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  • Cimbali Junior cleanup & a few questions

    Hello CSers

    My very kind cousin gave me a Cimbali Junior grinder, and I gave it a bit of strip and cleanup, mainly to clean it up and secondly because I enjoy a tinker and DIY!! 

    It was quite straight forward to strip, but geez the edges of the panels are like razor blades.

    These are the top and bottom burrs and the carriers prior to clean up (is that the right term for the brass bits?)





    Overall view of naked machine:


    The top carrier, view from the top:


    The bottom of the doser, the spring for the counter was broken, so it doesnt count anymore.  Not a major drama, I would never use it anyway:


    The dosing unit all cleaned up:

    This is a pic of the bottom carrier, lots of stuff stuck top and bottom:




    And it also had these casting burrs, which I filed off:


    All cleaned up after a good soaking in caffetto:


    Cleaned burrs and carriers:




    Assembled bottom burr:


    This thing is build like a tank, and almost weighs as much.  It was made in 1995 and still seems very decent. 

    Its very different to the built in grinder in my Nemox Cafe Del Opera, and I only used it today to try out on the Faema E98 A1 that I just got going (link to my slow fix it up of the Faema if you are interested: http://coffeesnobs.com.au/YaBB.pl?num=1303139144).

    I have a couple of queries that hopefully someone can help with.

    How can I assess if the burrs are still serviceable?  The edges are still fairly sharp but I have nothing to compare to, so am not sure how sharp brand new ones are.

    The grind can be set finer until the burrs clash, is this normal or should there be a stopper somewhere on the machine?

    I have only just started playing with it, and have never used a grinder of this calibre, but it seems strange that the espresso grind is only 3 numbers or so (on the dial) higher than the absolute minimum setting where the burrs start to touch.  Is this "normal"?

    As I ground finer for the shots to stop gushing, the grounds started to clump quite a bit, is there anything that can be done to avoid this?

    Has anyone modded this grinder to be doserless?

    I also noticed that the bottom burrs are slightly out of level and not properly centric.  When I spin the shaft, The but height varies less than about half a mm from lowest to highest point (hard to tell exactly, but its not fully flat), and I could not get the burrs to mount on the carrier so they were properly centric, its out by a mm or so.  Is this something to be concerned about?

    There is a fair bit of beans etc that get stuck in the top burr carrier above the burrs, I will fit a smaller diameter sleeve in there to try and prevent this, as I only do between 2 and 4 coffees a day, and would prefer to minimise how much stuff stays there.  I found an article on how to do this using a PVC pipe fitting.

    Cheers and thanks


  • #2
    Re: Cimbali Junior cleanup & a few questions

    I did the mod on the grinder today, to reduce the amount of beans sitting around inside the top burr carrier.

    I purchased a PVC pipe fitting from Bunnings, its a 40mm DWV fitting:


    Then I cut it down in length, by cutting off the threaded section and sanding smooth:


    I should have left around 5mm of the threaded portion as it would have sat better against the hopper throat, without a gap.  This height would depend on what setting you use to grind, and the burr carrier obviously moves up and down.

    I filed in 3 locations a bit of the outside wall, to enable this bit of PVC to squeeze in between the 3 protrusions of the burr carrier where the burr screws into:


    The PVC piece sits on top of the burr, in between the 3 protrusions, and is a tight fit, it doesnt move:


    I also had to sand off the corners of the hex, so the worm drive/number disc could be fitted.  Here is the completed setup:


    Now no stray beans remain in the mechanism.

    As I grind finer, the grinds start to accumulate in the throat between the burrs and doser, instead of shooting out into the doser as happens on coarser grinds.  This means that a heap of grind remain in the throat getting stale that cant be easily removed.  Is this normal for this grinder to do that?

    Cheers




    Comment


    • #3
      Re: Cimbali Junior cleanup & a few questions

      I also noticed that the bottom burrs are slightly out of level and not properly centric.  When I spin the shaft, The but height varies less than about half a mm from lowest to highest point (hard to tell exactly, but its not fully flat), and I could not get the burrs to mount on the carrier so they were properly centric, its out by a mm or so.  Is this something to be concerned about?
      No mate, this NOT normal....

      When you consider that grinders designed for espresso use are intended to consistently produce grinds that are within a narrow "micron" range of sizes, runouts, eccentricities and wobbles measured in the millimetre range will render a grinder useless for this purpose.

      Have you run a dial gauge on all of the axes as yet to determine just exactly what is going on? The motor shaft at the drive end may be bent, or the drive end bearing may be excessively worn for example. Vertical movement could be down to an irregular upper surface on the rotating burr carrier, preventing the lower burr from being fixed in a perfectly flat plane.

      Sometimes this can be down to contamination of the mating surface(s) which can be rectified by thorough cleaning, and sometimes it can be down to actual damage of the burr-carrier surface due to some form of impingement. If it is the latter, then this can only be rectified by removing metal from the high spot(s) and refitting the burr, until you are satisfied that it is sitting perfectly flat.

      Of course, all of the problems could be down to motor shaft or bearing issues and you will need to isolate these as a cause before expending any effort on possible burr carrier issues.

      Hope some of this is helpful mate....

      Mal.

      Comment


      • #4
        Re: Cimbali Junior cleanup & a few questions

        Yes, it is normal for espresso grind to be close to burrs touching. Proper espresso grind is quite fine.

        No, as Mal says, wobbles or eccentricities are not normal.

        Good luck finding the issue--and nice work so far.

        Greg

        Comment


        • #5
          Re: Cimbali Junior cleanup & a few questions

          Thanks for the info guys, I need to get hold of a dial gauge to measure things properly, but did some investigating in the meantime which revealed what looks like the cause of the problem (out of level at least).

          It seems the bottom burr carrier was resting on the "drive" pin, and not on the bottom of the shaft/inner bearing surface, hence it doesnt bottom out when tightened and is out of level as the drive pin skews it. drilled the recess for the drive pin in the burr carrier slightly deeper, and when I installed the carrier/burr, it was almost completely level, a vast improvement in any case. I do want to check the actual magnitude of any out of level burrs with a dial gauge though, but it does look to be almost dead on and I would guess it would be an acceptable tolerance. Are there any specs in this regard?

          The bearings appear fine, I cant detect any radial play in the shaft at all.

          I checked the shaft at the top for side run out by , it looks quite spot on also.

          So this should solve the out of level issue. Everything has been thoroughly cleaned, and there doesnt appear to be any imperfections in the mating faces.

          In regard to the eccentricity, having another look at it, its out by about half a mm or less. What would be an acceptable tolerance on this? This will be hard to measure as there is no real way of getting a dial gauge in there. I wont be able to stick it into the chute as the vertical "sweepers" of the carrier get in the way.

          I tried swapping the bottom and top burrs around, to see if I could get the eccentricity reduced, but not much luck.

          Are the burrs supposed to be a "interference" fit in between the vertical "sweepers" of the bottom carrier, and the recess of the top carrier? Mine have a bit of room to move, the burrs measure 63.7mm diameter, the recess 64.1mm.

          As I tighten the bottom burr to the carrier, the tapered bottom of the hold down screws pull the burr slightly off centre, which would be contributing to the problem. If the burrs fitted snugly, this would be better and would help the issue.

          Any suggestions for checking the top burr eccentricity and level?

          Thanks for the help guys, it should be improved significantly now, but I would like to try and rectify it further if the above is still considered a bit out of whack. I will let you know how the shot goes tomorrow morning.

          Cheers


          Comment


          • #6
            Re: Cimbali Junior cleanup & a few questions

            Ok, got hold of a dial gauge and did some measurements.

            Bottom burr on the motor shaft:
            Out of level by 0.02mm measuring on the outside edge of the burr, which I would think is acceptable?
            Eccentricity of 0.35mm, I guess this would be excessive? Any input/comments?

            Not sure how I can reduce the eccentricity, I just cant seem to get the burrs screwed on any better.

            Comment


            • #7
              Re: Cimbali Junior cleanup & a few questions

              Originally posted by 2635332A2629470 link=1309103467/5#5 date=1309958820
              Bottom burr on the motor shaft: 
              Out of level by 0.02mm measuring on the outside edge of the burr, which I would think is acceptable?
              If this is a High Spot that moves in sync with every rotation, then I think it is too much at 20 Microns - Perhaps Den from Cuppacoffee could comment as he has access to a Particle Size Analysis system. Coffee particle size for espresso is quite important and usually fits within a size range from around 20-100 Microns and another peak at around 280 Microns. So this 20 Micron drift may play havoc with being able to produce consistently great espresso in the cup.

              Originally posted by 2635332A2629470 link=1309103467/5#5 date=1309958820
              Eccentricity of 0.35mm, I guess this would be excessive?  Any input/comments?
              As per above and given that the cutting plane of the burr-plates is slightly conical, this will no doubt add to a consistency of grind issue....

              Originally posted by 2635332A2629470 link=1309103467/5#5 date=1309958820
              Not sure how I can reduce the eccentricity, I just cant seem to get the burrs screwed on any better.
              Sounds like more measurements might help, with the lower burr-carrier removed and start on the motor shaft itself... :-?

              Mal.

              Comment


              • #8
                Re: Cimbali Junior cleanup & a few questions

                Thanks for the comments Mal

                Yes, the 0.02mm represents the difference between the low/high point of the burr as it rotates, due to it being out of level (not perpendicular to the axis of rotation).

                You are right, I need to pull things apart further (remove the doser again etc) to measure the shaft at the end where the carrier sits through the chute, but measuring it below the burrs (and above the motor windings), it was less that 0.01mm variance radially, probably a bit of corrosion on the shaft.

                I will measure the carrier level by itself also, to see how that compares.

                Are the burrs supposed to be an interference fit in the carriers?

                Maybe my burrs are cheap aftermarket, is there a way to tell them apart?

                Cheers

                Comment


                • #9
                  Re: Cimbali Junior cleanup & a few questions

                  Originally posted by 3C2F29303C335D0 link=1309103467/7#7 date=1309965737
                  Are the burrs supposed to be an interference fit in the carriers?
                  Not on grinders Ive worked on but from your photos above, it looks probable that the Junior uses this option.

                  I guess one way to find out is to measure the O.D. of your burr-plates and post the results up here for other Junior owners to comment on. I know "beanflying" has a couple of similar grinders...

                  Originally posted by 3C2F29303C335D0 link=1309103467/7#7 date=1309965737
                  Maybe my burrs are cheap aftermarket, is there a way to tell them apart?
                  Possibly... "bf" might be able to chime in with descriptions of his grinders burr-plates,

                  Mal.

                  Comment


                  • #10
                    Re: Cimbali Junior cleanup & a few questions

                    Thanks Mal, I mentioned the sizes in a prior post above:

                    Are the burrs supposed to be a "interference" fit in between the vertical "sweepers" of the bottom carrier, and the recess of the top carrier?  Mine have a bit of room to move, the burrs measure 63.7mm diameter, the recess 64.1mm.
                    So they are not quite an intrference fit.  I will do some more measurements tonight and post my findings.

                    Cheers

                    Comment


                    • #11
                      Re: Cimbali Junior cleanup & a few questions

                      Originally posted by 2D3E38212D224C0 link=1309103467/9#9 date=1310024454
                      Thanks Mal, I mentioned the sizes in a prior post above:
                      Sheesh.... Im going blind : :P

                      Hopefully "bf" or another experienced owner can shed some specific La Cimbali Junior light on this for you mate....

                      Mal.

                      Comment


                      • #12
                        Re: Cimbali Junior cleanup & a few questions

                        Took it apart (which is surprisingly easy btw) and more measurements:

                        The shaft at the end is out radially by 0.002 mm or so, and the top face of the inner race of the bearing (that the bottom burr carrier sits on) is dead level, which means the basis of it are all good.

                        I then installed the bottom burr carrier and it was out of level by 0.04mm, which double compared to with the burr installed. I am guessing the carrier is out of whack for some reason, and installing the relatively stiff burr brings it back into shape slightly?

                        The eccentricity is still there in the mounting face, but the holes for the burr screws are not centric to the outside mounting face, so perhaps the mounting holes are actually centric and the eccentricity of the mounting face is not important, as it doesnt effect the burrs (the mounting holes do). I am not sure how I can confirm the hole eccentricity? maybe insert the screw and do some measurements with callipers to the centre hole in the carrier?

                        Any ideas on how to check the top butt for level? I dont think its dead level, as if I set the grind fine enough so the burrs just touch and spin the shaft by hand, instead of the rub being constant, it comes and goes with each revolution, which would indicate the top burrs are not perfectly level.

                        Who is "bf" you are referring to? Maybe I could send him a PM and ask him if he could shed some light on some of my questions?

                        Has any one measured the levels/eccentricity of a reliable grinder? I am curious as to what they find. I would have never even guessed to measure the burrs if I didnt have the original issue of the burrs being so far out of alignment.

                        On another note, I have thought of a way of making the grinder doser-less which should be quite easy. Make another front panel out of aluminium plate and make a small chute for the outlet.

                        Cheers

                        Comment


                        • #13
                          Re: Cimbali Junior cleanup & a few questions

                          Originally posted by 0112140D010E600 link=1309103467/11#11 date=1310051533
                          Who is "bf" you are referring to?  Maybe I could send him a PM and ask him if he could shed some light on some of my questions?
                          CSer "beanflying"... His details are here mate... http://coffeesnobs.com.au/YaBB.pl?ac...46E7B6B6C65020

                          Mal.

                          Comment


                          • #14
                            Re: Cimbali Junior cleanup & a few questions

                            Thanks Mal, I sent him a PM.

                            Cheers

                            Comment


                            • #15
                              Re: Cimbali Junior cleanup & a few questions

                              Wow what a tome to read through. Going home to crack a beer and then have a proper read through

                              Initial suspicion is the brass sweeper assembly (the bit the lower burr attaches to) may be a touch bent. Best way I can think of to check this initially is feeler gauges in through the doser chamber. If this is bent the lower burr will not sit flat. The upper burr due to the bulk of the carrier is going to be correct.

                              back a bit later

                              Comment

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