Burnt wires?

Discussion about the CNC Shark Pro Plus HD

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savannahdan
Posts: 8
Joined: Thu Oct 30, 2014 5:33 pm

Re: Burnt wires?

Post by savannahdan »

I've had my Shark since October 2014 and the wires finally did their burn. It happened about 2/3rds in a pocket job with the cut going off kilter. Fortunately I walked back into the shop and found the wires smoking but not an
20160410_104325a.jpg
active fire. I call NWA tech support and have heard no word from them. It happened last Wednesday. Barb shared my picture with them that day but still no word from NWA tech support. Attached is a picture of the damage to the cables and the piece I was working on. It affected the x and z wires which were in a boot together.
I am looking to fix this system and then get into one that is more reliable.
Thank you.

rsetina
Posts: 213
Joined: Sat May 04, 2013 5:05 pm

Re: Burnt wires?

Post by rsetina »

So the burnt wires are next to the connection at the controller. I thought they would burn next to the hot motor but I was wrong. It will be interesting to see what NWA will say when they get back to you. Keep us informed.
Rick

Rando
Posts: 757
Joined: Tue Jan 06, 2015 3:24 pm
Location: Boise, ID
Contact:

Re: Burnt wires?

Post by Rando »

One thing to remember is that when the controller is turned on, even if the axes are not moving, there is current going to the motors. If there were a loose connection from, say, the cable not being securely attached via the thumbscrews, or a bad pin or solder joint inside the molded connectors, that could force all of one pole's (there are two) current to go through one of those wires, which might cause it to overheat.

On mine, I've not had this problem, but I turn the controller off when I'm not cutting or going to soon, the cables are securely screwed in, and I long ago moved the black covering away from the connectors, back about 6" up the cable.

Hopefully there's a proven way to prevent it that doesn't involve replacing motors. And honestly, it's just a DB-9 connector with 8 pins used to connect to four wires...These are, quite literally, just old PC serial cables. If you have a DB9 male you can replace the connector by cutting off the burned wires and connecting them. I have an old dead controller board, and the pinout LOOKS to be the following. Test your own, however!

Pin 1 (right-hand pin in the long row on the receptacle, left-hand pin on the plug) appears to be a shield ground
Pin 2 and 6 are connected together and go to the motor's blue wire
Pin 3 and 7 are connected together and go to the motor's red wire
pin 4 and 8 are connected together and go to the motor's green wire
pin 5 and 9 are connected together and go to the motor's black wire

If you follow the wires in that split-loom covering, you'll find where the have the wire pairs tied together. At least that would save you the weekend ;-)

Regards,

Thom

P.S. to Next Wave: this is what happens when you use the cheapest possible components, instead of something properly rated for the load.
=====================================================
ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)

savannahdan
Posts: 8
Joined: Thu Oct 30, 2014 5:33 pm

Re: Burnt wires?

Post by savannahdan »

I got word from NWA that 2 new motors are on their way to me. That's a big plus and I want to thank them (Barb) here on the forum as well as by email I've already sent.
I also don't leave the motor on when not in use. Interesting thing is I had not used it for over a month. I'm making a wild guess that by having the x and z motor cables in the same boot that there may have been some problem. I also noticed there was a crossing of cables at the back of the control box when they were bundled this way. I plan to have all the cables separated so that the don't have any crossing over each other.
Dan

rungemach
Posts: 460
Joined: Mon Aug 02, 2010 8:24 am
Location: Sarasota, Florida

Re: Burnt wires?

Post by rungemach »

I have to agree with Rando,

The unit I had worked on in the past had the same computer style wiring with doubled up connections. I can't see why it would have been more expensive just to use a better gauge of wire and not have to double up on the connections. My gecko g540's use a db9 connector (with much bigger motors), with one pin for each motor lead (4 total). With 18g wires I have never had an issue.

With the doubled small wires, if one of the two wires break, the motor will still move and use the remaining single wire to carry all the current. That puts all the current through a single wire instead of two. There may not be any outward sign that one wire has failed, other than the heating up of the remaining conductor.

The motor wires on the y and z axis move a lot in operation, and if the flexing is concentrated on a small area (pinch point), the wiring can be flexed a lot in that small area. As the machine runs and the spot is constantly flexed the wire may fail from fatigue. It helps to use cable chain, as it will distribute the flexing along a larger length of the cable, and each section will flex less.

IMHO, Hot wires and sawdust are not a good combination, and there seems to be more than just one or two occurrences of this happening.

savannahdan
Posts: 8
Joined: Thu Oct 30, 2014 5:33 pm

Re: Burnt wires?

Post by savannahdan »

Just received the new motors. They each have their own covering. I'll be installing them and get back to a pocket cut job that needs to be completed before the weekend is out.

randywiz81
Posts: 1
Joined: Wed Jan 06, 2021 12:54 pm

Re: Burnt wires?

Post by randywiz81 »

Looks like the last reply to this thread was some time ago, possibly before the HD500, HD510, HD520, came out. I am not sure what I am going to do as far as adding a fourth axis to my HD510, but I purchased and installed the fourth axis power/driver card ($49) to see if I can control the axis through the HMI. I can jog and it runs a programmed Tap file, testing it with my Y motor, moved to the new port. Next step is was to buy a compatible step motor based on the specs people have posted on various sights, knowing the only risk would be to the new card. To lower the risk, I measured out the resistance of the DB9 connector on my Y axis to confirm the jumpering and coil connections listed below. The resistance of the motor coils came out to 1.9 Ohms. The resistance of the jumpers came out to less than one Ohm (short). This does not have to be accurate, but rather identified active wiring vs passive wiring, or empty pins. I can confirm that the wiring below is also correct for the HD5 series shark, based on that I now have full control of my aftermarket step motor. Now I can decide what I want to buy or build for my 4th axis. As usual, this is info only and you assume all risk to yourself or your equipment. Although not an industrial connector, the DB9 will handle the load of N.W. stepper motors due to the load sharing of two pins per phase conductor. I would rather they use that, than some odd ball connector that I would have to buy a thousand of to develop my own personal accessories.

"I am not an Electrical Engineer! I just play one on TV!"

Randy



Rando wrote:
Wed Apr 13, 2016 9:37 am
One thing to remember is that when the controller is turned on, even if the axes are not moving, there is current going to the motors. If there were a loose connection from, say, the cable not being securely attached via the thumbscrews, or a bad pin or solder joint inside the molded connectors, that could force all of one pole's (there are two) current to go through one of those wires, which might cause it to overheat.

On mine, I've not had this problem, but I turn the controller off when I'm not cutting or going to soon, the cables are securely screwed in, and I long ago moved the black covering away from the connectors, back about 6" up the cable.

Hopefully there's a proven way to prevent it that doesn't involve replacing motors. And honestly, it's just a DB-9 connector with 8 pins used to connect to four wires...These are, quite literally, just old PC serial cables. If you have a DB9 male you can replace the connector by cutting off the burned wires and connecting them. I have an old dead controller board, and the pinout LOOKS to be the following. Test your own, however!

Pin 1 (right-hand pin in the long row on the receptacle, left-hand pin on the plug) appears to be a shield ground
Pin 2 and 6 are connected together and go to the motor's blue wire
Pin 3 and 7 are connected together and go to the motor's red wire
pin 4 and 8 are connected together and go to the motor's green wire
pin 5 and 9 are connected together and go to the motor's black wire

If you follow the wires in that split-loom covering, you'll find where the have the wire pairs tied together. At least that would save you the weekend ;-)

Regards,

Thom

P.S. to Next Wave: this is what happens when you use the cheapest possible components, instead of something properly rated for the load.

Rando
Posts: 757
Joined: Tue Jan 06, 2015 3:24 pm
Location: Boise, ID
Contact:

Re: Burnt wires?

Post by Rando »

Dear Mr. Dunning-Kruger:
randywiz81 wrote:
Mon Jun 06, 2022 3:08 pm
... Although not an industrial connector, the DB9 will handle the load of N.W. stepper motors due to the load sharing of two pins per phase conductor.
...right up until one of those wires breaks. Or a solder joint cracks and starts to corrode in the humid air, turning itself into a resistor.

In reality, between the 28Ga wires in their serial cables, and the DB-9 pins, whether it "will handle" the current is a matter of how much temperature rise
you're willing to accept, and whether that will outright melt, or simply accelerate the aging of the insulation.

There are a LOT of different connectors you don't have to buy in bulk that are far safer than what they did. With even a simple search on Amazon
you can find five sets of 4-pin "Aircraft" connectors (panel mount male + cable mount female) that have 5A ratings on each pin. If you're doing a 4th axis,
and you took the time to replace the connectors, you'd have one extra for when you futz the soldering on the first one. Twelve bucks or a potential
fire...your choice. You spent all that money to make a 4th axis, but go el-cheapo on the connectors?

https://www.amazon.com/Aviation-Connect ... B07793H4CV

Heck, you'd have a better setup if all you did was get a solder-cup DB-9 and hand-solder 20Ga wires for the cable. At least those would easily carry
the current even if only one pin-set was in use. For me, I've removed the driver modules from the Shark controller, and replaced the motors with
4Nm (560 oz-in, double what's on the HD2/3/4 series) hybrid stepper-servos and the appropriate driver modules. 48V 8A power supplies, one per
axis. Gobs of torque, over 400 IPM rapids and I use 18Ga wiring from the module to the motors. Oh...and instead of 1600 steps per inch (200 steps/rev
in the motor and 8x micro-stepping), I now have 20,000 steps per inch. That's right, 0.0001" resolution. I take the logic-level step/direction signals
directly off the controller board and send those to the driver modules. I don't even use their metal box anymore.

And yes, I **am** an electrical engineer; I don't "play" at it one little bit. I always love how people who have figured out how to connect stuff together
think they're somehow doing engineering. Bless Y'er Heart!

What I find interesting is that after you make your pronouncement, you then disclaim that everyone's on their own. Way to own your solution.

Below is a diagram I cooked up recently, per someone else's request for the information.
2022-010 Shark DB-9 wiring.jpg
Have a Nice Day.

Rando
=====================================================
ThomR.com Creative tools and photographic art
A proud member of the Pacific Northwest CNC Club (now on Facebook)

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