Optimum Mill/Drill BF20 Problem

Hi

I'm experiencing a problem with my Mill Drill, if anyone can help it would be much appreciated;-

One day switching the drill on the motor started to turn with hesitation and then the electronics blew with a loud bang, opening it up I found two thyristors blown! I checked the motor is free to rotate and nothing seems to restrict the gears. So I replaced the thyristors and it ran great first time, but!, that start up hesitation slowly creped back in, not all the time though but am worried it is not right and may blow again.....

Has anyone experienced the same thing? or any pointers for me to follow?

The machine is like the Chester Champion 20v and others....

Thanks in advance

Thumbs up to editor and staff for the large photos in MEW at last

Eoin

Hi Eoin,

I'd suspect the motor, sounds like it's drawing too much current. I don't know what the 20V uses, but it's probably DC. If so, have you checked the brushes?

With luck one of the motor experts or a Optimum owner will see this and comment.

Dave

Edited By SillyOldDuffer on 12/03/2017 10:36:59

Hi Eoin

I have not had such a problem with my BF20. Here are just some thoughts.

That machine has circuitry to ramp-up the motor speed when it is turned on. Possible that the ramp-up circuit is misbehaving?

The back of the controller box is a HEAT SINK for the controller. Make sure it is not covered otherwise things might overheat.

There are a number of adjustments on the controller board. Miximum speed (Vmin) should NOT be set lower than 50rpm.

There is also a current limiting adjustment (which is set by the factory) - which should (I would imagine) prevent this sort of thing from happening. So there might be more wrong with the board than just the 2 thyristors.

Did you ever replace the motor? If so, you should have re-set most of the controller settings (Vmax, Vmin, Torqu and Slope) - see the machine instructions.

Speaking of those instructions they contain the very confusing statement, "Furthermore, make sure that any settings are only being performed when the housing is closed." Using, I presume, a magic screwdriver that can pass through metal!

Good luck with sorting it out. Hope you come right.

Alan

Thanks Dave & Alan for help;-

The brushes are fine with about 12mm left and springs are OK

The motor runs fine when the gearbox is set to neutral, but when in gear- the hesitation is happening and then it runs fine, I'm now hearing a mechanical clunk sometimes when switching on and suspect something dodgy is going on in the gearbox, I'm going to strip it down and have a look.....

Yes Alan the instructions a badly translated

Thanks

Eoin

Hello Eoin,

See, please, **here**
http://www.model-engineer.co.uk/forums/postings.asp?th=117944

Not the same symptoms but, perhaps, the same cause.

Best regards
Dias Costa

Hi Dias

Thanks for the link, I also had a problem with the power switch some time back- the solenoid would not engage a buzzing sound happened, I replaced it with same kind but they are not a great switch!

Though I think this is a mechanical problem

I spent some time this evening playing at the machine and found the problem only happens in low gear- I suspect the low gearing may be damaged. Also searched the internet and I found a guy on Youtube showing how to replace this gearing after it broke.....

Thanks

Eoin

Eoin,

If you go here and download the installation instructions (pdf) for the belt drive kit, it's a pretty handy, and very nicely done, guide to stripping down these machines to get at the gears (and spindle).

Hi Bandersnatch

Thanks for that link, a very handy PDF file for this job.

I'm consider installing a belt drive, but was only thinking of drive from motor to quill and not include high and low gear pulleys, noise was what prompted this idea

Thanks

Eoin

PS; just thinking, I will need high and low gear so that kit is the thing....

Edited By Eoin Murray 1 on 14/03/2017 15:09:41

You're welcome Eoin.

I have recently installed that belt drive (on a recommendation from John Alexander Stewart) and it sure quietens-down the machine. It does drive directly from motor to quill with two pulley levels that replace the two speed gear set - and you retain the variable speed from the motor controller of course.

(I am keeping half an eye open for a suitable 3-phase motor to drive from a VFD).

The rest of that site is worth a look too. Of particular interest (to you and others) might be the 3D model CAD files for the BF20 (and, by extension, the G0704, WM16, etc).

.... no connection .... yada yada yada.

Thanks for the link; have downloaded & saved to my files. Haven't planned on doing it soon but if/ as & when I need to I have the instructions.

​George.