SightLine
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So last night I got to thinking some after reading this older thread on Mimaki printers, bulk systems, and head starvation and it struck me that many have been thinking about how the ink train on these Mimaki machines works is somewhat flawed. This is also why many if not most of the bulk systems that have been made have it wrong. Now this is only specific to some Mimaki models as I do not have experience with other machines and how they do their thing as far as getting ink to the print head(s). Specifically this applies to pretty much all JV series machines. These machines are NOT specifically gravity based but rather slightly gravity based but more so pressure based. They are negative pressure based and from what I can figure they need to range from around zero to a slight negative amount of pressure in the ink train to function correctly. Changing the level of tanks and whatnot (changing the gravity force) can and will affect pressure in the system but that it going about it and compensating for incorrect pressure in the wrong way. Physical level does indeed play a very significant role but not as much as the ink train itself – it plays even less of a role on the newer ink train introduced with the JV33 and JV5 machines which use a solenoid controlled valving system behind the cartridge slots as the machine closes the valves when it is not actively pumping ink. Hence – if the valving system is in-tact you could set the tanks and cartridges 20 feet in the air and it’s still not going to flood the heads unless the valves are open. Gravity, atmospheric pressure, viscosity, temperatures, etc. all DO play a very significant role but in what I’m attempting to explain and for simplicity I’m leaving most of those factors out. Again – the physical height does play a role and cause both problematic negative pressures and overwhelming positive pressures but that’s not what I’m leading to.
Here is what is happening – the printhead needs ink so the pumps kick on while the head is on the capping station. This creates negative pressure (suction) in the ink train. This in turn causes negative pressure in the dampers. The dampers are called dampers for a reason, the flexible sides are not there just so you can see in them, that flexible membrane is specially designed to flex a specific amount to dampen the pressures in the ink train. On a side note – the DX5 head machines introduced a new style damper that instead has a spring loaded internal valve to serve the same dampening function but also adds the benefit of one-way flow control. As the damper takes the negative load from the pumps the membrane/valve dissipates the shock of the somewhat harder rapid negative pressure load from the peristaltic pumps and softly applies the negative pressure to the ink line which draws ink from the cartridges.
As most are aware standard ink cartridges have the ink contained in a bag inside. This ink bag has no pressure to it, it is under neither negative or positive pressure. What this does is as ink is draw from the bag the bag simply collapses as it empties – this creates no undue pressures on the ink system. This is why the ink cartridges have a physical plastic panel adhered to the ink bag that when the bad flattens to near empty this plastic panel sticks partially out of the cartridge triggering a micro switch in the cartridges slot to stop the machine from drawing any more ink from this ink bag. This has a couple of purposes – primarily to let the machine operator know they need to replace the cartridge but also just as importantly is to prevent the machine from creating a huge negative pressure situation which would happen if the bad were to be totally emptied. This is specifically why cartridges always have (depending on a few minor factors) anywhere from 10cc to as much as 100cc of ink left in the bad even though the cartridge said it was empty.
In the past most bulk systems did not account for this issue in any way. They simply put a bulk cartridge in the slot (feed by a tank) and then set it up so that the bulk cartridge is essentially sealed. Most though this is good – no contamination from dust etc. in the air. Not good. That bulk cartridge is rigid and if also sealed it cannot collapse like an ink bad in a regular cartridge can. As the printer tries to draw ink it struggles because of the rigid sealed cartridge. This is causing massive amounts of negative pressure. I think this is part of how leaks are eventually caused in o-rings, dampers, capping station tops, etc. The o-rings on the ink lines on these are tough buggers that can handle far more pressure than the ink train should even be capable of. Over time though the huge negative pressures can cause some of the softer ink lines to partially collapse, causes big deflection on the damper membranes/valves which wears these out very quickly. Of course the most visible and noticeable problem is nozzle dropouts from ink starvation. Other things such as premature wear on the pumps, etc. are also caused by this situation.
When the pumps create their negative pressure to draw ink they must not meet undue resistance. This can happen with multiple types of systems. Even those with floats to control the ink level in the cartridge. The ink system must overcome the resistance of the rigid cartridge until the ink drops enough to allow the float to open the valve. This allows a sudden release of the negative pressure buildup in the cartridge and things will print great again for a little while. The only solution is to either have the ink in a bag or with a rigid cartridge you have to allow the cartridge to replace the ink being drawn out with something else – either more ink or air and it must do so without causing any pressure effects on the system.
So far there have been few bulk systems designed to deal with this effectively. What you will see are most main stream aftermarket ink vendors are now introducing ink bag based bulk in systems. I know Triangle Inx introduced one (actually back in 2010) that uses 2L (nice!) bags but you rarely see or heard about that one and there is little to no information about it available online other than the actual ink bags and a photo or two of the stand that sits on top. Bordeaux also has a bag based bulk system now using 900ml bags (or 1L – I’ve seen both) and SolventCatridges/HP9000Inks also offer what appears to be the same design as what Bordeaux has. With much similar wording I’m thinking SolventCartridges is actually an OEM of Bordeaux… Even Mimaki’s own bulk system (MBIS) uses bags – actually Mimaki has 2 bulk systems – their main one which uses 2L bags and a rather obscure one that uses (I think) something like 600ml bags. As times goes on I think the most others will also be going to a bag design. The way they work is the bag actually fits in a plastic cartridges that then locks onto a stand letting the rubber nipple on the bag get pierced to allow the ink to flow. Pretty much just like the ink bags in standard 440ml/220ml cartridges. This eliminates all the problems with contamination and spills as a nice side benefit as well and also eliminates waste since plastic bottles and plastic cartridges do not have to be disposed of, just empty foil bags.
I have not seen any of the bag systems up close or firsthand though so I still do not know what they are doing at the cartridge slots to feel the ink to the system. In pictures of Mimaki’s MBIS there are obviously cartridges in the slots but my guess is they do not actually have any ink in them at all – the tubes from the bulk containers actually go right through the dummy cartridges directly to the slots ink nipple. The main purpose if the dummy cartridges actually being just to make contact with the chip readers….. I am planning on trying to make it down to Orlando for the ISA show though where I will be taking a close look at things.
Anyways hope someone might find this enlightening. Heck, I may even be way off base and totally wrong about my assumptions. Please say either way – if I’m wrong on something of I do want the correct information known. This is all just what I’ve pretty much come up with on my own as I’m suddenly exploring bulk ink systems for our JV33 and I don’t want to go with some problematic system. With the problems I posted about in another thread with defective cartridges I’ve decided we are done with cartridges. We have run bulk systems before with excellent results on our JV3 so it is time to go that route on the JV33 as well. Amazingly the bulk system I used on our older JV3 was a very obscure but fairly well designed system that actually used sealed ink bottles which were pushed onto a nipple much like a cartridge. I think AGFA or Fujifilm offered the same system for a time and only one other vendor in the US ever offered it that I’m aware of - Digital Rainbow (Micro-Ink) of California. It actually worked very well and their ink worked fine as well. PS - I still have that bulk system from our old JV3, if anyone is interested in buying it for cheap let me know…
Here is what is happening – the printhead needs ink so the pumps kick on while the head is on the capping station. This creates negative pressure (suction) in the ink train. This in turn causes negative pressure in the dampers. The dampers are called dampers for a reason, the flexible sides are not there just so you can see in them, that flexible membrane is specially designed to flex a specific amount to dampen the pressures in the ink train. On a side note – the DX5 head machines introduced a new style damper that instead has a spring loaded internal valve to serve the same dampening function but also adds the benefit of one-way flow control. As the damper takes the negative load from the pumps the membrane/valve dissipates the shock of the somewhat harder rapid negative pressure load from the peristaltic pumps and softly applies the negative pressure to the ink line which draws ink from the cartridges.
As most are aware standard ink cartridges have the ink contained in a bag inside. This ink bag has no pressure to it, it is under neither negative or positive pressure. What this does is as ink is draw from the bag the bag simply collapses as it empties – this creates no undue pressures on the ink system. This is why the ink cartridges have a physical plastic panel adhered to the ink bag that when the bad flattens to near empty this plastic panel sticks partially out of the cartridge triggering a micro switch in the cartridges slot to stop the machine from drawing any more ink from this ink bag. This has a couple of purposes – primarily to let the machine operator know they need to replace the cartridge but also just as importantly is to prevent the machine from creating a huge negative pressure situation which would happen if the bad were to be totally emptied. This is specifically why cartridges always have (depending on a few minor factors) anywhere from 10cc to as much as 100cc of ink left in the bad even though the cartridge said it was empty.
In the past most bulk systems did not account for this issue in any way. They simply put a bulk cartridge in the slot (feed by a tank) and then set it up so that the bulk cartridge is essentially sealed. Most though this is good – no contamination from dust etc. in the air. Not good. That bulk cartridge is rigid and if also sealed it cannot collapse like an ink bad in a regular cartridge can. As the printer tries to draw ink it struggles because of the rigid sealed cartridge. This is causing massive amounts of negative pressure. I think this is part of how leaks are eventually caused in o-rings, dampers, capping station tops, etc. The o-rings on the ink lines on these are tough buggers that can handle far more pressure than the ink train should even be capable of. Over time though the huge negative pressures can cause some of the softer ink lines to partially collapse, causes big deflection on the damper membranes/valves which wears these out very quickly. Of course the most visible and noticeable problem is nozzle dropouts from ink starvation. Other things such as premature wear on the pumps, etc. are also caused by this situation.
When the pumps create their negative pressure to draw ink they must not meet undue resistance. This can happen with multiple types of systems. Even those with floats to control the ink level in the cartridge. The ink system must overcome the resistance of the rigid cartridge until the ink drops enough to allow the float to open the valve. This allows a sudden release of the negative pressure buildup in the cartridge and things will print great again for a little while. The only solution is to either have the ink in a bag or with a rigid cartridge you have to allow the cartridge to replace the ink being drawn out with something else – either more ink or air and it must do so without causing any pressure effects on the system.
So far there have been few bulk systems designed to deal with this effectively. What you will see are most main stream aftermarket ink vendors are now introducing ink bag based bulk in systems. I know Triangle Inx introduced one (actually back in 2010) that uses 2L (nice!) bags but you rarely see or heard about that one and there is little to no information about it available online other than the actual ink bags and a photo or two of the stand that sits on top. Bordeaux also has a bag based bulk system now using 900ml bags (or 1L – I’ve seen both) and SolventCatridges/HP9000Inks also offer what appears to be the same design as what Bordeaux has. With much similar wording I’m thinking SolventCartridges is actually an OEM of Bordeaux… Even Mimaki’s own bulk system (MBIS) uses bags – actually Mimaki has 2 bulk systems – their main one which uses 2L bags and a rather obscure one that uses (I think) something like 600ml bags. As times goes on I think the most others will also be going to a bag design. The way they work is the bag actually fits in a plastic cartridges that then locks onto a stand letting the rubber nipple on the bag get pierced to allow the ink to flow. Pretty much just like the ink bags in standard 440ml/220ml cartridges. This eliminates all the problems with contamination and spills as a nice side benefit as well and also eliminates waste since plastic bottles and plastic cartridges do not have to be disposed of, just empty foil bags.
I have not seen any of the bag systems up close or firsthand though so I still do not know what they are doing at the cartridge slots to feel the ink to the system. In pictures of Mimaki’s MBIS there are obviously cartridges in the slots but my guess is they do not actually have any ink in them at all – the tubes from the bulk containers actually go right through the dummy cartridges directly to the slots ink nipple. The main purpose if the dummy cartridges actually being just to make contact with the chip readers….. I am planning on trying to make it down to Orlando for the ISA show though where I will be taking a close look at things.
Anyways hope someone might find this enlightening. Heck, I may even be way off base and totally wrong about my assumptions. Please say either way – if I’m wrong on something of I do want the correct information known. This is all just what I’ve pretty much come up with on my own as I’m suddenly exploring bulk ink systems for our JV33 and I don’t want to go with some problematic system. With the problems I posted about in another thread with defective cartridges I’ve decided we are done with cartridges. We have run bulk systems before with excellent results on our JV3 so it is time to go that route on the JV33 as well. Amazingly the bulk system I used on our older JV3 was a very obscure but fairly well designed system that actually used sealed ink bottles which were pushed onto a nipple much like a cartridge. I think AGFA or Fujifilm offered the same system for a time and only one other vendor in the US ever offered it that I’m aware of - Digital Rainbow (Micro-Ink) of California. It actually worked very well and their ink worked fine as well. PS - I still have that bulk system from our old JV3, if anyone is interested in buying it for cheap let me know…
