Seig SX2P mill cutting out

[Ches Green UKParticipant @chesgreenuk]

I wonder if anyone has any advice on this recent problem on my 4 yr old Arc Mill.

The spindle has now stopped rotating when cutting 3 or 4 times, in the past fortnight. The mill still has power, no bad sounds or smells – the cutter just gently stops rotating over about 1 -2 seconds.  I quickly turn the speed dial to zero, carefully withdraw the cutter from the workpiece and then turn the speed dial back up, rotation resumes and I can cut again.

I haven’t been milling any other materials apart from Aluminium this year. I was using 10mm, 6 mm and 1/16″ cutters, taking 0.010″ – 0.003″ cuts.

It may be happening after I have been using the mill for more than 15 mins appx….so something could be overheating although putting my hand on the motor etc doesn’t indicate any high temperatures.

I managed to ask the question of one of the helpful Arc employees a few days before they closed down and the advice was to break and make all the electrical connectors on the circuit board as they can oxidise, which I have now done.

But the problem still persists.

Some pics follow….

Below – The mill itself. 4 yrs old, been problem free. Stays in a wooden shed so subject to some condensation during wintertime.

Below – The electrics box with circuit board. No burning visible. Capacitors looked OK eg no swelling etc.

Below-  4 ‘hidden’ connections underneath the small filter board.

Any thoughts?

Thanks, Ches

 

 

[noel shelleyParticipant @noelshelley55608]

A shot in the dark but a damp atmosphere may be causing the speed pot to fail, turning down and back up will wipe the contacts and all is well till next time. If so then a new pot will cure it and cheap enough to do. Noel.

[Ches Green UKParticipant @chesgreenuk]

Thanks Noel,

That would be a good outcome.

The pot does feel quite smooth and linear when in operation though and I wasn’t ‘tweaking’ the speed as the cuts were being made.

But something to add to the list of possible culprits.

Arc did advise that Axminister should be able to supply any spares I need if it comes to that. I do wish I’d bought a spare circuit board when Arc was still trading since that board now looks a bit pricey.

Ches

[SillyOldDufferModerator @sillyoldduffer]

Noel’s suggestion is likely, and you should act on his advice.  The pots used are the domestic variety, unsealed and liable to pick up dirt, damp etc.  The wiper arm loses contact due to vibration and temperature.  Track damage tends to wear concentrate at popular settings, so the pot behaves across most of the range, but it’s sick.

Worth giving the pot’s innards a squirt of switch cleaner – I use Servisol.   Also good when reseating contacts as suggested by Arc.  It dislodges dirt and grease, and lubricates.

Although domestic potentiometers aren’t ideal in a workshop, they are cheap and easy to replace.   I wouldn’t recommend an industrial grade sealed component – expensive, e.g. Vishay 4k7 at £74.71 from Mouser, which may not include VAT or p&p!

Dave

 

[Ches Green UKParticipant @chesgreenuk]

Dave,

I’ve got a couple of small cans of Servisol so will give the pot a spray and wiggle tomorrow.

The more I think about it the more the issue does feel like a pot could be the reason. The vibration from the cutting might just slighly move the wiper to a bad area and so the mill loses power.

Thanks chaps.

Ches.

[old martParticipant @oldmart]

I had to replace the speed pot on my 7 X 12 lathe which also had a switch built in, years ago. I bought one from Maplins but the switch worked the wrong way, not off-on but on-off. I managed to bodge it to work the way it needed to go and it has worked ever since, and not sealed. As already advised, that part is the first to go for in your fault tracking, good luck.

[Ches Green UKParticipant @chesgreenuk]

Old mart,

Good to know. I’ve got a (Seig) 7×12 lathe too.

Tomorrow I’ll examine the pot and give it a clean. And then report back if/when matters improve.

Thanks, Ches

 

[Robert Atkinson 2Participant @robertatkinson2]

Just to highlight something old mart mentioned. There are two verions pof potentiometer (pot) used on this series of lathe. One is the “normal” arrangement of contact open with knob fully counter clockwise (FCCW). The other is switch closed when FCCW.

If (when) the speed control on my SX2LP fails I’d be tempted to use a pot without a switch and add a Start-Stop switch arrangement. This saves having to re-set the speed every time. I’d have a No-Volt Release (NVR) circuit as part of that so it can’t re-start after a power innerruption or E-Stop reset.

Interesting to see the amount of filtering in the machine. I’m nor surprised to see it in a ARC Euro Trade machine but you can see why cheap machines may leave it out. I count 9 inductor and 4 capacitors.

Robert.

[Ches Green UKParticipant @chesgreenuk]

Robert,

I’ll keep that in mind if my Seig lathe ever plays up.

My SX2P mill controls have a separate On/Off switch so the potentiometer only has one job to do. My lathe is similar.

Yes, Arc did go that extra mile to make sure the equipment they imported was fit-for-purpose but at a marketable price.

I was looking online today for a couple of small end mills and of course the Arc offerings still appear in the search results but are now Unobtainium. I’m missing them already!

Ches

 

 

[Ches Green UKParticipant @chesgreenuk]

I’ve now opened up the Switch Box on the SX2P mill to get access to the Potentiometer.

See below. The wiring was a bit tight inside but just enough slack to get the Pot out and also disconnect the white connectors. I noticed one of the spade terminal connections on the main On/Off switch could easily slide up and down about 1mm+, so I gently crimped the female part- that made the fit tight.

 

One connector isn’t used…I guess that is for the speed readout accessory.

 

Below. The pot has an opening on the underside that allowed the cleaner spray access to the insides. Before using the spay I noted that the spindle was quite stiff to turn – has the grease hardened up? Anyway, after spraying (and removing the grease?) the spindle rotation was almost frictionless. I did check on the web to see if I needed to somehow replace the grease but apparently Servisol is non-acidic and does leave a thin protective lubrication layer.

I let the parts dry out for about an hour before reassembly into the box. Now I can get back to milling.

As the fault was intermittent it could be anywhere between a day to a week or so before I have some confidence the issue has been sorted.

Thanks for the advice and I will report back.

Ches

 

[old martParticipant @oldmart]

It’s also agood idea to unplug each of the multi pin connectors in turn and give them a spray of Servisol. The spray is useful to use on connectors in car and motorcycle wiring looms

[Ches Green UKParticipant @chesgreenuk]

good idea to unplug each of the multi pin connectors in turn

Yes, did that and mated each connector a couple of times to wipe the contacts.

Did about 30 mins of milling this afternoon. So far, so good 🙂

Ches

PS: I read elswhere the spare white connector may possibly be for adding a reversing switch.

[Robert Atkinson 2Participant @robertatkinson2]

Intestingly that Pot appears to be different to the one fitted to later models. As far as I can see it has no switch.

Robert.

[Ches Green UKParticipant @chesgreenuk]

Robert,

Definitely no built-in switch. The mill is 4yrs old and supplied by Arc.

Maybe other suppliers of the same Seig mill design fitted a pot + switch?

Richard

[Ches Green UKParticipant @chesgreenuk]

The mill spindle stopped again today at noon, shed temp 15C.

It was just after I first powered up the mill and no cut had yet been taken so no load on the machine….the 1/16″ cutter had been rotating for about 10 secs as I let the bearings etc warm up.

I had also, whilst the mill was running, moved the mill head up and the bed in the Y plane, both by a few mm ready to take a cut in a different position.

It cut out and, I think, may have restarted restarted by itself after about 1 second. I can’t be sure of that though – I may have instintively turned the pot to zero and then back up.

Off for another think.

Ches

Edit: I’ve just ordered a new pot….should arrive late Oct/early Nov.

 

 

[Robert Atkinson 2Participant @robertatkinson2]

Hmm, might be a speed control board fault. Have a look at all the electrolytic capacitors for signs of leaking or buldging. It’s mostly the small ones that fail not the four larg black ones. It might just be the light but the top of the green one at the top of the board looks a bit buldged.

I mistyped my mill model in a earlier post it’s a SX1LP.

Robert.

[Ches Green UKParticipant @chesgreenuk]

Robert,

Below, a crop of the area I think you refer to. That cap is slightly out of focus but kinda looks OK?

As I mentioned earlier, I have ordered a new potentiometer. If that doesn’t work then I’ll dig in to the control box again…a replacement board isn’t cheap, but if I can identify a bad capacitor I can fairly easily replace that myself.

After today’s fault I then milled about 60 cuts x 50 mm long x 0.1mm deep with a 1/16″ cutter without further any issues – the mill performed well.

It’s a strange intermittent fault …. I don’t know if a capacitor would cause that, but don’t really have the experience to be sure.

Ches

 

[old martParticipant @oldmart]

I think I can see another electrolytic capacitor lurking under the top board, is it the only one? Check for any hidden ones, the tops tend to start to bulge before they fail.

[Ches Green UKParticipant @chesgreenuk]

Old Mart,

Thanks. I’ll check the original pictures I have on my desktop – I’m away from it at the moment. There may well be hidden caps.

Getting to the control board at the back of the mill is a half day exercise for me…the mill is bolted down and other equipment needs moving first. Also my back is recovering from a strain. So I will postpone having another look at the circuit board till I have tried out the new potentiometer in a couple of weeks or so.

I will report how things go.

Ches.

[old martParticipant @oldmart]

The long black chips may be in sockets and the top board may also plug into the lower one, at CN1 and CN2, perhaps.

[Robert Atkinson 2Participant @robertatkinson2]

The capacitor at the top does look distorted. even with the focus. Compare it to the one at the bottom of the picture.
A way to rule out the pot is to replace it with a pair of fixed resistors two 2.7k will set half speed. You could as set it mid way and put a pair of 10k resistors across it one from each end to the wiper.

If it’snot the pot or a capacitor it’s likely the self protection circuit is cutting in when it shouldn’t

Robert.

[Ches Green UKParticipant @chesgreenuk]

old mart/Robert,

Thanks for the feedback.

I will re-open the control box to examinine the caps etc closely, but that will be after I fit the new pot in a week or two, and if the problem still persists.

I’ve had 4 good years use out of the mill so am keen to keep using it.

Ches

[Dave HalfordParticipant @davehalford22513]

As you moved the head before it cut out, try wiggling the cables going into the head with the mill running just to discount a bad cable causing it.

[Ches Green UKParticipant @chesgreenuk]

Dave,

I should have thought of that …. I’ll give it a try. Thanks.

Thinking a bit more…I added gas struts to the mill earlier in the year…and didn’t really use the mill till recently, when the fault was first noticed. Adding the struts meant moving the DRO wiring and the main plastic conduit power cables – you can just see one of the conduits on the top left of the first pic I posted.

But…if moving the head caused one of the power lines to disconnect, the entire machine would switch off and I’d have to press the green On button again…but that doesn’t happen….the motor is still live after the fault….to get the motor turning again all I have to do is wind the speed pot down to zero and then back up to the chosen speed.

But I will give the cables a shoogle to see if anything does happen.

Ches

 

PS: I’ve beeen milling this morning …. the mill was running for maybe 15-20 mins total…no issues.

[andy198712Participant @andy198712]

What kinda noise does it make when it stops?

my sc2 lathe uses the same board and was stopping with a clonk, I thought it was belt related but all spins fine by hand. And spindle moves freely so ruled that out.

 

it would start again if I turned the speed down to zero then up again. Sometimes it would go for hours without doing it then do it a couple times in a row.

this this sort of clonk.

 

 

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