Sieg SC3-400 upgrade progress

As asked for by forum members, here is an update on how my my Sieg sc3-400 upgrade is fairing. My previous post has been moved or deleted so I will give a quick refresher.

The motor control board blew in the lathe after a jam. I repaired the control board with new chips, transistors, capacitors and diodes and the lathe worked as new for about three weeks and then switched on one morning and everything was dead. No fuses blowing this time, no tripping RCDs just totally dead beyond the filters so rather disheartened I figured the repaired board was not worth another attempt to bring back to life as I had somewhat butchered it on the initial repair.

So the choice was to buy a new control board £200ish (not a good idea as the original didn’t last a year) or upgrade. I bought a TEC motor and controller, and pinched a few bits from my stock of electrical parts.

VFD is a TECDrive IP20 0.75kW 230V 1ph to 3ph AC Inverter Drive, EMC

Motor is a TEC IE2 0.75kW Aluminium Three Phase Motor 230V/400V 2 Pole 71 Frame

Lathe has a speed controller in the same place as before and a forward/off/reverse switch on the front. At the moment the rest of the original fittings are there to keep out dust and debris. Power on/off is via the 10 amp MCB in the supply box.

It’s a beast of a set up but nice and quiet. Very impressed with TEC.

At the moment, because I need to make a few parts, the motor is fixed to a welded frame and fitted to the original motor mount on the lathe. This moves the drive spindle off centre due to the size of the motor but it is only a temporary set up.

The plan then is to extend the motor drive shaft a couple of inches and bring the spindle and thus belt closer to its original position. Hopefully this will enable me to refit the gears and selector as well as the protective cover (with a shaft hole in it). If not I shall ponder alternatives.

Will keep this post updated as things progress.

Mod edit: rotated photos

Edited By SillyOldDuffer on 15/03/2022 14:14:56

Your setup looks great and to me is much more sensible than playing around with the iffy controllers and motors the small machines often come with. I've often wondered why more people having trouble with controller / motor don't just scrap the iffy OEM controllers / motors and go with a similar setup to yours, I would expect you will get many years of service from it. Well done!

I think you could also adjust (swap) the spacer between the pulley and the gear for a better alignment.

Why was Drew's original post deleted?

Martin.

Drew, I think this is your original post on your cactus control board here? LINK

It does seem to be the only problem we ever hear of on the forum with these smaller Chinese lathes. Never seems to be any mechanical issues or accuracy issues etc with them. (With the rare exception of one Optimum micro lathe) They seem to perform flawlessly in those departments. But of course we only hear about the control boards/motors that play up, not all the others that perform up to snuff.

You seem to have come up with a great solution for your problem. How much was the approximate cost? Probably more than a board I presume, but upgrading the lathe's power and versatility into the bargain. Other users with similar problems in the future may be interested to know.

Edited By Hopper on 16/03/2022 11:34:46

I had never owned a lathe before and couldn't see the point of spending a small fortune on one when initially it was only going to be used to make a few parts for a motorcycle. Trouble is they are so addictive once you start using them..

It's absolutely brilliant for me and i'm perfectly happy to do this sort of repair/upgrade. I have learnt lots and still so much more to learn. I now have a much better understanding of what i want from a lathe, what's good, bad, annoying and just plain stupid and when retirement looms i may upgrade.

I did forget to post a pic of the drive controller (see below). It's wired from a circuit on the house consumer unit which is 30mA RCD protected. The 10Amp MCB is what i use to switch on and off. There is a quick blow fuse wired next to it (don't think it will go before the MCB or RCD but was specified in the book for the drive). The control box is Earthed to the main earth terminal. The motor is fed through screened cable that is earthed on the VFD. The control cables are earthed only at the VFD control box as earth loops are to be avoided. I did not fit fans as i prefer to leave the door open and have the motor speed display.

It is working great. On to stage two..

Edited By JasonB on 16/03/2022 12:17:40

Hi Hopper,

Motor was about £100

VFD was £130

All the electrical parts, wire etc.. i had knocking about already.

Edited By Drew Mason 1 on 16/03/2022 11:53:04

I think Drew's is the first Brushless board I've heard of blowing, but it is common for the Brushed power supplies to fail.

My Clarke CL300 'popped' twice before I replaced the motor & electrics with an industrial (750 watt) Brushless sewing machine motor setup.

I managed to keep the motor in its original location and It's worked without fault ever since. It is quite similar in operation to the current Brushless offerings.

Martin.

Edited By blowlamp on 16/03/2022 12:03:19

That's pretty reasonable cost for what you got. No idea how it compares with the cost of a board. A little bit more, I think, but you got a whole new and larger motor etc.

Yes they can be quite addictive. I am the same. Lathe was supposed to be for making old motorbike parts but seems to have taken over as a hobby in itself.

Edited By Hopper on 16/03/2022 12:00:57

https://inverterdrive.com/

I have since found a drive on there that would supply the original dc brushless motor that the lathe came with (but where's the fun in making things easy!!)

All too easy for people to see "Mini-lathe" and group them all together, as Blowlamp says I think this is the only Brushless one I have seen with a board problem.

Also care needs to be taken if doing a similar upgrade to the brushed versions of mini-lathes as the other problem that does regularly come up is stripped gears. The more powerful motor is likely to encourage the user to take a bigger cut and then the plastic gears will be even more likely to give problems. Not as issue for the Brushless ones as they don't have the gears to start with.

Drew.

Is there any chance you could show the link for this drive? I've looked on their website, but couldn't identify anything I thought suitable.

This might be handy in the future, if I install another Brushless motor.

Martin.

A search on Amazon for industrial sewing machine motors 750W give offers between 99 to 150£ postage to UK included.Is the VFD route worth the higher cost?

It was the easiest option for me. 1 motor, 1 VFD, 1 10k pot and a three way switch.

British made motor and drive. 2 year warranty as they were bought together.

Can't fault it so far.

Hi Martin

Link to drive

https://inverterdrive.com/group/AC-Inverter-Drives-230V/Invertek-Optidrive-E3-750W-1ph-3ph-IP20/

Thanks Drew.

I'll download the manual and study its features.

Martin.

Well this thread now resembles 'selective' swiss cheese! So let's ignore that for now (i WILL address it later) and crack on..

The metal for the motor shaft extension is on its way and hopefully here by the weekend (playtime) so will post info and pics as i make progress. I hope we can get away without any attenuation from the moderators over merely making something with a mini lathe on a forum devoted to mini lathes etc, but you never know..

Drew

Edited By Drew Mason 1 on 17/03/2022 10:15:26

could one of the moderators explain the TRUE reason why some posts on drews thread have been deleted. members have a right to know.

It was not me but as Drew seemed unhappy with posts by other members mucking up his thread I assume they were removed due to that reason.

Drew best get used to threads going a bit off topic, it happens all the time on this forum.

This is the first time I recall posts being removed from a topic for such a reason, perhaps it was not what was said but by whom.

Emgee