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

Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

Expand Messages
  • Ipeerbhai
    As far as I can tell, both the metric Steel linear bearing shaft, and the ceramic coated Al shaft, is straight to .001 /foot. Thats .0254mm/304mm. The metric
    Message 1 of 25 , Jul 15, 2013
    • 0 Attachment
      As far as I can tell, both the metric Steel linear bearing shaft, and the ceramic coated Al shaft, is straight to .001"/foot.  Thats .0254mm/304mm.  The metric shaft at McMaster is .03/300, but the inch stuff is .002"/foot( or 0.0508/304 ).  So, the metric steel rod is nearly the same tolerance( and probably is the same -- both would report as .001"/foot if using imperial units. )

      Why the metric stuff is more precise as the inch stuff beats me.  Misumi matches McMaster's tolerances, but cuts to any size.  Same cost as the Al shaft, same tolerances, but 4x the strength -- at least on paper.  With steel, can use rolling element bearings ( which I keep hearing beats plain bearings to the curb... ).  Rolling element bearings are easy to use as inserts into a printed part...

      Funny thing -- this is the one that confuses me -- MakerBot uses bronze bushings and PCB linear bearings in the printer, on a mix of steel and Al rods. Steel/Bronze on X/Y, but their Z axis, which for years they had trouble with getting straight enough as a cantilever system, they switched to Al rods + PCB linear bearings.  Thinner rods -- I think maybe 5/16" -- and a floating Z lead screw. A thing that makes me go, Hmmm...  Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?




      -----Original Message-----
      From: Dan Andersson <dan@...>
      To: micRo-cnc <micRo-cnc@yahoogroups.com>
      Sent: Mon, Jul 15, 2013 11:27 am
      Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

       


      Cheap and precision doesn't normally mix...

      The alu rods have ceramic coating.

      I'm not defending LL as such but the design is the best I've seen below 15k US$.

      /danand

      On Mon, 15 Jul 2013 09:57:21 -0700
      Imran Peerbhai <ipeerbhai@...> wrote:

      > Why not use steel rods? It's 4 times stronger than AL, and it's cheap. Even if chrome plated.
      >
      > Sent from my iPhone
      >
      > On Jul 15, 2013, at 9:41 AM, Dan Andersson <dan@...> wrote:
      >
      > >
      > > Yup,
      > >
      > > My thought two milliseconds after I pushed <submit> on my email. And I'd even consider 3 ( Three ) rods on the Y axis ( gantry ) as it' tends to flex x way.
      > >
      > > //danand
      > >
      > > On Mon, 15 Jul 2013 15:43:21 -0000
      > > micRo-cnc-owner@yahoogroups.com wrote:
      > >
      > > > I vote for using two rods, with the screw in the middle. This will minimize any leaning of the blocks holding the spindle rods as you move it back and forth.
      > > >
      > > > Rick
      > > >
      > > > --- In micRo-cnc@yahoogroups.com, Dan Andersson <dan@...> wrote:
      > > > >
      > > > >
      > > > >
      > > > > Hi All,
      > > > >
      > > > > As I'm looking to make me another micRO M2 or M3, one of the modifications
      > > > > I'm going to make is to swap the screw and linear bearing ( rod ) so I have the rod on the upper side.
      > > > > Doing so increases the horizontal accuracy as it prevents base plate bending. I might even use two rods for theXD axis. I have a home made 1" spindle that I can use with a DC brushless or with the standrd flex wire.
      > > > >
      > > > > I'm buying a 3D printer for Xmas ( reprao 2 tri colour ) so I'll print up spare parts as well as a new
      > > > > design.
      > > > >
      > > > > Mi micRO is still going strong btw!
      > > > >
      > > > > //Danand, M0DFI
      > > >
      > > >
      > >
    • Dan Andersson
      On Mon, 15 Jul 2013 15:00:51 -0400 (EDT) ... Yes. I haven t seen reasonably priced chrome-plated metric steel rod with a ball-bearing liner with better
      Message 2 of 25 , Jul 15, 2013
      • 0 Attachment
        On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
        Ipeerbhai <ipeerbhai@...> wrote:

        > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?

        Yes.


        I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
        with better accuracy than the LL solution.

        If you really(!) have a deep wallet, sure.

        //danand
      • Ipeerbhai
        Misumi s PSFJ20-600. Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4 -- so we ll call it 3/4 ). Tolerance spec to .03/300 ( probably the same
        Message 3 of 25 , Jul 15, 2013
        • 0 Attachment
          Misumi's PSFJ20-600.


          Hard chrome plated.  20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ).  Tolerance spec to .03/300 ( probably the same as the Al used by LL ).  $25.20 for 600mm ( or 2ft. ).

          Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping.  Get yourself a shipping account and FOB it...  Or call them and order by phone...






          -----Original Message-----
          From: Dan Andersson <dan@...>
          To: micRo-cnc <micRo-cnc@yahoogroups.com>
          Sent: Mon, Jul 15, 2013 12:52 pm
          Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

           
          On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
          Ipeerbhai <ipeerbhai@...> wrote:

          > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?

          Yes.

          I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
          with better accuracy than the LL solution.

          If you really(!) have a deep wallet, sure.

          //danand
        • Dan Andersson
          The ceramic coated Alu rods have Dia. Tol -0.0004 to -0.0012 . That is -0.010mm to -0.030mm. And dirt cheap! 20$ for 2 of 3/4 The screws - Travel accuracy
          Message 4 of 25 , Jul 15, 2013
          • 0 Attachment
            The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.

            And dirt cheap! 20$ for 2' of 3/4"

            The screws -

            Travel accuracy per foot is better than 0.009"

            And around 60$ for 6'


            ////

            Now take some time and compare this with the garbage you find on Ebay etc!

            I need to take a look at Misumi but your number is a decimal of for worse...


            Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.

            //Danand, M0DFI


            On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
            Ipeerbhai <ipeerbhai@...> wrote:

            > Misumi's PSFJ20-600.
            >
            >
            >
            >
            > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
            >
            >
            > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            > -----Original Message-----
            > From: Dan Andersson <dan@...>
            > To: micRo-cnc <micRo-cnc@yahoogroups.com>
            > Sent: Mon, Jul 15, 2013 12:52 pm
            > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
            >
            >
            >
            >
            >
            >
            > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
            > Ipeerbhai <ipeerbhai@...> wrote:
            >
            > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
            >
            > Yes.
            >
            > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
            > with better accuracy than the LL solution.
            >
            > If you really(!) have a deep wallet, sure.
            >
            > //danand
            >
            >
            >
            >
            >
            >
          • Dan Andersson
            Misumi does the rods but no alu ceramic coating. I don t like the dead weight of the steel rods. Accuarcy ok. Screws, looks like 380mm is max and I can t find
            Message 5 of 25 , Jul 15, 2013
            • 0 Attachment
              Misumi does the rods but no alu ceramic coating. I don't like the dead weight of the steel rods.
              Accuarcy ok.

              Screws, looks like 380mm is max and I can't find the accuracy that easy.,

              //danand


              On Mon, 15 Jul 2013 21:38:47 +0100
              Dan Andersson <dan@...> wrote:

              > The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.
              >
              > And dirt cheap! 20$ for 2' of 3/4"
              >
              > The screws -
              >
              > Travel accuracy per foot is better than 0.009"
              >
              > And around 60$ for 6'
              >
              >
              > ////
              >
              > Now take some time and compare this with the garbage you find on Ebay etc!
              >
              > I need to take a look at Misumi but your number is a decimal of for worse...
              >
              >
              > Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.
              >
              > //Danand, M0DFI
              >
              >
              > On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
              > Ipeerbhai <ipeerbhai@...> wrote:
              >
              > > Misumi's PSFJ20-600.
              > >
              > >
              > >
              > >
              > > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
              > >
              > >
              > > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
              > >
              > >
              > >
              > >
              > >
              > >
              > >
              > >
              > >
              > >
              > >
              > > -----Original Message-----
              > > From: Dan Andersson <dan@...>
              > > To: micRo-cnc <micRo-cnc@yahoogroups.com>
              > > Sent: Mon, Jul 15, 2013 12:52 pm
              > > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
              > >
              > >
              > >
              > >
              > >
              > >
              > > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
              > > Ipeerbhai <ipeerbhai@...> wrote:
              > >
              > > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
              > >
              > > Yes.
              > >
              > > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
              > > with better accuracy than the LL solution.
              > >
              > > If you really(!) have a deep wallet, sure.
              > >
              > > //danand
              > >
              > >
              > >
              > >
              > >
              > >
            • Ipeerbhai
              Yeah, I can t find the screw accuracy either. The ceramic coating is available for extra $ as a different part number -- but if you use a ceramic coating, no
              Message 6 of 25 , Jul 15, 2013
              • 0 Attachment
                Yeah, I can't find the screw accuracy either.

                The ceramic coating is available for extra $ as a different part number -- but if you use a ceramic coating, no more ball bearings, as the bearings would wear the surface ceramic quickly.   AFAIK, Chrome--plating is stronger than surface ceramic, and has better wear characteristics and temperature characteristics.  I don't think you can chrome-plate Aluminum, so they use ceramic instead.   Ball bearings are 5x less friction than plain bearings.  Of course, ball bearings can clog...

                The laws of physics says, "Al rod must have a diameter = 2 times diameter of steel rod for same flexural stiffness, or there must be 4 of them if the same size."  So, in theory, a 12mm steel rod is as strong as a 24mm Al one, or as four 12mm thick Al rods( exponential function -- thickness increases strength more than number.)  Here's the formula and measured constants for some common materials: http://en.wikipedia.org/wiki/Young's_modulus.  
                In theory, these steel rods would have to be replaced by 40mm thick Aluminum rods for the same flexural strength.

                So, a misumi rod with a metric rolling insert bearing should be:
                1. Stronger in flex -- a lot stronger.  Just replacing the rods in the existing micRo with these rods from Misumi( and ream to 20mm ) should increase stiffness considerably -- and at very low cost.
                2. roll much more smoothly.

                Downside -- rolling bearings can clog and can need oiling from time to time..

                I saw that LL had originally used chrome-plated steel supported rods in an earlier versions of the machine, then switched to Al/machined HDPE motion system.  I can't figure out why, and I'm trying to figure out what they learned before they made the switch.  Was it just the cost( they used supported steel rails -- pricey, even from China, and often with months of delay time to get... ), or was there a technical reason?


                I've been leaning towards dropping the ballscrew.  This conversation seems to have sealed the deal.  The ballscrew added so much cost, and I wasn't sure it would return in both accuracy and backlash as much as I hoped...  I'm still in the steel camp for now, but maybe a hybrid.  main ways of steel, secondary Al ones( much thinner ) to help stop any rotations...

                I have one design constraint I want to keep -- no hand-work.  If I need to tap something, it's out.  I have carpal tunnel, and turning things by hand weakens me for weeks...  So, if I use ACME rods, then I have to have matching nuts.  

                -----Original Message-----
                From: Dan Andersson <dan@...>
                To: micRo-cnc <micRo-cnc@yahoogroups.com>
                Sent: Mon, Jul 15, 2013 1:48 pm
                Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                 
                Misumi does the rods but no alu ceramic coating. I don't like the dead weight of the steel rods.
                Accuarcy ok.

                Screws, looks like 380mm is max and I can't find the accuracy that easy.,

                //danand

                On Mon, 15 Jul 2013 21:38:47 +0100
                Dan Andersson <dan@...> wrote:

                > The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.
                >
                > And dirt cheap! 20$ for 2' of 3/4"
                >
                > The screws -
                >
                > Travel accuracy per foot is better than 0.009"
                >
                > And around 60$ for 6'
                >
                >
                > ////
                >
                > Now take some time and compare this with the garbage you find on Ebay etc!
                >
                > I need to take a look at Misumi but your number is a decimal of for worse...
                >
                >
                > Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.
                >
                > //Danand, M0DFI
                >
                >
                > On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
                > Ipeerbhai <ipeerbhai@...> wrote:
                >
                > > Misumi's PSFJ20-600.
                > >
                > >
                > >
                > >
                > > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
                > >
                > >
                > > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                > >
                > > -----Original Message-----
                > > From: Dan Andersson <dan@...>
                > > To: micRo-cnc <micRo-cnc@yahoogroups.com>
                > > Sent: Mon, Jul 15, 2013 12:52 pm
                > > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
                > >
                > >
                > >
                > >
                > >
                > >
                > > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
                > > Ipeerbhai <ipeerbhai@...> wrote:
                > >
                > > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
                > >
                > > Yes.
                > >
                > > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
                > > with better accuracy than the LL solution.
                > >
                > > If you really(!) have a deep wallet, sure.
                > >
                > > //danand
                > >
                > >
                > >
                > >
                > >
                > >
              • robin turner
                As far as straightness is concerned, it s a toss-up between aluminum rods and steel. The shiny chrome coating isn t hard-chrome BTW (hard chrome is typically
                Message 7 of 25 , Jul 15, 2013
                • 0 Attachment
                  As far as straightness is concerned, it's a toss-up between aluminum rods and steel.  The shiny chrome coating isn't hard-chrome BTW (hard chrome is typically gray)- though there are processes for putting chrome on aluminum, most need an intermediate plating- effectively doubling the tolerance and the price.  The ceramic coating put on aluminum is harder than chrome anyway AFAIK.  We moved away from supported ways because of quality issues- the supports are basically aluminum extrusion (imagine the spaghetti extruded in a playdoh factory, and you get the idea), and typically come minimally machined.  The bearings had similar issues.  The biggest was getting the slop out of the bearing without stripping the adjustment screw.  seriously annoying.  

                  Ballscrew and leadscrew are kind of a toss-up.  You'll sacrifice some accuracy with a ballscrew vs. leadscrew simply because there are a finite number of microsteps per revolution- but..  microstepping isn't known for its accuracy to begin with.  the tolerances of the screws themselves are typically something on the order of .005" (pulling this out of my ass) per 12" or so regardless of whether it's a acme lead or ballscrew.  

                  Ideas to improve the micRo:
                  thicker leadscrews 10 tpi: less resonance, faster speed
                  nema 23 motors, more power at higher speed
                  replace some HDPE parts with PET parts, less flex
                  switch out aluminum for steel ways, or use larger aluminum ways



                  On Mon, Jul 15, 2013 at 5:30 PM, Ipeerbhai <ipeerbhai@...> wrote:
                   

                  Yeah, I can't find the screw accuracy either.


                  The ceramic coating is available for extra $ as a different part number -- but if you use a ceramic coating, no more ball bearings, as the bearings would wear the surface ceramic quickly.   AFAIK, Chrome--plating is stronger than surface ceramic, and has better wear characteristics and temperature characteristics.  I don't think you can chrome-plate Aluminum, so they use ceramic instead.   Ball bearings are 5x less friction than plain bearings.  Of course, ball bearings can clog...

                  The laws of physics says, "Al rod must have a diameter = 2 times diameter of steel rod for same flexural stiffness, or there must be 4 of them if the same size."  So, in theory, a 12mm steel rod is as strong as a 24mm Al one, or as four 12mm thick Al rods( exponential function -- thickness increases strength more than number.)  Here's the formula and measured constants for some common materials: http://en.wikipedia.org/wiki/Young's_modulus.  
                  In theory, these steel rods would have to be replaced by 40mm thick Aluminum rods for the same flexural strength.

                  So, a misumi rod with a metric rolling insert bearing should be:
                  1. Stronger in flex -- a lot stronger.  Just replacing the rods in the existing micRo with these rods from Misumi( and ream to 20mm ) should increase stiffness considerably -- and at very low cost.
                  2. roll much more smoothly.

                  Downside -- rolling bearings can clog and can need oiling from time to time..

                  I saw that LL had originally used chrome-plated steel supported rods in an earlier versions of the machine, then switched to Al/machined HDPE motion system.  I can't figure out why, and I'm trying to figure out what they learned before they made the switch.  Was it just the cost( they used supported steel rails -- pricey, even from China, and often with months of delay time to get... ), or was there a technical reason?


                  I've been leaning towards dropping the ballscrew.  This conversation seems to have sealed the deal.  The ballscrew added so much cost, and I wasn't sure it would return in both accuracy and backlash as much as I hoped...  I'm still in the steel camp for now, but maybe a hybrid.  main ways of steel, secondary Al ones( much thinner ) to help stop any rotations...

                  I have one design constraint I want to keep -- no hand-work.  If I need to tap something, it's out.  I have carpal tunnel, and turning things by hand weakens me for weeks...  So, if I use ACME rods, then I have to have matching nuts.  

                  -----Original Message-----
                  From: Dan Andersson <dan@...>
                  To: micRo-cnc <micRo-cnc@yahoogroups.com>
                  Sent: Mon, Jul 15, 2013 1:48 pm
                  Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                   
                  Misumi does the rods but no alu ceramic coating. I don't like the dead weight of the steel rods.
                  Accuarcy ok.

                  Screws, looks like 380mm is max and I can't find the accuracy that easy.,

                  //danand

                  On Mon, 15 Jul 2013 21:38:47 +0100
                  Dan Andersson <dan@...> wrote:

                  > The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.
                  >
                  > And dirt cheap! 20$ for 2' of 3/4"
                  >
                  > The screws -
                  >
                  > Travel accuracy per foot is better than 0.009"
                  >
                  > And around 60$ for 6'
                  >
                  >
                  > ////
                  >
                  > Now take some time and compare this with the garbage you find on Ebay etc!
                  >
                  > I need to take a look at Misumi but your number is a decimal of for worse...
                  >
                  >
                  > Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.
                  >
                  > //Danand, M0DFI
                  >
                  >
                  > On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
                  > Ipeerbhai <ipeerbhai@...> wrote:
                  >
                  > > Misumi's PSFJ20-600.
                  > >
                  > >
                  > >
                  > >
                  > > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
                  > >
                  > >
                  > > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > > -----Original Message-----
                  > > From: Dan Andersson <dan@...>
                  > > To: micRo-cnc <micRo-cnc@yahoogroups.com>
                  > > Sent: Mon, Jul 15, 2013 12:52 pm
                  > > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  > > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
                  > > Ipeerbhai <ipeerbhai@...> wrote:
                  > >
                  > > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
                  > >
                  > > Yes.
                  > >
                  > > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
                  > > with better accuracy than the LL solution.
                  > >
                  > > If you really(!) have a deep wallet, sure.
                  > >
                  > > //danand
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >


                • Dan Andersson
                  On Mon, 15 Jul 2013 20:24:55 -0400 ... ( switch out aluminum for steel ways, or use larger aluminum ways ) Use larger ceramic coated aluminium ways High speed
                  Message 8 of 25 , Jul 15, 2013
                  • 0 Attachment
                    On Mon, 15 Jul 2013 20:24:55 -0400
                    robin turner <rohabeen@...> wrote:

                    > Ideas to improve the micRo:
                    > thicker leadscrews 10 tpi: less resonance, faster speed
                    > nema 23 motors, more power at higher speed
                    > replace some HDPE parts with PET parts, less flex

                    ( switch out aluminum for steel ways, or use larger aluminum ways )

                    Use larger ceramic coated aluminium ways
                    High speed ACME screws instead of standard ACME screws
                    Add an extra way for each X-way
                    Increase Z to 3"-4" ( allows for mounting of a 1" thick T-slot base extension )
                    A more rigid base. Granite or 1"+ Aluminium. Maybe 2" with T-slots.


                    Proper clamping is a problem. T-Slot seems to be given solution. Also, it doesn't matter what we do as long as the base flexes.

                    //Danand
                  • Ipeerbhai
                    Ahh -- that makes sense on why you moved away from the supported ways -- it was the supports that were the problem. Out of curiosity -- did you have any
                    Message 9 of 25 , Jul 19, 2013
                    • 0 Attachment
                      Ahh -- that makes sense on why you moved away from the supported ways -- it was the supports that were the problem. Out of curiosity -- did you have any trouble with the bearing carriages clogging up?  Supported rail has huge gaps for crap to enter and clog up the ball bearings, and I didn't see any Bellows or the like in those old prototypes.  How did you keep the bearings from clogging?



                      -----Original Message-----
                      From: robin turner <rohabeen@...>
                      To: micRo-cnc <micRo-cnc@yahoogroups.com>
                      Sent: Mon, Jul 15, 2013 5:24 pm
                      Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                       
                      As far as straightness is concerned, it's a toss-up between aluminum rods and steel.  The shiny chrome coating isn't hard-chrome BTW (hard chrome is typically gray)- though there are processes for putting chrome on aluminum, most need an intermediate plating- effectively doubling the tolerance and the price.  The ceramic coating put on aluminum is harder than chrome anyway AFAIK.  We moved away from supported ways because of quality issues- the supports are basically aluminum extrusion (imagine the spaghetti extruded in a playdoh factory, and you get the idea), and typically come minimally machined.  The bearings had similar issues.  The biggest was getting the slop out of the bearing without stripping the adjustment screw.  seriously annoying.  

                      Ballscrew and leadscrew are kind of a toss-up.  You'll sacrifice some accuracy with a ballscrew vs. leadscrew simply because there are a finite number of microsteps per revolution- but..  microstepping isn't known for its accuracy to begin with.  the tolerances of the screws themselves are typically something on the order of .005" (pulling this out of my ass) per 12" or so regardless of whether it's a acme lead or ballscrew.  

                      Ideas to improve the micRo:
                      thicker leadscrews 10 tpi: less resonance, faster speed
                      nema 23 motors, more power at higher speed
                      replace some HDPE parts with PET parts, less flex
                      switch out aluminum for steel ways, or use larger aluminum ways



                      On Mon, Jul 15, 2013 at 5:30 PM, Ipeerbhai <ipeerbhai@...> wrote:
                       
                      Yeah, I can't find the screw accuracy either.

                      The ceramic coating is available for extra $ as a different part number -- but if you use a ceramic coating, no more ball bearings, as the bearings would wear the surface ceramic quickly.   AFAIK, Chrome--plating is stronger than surface ceramic, and has better wear characteristics and temperature characteristics.  I don't think you can chrome-plate Aluminum, so they use ceramic instead.   Ball bearings are 5x less friction than plain bearings.  Of course, ball bearings can clog...

                      The laws of physics says, "Al rod must have a diameter = 2 times diameter of steel rod for same flexural stiffness, or there must be 4 of them if the same size."  So, in theory, a 12mm steel rod is as strong as a 24mm Al one, or as four 12mm thick Al rods( exponential function -- thickness increases strength more than number.)  Here's the formula and measured constants for some common materials: http://en.wikipedia.org/wiki/Young's_modulus.  
                      In theory, these steel rods would have to be replaced by 40mm thick Aluminum rods for the same flexural strength.

                      So, a misumi rod with a metric rolling insert bearing should be:
                      1. Stronger in flex -- a lot stronger.  Just replacing the rods in the existing micRo with these rods from Misumi( and ream to 20mm ) should increase stiffness considerably -- and at very low cost.
                      2. roll much more smoothly.

                      Downside -- rolling bearings can clog and can need oiling from time to time..

                      I saw that LL had originally used chrome-plated steel supported rods in an earlier versions of the machine, then switched to Al/machined HDPE motion system.  I can't figure out why, and I'm trying to figure out what they learned before they made the switch.  Was it just the cost( they used supported steel rails -- pricey, even from China, and often with months of delay time to get... ), or was there a technical reason?


                      I've been leaning towards dropping the ballscrew.  This conversation seems to have sealed the deal.  The ballscrew added so much cost, and I wasn't sure it would return in both accuracy and backlash as much as I hoped...  I'm still in the steel camp for now, but maybe a hybrid.  main ways of steel, secondary Al ones( much thinner ) to help stop any rotations...

                      I have one design constraint I want to keep -- no hand-work.  If I need to tap something, it's out.  I have carpal tunnel, and turning things by hand weakens me for weeks...  So, if I use ACME rods, then I have to have matching nuts.  

                      -----Original Message-----
                      From: Dan Andersson <dan@...>
                      To: micRo-cnc <micRo-cnc@yahoogroups.com>
                      Sent: Mon, Jul 15, 2013 1:48 pm
                      Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                       
                      Misumi does the rods but no alu ceramic coating. I don't like the dead weight of the steel rods.
                      Accuarcy ok.

                      Screws, looks like 380mm is max and I can't find the accuracy that easy.,

                      //danand

                      On Mon, 15 Jul 2013 21:38:47 +0100
                      Dan Andersson <dan@...> wrote:

                      > The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.
                      >
                      > And dirt cheap! 20$ for 2' of 3/4"
                      >
                      > The screws -
                      >
                      > Travel accuracy per foot is better than 0.009"
                      >
                      > And around 60$ for 6'
                      >
                      >
                      > ////
                      >
                      > Now take some time and compare this with the garbage you find on Ebay etc!
                      >
                      > I need to take a look at Misumi but your number is a decimal of for worse...
                      >
                      >
                      > Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.
                      >
                      > //Danand, M0DFI
                      >
                      >
                      > On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
                      > Ipeerbhai <ipeerbhai@...> wrote:
                      >
                      > > Misumi's PSFJ20-600.
                      > >
                      > >
                      > >
                      > >
                      > > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
                      > >
                      > >
                      > > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > > -----Original Message-----
                      > > From: Dan Andersson <dan@...>
                      > > To: micRo-cnc <micRo-cnc@yahoogroups.com>
                      > > Sent: Mon, Jul 15, 2013 12:52 pm
                      > > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >
                      > > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
                      > > Ipeerbhai <ipeerbhai@...> wrote:
                      > >
                      > > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
                      > >
                      > > Yes.
                      > >
                      > > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
                      > > with better accuracy than the LL solution.
                      > >
                      > > If you really(!) have a deep wallet, sure.
                      > >
                      > > //danand
                      > >
                      > >
                      > >
                      > >
                      > >
                      > >

                    • robin turner
                      If I remember correctly, the bearings for the supported ways had way wipers, and I personally never had a problem with the bearings getting clogged. Having
                      Message 10 of 25 , Jul 19, 2013
                      • 0 Attachment
                        If I remember correctly, the bearings for the supported ways had way wipers, and I personally never had a problem with the bearings getting clogged.  Having said that, I wouldn't want to machine too much abrasive material with the early micros



                        On Fri, Jul 19, 2013 at 4:13 PM, Ipeerbhai <ipeerbhai@...> wrote:
                         

                        Ahh -- that makes sense on why you moved away from the supported ways -- it was the supports that were the problem. Out of curiosity -- did you have any trouble with the bearing carriages clogging up?  Supported rail has huge gaps for crap to enter and clog up the ball bearings, and I didn't see any Bellows or the like in those old prototypes.  How did you keep the bearings from clogging?



                        -----Original Message-----
                        From: robin turner <rohabeen@...>
                        To: micRo-cnc <micRo-cnc@yahoogroups.com>
                        Sent: Mon, Jul 15, 2013 5:24 pm
                        Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                         
                        As far as straightness is concerned, it's a toss-up between aluminum rods and steel.  The shiny chrome coating isn't hard-chrome BTW (hard chrome is typically gray)- though there are processes for putting chrome on aluminum, most need an intermediate plating- effectively doubling the tolerance and the price.  The ceramic coating put on aluminum is harder than chrome anyway AFAIK.  We moved away from supported ways because of quality issues- the supports are basically aluminum extrusion (imagine the spaghetti extruded in a playdoh factory, and you get the idea), and typically come minimally machined.  The bearings had similar issues.  The biggest was getting the slop out of the bearing without stripping the adjustment screw.  seriously annoying.  

                        Ballscrew and leadscrew are kind of a toss-up.  You'll sacrifice some accuracy with a ballscrew vs. leadscrew simply because there are a finite number of microsteps per revolution- but..  microstepping isn't known for its accuracy to begin with.  the tolerances of the screws themselves are typically something on the order of .005" (pulling this out of my ass) per 12" or so regardless of whether it's a acme lead or ballscrew.  

                        Ideas to improve the micRo:
                        thicker leadscrews 10 tpi: less resonance, faster speed
                        nema 23 motors, more power at higher speed
                        replace some HDPE parts with PET parts, less flex
                        switch out aluminum for steel ways, or use larger aluminum ways



                        On Mon, Jul 15, 2013 at 5:30 PM, Ipeerbhai <ipeerbhai@...> wrote:
                         
                        Yeah, I can't find the screw accuracy either.

                        The ceramic coating is available for extra $ as a different part number -- but if you use a ceramic coating, no more ball bearings, as the bearings would wear the surface ceramic quickly.   AFAIK, Chrome--plating is stronger than surface ceramic, and has better wear characteristics and temperature characteristics.  I don't think you can chrome-plate Aluminum, so they use ceramic instead.   Ball bearings are 5x less friction than plain bearings.  Of course, ball bearings can clog...

                        The laws of physics says, "Al rod must have a diameter = 2 times diameter of steel rod for same flexural stiffness, or there must be 4 of them if the same size."  So, in theory, a 12mm steel rod is as strong as a 24mm Al one, or as four 12mm thick Al rods( exponential function -- thickness increases strength more than number.)  Here's the formula and measured constants for some common materials: http://en.wikipedia.org/wiki/Young's_modulus.  
                        In theory, these steel rods would have to be replaced by 40mm thick Aluminum rods for the same flexural strength.

                        So, a misumi rod with a metric rolling insert bearing should be:
                        1. Stronger in flex -- a lot stronger.  Just replacing the rods in the existing micRo with these rods from Misumi( and ream to 20mm ) should increase stiffness considerably -- and at very low cost.
                        2. roll much more smoothly.

                        Downside -- rolling bearings can clog and can need oiling from time to time..

                        I saw that LL had originally used chrome-plated steel supported rods in an earlier versions of the machine, then switched to Al/machined HDPE motion system.  I can't figure out why, and I'm trying to figure out what they learned before they made the switch.  Was it just the cost( they used supported steel rails -- pricey, even from China, and often with months of delay time to get... ), or was there a technical reason?


                        I've been leaning towards dropping the ballscrew.  This conversation seems to have sealed the deal.  The ballscrew added so much cost, and I wasn't sure it would return in both accuracy and backlash as much as I hoped...  I'm still in the steel camp for now, but maybe a hybrid.  main ways of steel, secondary Al ones( much thinner ) to help stop any rotations...

                        I have one design constraint I want to keep -- no hand-work.  If I need to tap something, it's out.  I have carpal tunnel, and turning things by hand weakens me for weeks...  So, if I use ACME rods, then I have to have matching nuts.  

                        -----Original Message-----
                        From: Dan Andersson <dan@...>
                        To: micRo-cnc <micRo-cnc@yahoogroups.com>
                        Sent: Mon, Jul 15, 2013 1:48 pm
                        Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )

                         
                        Misumi does the rods but no alu ceramic coating. I don't like the dead weight of the steel rods.
                        Accuarcy ok.

                        Screws, looks like 380mm is max and I can't find the accuracy that easy.,

                        //danand

                        On Mon, 15 Jul 2013 21:38:47 +0100
                        Dan Andersson <dan@...> wrote:

                        > The ceramic coated Alu rods have Dia. Tol -0.0004" to -0.0012". That is -0.010mm to -0.030mm.
                        >
                        > And dirt cheap! 20$ for 2' of 3/4"
                        >
                        > The screws -
                        >
                        > Travel accuracy per foot is better than 0.009"
                        >
                        > And around 60$ for 6'
                        >
                        >
                        > ////
                        >
                        > Now take some time and compare this with the garbage you find on Ebay etc!
                        >
                        > I need to take a look at Misumi but your number is a decimal of for worse...
                        >
                        >
                        > Buy American or German stuff. Swedish stuff is probably way to expensive for semi-pro hobby stuff.
                        >
                        > //Danand, M0DFI
                        >
                        >
                        > On Mon, 15 Jul 2013 16:11:06 -0400 (EDT)
                        > Ipeerbhai <ipeerbhai@...> wrote:
                        >
                        > > Misumi's PSFJ20-600.
                        > >
                        > >
                        > >
                        > >
                        > > Hard chrome plated. 20mm thick ( aka 0.8mm thicker than 3/4" -- so we'll call it 3/4" ). Tolerance spec to .03/300 ( probably the same as the Al used by LL ). $25.20 for 600mm ( or 2ft. ).
                        > >
                        > >
                        > > Misumi has a nasty habit of overnighting everything via Fedex, even if you select UPS ground shipping. Get yourself a shipping account and FOB it... Or call them and order by phone...
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > -----Original Message-----
                        > > From: Dan Andersson <dan@...>
                        > > To: micRo-cnc <micRo-cnc@yahoogroups.com>
                        > > Sent: Mon, Jul 15, 2013 12:52 pm
                        > > Subject: Re: [micRo-cnc] Re: Mods to the M3 ( and M2 )
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >
                        > > On Mon, 15 Jul 2013 15:00:51 -0400 (EDT)
                        > > Ipeerbhai <ipeerbhai@...> wrote:
                        > >
                        > > > Do you think milled HDPE blocks inserted as a liner into a printed part with an Al/Ceramic bearing would yield better tolerances than a chrome-plated metric steel rod with a ball-bearing liner inserted into the same printed part?
                        > >
                        > > Yes.
                        > >
                        > > I haven't seen reasonably priced "chrome-plated metric steel rod with a ball-bearing liner"
                        > > with better accuracy than the LL solution.
                        > >
                        > > If you really(!) have a deep wallet, sure.
                        > >
                        > > //danand
                        > >
                        > >
                        > >
                        > >
                        > >
                        > >


                      Your message has been successfully submitted and would be delivered to recipients shortly.