It's begun....

[Washout]

Quick update (no pics yet) - two parcels arrived from China today and I now have my rails, ballscrews, VFD and 2.2Kw spindle plus ancilliaries :-) I can, along with others recommend Chai for these components - very easy to deal with and will accomodate most requests (I needed FK bearing blocks rather than BK for example).

The rails are a little over sized, but that's better than undersized, so its out with the angle grinder to cut the stainless (hack saw is more eroding than cutting ;) ).

I'm going to need to make a few adapter plates for the ballscrew bearing housings and rail bearing blocks, so I'll need to track down a cheap supply of aluminium plate.

I'll get some pics when the bits start to go on the frame in the pic above.

[Jonathan]

I'll need to track down a cheap supply of aluminium plate.

Aluminium Supplier | Aluminium Stock | Aluminium Warehouse

Or if you just need a small bit let me know...

[Washout]

Thanks Jonathan - I'll grab a decent sized sheet from them, which I can use for adapter plates and also the Z axis - I'm thinking 15mm thick should be sufficient (I can also make the spindle mounts from this).

Cheers


Chris

[Washout]

Hi All,

Whilst waiting for my bed extrusions and some other components to arrive, I have been busy festooning the rack mount case with wiring (see pic below).

Stuff wired up are:
- the small PSU, which is powering the case fans (tested this and all is running fine).
- The 240v AC input, which goes to a front panel mounted On/Off switch (same kind you see on pillar drills etc)
- 240v AC from the On/Off switch to the two PSU's
- The CY cables for X, Y and Z from the drivers to the XLR sockets (shielding grounded to the star point) - I'm wiring my steppers in parallel, so am following the Zapp wiring diagram here: http://www.zappautomation.co.uk/down...%20%281%29.pdf
- The high voltage DC side of the drivers to the transformer (running it parallel off of one PSU output (hope that is right)

Still to do are:
- Low voltage DC side from the breakout board to the drivers (waiting on some lower guage wire for this job)
- Limit switch, spindle, e-stop wiring from the breakout board to the spare XLR connectors
- Find out if the earth lead I have on the main PSU is really where it needs to be, as there doesn't seem to be anywhere else to attach it to, or discard it if its not needed?
- Perhaps get some QA on my wiring, because although I am following the diagrams etc to the letter, a fresh set of eyes is always useful before throwing the power switch for the first time....

The mechanical side of things is on hold for the moment pending delivery of some extrusion channel nuts to start mounting the rails and some ali plate for mounting adapters.

More to come........

[irving2008]

Are you working to a circuit diagram or making it up as you go?

Be careful with that central bolt on the transformer. Have a look at the Printed Circuit board underneath. Does the bolt connect to a copper plane at all? If it does you should attach your earth to that side not the top or better, dont attach to that bolt at all, but use metal mounting posts for the PCB to earth it to the chassis. If it doesn't, i.e. its insulated from the circuit board, then you don't need an earth there at all. The way you have it wired could be a problem if the bolt should touch the chassis, or if its connected to something on the circuit board that could end up connecting to the chassis, because then what you will have created is a shorted turn on the transformer which will at best give some loss of power and at worst could cause overheating and melt things...

[Washout]

Thanks Irving

I'm working off of the circuit diagram in the pdf in my post, but that only shows the driver circuitry essentially and not the PSU specifically.

The PSU is this one Zapp Automation Ltd - Stepper motors & Stepper Motor Drivers - Servo motors and Servo Motor Drivers - Ballscrews & linear motion products. : PS806-5 Linear power supply [PS806-5] - £102.00

From what I can see the toroidal coil is bolted via that central bolt to a mainboard, which doesn't look like it has any copper substrate to it. The daughter board, which has the capacitors etc (rectifier?) is a standard PCB, which is wired to the coil(s) and that is also mounted on the main board by brass spacers. I currently have nylon spacers from the main board to the chassis, but could certainly replace those with brass also, if that's how its supposed to be earthed or maybe as you say it shouldn't have an earth connection at all (which I find a little difficult to believe, but I'm no expert).

I'll try and PM Gary @ Zapp and see if he can help (the data sheet for the PSU is next to useless, but that's normal for stuff like this I find).

Thanks for the sanity check in any case.


Chris

PS. I have removed the earth lead for now until I know how it should be wired.

[Washout]

Quick update:

Gary came back to me and the PSU doesn't have an earth, so I have removed the wire to the main bolt.

Just need some more bits to arrive now.....

[Washout]

Quick question for any of the more electrically minded amongst you all:

Looking at Irving2008's diagram showing an earth loop, when I had the earth wire from the transformer's bolt to my star point. Do I not also have an earth loop with the CY cable shielding going to my star point and that shielding also being grounded where the XLR sockets come into the chassis as the outside of the sockets is the earth conductor?

If that's the case, should I isolate the XLR sockets (or the plate they are mounted into) from the chassis? - I could do this with rubber O-Rings.

Apologies for all the electronics questions, as whilst I have some electronics experience (555 timer circuits and various PC input/simulation projects), those are generally a two wire solution i.e. +ve and 0 or -ve and little risk of zapping myself with dangerous currents ;-)

[irving2008]

Generally you should only ground shielding at one point. If there is a good ground for the shield at the XLR then good practice says you shouldnt ground it at the star point either.

However the issue is minor here as there is little likelyhood of induced current in that short a run. The real issue is where you run a long shielded cable alongside, say, an unshielded power cable. Grounding both ends of the shield allows the magnetic field from the power cable to induce a current in the shield which can cause strange effects. In one site I worked on this problem caused the 'ground' of the remote device a few metres away to be 7v AC relative to the controller. With no opto isolation it wasn't surprising that the logic circuits were having some difficulty. Disconnecting the shield reduced the offset to <0.1V and all was well...

[Washout]

Great - thanks for that, I'll leave that side as it is then.

My bed extrusion has turned up along with the M6 connectors I needed this morning whilst I was on one of my rare visits to the office, so I can also crack on with some of the mechanics as well (will make a welcome change from wiring) :-)