Thread: It's begun....
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...
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.
PS. I have removed the earth lead for now until I know how it should be wired.
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.....
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 ;-)
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...
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) :-)
Just a quick pic showing rails going on:
Another pic showing the beginnings of the Z axis.
I must be doing at least something right here as it moves nice and freely on its Y axis rails (as my crushed finger will attest to when I tilted it to put it back on the bed ;-) ).
Also I guess I should relate some areas of "interest" (read frustration) getting this far:
Firstly I had a problem with the profile from metallin having a slight ridge along the centre "flat area" on the 60x60 profile. This combined with Chai using hex machine head screws meant the rails would not sit flat to the profile bars but instead rocked side to side. This was easily fixed with replacment button head screws, which are lower profile and therefore the ridge in the profile can sit inside the rail supports and they can lie flat. Mine were very tight, but didn't have the stripped threads I see in another build log....probably air tools or something used to screw them in with too much torque.
Secondly screwing the extrusion together can be a pain, but I found that using a couple of turns on each screw using a similar pattern familiar to anyone who has torqued a cylinder head down seems to work well and almost pulls the extrusion into alignment itself (provided its cut at a nice right angle, which I'm using a TCT bosch blade in a chop saw for).
Thirdly I highly recommend a spiral flute tap (I think that's the correct name) for tapping the aluminium. The alloy for the extrusions seems to be stickier than most and was clogging up my normal taps after only a few turns. Even backing out to break the "chip" after every 1/4 or 1/2 turn didn't seem to help on my normal taps. IIRC I got the spiral flute tap from Arc Euro trade (is that John S's company?) - highly recommended and I'll be ordering more goodies from there in the future.
Of course there is much more to do, but it is nice to have a moving part operating correctly on the machine.
My ali plate also arrived today from Aluminium Warehouse (thanks for the link Jonathan), so I can get on with making the mounting plates to fix the X Axis bearing blocks to the gantry.
I am also having to do an on the fly redesign of the z axis, as the 120mm extrusion is not going to be wide enough for the two supported rails and ballscrew mount etc. Luckily I ordered a 1000x500x15mm ali plate so I have at least got plenty of material to make a wide version from.
More as I progress......
Build has been on a bit of a pause since my last post, partially due to waiting for a new circular saw (read more powerful and able to take my Bosch 210mm metal cutting blade), which I also needed for some other wood projects and also due to finally selling my house, which means I will (fingers crossed) be moving to premises with a nice 30x15 foot workshop :-)
Anyway here's a quick couple of pics of the wiring work in the control box (re-purposed rack mount servre case) progressing and its now pretty much complete, with the remaining XLR sockets wired to the BoB, which will be used for limit switches and spindle relay (need to find out how the latter is wired i.e. at the VFD directly if it has one built in or whether I need to grab a seperate unit). The second pic shows the mains on/off switch, which was a nice fit into a 3.5inch drive bay blanking plate.
Stuff I need to do in the control box are decide if I need the short CY cables shielding earthed (probably not) and work out where the parallel lead will go.
Which also leads me to a few questions:
1. What kind of parallel lead will I need, as there are data transfer and printer types and IIRC 1 is 25 pin straight through and the other has a pin 1/2 swap like a nul modem (been a while since I've used a parallel lead on anything).
2. Also has anyone run a 3metre parallel lead and is this likely to be an issue?
3. Finally has anyone used this unit? Zapp Automation Ltd - Stepper motors & Stepper Motor Drivers - Servo motors and Servo Motor Drivers - Ballscrews & linear motion products. : PLCM-E3 CNC Controller (For use with Mach3) [PLCM-E3] - £150.00
From reading up on it, it doesn't seem to do more than provide conversion from ethernet/USB to an existing Parallel port BoB (or BoBs), but using my structured cabling to connect the PC to the controller box is appealing.
Tomorrow I will likely attempt to chop my ali plate for the Z axis and the spacers to mount the gantry to the X axis bearing units.....will report back after that...
Ooops nearly forgot.
As I tend to cover all soldered connections with heatshrink I have kept a spreadsheet of conections and wire colours etc, so that if I am troubleshooting or adding new wiring I can work out what goes where and its function.
Might be of use to somebody, so attached.
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BUILD LOG: Web Goblin cnc has begunBy Web Goblin in forum DIY Router Build LogsReplies: 147Last Post: 12-02-2012, 07:49 PM