Snapmaker 2 heated bed cable hazard

[vvsahakian]

I have a Snapmaker A350 and have been using it for 3D printing for several months. I recently noticed that the cable that attaches to the heated bed was bending and twisting during the printing process in a way that was inducing wear and tear on the cable. A small lesion had developed already at the junction where the cable meets the heated bed. I wrapped the area with electrical tape to reduce the bending. A few weeks later, the printer stopped working and I noticed the cable had burned through the electrical tape! I am attaching four pictures to show people the problem. I will of course contact Snapmaker support for servicing, but I thought I should post the issue here given the potential for a fire hazard.

The first picture shows the damage as discovered. The second picture shows the damage after I removed the electrical tape. The third picture shows the area after I disassembled things and cut the cable; we see the side of the heated bed. The last picture shows the other side of the cut, where the damage originated: you can see that the red cable shorted/overheated as indicated by the melted red plastic; possibly a short between the red and white wires?

I suggest people put some sort of heat resistant support at the junction before a break appears so that bending and twisting is minimized. And if a breaks appears, stop using the heated bed immediately.

[xchrisd]

Thank you for sharing!

[wadee]

Thanks for sharing … does this mean the cable arming is not heat resistance and just normal power cable?
Could you please share with us what is the snapmaker2 tech. solution

[vvsahakian]

I don’t think it is a matter of the cable being heat resistant enough: the wear on the cable at the junction seems to be prone to gradually tearing the insulation, which can then create a short. I think it is the heating from the short circuit that escalated the problem, not the heat from the heat bed. This is the same issue that you see with phone charging cables that break at the junction. The printer’s back and forth motion creates more wear on the junction than usual. My guess is that, if one puts a thicker rubber reinforcement at the junction, it’ll be enough. If I had noticed the issue earlier, before the tear, I would have layered electric tape at the junction to restrict bending.

Customer service were super helpful and prompt. They are replacing the broken part, and they escalated the issue to the technical team to analyze the problem.

[sdj544]

I’m wondering if just adding some silicone sealant/caulk around where the cable meets the connector would just give it a little more
strength and spread out the stress.
-S

[Melanchrom]

I was thinking about printing a cable chain for moving cables when I get my snapmaker.

Something like this:

https://de.m.wikipedia.org/wiki/Energieführungskette

[jlee]

Maybe can use Suguru for this.

[vvsahakian]

Brilliant! Just ordered some Sugru from Amazon to use with the new heated bed Snapmaker is sending so that it doesn’t happen again.

[ChrisT]

An RCB has tripped several times recently at home, with no explanation until now. As I started a print, I noticed the bed was not heating. Then I saw smoke from the connection at the back. The photo is not very clear but you can see the cable has split and the insulation from at least one wire, the red, is damaged.
I’m going to open a case with support.

[vvsahakian]

I really hope they quickly fix this issue as it can be a fire hazard.

[Joel]

How far is the build plate from the wall? I didn’t think about this at first, but then noticed that if there is not enough room behind the printer, the wire gets bent when the plate moves all the way back. This constant bending can cause the issue. Since moving the printer far from the wall, the wire doesn’t get bent. When I placed the printer on the table initially, seemed like there was a lot of space, but move the plate all the way back and confirm the cable doesn’t touch the wall.

[ChrisT]

Hello Joel,

Thanks for your suggestion. My printer is sitting correctly in a Snapmaker enclosure, and the only thing between the connector at the back of the plate and the rear wall of the enclosure is some of the cable itself.

It’s possible that the cable is being pressed against the wall as the bed moves but I don’t know what I could do to stop that. I can’t fasten the cable anywhere without restricting the movement of the bed.

Regards,
Chris.

[brent113]

I’m tempted to loosen the cable clamp, install a large heatshrink over the entire connector, and reassemble. There should be strain relief as the cable comes out of that sharp plastic corner. Oh well, as soon as my replacement cables show up I’m ditching that heated bed and assembling my own with a silicone heater and glass plate.

[ConsummatePro]

Please do show us how you make that heated bed: will it get up to ABS temps (100C)? Are you routing another power supply for it?

[Nobrks]

Same issue here, after 1,5 kg of printing, fatique of the wires, the flat cable cannot tolerate to be twisted, hot bed cable routing is far from optimal.
Longer cable and cable-chain should be the solution here

[eh9]

@Nobrks

Longer cable and cable-chain should be the solution here

If you’re going to use drag chain, you’d also want a connector between the end of the cable and the heated bed. If you don’t do that you have to mount the drag chain in addition each time you mount the heated bed.

[Nobrks]

If it would be plugged into the bed, the socked would have to be intergrated to the bed, else it will be adding more potential week links (bending with high strain on cable), by having bed + short cable + plugs + long cable to controller.

Longer cable with or without a drag chain, would help taking the stress of the caple close to the bed, by allowing it only to flex in one direction ( as a drag chain).

Current cable is to short for that.
When printing large models, with short cable, it is un avoidable to add twisting load on cable.

[eh9]

@Nobrks

the socked would have to be intergrated to the bed

Absolutely. Because of (default) placement of the cable entry at the back of the bed, it would useful to use a ZIF (zero insertion force) connector of some kind. I looked into this a couple weeks ago. To make a long story short, there doesn’t seem to be anything off-the-shelf available for this application. Admittedly, I didn’t start calling up the sales engineers at companies like Amphenol that manufacture these connector, but that’s the next step.

What I did figure out is that it would be pretty straightforward to use an old-style ZIF socket for 14-pin DIP IC’s. Allocate two pins for the thermistor and gang up others pins for bulk power. Then protect the little DIP pins on the plug in a shroud that goes around the body of the ZIF socket.

[brent113]

I have been stewing on cable connectors for my bed heater replacement project. I’m looking for a high amp wire-to-pcb or wire-to-wire connector with low insertion force. In this application, something could replace the existing connection at the PCB pads, with a new 3D printed enclosure around it.

I was looking at the JST PSI series - other than being unobtainable and not coming in 4 circuits for most configuration it seems pretty decent for this application: http://www.jst-mfg.com/product/detail_e.php?series=667
12A, 300V, low insertion force, locking, available in side entry. Either of these:

The PCB side of the bed looks like this:

If the spacing works, could solder a connector straight to the pads, otherwise a wire-to-wire connector mounted in a housing would be better.

@eh if you come across connectors like this or better that can be actually bought somewhere please let me know. I’m still looking. My bed heater is 120V, 6.5A, the connector needs to be beefy.

[eh9]

@brent113

I’m looking for a high amp wire-to-pcb or wire-to-wire connector with low insertion force.

Barring an actual ZIF connector (or the very-low variant), the connector I’d pick would be a mixed-signal D-sub connector designated 7W2. The D-sub shell is that same as a low density 15 pin connector. Five of the small pins on either side are replaced with large power contacts. 5 pins remain in the center. The designation is thus “7 total = 5 small + 2 large” W “2 large”. From what I can tell this are non-proprietary, industry-standard, widely available, and not particularly expensive.

If there’s a downside, it’s that the standard housings aren’t the right shape, but new ones could be printed. You’d want to print them anyway, because you can also include a way of affixing drag chain to the housing, removing any need to do so separately.

I haven’t decided yet how much I want to modify my machine, but I have thought one of the useful things would be to replace the kind-of-awful proprietary connectors and cables that come with the machine. Fun fact: the power-carrying conductors in the cable are the same size as the signal ones, in other words, small. The large pins in the plug are apparently just for show.