View Full Version : Have I got a faulty 1.5kw spindle

01-07-2020, 12:49 PM
After building my cnc a couple of years ago with the help of the people of this forum I have a problem with the spindle .
The story goes like this
A couple off days a go I switched the spindle on and I thought I felt a slight tingle when I touched the frame off the cnc , I got my multimeter out and tested the frame for voltage when the spindle was running and I was getting a reading of it jumping from 30 to 100 to 160 the spindle seemed to be working 100% but then I realised that I had not earthed the frame, the cable was under the table but was not connected to the frame, I also found that the spindle had no earth wire, When i connected the earth wire and switch the vfd to run it would trip the trip in the house , I have checked the vfd and the trailing cable to the spindle and tested Ok , I have done a few test on the spindle and here is the video , Is the spindle faulty ? Any help would be much appreciated.


01-07-2020, 01:48 PM
Yes it looks as if you have a short from the windings to the case. The case should be grounded, so a short between the outputs of the VFD and ground will trip the RCD in your house.
You should be seeing open circuit between the windings and the metallic case.

Unless it is under some sort of warranty you might as well go a stage further and dismantle it to see if there is any obvious wiring short you can rectify. Failing that, you are holding a piece of scrap. Could it have been like this from new?

01-07-2020, 01:57 PM
Hi Muzzer
Its a year old so it could have been like this from new , When I got the tingle from the frame I was also the touching pilar drill with my other hand which is earthed, I will have a go at opening it up if i can work out how to open it

01-07-2020, 04:24 PM
If you are really lucky it could turn out to be the wiring between the connector and the stator windings, or one of the winding wires touching the housing somewhere accessible. The windings should be protected against abrasion with the laminations by means of tough insulation pieces lining the slots. Or that's generally the plan.

Fingers crossed.

02-07-2020, 01:01 PM
all wires seem to be fine must be something to do with the windings . looks like i am going shopping , Does anybody have a good source for these 1.5kw air cooled spindles?

02-07-2020, 01:26 PM
Bummer. They should be doing insulation tests before they ship the products. It's always a risk when you buy Chinesium stuff - the downside of the cheaper deals.

I guess this highlights the importance of correct installation protective earth connections ("equipotential bonding") to all exposed parts. As a general rule, protective earth wiring should be at least as thick as the supply wiring and the fuse rating should be low enough to prevent any of the wiring burning out before the fuse in a fault condition.

You have an RCD here which trips out before any fuses etc are blown or people are fried. Ideally you should have had your protective earthing connected up before this happened but hopefully now you can see how it's important. The danger of relying on a fuse rather than an RCD is that you might pop your VFD and the protection would rely on blowing the fuse which is more of a test of the wiring.

Bottom line is to ensure exposed metallic stuff (including the machine body itself) has a good hard earth connection, particularly if it's been sourced from China! I'm always careful to install and test the main earth connection and ensure everything has a good connection to the (grounded) cabinet / chassis. I'm sure there must be some real horrors in home workshops around the world.

02-07-2020, 02:30 PM
I'm sure there must be some real horrors in home workshops around the world.

More than people realize and it's not always down to the DIY builder.! . . . I've seen several machines sold by companies to home users with wiring that was dangerous and in one famous case which played out on this forum with the guy actually going to jail with machine potentially lethal had it been turned on.

I know of two cases of sheds being burnt down and one case with an attached garage where the house was badly damaged and the insurance refused to pay out because wasn't insured for machinery.!! . . . . . The simple rule is DONT MESS if don't fully understand what your doing and never cut corners because that 20 you saved on a RCD or fuses etc could easily turn into 20,000 or 200,000 if it burns the house down.!!

02-07-2020, 02:43 PM
Yes it was my fault , The earth for the frame was under the table off the router which I forgot to connect to the frame so it was without the frame being earth for 18 months , which is probably why the faulty spindle work as there was no way to earth . When i connect earth to frame trip went straight away. Is there a supplier for these spindles in Europe?

02-07-2020, 03:12 PM
I got my whole workshop tested by a proper sparky outfit and had it registered with the local building control (council). They do the whole set of tests, from earth wiring to continuity and insulation testing. I design electrical equipment (VFDs, PSUs, motors etc) that could kill people so have a reasonable understanding of the hazards and regulations but even so, I like to have a proper contractor to check it out.