Micro mill desperate help for a novice please

[TorontoBuilder]

A circuit breaker could possibly be used but are more complicated than you might think.
They typically do not trip at their rated current instantly, sometimes they take many minutes to trip at the rated current(a thermal trip). The ABB S201 linked to above was close to half an hour at the rated current. Often they will not trip quickly(electromechanical trip) until the current reaches 5 or 10 times or even more of the rated current.
A typical quick blow fuses by contrast will fuse in around 1/10th second at only double the rated current, or 1/100th of a second at three times.
Substituting a 2A quick blow fuse with a 2A circuit breaker could provide no protection at all.

Study the product data sheet and trip curves carefully.

Yes Simon, you are correct, however I wasnt specifying a specific circuit breaker merely illustrating the type. As always read product specs, there are plenty of fast trip circuit breakers available, if you have a electronics store close buy versus buying on the net they can help you make the correct selection.

the fuse for my mill was a special order shorter than normal product... I dont know about you but not being retired, I only have specific times I can machine anything, so equipment needs to work when I get to it.

 

[///]

Sorry for the misunderstanding TB, I was not having a jab at you per se, just providing a little extra info and a warning for Paul if he does choose to take this route. My main focus was on the ABB product linked to, which is definitely not suitable for this application.

 

[TorontoBuilder]

No problem Simon... I appreciate that you wanted to add more info, since circuit breakers are definitely a different animal than fuses resulting in circuit breaker selection well below that of the fast blow fuse rating.

 

[pmdevlin]

well I'm in a mess now, don't know what to do. The motor has been tested and reported to be burnt out. I took the motor apart before giving in to be tested, and could not see any evidence of this. The guy has connected up to 110v ac to test it, on the basis that the motor has a big spec sticker on it, and it does actually say 240v ac, however, on the arc euro site, the replacement motor says its a dc??????
He says the motor ran for a very short period, then gave up, and a possible short was causing the fuses to blow and the motor to spin up without potentiometer input. I'm confused? I thought it was a DC motor, so why on the big sticker on the can it does clearly say its AC?
So no further on really, except now I need a motor, and might still need a control board, anybody got any recommendations for a direct fit motor other than a massively expensive £88 from arc euro, and that might not even be the fix!

 

[Wizard69]

well I'm in a mess now, don't know what to do. The motor has been tested and reported to be burnt out. I took the motor apart before giving in to be tested, and could not see any evidence of this. The guy has connected up to 110v ac to test it, on the basis that the motor has a big spec sticker on it, and it does actually say 240v ac, however, on the arc euro site, the replacement motor says its a dc??????

Don't [/quote] me on this but I believe that the motors on these machines are actually universal motors. That is they can be run on either AC or DC. The controller feeds the motor DC voltage.

He says the motor ran for a very short period, then gave up, and a possible short was causing the fuses to blow and the motor to spin up without potentiometer input. I'm confused? I thought it was a DC motor, so why on the big sticker on the can it does clearly say its AC?

Motors will some times do that if the fuse doesn't trip fast enough.

So no further on really, except now I need a motor, and might still need a control board, anybody got any recommendations for a direct fit motor other than a massively expensive £88 from arc euro, and that might not even be the fix!

This is up to you really, the Chinese motors aren't all that reliable so it might pay to look into a real DC motor. Personally I'd out a better quality motor on the machine. The problem is they won't be cheap if you go industrial quality. You could also look into an AC 3 phase motor and VFD but I'm not sure about space on this machine. Either approach may require some fabrication effort.

The other gotcha here is that sometimes a bad motor, one that is shorted, can blow out the drive. Something to consider because you could find yourself replacing both the motor and the drive anyways.

 

[zebra7493]

Right....the motor is ac or dc. 110v applied directly should make it run.
Try that first.
If its labelled 240v you should be safe up to that voltage AC. I think up to 180 ish DC.
Try the controller with a 60w (or similar) light bulb connected instead of the motor.

If the motor runs at top speed when connected to the controller then there is a problem with the speed control pcb or possibly the pot.

I have repaired these pcbs before and the fault could be the speed control pot or any of the semiconductors. There are some little transistors which are involved in speed control and some large thyristors(?) on heatsink.
Any electronics person should be able to test the thyristors (if they are short circuit they are dead.)

I have a circuit somewhere of one of the versions of PCB which I may be able to find. A photo of the component side of your PCB would be useful.

Do you have a multimeter?

 

[pmdevlin]

I'll be collecting the motor and controller shortly. I am told the motor has emitted the magic smoke, and made all sorts of horrible crackling noises, so, if it was ok before it went to be tested, it certainly isn't now. I don't have a way to determine if it was faulty beforehand, the fuse in the controller could have been blowing prior to the smoke, I bet he tested without any circuit breaker, or he has fed ac when its a dc motor, I keep going back to the fact there is a large spec sheet on the motor, and it does say 240v ac on it, is that referring to the control panel? I will have difficulty laying the blame for the motor expiring on him with that sticker on it, and I'm no further on with knowing if the controller board or pot are actually faulty. Replacing bot motor and controller is out of budget, second hand, I doubt the machine is worth it.

I'll post up a pic later with motor spec,

Zebra, before I gave it in, I connected a 60w bulb to the output of the controller, with pot in off position, the bulb was very bright, turning the pot up made no difference to the brightness, and the glass fuse didn't blow. I have a multimeter, but it fills me with dread!! No idea what it does, its just a little cheapo one, very confusing, looks like this is going to be a dead machine for some time:fan:

 

[pmdevlin]

motor has been collected, controller later, as he has not yet checked the output from controller, I want him to do this to satisfy me its ac or dc, and the pot is doing something!. Big sticker says AC240, a small sticker on rear says dc240v

 

[pmdevlin]

quick google of the motor serial numbers, and I have found exactly same for sale at arc euro trade, and its a dc motor so he has fried it by lumping ac into it. The big sticker js the mill spec, not motor, I feel so stupid now!

So its a trip back later, and to argue the point that he should have known, and read the sticker on the reverse, lets face it, he is the expert, not me, that's why I took it in the first place

 

[zebra7493]

If the bulb came on at full brightness then I either the Devices (thyristors or in this case FETs I think) which control the motor are short circuit so basically on all the time OR possibly the pot which controls the speed could be open circuit.


I have posted a controller circuit at
http://sx-innovates.co.uk/SiegX2circuitboard.pdf
Its for the X2 mill but should be similar.

Your controller looks to me like its a lathe controller as it has reverse. I think they use the same boards for both.
The motors are probably AC/DC. As are things like mains powered drills. So AC mains shouldn't kill it.
Motors can behave oddly if the windings have shorted turns of insulation breaking down to earth. Sometimes the will run a bit until warm or just draw too much current whilst still seeming to work.

 

[DJP]

I would look at this failure as an opportunity. I was never happy with the speed control circuit on my mini mill and the internal plastic gears looked like a liability as well. With my set of end mill cutters the speed that I use does not change very much so I could do without the variable speed feature. Perhaps just a hi/med/lo option would be enough and a simple switch will do that very reliably.

Consider any new motor that will fit and make a simple controller for the voltage that the motor requires. I like the implementations where gears are removed and the mini mill is belt driven. That would be a robust and lasting machine in my opinion.

A fried controller board and burnt out motor are an opportunity to make the mill better. That's how I would approach this and for sure I wouldn't buy replacement parts to end up with the same weaknesses and liabilities.

My thoughts for your consideration.

 

[pmdevlin]

I don't really use the variable speed either, just rely on med, and low, so it is a consideration if the controller is finished.

I am picking it up from the "expert" in a few days, he has agreed, if I can prove its a dc motor he will take responsibility, not hard to do as it has a sticker on the can. Although I have twice provided the link for direct replacement and spec on the arc euro site, he seems reluctant to actually do any investigation. Strange, if he had spent 10 minutes doing this in the first place !:wall:

 

[zebra7493]

If you have all your parts back, a simple test of your controller.....
Connect up with the bulb instead of the motor. Get your multimeter out and set to DC 20v range and check the voltages at the pot.
One end should be 0v, the other end 12v and the middle terminal should vary as you turn the knob. You can check at the terminals on the PCB or at the actual pot.
If your pot also has a switch don't confuse the switch terminals with the variable resistor terminals. The variable resistor terminals are usually the 3 in a row on the side and the switch terminals normally are on the back of the pot.

If the voltage on the middle terminal varies as you turn the knob the pot is ok. If the voltage does not vary then the pot is bad. Replacement from a electronic component supplier is normally less than a pound (dollar if you are in the US)

 

[pmdevlin]

picking up controller tomorrow, thanks for advise!

 

[xpylonracer]

Hi, don't forget there were 2 stickers on the motor body and one of them stated 50-60 Hz, that means it will run with AC.
Hope the replacement controller and motor work for you.
Emgee

 

[velocette]

Hi, don't forget there were 2 stickers on the motor body and one of them stated 50-60 Hz, that means it will run with AC.
Hope the replacement controller and motor work for you.
Emgee

A bit late with this errant info it has already been established that the motor is DC and the the control is an AC to DC speed control unit.
Read the post Immediately after the one with the attached photos of the motor.

Eric

 

[zebra7493]

I think you are all on a bit of a wild goose chase with the AC or DC motor.
Most motors with brushes are AC or DC (things like power drills and vacuum cleaners) They have a stationary field winding and brushes which connect via the segmented commutator to the moving rotor windings.
I could explain the theory If anyone is really interested.

It seems to me that the most likely fault progression was the motor suffered an insulation breakdown resulting in a few shorted turns making it draw more current which blew fuses.
When put on the bench for a test run without the same size fuse protecting it the shorted turns became a 'hot spot' causing more shorted turns etc until it failed completely.

If you could identify which field winding had failed it is quite possible to rewind it by hand.
I have done it quite a few times by simply cutting the winding off, weighing it and winding on the same weight of the same thickness of wire. One needs to take care with the direction of the winding and the connections of the start and end but its not that difficult.

 

[BaronJ]

I think you are all on a bit of a wild goose chase with the AC or DC motor.
Most motors with brushes are AC or DC (things like power drills and vacuum cleaners) They have a stationary field winding and brushes which connect via the segmented commutator to the moving rotor windings.
I could explain the theory If anyone is really interested.

If it was a universal motor, I would agree with you. In this case the motor is a "Permag" type. This motor has a permanent magnet field consisting of two magnets where the field winding would usually be. It will only work with DC.

It seems to me that the most likely fault progression was the motor suffered an insulation breakdown resulting in a few shorted turns making it draw more current which blew fuses.
When put on the bench for a test run without the same size fuse protecting it the shorted turns became a 'hot spot' causing more shorted turns etc until it failed completely.

If you could identify which field winding had failed it is quite possible to rewind it by hand.
I have done it quite a few times by simply cutting the winding off, weighing it and winding on the same weight of the same thickness of wire. One needs to take care with the direction of the winding and the connections of the start and end but its not that difficult.

Yes this technique works well to replace a damaged winding as long as it is one that is on top and not buried beneath others, in which case the whole armature has to be rewound, along with re-lacquering and crimping to the commutator bars. On small motors it's hardly worth doing. Field windings are relatively easy.

 

[xpylonracer]

Hi Eric
Yes I should have read the message you referred to but see it is now a PM motor.

Did you read about the primary belt drive for that Velo ?
Emgee

 

[zebra7493]

Hi Baron
Permag? I'll take your word for it. Mine looks the same and has a field winding.

Armature windings are difficult because they are normally buried on one side. That's why I only suggested it for the field winding.