Posted Tue Aug 9, 2005, 8:22am Subject: Cimbali Grinder help needed, Pt II
As posted earlier, I purchased a "lightly used" Cimbali grinder on EBay. It showed up grungy and smelling of flavored coffee. I thoroughly cleaned the unit. While cleaning, I removed the burrs, upper and lower, and the carriers. I took great care during reassembly to make sure the burrs seat fully in their carriers. During reassembly I ran the upper carrier down until it just touch the lower and then backed off (motor off). After cleaning and reassembly I fired it up and ran some coffee through it. The coffee came out very coarse, slightly finer than a drip grind. With the motor on, I zeroed the unit again, backed off a couple of ticks and ran some more coffee through it. Still too coarse. I tried this several times, even to the point of letting the metal just touch (zero point) and still came up with coarse grind. I have since doublechecked and triple-checked the burr assemblies and everything looks properly seated.
While checking and inspecting, I noticed that a small portion of the normally flat machined surface of the burrs show signs of metal on metal wear. The sides of the burrs have discoloration in that area as if they heated up during the metal/metal process. I have used a set of calipers to verify things are flat. The upper carrier assembly appears flat. The lower rotating assembly appears to be 0.014" lower at the discharge chute than the opposite side. Rotating the shaft does not move the dip which seems to imply the shaft is straight but not square to the cast housing. If the house is not square to the shaft then the upper burr (threaded into the housing) will not mate properly to the bottom burr.
Questions:
Is 0.014" enough to be my problem?
Does the housing alignment seem like the problem?
Any ideas on how to fix this alignment?
It appears that the casting which sits atop the motor is held to the lower motor assembly via 4 long bolts pulling on a casting at the bottom of the motor. Is it possible the alignment can be altered by tightening one or two of the bolts or loosening the other two?
Any ideas are greatly appreciated. My feeling is that the seller won't refund the money since I have been inside it although I think it was defective to start with.
Posted Tue Aug 9, 2005, 9:01am Subject: Re: Cimbali Grinder help needed, Pt II
not completely. I used an Urnex solution on metal components and soapy water on plastic components. That made the components look and feel better but they still had a smell. I then used a diluted water/vinegar solution and soaked some of the platic bits in it. That helped a lot without adding a vinegary smell.
While it's not gone completely, it's much better. It certainly makes you wonder what kind of restaurant would have a Cimbali espresso grinder to grind flavored coffees.
If I get this grinding problem fixed, I may do another vinegar treatment; otherwise, anyone interested in a phenomenal grinder for flavored drip? (that's a joke son, that's a joke)
Posted Tue Aug 9, 2005, 9:40am Subject: Re: Cimbali Grinder help needed, Pt II
Jolly Joker!...quote Sgt Schultz... I imagine, once you/ve ironed out the grind problem, lots of ground coffee through your Jr will alleviate the flavored thing....hopefully.,...good luck
gscace Senior Member Joined: 19 Dec 2001 Posts: 237 Location: Laytonsville, MD USA Expertise: I live coffee
Espresso: La Marzocco Linea 2AV, Astra... Grinder: 3 Mazzers Robur, Kony,... Vac Pot: Cona D, Hario Nouveau Drip: Technivorm Roaster: Has Garanti 1kg. electric
Posted Wed Aug 10, 2005, 8:03am Subject: Re: Cimbali Grinder help needed, Pt II
sru_tx Said:
As posted earlier, I purchased a "lightly used" Cimbali grinder on EBay. It showed up grungy and smelling of flavored coffee. I thoroughly cleaned the unit. While cleaning, I removed the burrs, upper and lower, and the carriers. I took great care during reassembly to make sure the burrs seat fully in their carriers. During reassembly I ran the upper carrier down until it just touch the lower and then backed off (motor off). After cleaning and reassembly I fired it up and ran some coffee through it. The coffee came out very coarse, slightly finer than a drip grind. With the motor on, I zeroed the unit again, backed off a couple of ticks and ran some more coffee through it. Still too coarse. I tried this several times, even to the point of letting the metal just touch (zero point) and still came up with coarse grind. I have since doublechecked and triple-checked the burr assemblies and everything looks properly seated.
While checking and inspecting, I noticed that a small portion of the normally flat machined surface of the burrs show signs of metal on metal wear. The sides of the burrs have discoloration in that area as if they heated up during the metal/metal process. I have used a set of calipers to verify things are flat. The upper carrier assembly appears flat. The lower rotating assembly appears to be 0.014" lower at the discharge chute than the opposite side. Rotating the shaft does not move the dip which seems to imply the shaft is straight but not square to the cast housing. If the house is not square to the shaft then the upper burr (threaded into the housing) will not mate properly to the bottom burr.
Questions: Is 0.014" enough to be my problem? Does the housing alignment seem like the problem? Any ideas on how to fix this alignment?
It appears that the casting which sits atop the motor is held to the lower motor assembly via 4 long bolts pulling on a casting at the bottom of the motor. Is it possible the alignment can be altered by tightening one or two of the bolts or loosening the other two?
Any ideas are greatly appreciated. My feeling is that the seller won't refund the money since I have been inside it although I think it was defective to start with.
The important dimensional relationships are the degree of parallelism between the two grinding burrs. This may or may not be detectable with a calipers, depending on how you referenced your measurement. WRT the .o14 number that you mention, this is poor alignment, but may not be an accurate figure. Ways to determine an accurate figure are:
Coat one burr (on the flat surface only) with a thin layer of "Prussian Blue" machinist dye, which is used to determine contact between two surfaces in hard to measure areas. The dye does not dry out and transfers from one surface to another in areas of contact. Turn the burr carrier down until both burrs touch. Then remove the top burr and look for dye transfer. If the previously uncoated burr is marked uniformly on its circumference then the burrs are parallel. If it is marked in only one place then the burrs are not parallel.
If the burrs are not parallel, you can check the misalignment as follows: Wipe a light film of oil on both burr sets and apply a dot of colored RTV (silicone sealant) at positions 3:00, 9:00, 6:00,and 12:00 on the rotating burr that's on the motor shaft. Screw down the burr carrier until the burrs touch. Let the RTV harden and then remove the burr carrier. The relative thicknesses of the squashed RTV dots will give you the degree of misaligment of the two burrs.
Misalignment of the lower burr may not be due to housing machining errors. I own a Cimbali Jr. grinder - the second one that I purchased. I returned the first one after I discovered that the rotating burr was mounted on a defective carrier. In the case of this grinder, the rotating burr rotated eccentrically and the amount of eccentricity was enough that the grinder shook when starting up and winding down. It's possible that there are other grinders out there with defective carriers. You can check the level of eccentricity with a dial indicator if you have access to one. Or you can drag it to your local machine shop and have them do the measurements for you. Grinding burrs may not be parallel if the burr was mounted to a dirty carrier. You might remove the rotating burr and check the bronze carrier on the motor shaft for runout and parallelism. A dial indicator is needed for this as well.
Once you have the burrs demounted from the carriers you can check the thickness of the burrs at various places around the circumference to see if they were actually ground flat. The thickness should not vary. It's certainly possible that you have a bad burrset.
If your measurements show that the motor shaft is not perpendicular to the stationary burr, you will not be able to correct this by loosening a couple of the mounting bolts for the motor. You may have luck installing shimstock between the motor mounting faces and the screws, but this is a job for a person with a dial indicator, some patience and some skill in machinery. Unfortunately you're gonna be pretty much stuck with an ugly piece of artwork if that ain't you.
Posted Wed Aug 10, 2005, 10:27am Subject: Re: Cimbali Grinder help needed, Pt II
Thanks Greg for the advice. I agree with what you said, particularly the parallelism. It is very difficult to find a reference in which you can make all of these measurements from. Trying to measure distances from a cast surface to a machined surface is not very accurate or repeatable. Since my last posting I've done more measurements and investigation.
In reference to parallelism and using machinist dye and/or RTV to detect the problem I can add the following info:
The burrs are uniform thickness.
I directed a bright light down the throat of the grinder with the burrs zeroed/touching and could see a sizeable gap, on the order of 15-25 mil?, when looking up the discharge chute from the doser (you can see the light). Rotating the shaft by hand showed that the gap never closed, i.e., the burrs touching while in front of the chute. The burrs are touching on the side opposite the discharge chute. I see no point in using machinists dye when it's this far out of alignment/parallel.
By loosening the buttom carrier's mounting bolt to the motorshaft, allowing it float, it is possible to bring the pieces into parallel. The visible light gap disappears.
I used 8-mil cardstock (think subscription pullouts in a magazine) as a feeler gauge. I zeroed the grinder with the motor off and snaked a 1cm wide strip through the throat of the grinder and between the burrs. I noted where I could and could not place the stock. I rotated the shaft and noted that the area of interference did not move with respect to the housing. That seems to indicate the bottom carrier is not grotesqely out of true with respect to the shaft (or that the shaft is bent)which further confirms #2 above.
I removed the upper carrier, rotated the burr 120 degrees and remounted the burr. I reinstalled the assembly and found that the location of burrs touching did not move. This seems to remove the upper burr from the equation and points toward the carrier or the housing.
I believe there are several misalignments in the system. What I'm observing above are the gross misalignments. I believe there is still some slight wobble in the bottom carrier because the zero point changes slightly depending on the orientation of the shaft (0, 90, 180, 270 degrees).
Questions: How long does it take for the Cimbali grinder to spin down once power is turned off? This unit stops turning within a couple of seconds. My impression from reviews is that it should take quite a while. If this unit has a problem with the shaft alignment, there may be some binding which is causing it to spin down much faster.
It appears that the lower carrier rests on top of the sealed bearing. What if the bearing is not fully seated? The circlip is in place but perhaps it is slightly off square.
OK. OK. I realize this is becoming a long response, as was my opening post, but I was hoping I might have missed something really simple in the alignment. I've taken my Rocky apart many times and have never had a problem with it. I'm not mechanically inept.
I'm trying to negotiate returning the unit to the seller. It sounds like there's nothing I could have done that would make this happen while disassembling and cleaning it. If I can't return it, I'll look into checking runout etc. and think about shimming (ugh).
Please let me know approximately how long it take a Cimbali to spin down after turning power off.
BTW, Frescard, thanks for the input, but I know that burrs have a machined flat surface on them. The uniform machined surface is gouged in the interference area (no longer uniform machining marks).
gscace Senior Member Joined: 19 Dec 2001 Posts: 237 Location: Laytonsville, MD USA Expertise: I live coffee
Espresso: La Marzocco Linea 2AV, Astra... Grinder: 3 Mazzers Robur, Kony,... Vac Pot: Cona D, Hario Nouveau Drip: Technivorm Roaster: Has Garanti 1kg. electric
Posted Wed Aug 10, 2005, 12:47pm Subject: Re: Cimbali Grinder help needed, Pt II
sru_tx Said:
Thanks Greg for the advice. I agree with what you said, particularly the parallelism. It is very difficult to find a reference in which you can make all of these measurements from. Trying to measure distances from a cast surface to a machined surface is not very accurate or repeatable. Since my last posting I've done more measurements and investigation.
In reference to parallelism and using machinist dye and/or RTV to detect the problem I can add the following info: The burrs are uniform thickness. I directed a bright light down the throat of the grinder with the burrs zeroed/touching and could see a sizeable gap, on the order of 15-25 mil?, when looking up the discharge chute from the doser (you can see the light). Rotating the shaft by hand showed that the gap never closed, i.e., the burrs touching while in front of the chute. The burrs are touching on the side opposite the discharge chute. I see no point in using machinists dye when it's this far out of alignment/parallel.
By loosening the buttom carrier's mounting bolt to the motorshaft, allowing it float, it is possible to bring the pieces into parallel. The visible light gap disappears.
I used 8-mil cardstock (think subscription pullouts in a magazine) as a feeler gauge. I zeroed the grinder with the motor off and snaked a 1cm wide strip through the throat of the grinder and between the burrs. I noted where I could and could not place the stock. I rotated the shaft and noted that the area of interference did not move with respect to the housing. That seems to indicate the bottom carrier is not grotesqely out of true with respect to the shaft (or that the shaft is bent)which further confirms #2 above.
I removed the upper carrier, rotated the burr 120 degrees and remounted the burr. I reinstalled the assembly and found that the location of burrs touching did not move. This seems to remove the upper burr from the equation and points toward the carrier or the housing.
I believe there are several misalignments in the system. What I'm observing above are the gross misalignments. I believe there is still some slight wobble in the bottom carrier because the zero point changes slightly depending on the orientation of the shaft (0, 90, 180, 270 degrees).
Questions: How long does it take for the Cimbali grinder to spin down once power is turned off? This unit stops turning within a couple of seconds. My impression from reviews is that it should take quite a while. If this unit has a problem with the shaft alignment, there may be some binding which is causing it to spin down much faster.
I'm trying to negotiate returning the unit to the seller. It sounds like there's nothing I could have done that would make this happen while disassembling and cleaning it. If I can't return it, I'll look into checking runout etc. and think about shimming (ugh).
Please let me know approximately how long it take a Cimbali to spin down after turning power off.
Well it sure sounds like the motor ain't aligned with the stationary burr worth a ratsass doesn't it? It also sounds like there's a little runout in the bottom carrier as well, which doesn't surprise me. You shoulda heard the bullshit that the Cimbali rep tried to spew regarding the desireability of that runout when I returned my first grinder. Anyhoo you have to expect a little because it's tough to guarantee orthogonal surfaces unless you can machine the two surfaces in a lathe in one setup and unless you finish bore the center hole rather than drill and ream (drills tend to walk off of centers and reamers always follow drilled holes). I suspect the supplier of the carriers did a shitty job and the grinder manufacturer chose to accept lousy parts rather than fight with the supplier and let delivery schedules slip (meaning less money for the grinder mfr.). To be fair, absolute orthogonal surfaces are probably not that important and a couple of thousandths of runout are just fine. My Cimbali grinder does a wonderul job and its got a couple thousandths runout in the rotating burr carrier (I measured it).
WRT the motor alignment, sounds like you're capable of dealing with machinery in a way that produces desired results. Since you've demonstrated that the motor needs shimming then by all means shim it. You'll end up with a "blueprinted grinder that prolly kicks the ass of a lot of grinders out there. Tain't nuthin magical. It's just a machine.
Then again there's something that just sticks in yer craw about lame jerks selling garbage on ebay. They oughtta bring back public flogging.
gscace Senior Member Joined: 19 Dec 2001 Posts: 237 Location: Laytonsville, MD USA Expertise: I live coffee
Espresso: La Marzocco Linea 2AV, Astra... Grinder: 3 Mazzers Robur, Kony,... Vac Pot: Cona D, Hario Nouveau Drip: Technivorm Roaster: Has Garanti 1kg. electric
Posted Wed Aug 10, 2005, 12:50pm Subject: Re: Cimbali Grinder help needed, Pt II
Oh yeah, I forgot to tell you, if my grinder is empty it takes about 10 secs or so to spin down. There's a lot of inertia in the motor. However If the hopper has beans in it, then it stops very quickly - almost instantaneously.
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