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Re: [SherlineCNC] z axis stepper. and excess material

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  • RichD
    Tom, be aware that mass adds. Accelerating the additional mass may cause undesirable effects regardless of the counterbalancing effect. Spring force has little
    Message 1 of 24 , Aug 1, 2003
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      Tom,
      be aware that mass adds. Accelerating the additional mass may cause
      undesirable effects regardless of the counterbalancing effect.
      Spring force has little mass and will help quicker in acceleration.
      RichD

      Tom Hubin wrote:
      >
      > Hello Chris,
      >
      > I have Sherline P/N 67129 motors (3.2volt, 2.0Amp, +100 oz-in) steppers
      > on all 3 axes of my Sherline 5410 (metric 5400). I can run the x and y
      > axes up to 14 ipm, and often do so. When I first setup a year ago that
      > seemed to be the top end without skipping steps.
      >
      > The z axis tops out at about 5 ipm going up. I could run it faster going
      > down but I have the rapid limit set for 4.7 ipm so I don't loose steps
      > when the bit is raised rapidly during G81 drilling and G83 peck drilling
      > codes.
      >
      > I weighed the spindle motor and some of the attached hardware. About 10
      > pounds just hanging on the z axis, cantilevered out there several
      > inches. So the z stepper motor has to use it's first ten pounds of force
      > just to raise the spindle motor.
      >
      > I plan to add a 12 pound counterweight over some pulleys to negate the
      > effect of the 10 pounds of spindle motor and to preload by a pound or
      > two in the upward direction. I want a slight upward pull to reduce
      > backlash since all of my z references are in the downward direction.
      >
      > The nut on the z drive also binds from time to time. I find myself
      > adjusting it every few weeks.
      >
      > Somebody asked recently about handwheels on the motors. I kept mine and
      > am very happy I did so. Not only is it convenient when I want to do
      > something simple but they are also useful for maintenance. When the z
      > axis is skipping steps I depower and crank manually to see how it feels.
      > If the z axis is binding then I need to lube or adjust or fix something.
      >
      > Tom Hubin
      > thubin@...
      >
      > *********************
    • Randy Gordon-Gilmore
      ... Tom, I ve added a folder (transplanted from cad_cam_edm_dro) in the Files area showing my implementation of counterbalance springs for the head assembly.
      Message 2 of 24 , Aug 1, 2003
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        At 06:53 PM 7/31/2003 -0400, Tom wrote:

        >I plan to add a 12 pound counterweight over some pulleys to negate the
        >effect of the 10 pounds of spindle motor and to preload by a pound or

        Tom, I've added a folder (transplanted from cad_cam_edm_dro) in the Files
        area showing my implementation of counterbalance springs for the head
        assembly. I'm really happy with it from the motion smoothness standpoint,
        but I haven't tried to see how fast I could rapid z. There are two photos
        yet missing, since one of Yahoo's file servers has been offline for the
        past few days. They show the idler pulley and the back of the spacer block
        where I machined a pocket for the linear spring ends.

        Best regards,

        Randy

        Randy Gordon-Gilmore ,----.___________ ______________ _________________
        ProtoTrains // = = === == || == == == = || == == == = == =|
        Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
        zephyrus@... http://www.prototrains.com
      • Dave Hylands
        Hi Randy, I really like your design. I was thinking that with a slightly longer belt where both portions of the belt were on the left side of the column, and
        Message 3 of 24 , Aug 1, 2003
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          Hi Randy,

          I really like your design.

          I was thinking that with a slightly longer belt where both portions of
          the belt were on the left side of the column, and modifying the right
          hand side of the motor mounting bracket (so that it still cleared the
          column when the head was rotated 90 degrees), could continue to allow
          the modified spindle to be rotated.

          --
          Dave Hylands
          Vancouver, BC, Canada
          http://www.DaveHylands.com/


          > -----Original Message-----
          > From: Randy Gordon-Gilmore [mailto:zephyrus@...]
          > Sent: Friday, August 01, 2003 11:42 AM
          > To: SherlineCNC@yahoogroups.com
          > Subject: Re: [SherlineCNC] z axis stepper
          >
          >
          > At 06:53 PM 7/31/2003 -0400, Tom wrote:
          >
          > >I plan to add a 12 pound counterweight over some pulleys to
          > negate the
          > >effect of the 10 pounds of spindle motor and to preload by a pound or
          >
          > Tom, I've added a folder (transplanted from cad_cam_edm_dro)
          > in the Files area showing my implementation of counterbalance
          > springs for the head assembly. I'm really happy with it from
          > the motion smoothness standpoint, but I haven't tried to see
          > how fast I could rapid z. There are two photos yet missing,
          > since one of Yahoo's file servers has been offline for the
          > past few days. They show the idler pulley and the back of
          > the spacer block where I machined a pocket for the linear spring ends.
          >
          > Best regards,
          >
          > Randy
        • Alan Marconett KM6VV
          Hi Rich, Tom, Look at Randy s spring-balanced spindle modification. Was about a year back or so. Or contact Randy. I don t have the link right now. Randy?
          Message 4 of 24 , Aug 1, 2003
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            Hi Rich, Tom,

            Look at Randy's spring-balanced spindle modification. Was about a year
            back or so. Or contact Randy. I don't have the link right now. Randy?

            Alan KM6VV

            RichD wrote:
            >
            > Tom,
            > be aware that mass adds. Accelerating the additional mass may cause
            > undesirable effects regardless of the counterbalancing effect.
            > Spring force has little mass and will help quicker in acceleration.
            > RichD
            >
            > Tom Hubin wrote:
            > >
            > > Hello Chris,
            > >
            > > I have Sherline P/N 67129 motors (3.2volt, 2.0Amp, +100 oz-in) steppers
            > > on all 3 axes of my Sherline 5410 (metric 5400). I can run the x and y
            > > axes up to 14 ipm, and often do so. When I first setup a year ago that
            > > seemed to be the top end without skipping steps.
            > >
            > > The z axis tops out at about 5 ipm going up. I could run it faster going
            > > down but I have the rapid limit set for 4.7 ipm so I don't loose steps
            > > when the bit is raised rapidly during G81 drilling and G83 peck drilling
            > > codes.
            > >
            > > I weighed the spindle motor and some of the attached hardware. About 10
            > > pounds just hanging on the z axis, cantilevered out there several
            > > inches. So the z stepper motor has to use it's first ten pounds of force
            > > just to raise the spindle motor.
            > >
            > > I plan to add a 12 pound counterweight over some pulleys to negate the
            > > effect of the 10 pounds of spindle motor and to preload by a pound or
            > > two in the upward direction. I want a slight upward pull to reduce
            > > backlash since all of my z references are in the downward direction.
            > >
            > > The nut on the z drive also binds from time to time. I find myself
            > > adjusting it every few weeks.
            > >
            > > Somebody asked recently about handwheels on the motors. I kept mine and
            > > am very happy I did so. Not only is it convenient when I want to do
            > > something simple but they are also useful for maintenance. When the z
            > > axis is skipping steps I depower and crank manually to see how it feels.
            > > If the z axis is binding then I need to lube or adjust or fix something.
            > >
            > > Tom Hubin
            > > thubin@...
          • Alan Marconett KM6VV
            Hi Randy, Wow! I just gave you a plug not 5 minutes ago! Thanks for bringing the files over! Alan KM6VV
            Message 5 of 24 , Aug 1, 2003
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              Hi Randy,

              Wow! I just gave you a plug not 5 minutes ago! Thanks for bringing the
              files over!

              Alan KM6VV

              Randy Gordon-Gilmore wrote:
              >
              > At 06:53 PM 7/31/2003 -0400, Tom wrote:
              >
              > >I plan to add a 12 pound counterweight over some pulleys to negate the
              > >effect of the 10 pounds of spindle motor and to preload by a pound or
              >
              > Tom, I've added a folder (transplanted from cad_cam_edm_dro) in the Files
              > area showing my implementation of counterbalance springs for the head
              > assembly. I'm really happy with it from the motion smoothness standpoint,
              > but I haven't tried to see how fast I could rapid z. There are two photos
              > yet missing, since one of Yahoo's file servers has been offline for the
              > past few days. They show the idler pulley and the back of the spacer block
              > where I machined a pocket for the linear spring ends.
              >
              > Best regards,
              >
              > Randy
              >
              > Randy Gordon-Gilmore ,----.___________ ______________ _________________
              > ProtoTrains // = = === == || == == == = || == == == = == =|
              > Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
              > zephyrus@... http://www.prototrains.com
            • Tom Hubin
              Hello RichD, Let s say that the axis accelerates from 0 to 20ipm in one second. That is a change-in-velocity of 20 in / min = 20/60 in / sec = 0.333 in / sec.
              Message 6 of 24 , Aug 1, 2003
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                Hello RichD,

                Let's say that the axis accelerates from 0 to 20ipm in one second. That
                is a change-in-velocity of 20 in / min = 20/60 in / sec = 0.333 in /
                sec.

                Then axis acceleration = change-in-velocity/change-in-time = 0.333 in /
                sec / sec

                Acceleration due to gravity is 32.2 ft / sec / sec = 386.4 in / sec /
                sec

                So it appears that acceleration of the weight due to gravity is 1159
                times the acceleration due to the stepper.

                Putting it another way. A 10 pound weight will pull with 10 pounds of
                force when all is still. Z axis acceleration upward will reduce that
                force by a factor of 1/1159 of 10 pounds leaving 10-0.009 = 9.991
                pounds. Z axis acceleration downward will pull against the weight so
                that will make the effective weight 10 pounds plus 1/1159 of 10 pounds
                or 10.009 pounds.

                So my counter weight pulls upward with 10 pounds plus or minus 0.009
                pounds at all times.

                Common springs have force equal to length-change. So let's say that I
                use a 2 foot long, 5 pound/foot extension spring stretched 4 feet from
                my ceiling to the spindle bottom. That is 10 pounds of force pulling
                upward on my spindle assembly. The spindle has about +/- 3 inches of
                travel from center so the spring will vary +/- 1/4 foot in length over
                the range of travel. That is a +/- 1.25 pound variation in pull. So the
                upward force near the top of the z axis is 8.75 pounds and near the
                bottom of the z axis is 11.25 pounds.

                That certainly helps counter balance the spindle assembly but it varies
                more than a counterweight and it reaches the ceiling.

                I have not yet looked at Randy's arrangement but will do so as soon as I
                remember my Yahoo password.

                Tom Hubin
                thubin@...

                ************************************

                RichD wrote:
                >
                > Tom,
                > be aware that mass adds. Accelerating the additional mass may cause
                > undesirable effects regardless of the counterbalancing effect.
                > Spring force has little mass and will help quicker in acceleration.
                > RichD
                >
                > Tom Hubin wrote:
                > >
                > > Hello Chris,
                > >
                > > I have Sherline P/N 67129 motors (3.2volt, 2.0Amp, +100 oz-in) steppers
                > > on all 3 axes of my Sherline 5410 (metric 5400). I can run the x and y
                > > axes up to 14 ipm, and often do so. When I first setup a year ago that
                > > seemed to be the top end without skipping steps.
                > >
                > > The z axis tops out at about 5 ipm going up. I could run it faster going
                > > down but I have the rapid limit set for 4.7 ipm so I don't loose steps
                > > when the bit is raised rapidly during G81 drilling and G83 peck drilling
                > > codes.
                > >
                > > I weighed the spindle motor and some of the attached hardware. About 10
                > > pounds just hanging on the z axis, cantilevered out there several
                > > inches. So the z stepper motor has to use it's first ten pounds of force
                > > just to raise the spindle motor.
                > >
                > > I plan to add a 12 pound counterweight over some pulleys to negate the
                > > effect of the 10 pounds of spindle motor and to preload by a pound or
                > > two in the upward direction. I want a slight upward pull to reduce
                > > backlash since all of my z references are in the downward direction.
                > >
                > > The nut on the z drive also binds from time to time. I find myself
                > > adjusting it every few weeks.
                > >
                > > Somebody asked recently about handwheels on the motors. I kept mine and
                > > am very happy I did so. Not only is it convenient when I want to do
                > > something simple but they are also useful for maintenance. When the z
                > > axis is skipping steps I depower and crank manually to see how it feels.
                > > If the z axis is binding then I need to lube or adjust or fix something.
                > >
                > > Tom Hubin
                > > thubin@...
                > >
                > > *********************
                >
                >
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                >
                >
                >
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              • Tom Hubin
                ... Hello Bryan, Right out of the box, April 2002, my z axis was harder to crank than the x and y axes. This is especially true when cranking uphill. If I lift
                Message 7 of 24 , Aug 1, 2003
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                  Bryan Mumford wrote:
                  >
                  > At 6:53 PM -0400 07-31-03, Tom Hubin wrote:
                  > >I have Sherline P/N 67129 motors (3.2volt, 2.0Amp, +100 oz-in) steppers
                  >
                  > These are not 100 oz/in steppers. I know that some Sherline
                  > literature lists them that way. Why? Because Joe Martin wanted to be
                  > conservative in the rating. The motors are SKC part number SST57D3201
                  > rated at 9.7 kg/cm holding torque. This pencils out to 134.8 oz/in.
                  > For reference, see:
                  > http://www.afimotion.com/afi00009.htm
                  >
                  > Joe Martin and Ray Henry have been running the new system with
                  > standard motors at 20 IPM on the Z axis, no counterweight, but brand
                  > new machines. I will admit that my own mill, which is several years
                  > old, is outfitted with an SST58D5821 motor on the Z axis. It's rated
                  > at 14.2 kg/cm or 197 oz/in.
                  >
                  > --
                  >
                  > Bryan Mumford
                  > Santa Barbara, California
                  > http://www.bmumford.com

                  Hello Bryan,

                  Right out of the box, April 2002, my z axis was harder to crank than the
                  x and y axes. This is especially true when cranking uphill. If I lift
                  the spindle by hand then it is much easier to crank uphill.

                  If I detach the saddle nut so that the spindle assembly is free to drop,
                  it does not drop. I can slide it up or down by hand but gravity is not
                  enough to make it fall.

                  So, pehaps I have a binding problem of some sort.

                  I do not have way lube so I use 3-in-1 oil to lube the ways. I use the
                  same oil on the x and y axes and no problems there. Is there something
                  in the z axis, like the gibs, that I need to adjust?

                  Tom Hubin
                  thubin@...
                • Tom Hubin
                  ... Hello Randy, Very nice solution using a constant force spring. I m hunting for data sheets for the spring now. Got some info in the printer queue. Will
                  Message 8 of 24 , Aug 1, 2003
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                    Randy Gordon-Gilmore wrote:
                    >
                    > At 06:53 PM 7/31/2003 -0400, Tom wrote:
                    >
                    > >I plan to add a 12 pound counterweight over some pulleys to negate the
                    > >effect of the 10 pounds of spindle motor and to preload by a pound or
                    >
                    > Tom, I've added a folder (transplanted from cad_cam_edm_dro) in the Files
                    > area showing my implementation of counterbalance springs for the head
                    > assembly. I'm really happy with it from the motion smoothness standpoint,
                    > but I haven't tried to see how fast I could rapid z. There are two photos
                    > yet missing, since one of Yahoo's file servers has been offline for the
                    > past few days. They show the idler pulley and the back of the spacer block
                    > where I machined a pocket for the linear spring ends.
                    >
                    > Best regards,
                    >
                    > Randy

                    Hello Randy,

                    Very nice solution using a constant force spring. I'm hunting for data
                    sheets for the spring now. Got some info in the printer queue. Will look
                    more closely at all next week.

                    What would you think about getting the motor off the z axis completely?
                    Maybe motor and pulleys seperate from mill z column. Connect second
                    pulley (normally on spindle) to spindle via some kind of flexible drive
                    shaft.

                    Or motor at the base in the rear. Motor pulley where you now have your
                    motor pulley but the motor lowered to the base. Then a long shaft from
                    the motor to the motor pulley. Pulley keyed to drive shaft but not
                    pinned so free to travel vertically.

                    Tom Hubin
                    thubin@...
                    Tom Hubin
                    thubin@...
                  • Randy Gordon-Gilmore
                    ... Thank you. :-) I will probably update the photos since I ve upgraded to the 10k pulley set. ... The first version of my springs had them flanking the
                    Message 9 of 24 , Aug 1, 2003
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                      At 11:53 AM 8/1/2003 -0700, Dave wrote:

                      >I really like your design.

                      Thank you. :-) I will probably update the photos since I've upgraded to
                      the 10k pulley set.

                      >I was thinking that with a slightly longer belt where both portions of
                      >the belt were on the left side of the column, and modifying the right

                      The first version of my springs had them flanking the spacer block and
                      attached to its sides, and the head could still be rotated. I will dig up
                      the photos and drawings of that version and upload them later tonight.

                      I decided that since I've dedicated the mill to CNC, I would optimize as
                      much as possible for that configuration. The motor in back balances the
                      head assembly almost perfecly, and reduces any binding on the z-axis ways
                      enormously. With the leadscrew nut detached, I could easily move the head
                      up and down with a single finger.

                      I think you will have an interesting job designing a motor bracket to allow
                      rotating the head with the rear motor position!

                      Best regards,

                      Randy

                      Randy Gordon-Gilmore ,----.___________ ______________ _________________
                      ProtoTrains // = = === == || == == == = || == == == = == =|
                      Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
                      zephyrus@... http://www.prototrains.com
                    • Randy Gordon-Gilmore
                      ... You re welcome, Alan. They more properly belong here (now that this group exists!) than in the general cad_cam_edm_dro group. I will delete the old
                      Message 10 of 24 , Aug 1, 2003
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                        At 12:37 PM 8/1/2003 -0700, Alan wrote:

                        >Wow! I just gave you a plug not 5 minutes ago! Thanks for bringing the
                        >files over!

                        You're welcome, Alan. They more properly belong here (now that this group
                        exists!) than in the general cad_cam_edm_dro group. I will delete the old
                        copies over there after I'm done transplanting here.

                        Best regards,

                        Randy

                        Randy Gordon-Gilmore ,----.___________ ______________ _________________
                        ProtoTrains // = = === == || == == == = || == == == = == =|
                        Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
                        zephyrus@... http://www.prototrains.com
                      • Randy Gordon-Gilmore
                        ... Thanks, Tom. The only dealer I know of that carries the springs is Stock Drive Products. If you go to https://sdp-si.com/eStore/ and type constant
                        Message 11 of 24 , Aug 1, 2003
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                          At 08:04 PM 8/1/2003 -0400, Tom wrote:

                          >Very nice solution using a constant force spring. I'm hunting for data
                          >sheets for the spring now. Got some info in the printer queue. Will look
                          >more closely at all next week.

                          Thanks, Tom. The only dealer I know of that carries the springs is Stock
                          Drive Products. If you go to

                          https://sdp-si.com/eStore/

                          and type "constant force" in the search box, the first link will be the
                          springs.

                          >What would you think about getting the motor off the z axis completely?

                          That would actually be a step backwards. With the motor behind the column,
                          the center of gravity of the whole head assembly falls very near the front
                          of the column, so the binding force on the ways (due to overhung weight) is
                          negligable. With the motor mounted remotely, the c/g would be ahead of the
                          column, but not as badly as the stock setup (which I'm not knocking, since
                          it was designed for maximum versatility--rotating, etc.)

                          Best regards,

                          Randy




                          Randy Gordon-Gilmore ,----.___________ ______________ _________________
                          ProtoTrains // = = === == || == == == = || == == == = == =|
                          Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
                          zephyrus@... http://www.prototrains.com
                        • Randy Gordon-Gilmore
                          ... My bad! I put the 10k pulley set on the Sherline head on my gantry. No photo update necessary on the Sherline mill (at least, until I learn to take
                          Message 12 of 24 , Aug 1, 2003
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                            At 06:10 PM 8/1/03 -0700, Randy Gordon-Gilmore wrote:

                            >Thank you. :-) I will probably update the photos since I've upgraded to
                            >the 10k pulley set.

                            My bad! I put the 10k pulley set on the Sherline head on my gantry. No
                            photo update necessary on the Sherline mill (at least, until I learn to
                            take better pictures!)

                            Randy

                            Randy Gordon-Gilmore ,----.___________ ______________ _________________
                            ProtoTrains // = = === == || == == == = || == == == = == =|
                            Rio Vista, CA, USA /-O==O------------o==o------------o==o-----------o==o-'
                            zephyrus@... http://www.prototrains.com
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