Milling Machine problem

[GriffParticipant @griff]

Hi,

I am hoping someone can help.

I am new to Model Engineering and purchased an Amadeal AMA 25LV Milling Machine around 18 months ago to mill parts for Model Helicopters.It has not run for more than around 6hrs in total.

Whilst machining an aluminium plate the machine cut out and would not re-start. After checking the obvious I contacted Amadeal as it was still under guarantee and they sent me a new motor and controller board to fit as they were unsure what had caused the problem.

I installed both and adjusted the potentiometers as instructed to achieve the correct spindle speeds in high/low gear – this has only been done in the last week as I have been working away from home.

The speeds are working fine but the machine has no torque – I can stop the quill at any speed with ease. If I try mill anything taking the very lightest of cuts, after a few minutes the machine trips the RCD in the consumer Unit.

Thanks

Richard

[GriffParticipant @griff]

[The Novice EngineerParticipant @thenoviceengineer]

Hi

I had a similar Chinese Mill that made horrible noise at speed and kept cutting out.

Turned out to be worn out /broken carbon brushes and burnt communtator.

I replaced the brushes and skimmed commutator ……fixed my problem.

I had read that some folk had replaced the early Chinese controller electronic boards with USA or Twianese manufactured items.

A friend has recommended that to check on the board to see if there is a current limit control. That will control the torque the motor willl deliver.

I had considered changing the DC motor for an AC 3 phase with an electronic controller. but thats another project …..

Good Luck

[John Stevenson 1Participant @johnstevenson1]

Sounds like the wrong resistor fitted to the speed board.

[Les Jones 1Participant @lesjones1]

Hi Richard,
I think John is correct about the wrong value current sense resistor being fitted to the new controller board. This resistor will probably be a ceramic high power resistor with a low value. (The one on the X3 controller board is 0.01 ohms I think.) If this resistor is higher in value than the original it will cause the low torque problem. I think the tripping of the RCD is different fault. I think leakage to earth in the motor is the most likely cause of this but further testing will be required to prove it. If you connect a 100 watt light bulb (A normal 230 volt 100 watt filiment bulb.) in place of the motor and it no longer trips the RCD then the fault is in the motor. If it still trips the RCD then the fault is somewhere else.

Les.

[GriffParticipant @griff]

Thank you all for the advice, I will investigate further.

Regards

Richard

[GriffParticipant @griff]

Hi,

I have checked the Current Limit pot and ii is set at the fully clockwise position as was the original.

The current going to the motor which is labelled 850w 220v is as follows;

Lowest speed setting – 11v dc

Highest speed setting – 111v dc

The pictures below are of the currently installed board and the original – the arrows indicate the two failed Mosfets on the original board

[Les Jones 1Participant @lesjones1]

Hi Richard,
I think the white ceramic resistor (Marked 5WR1J) on the right hand side of the original board is the current sense resistor. (Value 0.1 ohm) The new board looks to be different design to the original so the current sense resistor could need to be a different value to give the same current limit value. The value of voltage across this resistor which causes the controller to start shutting down could be different. If you monitor the motor current I would expect it to get to about 4 amps at the point when the controller limits the current.

Les.

[GriffParticipant @griff]

Thanks Les I will check it.

Richard.

[GriffParticipant @griff]

Hi again,

The high power resistors are reading the same on both boards and I am only getting around 2.5amps current draw.

What I can't understand is why the RCD only trips when the machine is under load. It seems to me like the problems are related but I am at a loss as to why.

The machine is now out of guarantee but in my opinion the machine has never been right since I purchased it. I was hoping I could find a solution that I could sort myself but it looks like I will have to take this up with Amadeal again.

[denton barberParticipant @dentonbarber66787]

There's a problem with your RCD and needs to fix that's why the trip happens when you want the lightest cuts. Try to consult it on Amadea to fix the problem.

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