Loading ...
Sorry, an error occurred while loading the content.

Re: [taigtools] Documentation on the Progress of my Many Projects, as Promised...

Expand Messages
  • Ken Cline
    ... Adam, I really do hope my comments are helpful. The last thing I want to do is discourage anyone. Machining is hard enough! My hopes for the Taig were
    Message 1 of 15 , Sep 8, 2010
    • 0 Attachment
      On 7 Sep 2010, at 5:40 PM, Adam Collins wrote:

      > Ken,
      >
      > Thank you for sharing that-my plans so far haven't included any modifications to
      > the base because I thought they wouldn't be needed. The Taig's "backbone" is
      > more rigid than other mills of this size (i.e. the Sherline 5400 milling
      > machine) is what I was trying to say in the last message, but I also know the
      > square steel tubing that the base and Z column is made from has its own
      > drawbacks and limitations.

      Adam, I really do hope my comments are helpful. The last thing I want to do is discourage anyone. Machining is hard enough! My hopes for the Taig were dampened when I saw the incredibly fast tool wear that can occur when pushing it limits (due to chatter), and more than one user here has switched to bigger machines or offered advice and then admitted they don't use the Taig for powerful operations.

      My guess is that 100 lbs is the upper limit of machining force you can expect the lead screws to withstand without binding. This alone will limit the power in your machining operations, especially at lower spindle speeds.

      On top of that, when you apply the 100lb force 6" up on the column, you will generate about .001" deflection. There's also resonance to deal with, which can amplify the deflection. And even if you secure the back of the column to an infinitely rigid bracket, you'll still see movement due to torsion. That square tubing is simply not as rigid as the massive parts used in large mills, nor is the base, or table, etc.

      My point is there are a lot of variables; it may be hard to anticipate them all; and it only takes one weak link to foil your plan.

      > I've tried to list disclaimers in many posts stating that I'm not an engineer
      > and have only been operating machine tools for the last year, and while I have
      > been employed as a steelworker, CNC plasma operator, welder, and similar jobs
      > and hobbies working with metal for many of the last ten years I know I'm no
      > expert on anything. I don't exactly have the budget to hire a mechanical or
      > structural engineer either, so these mods are based upon the present performance
      > of my Taig, what I believe its performance should be, and what I think
      > is actualy possible from it.

      If I were you, I would start by getting a feel for what is possible with the stock Taig mill. For example, I find I have to ignore feed rates given in feed and speed tables, instead opting for tiny cuts - typically < .001" per tooth. (I still hope someone will chime in and explain that I am doing something wrong, and show me how to get good performance out of a 1/8" end mill. but no luck thus far.) Ask yourself how much increase in performance is reasonable, and whether your goals are attainable.

      As for the column, it should not be moving out of position when you use the mill. Mine is shimmed with aluminum foil, which has a lower coefficient of friction than steel on steel, and it is able to cope with operations that have stalled my X axis. Make sure you don't have anything (dirt, scratches, etc) interfering with the mechanical connection of the ground surfaces.

      Anyway, good luck!



      [Non-text portions of this message have been removed]
    • Adam Collins
      Ken, I apologize for the delayed response; I ve been busy with multiple projects and have attempted to research this problem to decide if the end result is
      Message 2 of 15 , Sep 11, 2010
      • 0 Attachment
        Ken,

        I apologize for the delayed response; I've been busy with multiple projects and
        have attempted to research this problem to decide if the end result is going to
        be worth the effort required.  At this time, I don't believe I'll change many
        of my plans to modify my Taig since I'm quite sure it will aid in some of the
        quirks I have with the machine, but I will eventually own larger machines in
        both manual and CNC versions (as soon as I move to a home with a garage that I
        both own and I can fit the large machines into quite easily).

        The issues you mentioned would most likely be the limiting factor on my finished
        project.  While I've planned to rigidly (well, in a Taig-scale sense) secure the
        Z column to the same thick steel plate the base is mounted to (possibly even
        adding additional supports to the steel mounting plate), I hadn't considered
        changing anything within the Taig's table assembly to compensate for additional
        strain at this point in the project.  If I ever get the chance to play around
        with casting my own parts and have access to or own the necessary foundry tools
        and equipment in a size large enough, I would like to replace the aluminum
        components on my Taig with iron versions and the square tubing of the base and Z
        column with rigid cast iron components of my own design, but that's not going to
        be anytime soon if ever at all.  A quality larger machine is the quick answer to
        my issues, but that's just out of reach at the present time.

        In reality, I'm sure that if I were to call or email Taig and complain about the
        problems I'm attempting to resolve in this machine, they would probably check it
        out and correct anything they found out of spec, but since I currently have
        access to all these industrial machines I'd much rather go through the mill and
        modify it in the process to better suit my needs.  This machine's capabilities
        should exceed those of a Sherline mill by a great deal more than what I'm
        seeing, which leads me to believe that either something is out of spec or I just
        got a machine that had all the tolerances of the major parts in the Z column
        stacked at the limits in one direction.  The experience of fixing these issues
        on my own is essential to me, as I'll eventually need to know exactly what to do
        without consulting others to maintain and repair my future CNC production
        equipment.

        Although I seem to have gotten calculating speeds and feeds down on the full
        size machines, the limited arrangement of only six speeds (or possibly more if
        one were to play with positioning of the pullies, which would be an inconvience
        to me) in the stock configuration makes optimal cutting conditions very hard to
        achieve.  On the big machines-manual or CNC, I can perform the majority of
        machining operations while keeping the workpiece at a temperature that's only
        slightly warm to the touch, but that hasn't always been possible with my Taig. 
        Filling the steel tubing with concrete may help a bit with resonance, but I
        believe I'll just try to complete projects involving larger parts or harder
        materials on the big equipment whenever possible.

        Anyway, there are other spindle motor options, so it would probably be wise if I
        were to at least try some smaller motors first before securing the beast (that
        would make a great spindle motor for a Sieg X3-sized or larger machine).  I
        still want the option of holding 1/2" or larger shank tools in collets instead
        of end mill holders, my Taig needs a variable speed controller and DC motor, I
        want to add the Z axis to base plate supports for improved rigidity, and I
        believe that removing the weight of the spindle motor from the headstock will
        greatly aid in improving the overall use and capabilities of the Taig, so I'm
        going to continue with the majority of my plans but trying other motors to power
        the spindle first.  My plans for the Emco Unimat 3 bed consist of using both the
        spare 3/4-16 headstock I have and the ER16 headstock that's currently in place
        on my Taig for the Emco's lathe spindle and the vertical milling attachment
        respectively, so building my own headstock for the Taig is essential to keeping
        those plans for the other machine.  The new headstock for the Taig will be
        constructed from steel and will provide a throat depth equivalent to a 3/4"
        spacer behind the stock dovetail mounting plate, it will incorporate the LM67048
        tapered roller bearings I have and the ER32 spindle I've already started
        building, and will provide a much better mounting arrangement the Z axis
        carriage then the stock dovetail plate and faux gib. 


        I will try your suggestion of aluminum foil between the base and Z column a soon
        as I tear the machine down again.  The front-to-back alignment of the Z column
        on my machine seems to be in decent order (out by a little over a thousandth in
        about four inches), but I plan to correct as much of that as reasonably
        possible during the series of mods.  My Taig is the 2019ER-CR ("computer-ready"
        model with long table and ER16 spindle), but it's currently in use as a manual
        machine with stock Taig hand cranks installed instead of the stepper mounts and
        motors.  After thorough testing of the completed modifications, I plan to
        exchange the hand cranks with the 276 oz-in NEMA 23 Keling steppers I purchased
        for the conversion, but I just don't feel that the machine is ready for computer
        control in its stock form.  I know my mods won't turn it into a Bridgeport and
        will amplify any weak link present in the machine, but I'd rather be safe than
        sorry and fix the known issues before the conversion.  Any weak link that rears
        its head will either be resolved in further modifications or smaller DOCs, feed
        rates, etc. will be used when programming the CAM software.  My goals aren't to
        abuse this machine, but to just help it become rigid enough for reliable,
        repeatable, and accurate work under CNC operation; while I'd like to see
        increased capabilities from the finished machine, the added features alone
        should be enough to ease my mind when powered by steppers if no increase in
        capability is discovered.

        My original expectations may have been high for this machine and the series of
        upgrades I've planned, but I still believe the modifications are essential for
        the longevity and precision of this mill.  As conservative as I am, I'd rather
        be more proactive in the preparation of my Taig and spend more now then after
        the CNC conversion.  I've never subscribed to the "don't fix it if it isn't
        broken" mantra, instead modifying and upgrading everything feasible as I see fit
        for any reason I feel is rational, so I'll still be satisfied with the mods if
        the only worthwhile outcome is a longer life of the mill and it's components
        as compared to the stock form.  It will still be used on regular basis after I
        have acquired larger machines, so the experience gained by taking this route and
        ensuring the parts it produces will be repeatable and accurate will no doubt
        prove beneficial to me further down the road while also providing a good
        starting platform for a small scale and part time production machine. 


        Anyway, I really appreciate your time and help pointing out these limitations
        and issues.  My hopes for this machine may have been a bit optimistic, but I
        will have larger machines as soon as possible to make bigger parts and other
        components from harder materials.  If nothing else, my upgrades should at least
        provide a better starting platform for a CNC machine, but I would like to see
        it's capabilities expanded.  I'm sure I'll see better results then what I have
        been seeing from my Taig after the mods are completed, even if they only
        bring it back to ideal factory specs, so I still have my justification for the
        majority of the changes.  Thanks!

        Sincerely,

        Adam Collins

        Progress and various other projects updated almost daily (loads of pics):
        http://operationoverkill.blogspot.com/



        ________________________________
        From: Ken Cline <cline@...>
        To: taigtools@yahoogroups.com
        Sent: Wed, September 8, 2010 4:03:30 PM
        Subject: Re: [taigtools] Documentation on the Progress of my Many Projects, as
        Promised...

         

        On 7 Sep 2010, at 5:40 PM, Adam Collins wrote:

        > Ken,
        >
        > Thank you for sharing that-my plans so far haven't included any modifications
        >to
        >
        > the base because I thought they wouldn't be needed. The Taig's "backbone" is
        > more rigid than other mills of this size (i.e. the Sherline 5400 milling
        > machine) is what I was trying to say in the last message, but I also know the
        > square steel tubing that the base and Z column is made from has its own
        > drawbacks and limitations.

        Adam, I really do hope my comments are helpful. The last thing I want to do is
        discourage anyone. Machining is hard enough! My hopes for the Taig were dampened
        when I saw the incredibly fast tool wear that can occur when pushing it limits
        (due to chatter), and more than one user here has switched to bigger machines or
        offered advice and then admitted they don't use the Taig for powerful
        operations.

        My guess is that 100 lbs is the upper limit of machining force you can expect
        the lead screws to withstand without binding. This alone will limit the power in
        your machining operations, especially at lower spindle speeds.

        On top of that, when you apply the 100lb force 6" up on the column, you will
        generate about .001" deflection. There's also resonance to deal with, which can
        amplify the deflection. And even if you secure the back of the column to an
        infinitely rigid bracket, you'll still see movement due to torsion. That square
        tubing is simply not as rigid as the massive parts used in large mills, nor is
        the base, or table, etc.

        My point is there are a lot of variables; it may be hard to anticipate them all;
        and it only takes one weak link to foil your plan.

        > I've tried to list disclaimers in many posts stating that I'm not an engineer
        > and have only been operating machine tools for the last year, and while I have

        > been employed as a steelworker, CNC plasma operator, welder, and similar jobs
        > and hobbies working with metal for many of the last ten years I know I'm no
        > expert on anything. I don't exactly have the budget to hire a mechanical or
        > structural engineer either, so these mods are based upon the present
        >performance
        >
        > of my Taig, what I believe its performance should be, and what I think
        > is actualy possible from it.

        If I were you, I would start by getting a feel for what is possible with the
        stock Taig mill. For example, I find I have to ignore feed rates given in feed
        and speed tables, instead opting for tiny cuts - typically < .001" per tooth. (I
        still hope someone will chime in and explain that I am doing something wrong,
        and show me how to get good performance out of a 1/8" end mill. but no luck thus
        far.) Ask yourself how much increase in performance is reasonable, and whether
        your goals are attainable.

        As for the column, it should not be moving out of position when you use the
        mill. Mine is shimmed with aluminum foil, which has a lower coefficient of
        friction than steel on steel, and it is able to cope with operations that have
        stalled my X axis. Make sure you don't have anything (dirt, scratches, etc)
        interfering with the mechanical connection of the ground surfaces.

        Anyway, good luck!




        [Non-text portions of this message have been removed]
      • Ken Cline
        Hi Adam, Are you sure the parts on your mill are out of spec? Taig has a reputation for making quality parts. I shimmed my column and headstock mount in
        Message 3 of 15 , Sep 13, 2010
        • 0 Attachment
          Hi Adam,

          Are you sure the parts on your mill are out of spec? Taig has a reputation for making quality parts. I shimmed my column and headstock mount in order to dial in YZ plane angles closer than is truly necessary, but the twist you complained about (XZ plane, if I understand correctly) should be easily corrected by adjusting the headstock mount and Z gib (if I recall correctly, a machinist's square is useful here). There will be minimal play if the gib is set up correctly. Even if the mount is out of spec and you don't want to return it, it should be a simple matter to file the screw holes to allow you to set it up correctly.

          By the way, the aluminum foil shims do not improve the connection between column and base - aluminum on steel has less friction than steel on steel.

          I use compressed air for cooling and don't have a problem with my parts getting hot while cutting. Heating is not be a compelling reason for me to want to slow the spindle, tools wear and surface finish are the reasons I'd like to be able to slow down, especially when facing parts with a fly cutter.

          Again, good luck.
        • Adam Collins
          Ken, Yes, my main gripe about the Taig is the XZ plane alignment.  Even after squaring the dovetail mounting plate to the Z axis carriage with a DTI mounted
          Message 4 of 15 , Sep 18, 2010
          • 0 Attachment
            Ken,

            Yes, my main gripe about the Taig is the XZ plane alignment.  Even after
            squaring the dovetail mounting plate to the Z axis carriage with a DTI mounted
            to a 1-2-3 block secured to the table, the addition of the weight of the spindle
            motor on the left-hand side of the headstock throws the alignment off every
            time.

            The gibs on all three axes seem to be adjusted correctly as there is no
            excessive friction while operating the hand cranks in either direction on any
            axis and no noticable play when attempting to twist the table or Z carriage by
            hand, but there is a frightening amount of additional friction introduced when
            moving the headstock in the +Z direction after the spindle motor has been
            installed (compared to motion of the Z axis in the positive direction without
            the spindle motor or in the negative direction with or without the motor).  I
            should check for play in all axes with a DTI mounted to the table or the base
            plate and will do that as soon as I tear her down again.

            I'm sure that the weight of the spindle motor could be compensated for by filing
            or slightly removing a tiny bit of material on the correct side and in a proper
            radius from the center of the mount relative to where the headstock usually
            rests on it (which I would think to be the proper way to modify the mounting
            plate) as you had mentioned, and I'm sure I could make the calculations required
            to figure out the amount of material to remove from each mounting hole on my
            first attempt and without multiple test-fit-and-file/cut sessions (provided the
            gib in my Z carriage is properly adjusted), but the last time I squared and
            trammed the mill (not very long ago) I installed a new dovetail mounting plate
            because that's where I presumed the problem was, but the issue has yet to be
            corrected.

            The YZ alignment of my Taig could use a bit of tweaking to get it closer to
            square than it currently is, but I estimated that I'd only need a very thin shim
            to bring it into better specs-something along the lines of about 0.0002-0.0003",
            which I could do by adding a single thin cylindrical spacer of the same diameter
            as the column to base joint, ground with a very slight out of square condition
            on the face of the spacer (> 0.001") to add between the Z column and base.  This
            would allow for variable adjustment of the Z column within the out-of-square
            range of the face of the spacer-the drawback here being the perpendicularity of
            the base of the headstock and entire Z column to the travel of the Z axis (which
            I can't forsee being a problem at all because the headstock could be mounted at
            literally any angle as long as it's rotated around the same plane as the travel
            of the Z axis, but I also haven't fit any tolerance "build-up" into the equation
            just yet).  It's hard for me to describe in words, but it should be a fairly
            easy component to build; getting it out-of-square to such a small fraction of a
            degree and maintaining a tight tolerance on it would be the hardest part of its
            construction.  In other words, I'm thinking of a piece of round bar turned to
            about a 3.5" diameter with a 0.501" center hole to provide a close sliding fit
            on the column retaining bolt but of a very small thickness, less than 0.250"
            nominally to keep the loss of throat depth to a minimum, but the lowest point
            along the thickness/length of the spacer measuring right at or very close to a
            thousandth under the measurement obtained 180-degrees from it.  Small indexing
            marks could be made (even with a pencil) on the approximate high and low points
            and it rotated around the column securing bolt to compensate for any
            out-of-square situation in the YZ alignment from the mounting faces of the Z
            column's and base's ground mating surfaces (working on a similar principle to
            that of a cylindrical square).

            That should provide more than enough adjustment for aligning the YZ plane of
            these machines closer to square than possible without any kind of shim or
            spacer, but aligning both it and the Z column correctly could be time
            consuming.  This is provided that my estimate of angular and chordal
            misalignment for the overall length of the Z column is correctly proportioned. 


            The XZ alignment of the headstock to the table and travel of the Z axis could be
            accomplished in a similar fashion to your description like I had mentioned
            above; simply drilling the holes oversize would allow for more adjustment in the
            center holes then at the top and bottom rows of mounting holes with either the
            6- or 8-hole dovetail mounting bracket and could also allow more of a
            misalignment in the XZ plane because of the spindle motor's weight.  Removing
            material on the left hand side of the upper two mounting holes and the right
            hand side of the lower ones, both along the correct radius from the center of
            the mount (1" radius for 6-hole mounting plates or 1.5" radius for 8-hole
            plates) and proportional to the amount of offset of the headstock with the
            spindle motor attached would be the proper way to modify the dovetailed plate
            after the Z axis gib had been checked and verified to be correctly adjusted, I
            would think.  I'm sure this is what you meant in your previous reply because you
            seem to know what you're talking about.

            Would you care to enlighten me to your profession?  From your previous responses
            I've assumed that you were an engineer of some sort.  Not that it matters-the
            points you've mentioned would still be worthwhile whether they came from an
            engineer or a cook.  I'm just curious if you don't mind sharing...

            My plans of building a single-piece headstock to bolt directly to the Z
            carriage, eliminating the dovetail mounting plate, and removing the weight of
            the motor from the headstock should resolve the issues with the XZ alignment I'm
            seeing, provided the concentricity of the spindle bore, the spindle's outer
            diameter, the taper and inner bore of the spindle and its threads, and the
            mounting holes and surfaces in the new headstock are held to tight enough
            tolerances.  The CNC equipment at school will aid in much of that, but the
            cylindrical grinder is still a manual machine and I don't have much experience
            using it, so the actual bearings used may change if I fail to achieve the
            correct dimensions or screw up the set-up of the machine too badly before final
            grinding, but I'm hoping that won't be the case as I'd prefer to keep a minimum
            0.250" wall thickness on any single part of the spindle and my goal of a 0.750"
            bore through it, so the use of the 1.2495" ID LM67048 tapered roller bearings I
            have on-hand for the new spindle and headstock assembly would be a necessity for
            maintaining those goals and using the spindle blank I've already started
            machining.

            Anyway, enough rambling.  I'm not certain that anything is out of spec on my
            Taig but I would like to think that most other Taig owners aren't experiencing
            the same problems and to the same extent that I am.  Maybe I'm being a bit
            optimistic about squaring the Z column to within 0.0005" in 6" of travel and the
            headstock to the same while sweeping a 6" area (preferrably a 6" radius, but I
            could live with 0.001" out of square in a 12" diameter) with a DTI mounted in
            the spindle.  Adding the previously mentioned adjustable supports for the Z
            column seemed (and still seems) like a reasonable way to decrease the probablity
            and frequency of the need to check and realign the column and headstock if it
            doesn't add much or any increased capabilities or rigidity to the machine.  But
            then again I'm no engineer (four semesters of calculus scared me away from that
            degree) either...

            Again, thanks for your time, help, and information!

            Sincerely,

            Adam Collins




            ________________________________
            From: Ken Cline <cline@...>
            To: taigtools@yahoogroups.com
            Sent: Mon, September 13, 2010 11:44:47 PM
            Subject: Re: [taigtools] Documentation on the Progress of my Many Projects, as
            Promised...

             
            Hi Adam,

            Are you sure the parts on your mill are out of spec? Taig has a reputation for
            making quality parts. I shimmed my column and headstock mount in order to dial
            in YZ plane angles closer than is truly necessary, but the twist you complained
            about (XZ plane, if I understand correctly) should be easily corrected by
            adjusting the headstock mount and Z gib (if I recall correctly, a machinist's
            square is useful here). There will be minimal play if the gib is set up
            correctly. Even if the mount is out of spec and you don't want to return it, it
            should be a simple matter to file the screw holes to allow you to set it up
            correctly.

            By the way, the aluminum foil shims do not improve the connection between column
            and base - aluminum on steel has less friction than steel on steel.

            I use compressed air for cooling and don't have a problem with my parts getting
            hot while cutting. Heating is not be a compelling reason for me to want to slow
            the spindle, tools wear and surface finish are the reasons I'd like to be able
            to slow down, especially when facing parts with a fly cutter.

            Again, good luck.







            [Non-text portions of this message have been removed]
          Your message has been successfully submitted and would be delivered to recipients shortly.