KX3 Spindle Problem

[ModelSteamKen]

Have owned a KX3 for some years now and I'm having no spindle rotation for the second occasion. The provblem was sorted by the late John Stevenson and at that time I replaced the spindle motor control board. The problem has happened again and going through the same test proceedures as before I find that I am not able to get anywhere 10 volts out of the breakout board. I have tried changing step pulses, pulleys and have the voltage adjuster turnned up full and can only get 4 volts. Is my problem in the breakout board this time or is it the motor control board again. X,Y & Z are working normally.

[JAZZCNC]

We need more info. I'd guess the BOB generates the isolated 0-10v and feeds this to the Spindle control board which I'd guess is a DC motor controller.

However, I'm guessing so it would be best if you could give more info and post pics of what's inside.! . . . . . Or because Basic BOB's are so cheap these days just swap out the BOB.!

[ModelSteamKen]

Hi Jaz
Yes the 0-10v comes from the BOB in the right hand side electrical compartment and then goes to the DC spindle control board in the rear compartment. All the works are as the standard Sieg KX3. I'll take some photos and post them to-morrow.
Thanks
Ken

[JAZZCNC]

Hi Jaz
Yes the 0-10v comes from the BOB in the right hand side electrical compartment and then goes to the DC spindle control board in the rear compartment. All the works are as the standard Sieg KX3. I'll take some photos and post them to-morrow.
Thanks
Ken

Ok well that's simple enough to check. Disconnect the wires going to the Spindle control board and measure the voltage at commanded speeds. If you haven't changed any of the Spindle settings in control software (mach3 I presume) then you should get 10v at full commanded speed. If you don't then it's the BOB at fault not the spindle control board.
If you have changed the spindle settings then I can't help anymore without knowing the BOB your using, but Knowing John S it won't be anything too fancy as he liked to keep it simple and cheap.

[ModelSteamKen]

Hi Jazz
Having problems putting a photo on but have checked the voltage and only getting 3.9v at full command speed. All setting are at original settings.seems like it is probably is a BOB fault.There is an web site visible on the board www.cnc4pc.com. Any other suggestions as to a make of board.
Ken

[JAZZCNC]

Good old John S probably just saved you some money by fitting decent gear.?
I think that's old or should say, early C11 board.? If you notice the board is full of plug-in chips rather than surface mount like many cheaper boards use, this is done so can easily swap them out if one blows up.

Cnc4pc is owned and run by a guy called Arturo who's a very helpful guy so maybe worth dropping him an email. He'll tell you which chip you need and more than likely sell you one.

[JAZZCNC]

The picture isn't great but it looks to me like there's a group of 3 capacitors near the center of the board and the middle one looks like it's blown.? I'm not into electronics but I'm pretty sure something like this would still allow to work but lower the voltage.? . . . I'm sure Doddy or some of the Electronic wizards will tell you quickly enough if it can.

It may be worth you taking it out and giving a close inspection.!

[ModelSteamKen]

Hi Jazz
Thanks for the info I'll try and get in contact with Arturo at cnc4pc.
Ken

[Clive S]

Hi Jazz
Thanks for the info I'll try and get in contact with Arturo at cnc4pc.
Ken

Jon swift on this forum seems to collect a lot of bob schematics and might be able to help.

[Doddy]

looks to me like there's a group of 3 capacitors near the center of the board and the middle one looks like it's blown.?

Pfft, you have better eyes than me.

I did google the KX3 when Ken first posted - I think I agree with the C11 board and this was the original spec for the machine so a like-for-like replacement at the time? A new card is (only?) $68 and if OP has the confidence to replace then it might be the easiest solution all around. The chip that's going to be responsible for the analogue output is the LM<something-or-other> on the far left of the photo. That's likely a £1 replacement, though it could be with the ancillary circuitry around there (caps, resistors) or the opto-isolator (the white chip), or the power from the spindle-controller card (I'd expect that to export 12Vdc to the BOB for the purpose of isolated power supply between the BoB logic and the spindle-controller) - worth checking that.

OP: If you find yourself in a rabbit hole with this (and I don't think you need to) if you're prepared to post the board I could always take a look to overhaul it. That's a casual offer - I think it'd be quicker/easier for you to contact CNC4PC in the first instance.


EDIT:

Just re-reading the thread, OP - if you have the 10V supply from the spindle board then try throwing a 10k potentiometer across this and the spindle 0V, with the wiper connected to the analogue input - that should give you full manual control of the spindle speed and verify that the spindle board is okay - just to confirm the BOB is suspect. (there's a chance of a fault on the spindle board dragging the analogue output from the BOB down - this just helps to isolate the problem).

[JAZZCNC]

(there's a chance of a fault on the spindle board dragging the analogue output from the BOB down - this just helps to isolate the problem).

This is why I said to disconnect the BOB from the spindle board when checking volatge so hopefully Ken did this.?

Also I'm not sure which Spindle board it's using but I know a lot of these spindle boards have mains voltage kicking around the Analog input so be careful Ken.!

[ModelSteamKen]

Thanks everyone for the comments. I have since put a question on CNC4PC forum and I await comments. It's looking very like the BOB. I'll post the result as it might be of interest to someone else.
Ken

[ModelSteamKen]

Hi Folks
Still chasing the problem of having no spindle. I've been working with Aturo at cnc4pc but have had little sucess. The only board that hasn't been replaced is the small AP2 board which lies between the BOB and the main motor board. All the necessary voltages are now coming out of the new BOB to the connections at the board. Does anyone know what this sall board does and if outputs can be tested? Getting new AP2 board being hampered by present world situation.

Thanks
Ken

[Doddy]

Okay, I've spent 20 minutes too long trying to find out what the AP2 is, and failed. There's various talks of step/dir controls on the KX3 but I'm minded not to read too much into that at this time. Can you get a photo of the board to perhaps help us understand it better?

[ModelSteamKen]

Hi Doddy
Thanks for your prompt reply. Here is a photo ofthe suspect AP2.27735
Hope this works.
Thanks
Ken

[JAZZCNC]

I think it is the speed control board, does it have a potentiometer on it.? I think the AP stands for Analog Potentiometer Board.

[Doddy]

Ugh. I wish I'd never asked, now. I'm throwing an awful, awful lot of guesswork into this that might be completely misleading.

Have you seen this link and does it look sensible and appropriate?

https://littlemachineshop.com/images/gallery/instructions/4213CNCSpindleControlUpgradeKit.pdf

If only for the association with the board. I'm reading more, and this is hitting the territory I'm in with spindle speed control on a SX2.7. But, my interest lies if this is OEM or a modification to the KX3

EDIT: Though read somewhere that Sieg used these boards themselves for the CNC machines.

I'm out of ideas here - there's clearly two opto-couplers that are connected to the spindle-control board - these could be step/dir but that's guesswork. I would expect that these would be involved with the speed control given the nature of this board - if you had access to a scope it would fall into the "interesting" category of investigation, but you're looking at a fairly proprietary interface now between this and the BLDC controller in the Seig.

But you've convinced yourself that your analogue wiring to the board is correct?

EDIT 2: I'd check through that link and verify your wiring as a first port of call.

My experience of the BLDC board is that can be fragile (mine popped two IGBT and a fair bit of collateral circuitry early in its life - replaced under warranty), and you've suggested that you may have had similar problems and replaced the board yourself in the past. So there's a question that you have no spindle control (no rotation)... is it the BoB - you suggest not / this is replaced. Is it this board or the spindle board (BLDC controller) - and that can be a challenge to understand (sorry, that's not very helpful I know)

[Doddy]

Anecdotal footnote: When I get around to it I'm tempted to replace the whole Sieg board with a Chinese BLDC controller - they appear quite reasonable in cost, and offer 0-10V speed control out of the box. I did start looking at the start of this enforced isolation business but got distracted. I may pick up on this again.

[Kitwn]

I think it is the speed control board, does it have a potentiometer on it.? I think the AP stands for Analog Potentiometer Board.

The blue thing, top right hand corner of the photo is a trimmer potentiometer, possibly a multi-turn type. The label under it looks like "START/STOP". If you adjust it keep track of how many turns and in which direction so you can put it back where it was.

Edit: Just made time to read Doddy's link. START/STOP is a label on one of the connectors. The potentiometer is for the speed at max control voltage. Pots can become faulty and go high resistance but it's possible to clean the track inside by simply adjusting it up and down a few times. Certainly worth a try for the time it takes.

[dazp1976]

That board looks exactly like little machine shops upgrade board.
Was the machine bought new by you are did you buy it used? Might be the LMS board in there already. Straight swap.

[Doddy]

I'd tread carefully here with blindly replacing boards - the problem is not (as I understand it) known to be with that card at this time. That is what OP is asking about and unfortunately I don't know enough about that card to understand the protocol between itself and the (modified) spindle control card in the mill (the same kit, even if OEM with SIEG, requires a modified micro controller on the spindle control card).

This link provides a really interesting bit of reverse engineering which explains a bit about the protocol used on the "LMS" board (aka Sieg board).

https://blog.familjenjonsson.org/blog/2015/12/28/cnc-mini-mill-9-spindle-and-coolant-control/

I'm about to head to my SX2.7 and see if this is similar to the touch-panel interface (nothing is ever that easy! and I fear the LMS interface will be different)

[ModelSteamKen]

Here's an update to the no spindle rotation problem. Yes I've seen the Little Machine Shop's upgrade and now realised that this is an alternate board used by Seig to enable the speed to be altered by the BOB output. I have been in contact with Arturo at CNC4PC and he suggested that I check the wiring of the actuation circuit as everything else checked out OK. This consists of the mains feed passing through a small transformer on the AP2 board and is switched by the relay on the BOB. On investigation I found that I was not getting any mains voltage at the input to the relay in any position. Mains was found at one of the pins going to the transformer. Checking the primary of the transformer for continuity through the transformer I found that it fails( No Continuity) Followed the tracks to the transformer and when tested these were OK to the pins. The secondary circuit tested OK. That's my problem - burnt out primary winding on the transformer. The relay was unable to make a circuit and hence activate the board. So I have to get a new AP2 board from Arceuro when things free up again.I've been round the houses with this problem but at least the machine has go a complete facelift as regards electronic boards. The machine was bought new by myself maybe 10yrs ago now and it has served me well doing the bits and pieces that I come accross. Hopefully for many more years when I get this board replaced. Thanks for the pointers everyone.

Ken

[Doddy]

Oooer.

So, one experience I read (amongst many) was someone modifying the AP2 board to remove the transformer as they could feed a local 12V DC straight into the onboard regulator on the AP2 PCB. They removed the transformer and inserted 2 pieces solid-strand wire from the two primary terminals to the two secondary terminals, then removed the 110VAC (this was an American site) input to the board and sourced 12V from "elsewhere". That fed into the local bridge and onto the local 7805 regulator. That could be a very easy fix for you if you want to avoid the cost of a new AP2.

Chances are its an embedded thermal fuse in the primary that's gone.

Very useful information and follow-up. Thanks.

[ModelSteamKen]

If it's definitely 12v I think I will try and source a new transformer. RS is still online. Desolder and drop the new one in. Nothing beats a try! Could always fall back on the 12v direct supply as plan B.

Ken

[Doddy]

See the link in post #21 - it's part-way down that page that describes the removal of the PSU. You sound like you know what you're talking about so you be able to eyeball the rectifier / smoothing / regulation in establishing a suitable transformer replacement.

[ModelSteamKen]

Interesting

Thanks
Ken

[ModelSteamKen]

Hi Folks
Final update on the goose chase. It wasn't the BOB, it wasn't the main motor board, nor was it the AP2 board. It was a circular magnet that had fell off the bottom end of the motor spindle which must send some signals via sensors back to the motor board. Discovered when I went to investigate the last area possible, the motor and the leads from the motor board. The magnet shaped like a polo mint was lying inside the plastic cover when removed. Machine is well enough dismantled now all I have to do is reassemble. Secured the magnet back on to it's register on the main shaft with some Superglue. Motor back into life. What a chase. For anyone experiencing the same problem I would recommend lifting the motor out and checking it would save alot of time and head scratching. Thanks all for the feedback and encouragement. Soon get swarf flying out the door!