Shouldn't print heads clogs be "backflushed"?

[turbguy]

Rather than trying to force dried/foreign material through the nozzles, wouldn't it make make better sense to flush them out toward inlet screen instead?

Wayne

 

[ghwellsjr]

I agree. And sucking on an inlet port on the top of a print head has the advantage that you cannot exceed 14.7 psi. If you use a syringe or some other type of mechanical device to force a cleaning solution into a port, you can easily generate pressures so high that they can damage the internal seals inside the printer. That's why I'm suggesting that you don't use a mechanical device but instead use your mouth to suck on a piece of tubing that fits over the inlet port (after you remove the rubber seal). You want the bottom of the print head to be embedded in a shallow solution of Windex or other cleaning solution and a long enough piece of tubing that you don't get any in your mouth. Turn the print head and tubing upside down to drain out the solution in the tubing.

 

[guyg]

I don't quite follow how you figure 14.7 psi. You would be applying a vacuum to the filter basically, and vacuum can be a very powerful force. A vessel may hold 150 psi but will crumple like a tin can under vacuum. Are you thinking if to much vacuum is applied it would suck down air thru the solution instead, thus only atmospheric pressure? Has any one used a vacuum pump to do this? Although with a bad clog I could see vacuum easily doing damage if the head is not designed for it, which I don't think it is. Any thoughts ?

 

[ghwellsjr]

14.7 psi is the nominal atmospheric air pressure. A perfect vacuum is merely the difference between atmospheric pressure and zero psi. You can't go any lower than a perfect vacuum.

You can easily create a perfect vacuum starting with the plunger of a syringe all the way in, placing your thumb over the end of the syringe (no needle, of course) and pulling on the plunger as far as you want. The cross sectional area of your syringe is probably a quarter of a square inch which means it only takes less than four pounds of force to pull the plunger. The vacuum cannot overcome your ability to pull on that plunger.

Now try it the other way. Start with the plunger extended, plug up the outlet and try to push the plunger all the way in. Can't do it, can you? That's because the more you push, the higher the pressure is inside the syringe and there's no upper limit. If you ever got it all the way in, it would be an infinite pressure.

A vessel designed to withstand pressure may not be able to withstand a vacuum.

I'm not sure what you are asking about with regard to sucking down air thru a solution. I was talking about sucking up a cleaning solution through the nozzles into the print head and out the inlet port. If you use a syringe to do this (like I did once) by pulling on the plunger and you also apply positive pressure (like I also did) by pushing on the plunger, you can probably create over a hundred psi in a very small volume which can easily break through the seals that channel the different colored ink to their respective locations. I'm warning against using a syringe because even if you only mean to create a vacuum, it will be very difficult to avoid also creating a positive pressure. I you do it with your mouth, you will have better control to only create a vacuum.

 

[ThrillaMozilla]

GHWells is right. Maximum vacuum is 14.7 psi (and you'll never get even close to that). With pressure from a syringe you can probably get much higher.