Semco cnc mill problem

[scottmk1]

Sounds like the power supply may be knackered but strange how X and Y are working.
If you have a 3x AA batteries you could series connect them and connect to the Z encoder and see if it works.

Good suggestion, I'll see what I can do.

 

[scottmk1]

I notice that the earth wire from the power supply input isn't connected, should it be?

 

[Hood]

I notice that the earth wire from the power supply input isn't connected, should it be?

I like earths connected and definitely if it is mains input.
Wonder if it was removed at some point because there was an internal fault on the PSU and it was going to earth.

 

[scottmk1]

Well I just checked and I'm getting 114V across live and neutral, 55V across live and earth and 55V across neutral and earth. All AC.

 

[scottmk1]

That servo seems to have a tachogenerator and an encoder fitted. The tachogenerator gives out 9.5v per 1000rpm so if it's not working or connected than something in the control might not be receiving the RPM signal.

Scott I have a couple of industrial encoders i'll dig one out and see if it might suit you for testing.

Hi Pete, I'd be interested to see what encoders you have, hopefully one might be suitable.

 

[Hood]

Well I just checked and I'm getting 114V across live and neutral, 55V across live and earth and 55V across neutral and earth. All AC.

Sounds like the input is ok, the PSU, if I recall, said it was 10Amp out on the 5v so no way should it not be delivering the correct voltage unless something is hauling it down.
Hopefully you can get a test with the batteries or maybe even a USB charger or something like that. Wouldn't need to be a big power supply as an encoder should just draw mA.

 

[scottmk1]

With nothing connected to the output the PSU was giving 1V from the pins on the right, which is where the plug was originally fitted and it remains at 1V with all 3 encoders connected and with only the Z axis encoder connected.

 

[Pete.]

Hi Pete, I'd be interested to see what encoders you have, hopefully one might be suitable.

I just checked and they are only 100 pulse/rev. Not much use to you I think.

 

[scottmk1]

I just checked and they are only 100 pulse/rev. Not much use to you I think.

Thanks for checking anyway

 

[scottmk1]

OK so this morning I remembered that I have a nice little PSU for electroplating, minimum output of 5Vdc, that's after spending ages looking for a USB charger to butcher! Anyway with the temp power supply it's working pretty well. So looks like that original PSU is faulty.

 

[Pete.]

A PC power supply has a decent stabilised 5v output.

 

[scottmk1]

A PC power supply has a decent stabilised 5v output.

OK that might be a good option for me rather than spending £££ on something

 

[Hood]

A PC PSU will need 240V input, yours is 110V I think.
Personally I would just for something like this, nice neat and tidy and just over £20 incl VAT.

https://uk.rs-online.com/web/p/din-rail-power-supplies/7127391/

 

[scottmk1]

A PC PSU will need 240V input, yours is 110V I think.
Personally I would just for something like this, nice neat and tidy and just over £20 incl VAT.

https://uk.rs-online.com/web/p/din-rail-power-supplies/7127391/

Great I'll go for one of those.

 

[scottmk1]

The new PSU arrived today so I'll get it fitted. If I don't reply with the results soon it'll be because I've electrocuted myself.
Anyway here is a picture of the old and new PSU's, some size difference.

 

[scottmk1]

OK, thankfully I haven't electrocuted myself yet but the problem is still there with all 3 encoders connected to the PSU. The problem goes away with only the Z axis connected however the reading on the screen is way off, full travel from the upper limit switch to as low as I can get it is around 530mm,but the screen tells me something different every time. First it was telling me just over 300mm then 340mm, and when I went back it was 70mm short of 0 when it hit the upper limit.

 

[Hood]

Not so good, looks like the encoder itself may be knackered.
Was it showing these problems the last day when you had it hooked to the other PSU you had?
What is the voltage on the new PSU with the Z only and also with All connected.
I can't imagine encoders will draw much current so not sure why the new PSU is not fit for them all unless one is faulty and pulling it down.

 

[Pete.]

Could it be a foreign object on the encoder disc or reticle perhaps?

 

[Hood]

Could it be a foreign object on the encoder disc or reticle perhaps?

That is a possibility, maybe even the LED failing, had that on a few encoders.

 

[scottmk1]

It's showing 5v with only the Z axis connected and with all 3 connected. With the measuring mismatch I didn't check what the scale was doing unfortunately, so can't say if that's changed.