HELP - Blowing Fuses & melting Switches

[TimAustinTX]

I have a couple of the red 60W 500x70mm machines and both of them have been blowing fuses.

The first unit melted an e-stop switch and then started to blow fuses to the point the machine won't do more than power up and blow a fuse.

Our second machine seems to have melted the main power switch and is also blowing fuses.

Any pointers would be great!

Tim

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[john-100]

Hi Tim

going by the poor quality the connectors use in my "mini lathe" resulting in high resistance connections

its possible the E-stop & power switch was damaged by the heat from poor connections

do the switch wires show signs of head damage ??


the question is did faulty e-stop switch & power switch cause damage to the laser cutters power supplies and / or laser power supplies ??

or the over current taken by a faulty power supplies and / or laser power supply damage the switches ??

I would replace the damaged switch & blown fuse then disconnect the mains supply from the laser power supply
and then test the controls power supply on its own

depending on the result ,then test the laser tubes power supply on its own

John

[TimAustinTX]

The e-stop on one machine was the first to show heat damage and I replaced it.

I have the main power switch on both machines show signed of heat damage.

Any good places to get better quality switches from?

Tim

[john-100]

Hi Tim

living in the UK I would start with
Farnell element14 UK - Electronic Components Distributor
RS Components | Electronic and Electrical Components

but I assume your in USA so try
https://www.digikey.com/
Mouser Electronics - Electronic Components Distributor

from the likes of E-bay its not easy to know how good spare parts will be - they may be as bad as the suspect ones fitted to your machine


John

[TimAustinTX]

The main power switch I have not looks more like the e-stop linked below but both sides are green. Is that NO/NO or NC/NC?

Emergency Push Button Switch with lock

[VimCommando]

Hey, I got a 60W Chinese laser in January and I had the same issue. I thought I posted in this forum, but I can't find it.

Here is what I found after 1) Melting the main switch, 2) Melting the E-Stop swtich, and 3) Blowing a fuse and melting the fuse holder.

The #1 tip I can give you is to make sure you are NOT running your exhaust fan or air assist pump from the AC outlets on the back of the machine.


The exhaust fan that was included with my machine was rated at something like 6A or 550W--all of this power has to go through the main fuse if you use the outlet on the back of the machine. This really only leaves about 4A to power the laser, and if you have to use over 70% power or are running a long cutting job, it can melt switches (thats what happend to me.) The power plug on my fan was not a US style plug, so I had to cut and replace the end to make the switch (found a replacement extension cable plug at a local hardware store).

Double-check the rating on your main fuse. The ones that came with the machine were rated for 250v/10A, which will not reliably blow at 10A at 120V; this is probably why the switches are melting first (Also 10A rated)

In getting my machine back up and running, I replaced the main power switch with a 20A metal toggle switch. It is overkill, but it works great. The fuse should blow first anyway. The E-Stop should have a red contact block, the main switch a green contact block. The only real difference (aside from the style of switch) is the E-Stop is normally closed, and the Main Power is normally open.

My new setup has the Laser Cutter, Air Pump, Water Pump, Water Chiller and Exhaust Fan all running on their own outlet on a shared surge protector (nothing on the back of the laser)--I've had no power issues since.

[zxhoon]

Just replacement them..or add a breaker, it is safer.

I disagree, circuit breakers are slower to react and are too easy to simply reset after they have tripped, assuming circuit breaker and fuse are correct rating for the load.

A fuse requires some checking of the circuit before replacing (assuming someone doesn't want to just blow another fuse), I've seen my share of circuit breakers simply reset into a short circuit resulting in arc flash and further equipment damage.

Fuses are faster to clear a fault resulting in safer operation and typically less damage to equipment.

Ceramic fuses with a correct load rating and fault clearance rating should be used.

[davek0974]

The "best solution" is just replace, and when it happens again, and replace it again..
However, if you don't want to replace it often, I think breaker is an options, but don't reset it right away when it breaks.

Sorry to disagree but but a fuse that blows or a breaker that pops is telling you something is wrong i.e. not right!

The correct action would be to investigate what is pulling more current than the circuit is designed for then replace, rewire, or redesign the circuit.

Fuses and breakers should never go in a correctly functioning circuit.

[davek0974]

No worries

I only mentioned it as these machines get put in the home etc and keeping on flicking a breaker or fitting fuses usually leads to overheating which can lead to fires etc.

Much better to fix the problem and be safe.

[osumartz]

This is a similar issue as we are having on our dual laser. Any additional input would be really helpful. This has melted twice in the past week.. Just want to make sure we are making the correct moves.

[john-100]

going by your photo


it looks like it could either be due to faulty riveting of the joint between the metal strap & the fuse clip or

a poor connection between the fuse and connector - possibly due to the fuse being under size or the connector not providing enough contact pressure ,

very often the fuse holder can be damaged when a glass fuse is blown by a large fault current
with a 20mm glass fuse not only does the glass tube explode but the copper fuse wire is vaporised ,
coating the inside of the fuse holder with a conductive film of copper

a HRC Fuse (High Rupture Capacity Fuse ) should be used as the ceramic tube contains the explosion if you short circuit the mains supply
the sand filling quenches the arc

John

[osumartz]

Thanks John! I will give the ceramic fuses a shot!

[grg12]

Double-check the rating on your main fuse. The ones that came with the machine were rated for 250v/10A, which will not reliably blow at 10A at 120V; this is probably why the switches are melting first (Also 10A rated)

.

Hmmm as far i know 250v/10A fuses should reliably blow at 10amps /120v (or even 12v ). 250V ratings means that you can use them on 250V mains - they should not "hold" arc after blowing. Automotive fuses cannot be used in 250V (or 120v) mains since they are rated for lower voltage.
I think "melting switches" problem has more to do with the fact that switch is rated for the same amperage as fuse - which sounds ratcher... echem... interesting choice. Probably components chosen by "use the cheapest" method


Wysłane z mojego GT-N7100 przy użyciu Tapatalka

[Al_The_Man]

Sounds to me as the machine is miss-wired somehow, probably done for cheapness, an E-Stop circuit traditionally does not carry high current, it is often just a control relay that in turn removes coil voltage etc from contactor coils and other power controlling devices.
If these machines or any that are of Chinese origin, the wiring has not always conformed to NFPA79/NEC/CEC.!
Al.

[osumartz]

So while we have been waiting on the ceramic fuses (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1), we replaced the receptacle and put in another glass fuse. This morning that one melted as well. I dissected the last one that melted and it appeared that the glass on the fuse broke, but the wire did not pop. Conversely, the melted outlet this morning had no broken glass, but a popped fuse wire. Keep in mind that this has only started happening in the past few weeks and has happened two separate times on two separate machines. Really the only thing I can think of is it has to be garbage fuses. Maybe I'm using the wrong fuses all together? I am using 10A 5x20mm (https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1). So, so frustrating.

[Al_The_Man]

That type of fuse is seldom seen in industrial machinery, especially for power circuits, it would pay to replace with industrial style such as CC or similar type fuses, and suitable fuse holder.
Al.

[osumartz]

Well, tried the ceramic fuses and we are still melting. However, the ceramic fuse did not seem to pop. So for some reason, there is so much heat going into the plug it is melting without popping the fuse. Also, this is happening on two different dual laser and started happening around the same time with both. What the bloody hell? I could always get a metal plug inlet, but I don't think that would really be solving the issue.

[john-100]

with your new photos it looks like its the fuse is making a poor connection

a good quality IEC inlet with a fuse holder like this made by Bulgin is OK up to 10A :-

PF0001/63 BULGIN, Power Entry Connector, Plug, 250 VAC, 10 A, Flange Mount, Quick Connect | Farnell UK

If I guess the Laser power supply takes 120W ( only half of which is converted into the LASER output)
and the stepper drivers & control is 200W
then the Laser engraver will only take about 3A from your 110V supply
what amperage fuse did you use ?

so the question is what else is taking so much power that its melting the inlet ??
does the engraver have sockets to power a water pump and water chiller ???


John