. Letting someone with experience and knowledge look over your parts will provide this insight immediately. Whether that insight will be delivered politely is a completely different issue.

                      At work we are blessed with a crusty old bastard of a machinist with 50+ years of experience doing most everything. He grew up working in his dad's shop, took it over when his dad retired, started 2-3 other manufacturing job shops over the years. Even though most of his current work is one-off, he admits he looks at every drawing with the idea of "how can I get 10,000 of these out the door by Thursday?" He is extremely efficient at both manual and CNC machining, everything he delivers is spot on perfect, and he freely admits that he paid for his skill with time and a mountain of scrapped parts. I run everything past him, even stuff I'm doing at home. He never fails to give me his honest assessment (old crusty machinists are like that, and I admire them for it), and is always followed up with excellent ideas how to do it better.
                      Last edited by DrMike; 06-21-2020, 06:45 AM.
                      SE MI, USA

                      Comment


                      • #56
                        Originally posted by mechanica View Post
                        After a lot of thinking, I'm planning to go with :

                        MicroMill DSLS 3000AB System

                        Info on it can be found here :
                        http://www.microproto.com/vss_micromill_dsls_3000ab.htm

                        Its an upgraded Taig with :

                        - ballscrews
                        - closed feedback loop servos (i.e. no slippage or missing steps which even Tormach 440 does not have)
                        - 3/4 hp motor (i.e. looks like the famous sewing machine motor)
                        - 4th axis rotary table and tail stock (i.e. i won't use it as a make shift lathe for fear of damaging the mill, only gentle cuts)

                        Might cut out the 4th axis if the price is too high.

                        I'm wondering if I should order the above without the standard ER16 headstock supplied and instead replace it with a GlockCNC R8 or ISO-20 headstock for the Taig instead.
                        I'm not quite clear on what the pros and cons would be between ER16 vs R8 vs ISO-20 other than I would not have to re-calibrate the Z axis during tool changes for the latter 2.

                        As most of the parts I machine will be small and in aluminum, I don't need anything bigger than this machine.
                        Its size makes it portable should I need to pack it up and move which is harder to do with a Tormach 440.
                        Getting it in the basement itself would be a challenge.


                        I looked into other options like getting a G0704 type machine and re-fitting it with ballscrews, steppers, stepper controllers... etc. and realized I didn't want to bite off more than I can chew as a newbie. There's a lot of meddling and tinkering with stuff to get it working well even after the conversion has been completed.

                        The Tormach 440 seems out of my budget range.
                        Have at it...

                        Comment


                        • #57
                          I've read this entire post and want to wish you luck, you're going to need it.

                          I was in your shoes in the late 1980's. I had finished building 5 prototypes the previous year for one of my inventions. All parts were made using manual industrial size machines, lathes, mills, sheetmetal tools. Now it was time for my first production run of 100 units and like you I decided to build the parts myself. With one very critical exception. I had a good handle on basic machining, tooling and metallurgy even though I'm not a machinist by trade. The first run of 100 units was all I could do while holding down a full time job and doing family stuff. The next production run of the parts was handled by those that had cnc machines and better skills than I.

                          My point is that having cnc or manual machines and making the parts yourself is not necessarily the best way to go especially with no machining experience. Then add the urgency of getting the parts made doesn't make sense from a business perspective. Several people have suggested you find someone to help you with the machining or better yet have them build at least your first run of parts while you learn the ins and out of producing said parts. I've been there and would have saved thousands of dollars and been in the market place much sooner had the guys on this forum been coaching me. Just my 2 cents.

                          Ron

                          Comment


                          • #58
                            I get that you want to try different prototypes on your own time, as outsourcing a string on one-offs could get expensive and don't provide much learning for yourself. Not sure though whether you'd want to read up a bit while learning CAM on a $200 chinese mini cnc mill chopping up blocks of wood instead of spending all your money now and finding out later you wanted something else.
                            Not to mention crashing your expensive mill.
                            Even if outsourcing is the most economic option, there's no fun in that and certainly little to learn. Get something to play with as a better understanding of machining will allow you to make better designs.
                            Good luck and enjoy.
                            Igor

                            Comment


                            • #59
                              Read the whole thread, and do not want to clutter the posters mind with technical stuff, there is enough here for 5 posts

                              Suggestion one---Go to the Tech College - You will not be disappointed !

                              Suggestion two--Don't know where you live but you need to check out 'Makers" or "Makerspace"
                              They are most famous for "Makers Faire" but they have Makerspace in some locations that have CNC machines for you to use and learn !
                              There are many around the world, you need to find them near you

                              You can also pay someone ( not a job shop ) to do the work
                              https://making.engr.wisc.edu/

                              There are Non-College Makers Spaces as well - and some are like clubs. You join and 5 or 10 dollars an hour and use any of their equipment
                              Here is one for example
                              https://www.thebodgery.org/the-space/
                              Note, they have Tormach CNC for you to use and fellow members help with setups

                              For a Newbie, I highly recommend this approach

                              Rich
                              Green Bay, WI

                              Comment


                              • #60
                                I just want to say that I am a computer guy, a maker, my soldering technique was perfected by the guy who invented audio cassettes, and surround sound, know my way around microprocessors and computer programming.
                                THANK HEAVENS I can manual machine, and have used manual machines before diving into the world of CNC with my TAIG. Things that are very trivial and easy to compensate for on a manual machine are not so with CNC. Things you take for granted with manual machining, you cannot with CNC in terms of machine setup. I could care less if my manual mill has 30 thousandths backlash, .003 on a CNC makes you want to pull your hair out.
                                I am done trying to convince you of skipping the Taig. I see that you made up your mind, so have at it.

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