Where I can buy 100-ohm high-flex flat cable in small quantity?

[hanakp]

Hi everyone, as I asked here earlier, we've had problems with corrupted inkjet print head data in a full-color powder 3D printer. Since the printer is not covered by service contract anymore, we resorted to long (and quite expensive) component swapping. Eventually, we isolated the problem to a faulty cable that's called "festoon cable assembly" in the printer service manual. Except a replacement cable costs whopping 1200 EUR and we already exceeded our budget. So I looked if I could make a DIY copy. The "festoon cable assembly" is actually comprised of 4 different cables - earth, power delivery, stepper motor control and data for the print heads. All these cables are of high-flex type, meaning their copper cores are super-finely stranded to withstand the constant motion during printing. The problem is, the data cable is Amphenol 191-2811-034 which isn't produced anymore. There were some leftovers in stock at Digikey, but not the 34-way variant. For my tests, I had to buy two strips of 26-way variant, then tear and glue them together to make 34 ways. That worked, but it won't probably last long due to mechanical strain in the IDC connectors.

Of course, I can't drop in any random flat cable I'd find, it must have a specific impedance, because the data rates are high. There are SN65LVDM1677 LVDS transceivers in the printer, so theoretically, the cable should have 100 ohm. The Amphenol cable indeed has that, in "ground-signal-ground" mode. Except in the printer, LVDS pairs actually use adjacent wires, with no ground betweent them. The pair impedance is not listed in the datasheet, but I measured it with RLCG meter and got 150 ohm. I have no idea how the LVDS works properly in this situation, but... it just does. Maybe they do some trick that they interleave transmission between the pairs, so the neighboring wires temporarily act like ground?

Anyway, since the Amphenol cable isn't manufactured anymore, I looked for other sources or alternatives. The closest alternative is probably 3M 3319/34 (PVC) or HF319/34 (polyofein). Their pair impedance is different (171 ohm, 3M calls it "balanced mode"), but I'm willing to try them. The real problem is, all vendors I could find only sell them at 100 feet (30 meters) multiples. I also tried Ebay, but I could find only listings from "dodgy" sellers who either didn't respond to my messages and/or removed the listing shortly afterwards. So my questions are:

1. Do you happen to know where I could get Amphenol 191-2811-034, 3M 3319/34 or HF319/34 in smaller quantities?
2. Alternatively, do you know about any other high-flex flat cables with required/similar impedance?

Thanks!

(I plan to write up how to make copy of the entire "festoon cable assembly" later, but I'll probably post it to 3D print-related forums, not here).

[thm_w]

I'm missing something here, why would connecting two 17 way ribbon cables side-by-side create additional strain on the IDC connector?
Why would they need to be glued?

[hanakp]

I don't think that's particularly important here, but since you've asked... the printer doesn't use any sophisticated mechanical support for the "festoon cable". Basically, the 4 cables are bundled and bound together with electrical tape and corrugated tubing. In order to do that, the flat cable is torn to 16 and 18-way strands which are folded on themselves. You can't tear the cable in half, since the LVDS uses pairs. I did that exactly as the original. But two separate strips create problems at the endpoints, particularly within the print head carriage. They deform and cruple near the IDC connector, even when I tried to reinforce them with "genuine" strong duct tape. The original 34-way cable is not torn all the way, so it's stiffer there.

[thm_w]

Use a wraparound IDC connector, this will provide additional strain relief.
Hold the cables in the same plane with some tape, apply silicone RTV on the connector below and above where the cable comes in.

If you have TPU you could even 3D print a strain relief boot, but I don't think that is necessary.

[hanakp]

The original connectors are 3M 3414-6634 with strain relief (I used the same type), but the cable still crumples. You can't experiment with these things forever, the connectors officially have ~50 mating cycles and we're nearing it. That's particularly problematic in the control box which is full of 8-layer PCBs with hair-like traces, I doubt I'd be able to replace the male connector on it. And a new box costs around 6000 EUR these days.

[hanakp]

It's been a while, but I've finally written instructions how to make a copy of the entire festoon cable assembly:

https://3dprintboard.com/showthread.php?58955-DIY-copy-of-festoon-cable-assembly-for-Zprinter-650-850-and-Projet-660-860

[jonpaul]

Replace printer inkjets are high cost and short life

[tooki]

Replace printer inkjets are high cost and short life

What a stupid comment. (Though I’ve kinda come to expect those from you: bold statements based on a superficial skim of the post, combined with insufficient knowledge.)

1. You can’t make a blanket statement about inkjet printers. Low-end inkjets are junk, because they’re low-end. (The same goes for low-end lasers, whose toner is spectacularly expensive.) More expensive inkjets last a long time and are extremely cheap to run. Inkjet is now used widely for commercial applications, printing reliably at high speed in high quality at low cost. It’s also used for nearly all digital photo printing now, because the technology is capable of outstanding image quality.

2. You didn’t read the posts. This isn’t printing ink onto paper at all. It says right in the post “3D printer”.