This was definitely not print shop volume

Post #438,679 by drook 3/14/21 12:05:24 AM 3/14/21 12:05:24 AM Reply	This was definitely not print shop volume This was in a college computer lab. Noobs like me didn't get to use the high speed printer. We rarely needed more than 2 or 3 pages at a time anyway, so we could wait. I would sometimes be in there for an hour or more and no one fired it up. But when they did it sounded angry. I'm pretty sure they had it behind a table so even if you were allowed to send jobs to it you still needed a staff member to pick up your output. -- Drew
Post #438,682 by crazy 3/14/21 8:55:10 AM 3/14/21 9:14:35 AM Reply	You were hearing the band spin I'm not sure if you can visualize what's happening here. At least not if you've never seen the band. The band is a strip of metal, circular, that is embossed with every letter of the alphabet and every character you want to print. It doesn't just have a single one for one mapping. Certain letters will be repeated at certain intervals such as the letter e because that is so common. The hammer has to hit the band at the exact moment the desired character appears before it. There is a hammer for every character position across the page. That spinning band of metal never slows down. The band gets placed on a track that allows it to spin in front of the paper and on the other side is the ribbon. The band spins really really fast. What you hear on startup is that band engaging and spinning up. Also everything I just described is really strong reason for print shop personnel to never wear loose fitting clothing or ties. There are so many bits and pieces of this one printer that could grab you and just drag you in. Edited by crazy March 14, 2021, 09:07:10 AM EDT Edited by crazy March 14, 2021, 09:14:35 AM EDT Expand All History
Post #438,684 by drook 3/14/21 10:19:54 AM 3/14/21 10:19:54 AM Reply	Hold on, mind blown The printers I got to use were dot matrix.I apparently never got a close look at the output from the high speed printer, but I always thought it was a dot matrix with a horizontal matrix of pins instead of vertical that moved back-and-forth. [google-fu ...] Okay, that would be called a line matrix printer. Based on the sound from the one video I could find where they were running one open, I'm guessing that's what I was seeing. I'd love to see a band printer up close-ish. Your description of it sounds like something that shouldn't possibly work as fast as the videos I've seen of it. -- Drew
Post #438,685 by crazy 3/14/21 12:51:51 PM 3/14/21 12:51:51 PM Reply	Yeah that was old technology that still blows me away No inkjet head. No spray of any sort. No laser. Incredibly fast mechanical things spinning around and having perfect timing. Seriously, band printers are mind-boggling in their mechanical technical perfection. This is practically steampunk. I would like to see the micro code that ran on those hammers and determined when to slam. It had to have some type of start on the band that sent a signal and then there had to be lookup tables and assumptions because there was nothing that was telling those hammer banks what was where, they had to figure it out themselves.
Post #438,688 by Another Scott 3/14/21 1:44:13 PM 3/14/21 1:44:13 PM Reply	Speaking of old mechanical tech... https://arstechnica.com/science/2021/03/scientists-solve-another-piece-of-the-puzzling-antikythera-mechanism/ ~ 125 BC Modern people still haven't figured out all the details of how it worked (like did it have a part made of concentric cylinders, and if so, how were they made before the lathe was invented?). Clever beasties. Cheers, Scott.
Post #438,692 by boxley 3/14/21 10:29:53 PM 3/14/21 10:29:53 PM Reply	The lathe is an ancient tool, dating at least to ancient Egypt and known and used in Assyria https://ravimachines.com/history-of-lathe-machine/ greece as well "Science is the belief in the ignorance of the experts" – Richard Feynman
Post #438,693 by static 3/15/21 12:11:40 AM 3/15/21 12:11:40 AM Reply	What happens when something mechanical gets scaled up. They took the whole printing idea and just made everything faster, sometimes by duplicating hardware (many more hammers), other times by increasing speed (paper feed). Some of the "scaling up" is obvious: a lot more metal in a drum or band than a simple print head, but the difference in cost would be negligible next to how much they could charge rental (or even sale) for being able to make it print so much faster. Far from the first time us humans have done this with technology. Modern gasoline engines can be insanely complicated, even before they got tiny computers everywhere. One of my favourite purely mechanical examples is Bosch's K-Jetronic fuel injection system, used by a wide range of performance engines in the 70s and 80s. Another example I love is helical scan videotape. Four head drums needed four rotary transformers between the two halves of the drum. And later prosumer VCRs had way more than four heads... Wade.
Post #438,694 by pwhysall 3/15/21 3:03:55 AM 3/15/21 3:03:55 AM Reply	Band printers were cool OTOH, they were invariably used to print your bills, so. So loud.
Post #438,686 by crazy 3/14/21 1:08:28 PM 3/14/21 1:08:28 PM Reply	Shouldn't possibly work as fast? That is what I've been trying to impress upon you. Didn't I say really really fast a post or 2 above? That band of metal is spinning around faster than you can see. But those hammer banks hit those letters at whatever moment as it spins by and chugs to the next line. That's the chugga chugga chugga noise going on. From the human perspective that line printer has just printed that entire line instantaneously and has progressed to the next line. But from the microcode level you know there's a hell of a dance going on.
Post #438,690 by drook 3/14/21 7:07:54 PM 3/14/21 7:07:54 PM Reply	Yes, but I was picturing the line matrix Still impressive, but not nearly as frightening. -- Drew
Post #438,695 by crazy 3/15/21 6:32:10 AM 3/15/21 6:32:10 AM Reply	Line matrix is easy Line of data shows up into buffer. Map those points to pins that you're going to slam. Slam the pins. This is a simple bitmap manipulation. Move to next line. That is the simplest s* in the world. Nothing impressive about it. I could code that in 20 minutes. Compare that to having to figure out where those spinning band characters are versus what you are attempting to print and hit the hammers at the exact moment individually while those particular characters are spinning by. That s*'s mind-boggling. I'd have to take into account synchronization with the band. Then I'd have to know when a character was flying by at the micro second level. I'd have to take into account stepper motor timing. Oh, by the way, there were multiple bands. We had to change out the bands if we wanted different character sets. Also, did you see the tape on the right hand side in that video? That is form layout control. There were series of signals you had to throw to the printer so it would go to a particular position on a form and those forms were controlled by those paper tapes. Paper tapes break easy.
Post #438,696 by drook 3/15/21 8:57:30 AM 3/15/21 8:57:31 AM Reply	Me with hardware control is like me watching figure skating I know what I wouldn't be able to do, but not enough to know what's hard for people who know what they're doing. -- Drew

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