Sunday, November 27, 2016

Odd PK to MK Swap Behavior

The purpose of this blog is to document weird, unusual, or comment-worthy happenings with my 7900. This fills all of those categories:

I've been very busy with client print work over the last two months, with a couple of breaks for travel. I've just wrapped up a printing job for a long-time client. I made two large (20 x 30 inches) prints on an old roll of the "original" Ilford GGFS. The rest of the job consisted of 24 small prints (six copies each of four different images) on Epson Enhanced Matte sheets. This required switching from PK to MK.

I don't often print on matte papers, but over the five years (!) I've owned the 7900, I'd guess I've done the Epson Ink Shuffle several dozen times. I should know what to expect.

MK showed 62%, PK showed 61%, LK 51%, and LLK 1%. I initiated the swap as usual. After ten to fifteen seconds the printer stopped making the usual noises and required a replacement ink. Assuming the offending cartridge was the LLK (recall that the printer doesn't tell you which of your low inks it's complaining about), I replaced that with a new cartridge. The machine thought about this for a few seconds and then raised the same "not enough ink to continue" message. I then swapped all remaining low inks just to get on with the job. Those were Y at 9%, and VLM at 1%. The printer then displayed "Cleaning".

That's new; I don't think I've ever experienced a cleaning prior to the ink swap. The printer did the usual thing, moving the head around, making the expected "I'm wasting ink" sounds, but this went on, and on, and on. I didn't time it, since I'd no reason to expect this behavior, but it seemed to take three to four times longer than the normal "standard cleaning" I might initiate manually to clear a clog. When it finally completed, the LCD displayed the progress bar normally shown for ink swaps. It seemed all was well.

But wait, there's more: when the swap completed, the machine once again displayed "Cleaning" on the LCD. And once again this took a very long time. When this finished the machine appeared to be ready to print. The waste tank showed a drop in free space from 27% to 21%. As you know if you've read my increasingly infrequent postings here, I keep pretty good records of my 7900's numbers. I looked back to the last time I did a PK to MK swap, and found the waste tank had dropped only 3%, and looking at older records confirmed this is typical. I also found that every ink took a larger than expected hit during those cleanings, clearly showing the machine pumped ink through all channels, not just the blacks.

It's normal for the machine to clean after an ink swap, but not before. The after-swap cleaning has always seemed typical in terms of time required. I've no idea why it behaved differently this time. Once the machine made itself ready, the printing went perfectly. I made 18 of the 24 prints. One day later I printed the last six. Most likely my next print job will require PK; I'll swap back to that when the need arises, and report here if it seems warranted.

  --Jay