AndyUK's Build - 1.2x1.0m Gantry

[fgfreek32]

looks like mine,like it

[Doddy]

Just a thought with the selection of a transformer - ignoring core flux (not realistic, but bear with me) - you can use the typical twin secondaries not so much in parallel, but as two separate supplies. It costs an additional capacitor (though lower capacitance) and an additional rectifier. It means that your copper losses are reduced on individual supplies and regulation is arguably better. It's an approach that I'm trying with my type of machining (typically machining In X/Y, not 3d profiling) - so I intend to bond Y/Z on one supply and X/A on the second - my thoughts are that only one stepper is likely under load at any point in time on any one supply.

80V drivers?, some common ones in this range are AC/DC - if so just remember that the first thing these will do is rectify/smooth the supply internally.

Your preference to rate the caps at 2x VDC - your money. A bit of head-room is a good idea but 2x is a little bit frivolous. Admittedly mine are more so - at 160VDC (50V secondaries) but that's simply because I had them in the shed as part of a bulk-buy.

[AndyUK]

looks like mine,like it

Thanks! They certainly share a few design ideas don't they? :)

Just a thought with the selection of a transformer - ignoring core flux (not realistic, but bear with me) - you can use the typical twin secondaries not so much in parallel, but as two separate supplies. It costs an additional capacitor (though lower capacitance) and an additional rectifier. It means that your copper losses are reduced on individual supplies and regulation is arguably better. It's an approach that I'm trying with my type of machining (typically machining In X/Y, not 3d profiling) - so I intend to bond Y/Z on one supply and X/A on the second - my thoughts are that only one stepper is likely under load at any point in time on any one supply.

Interesting idea - I don't know much about power supplies and transformers though, so I'll need to do more research! On mine with the two drives on X, I'd be wary of joining the X/A because they'll be drawing significantly more that Y/Z, and they'll be doing so at the same time as each other.

Your preference to rate the caps at 2x VDC - your money. A bit of head-room is a good idea but 2x is a little bit frivolous. Admittedly mine are more so - at 160VDC (50V secondaries) but that's simply because I had them in the shed as part of a bulk-buy.

Good point - but it looks like I'll end up paying about £12-15 for the four capacitors I need, at that price I can afford to over-rate them!

[AndyUK]

So, because I've sorted my motors and drivers before the rest of the control system, I've spent the evening checking that everything works as expected before I pack them away and let the warranties tick away.... At least I'll know they all worked at least once eh?



Simple setup with a 48VDC power supply I had lying around and an Arduino to generate the pulses. Always nice to see a stepper womble back and forth, and it means as soon as my mechanicals are ready I can test the steppers in place without needing the control system finalised.

[AndyUK]

1x PSU Fabracobbled together.





Still needs some hot glue on the caps (I've misplaced the glue gun - d'oh) - Testing will need to wait until the Wife gets back from a work trip, I'm not turning this one on whilst I'm alone in the house! Went with a 625VA with 2x 40V secondaries in the end, gave me 45V on the secondary, so hopefully about 63V after rectification and smoothing.

Oh, and yes I'm a muppet and ordered the wrong size capacitor clamps. 3D Printer to the rescue!!

[Nickhofen]

It looks good!

[AndyUK]

Hi All,

Wiring Diagram, V1 attached! Please note future builders, this is a very early days schematic - I don't have half the components and most of these connections are untested.

Questions I'm currently pondering:

• Theres currently no ground to the UB1, and by extension anything that it connects to, other than cable shielding. I feel like I should be grounding the motor drivers or something...!
• Does the E-Stop circuit look okay?
• Need to find Limit and Home switches and then tailor diagram to their requirements.
• Need to figure out what I'm doing with the 4th pin on the spindle re grounding. Does the ground go to the VFD like I've shown?
• Noise suppression - The VFD and the 24V/60V PSUs will be sharing a mains connection. The garage is on a 16A spur, so it's quite hard to get cable distance between them, is there something I can put into the system to suppress the noise from the VFD?

Thanks Nick, I've been using a few of your diagrams on here and CNC Zone :)



Edit - Heres the updated version, don't use the one above.

Circuit Diagram v2.3.pdf

[Doddy]

Hi All,

Wiring Diagram, V1 attached!

Questions I'm currently pondering:

• Theres currently no ground to the UB1, and by extension anything that it connects to, other than cable shielding. I feel like I should be grounding the motor drivers or something...!
• Does the E-Stop circuit look okay?
• Need to find Limit and Home switches and then tailor diagram to their requirements.
• Need to figure out what I'm doing with the 4th pin on the spindle re grounding. Does the ground go to the VFD like I've shown?

Thanks Nick, I've been using a few of your diagrams on here and CNC Zone :)

1) Why? you're driving the stepper drivers through their own opto isolation - no need for common ground there, and I *think* the analogue output from the UB1 for spindle speed control is also an isolated supply. Don't worry about galvanic shielding - the UB1/UC300 isn't shielded so you're gaining nothing.
2) Let someone else answer
3) Let you answer
4) Should ideally go to a common/star earth point, similar to the VFD earth (and the supply lead earth)

Not familiar with the UB1 - can it drive the 24V contractor coil directly?, and back emf?

[AndyUK]

Thanks Doddy,

1) That makes sense. I think I just have a pathological need to make sure everything is grounded as much as possible..!!

4) That's my plan - it looks like that connection is the only place on the VFD to earth it, so I may end up connecting that to both the spindle body via pin 4 and the mains gnd.

Not sure, haven't spec'd a contactor yet, but will look into it. At the moment I don't think I'm asking the UB1 to drive it directly? Its driven by the 24V PSU via the PNOZ.

Re Back EMF, from the VFD? If so I've added a question above about noise suppression above. I guess I'll also get back EMF in the 60V PSU, but was expecting the capacitor bank to help out with that, will that cause issues upstream?

[Doddy]

Back emf: from the coil of the contactor/relay.

But I don’t know the particular UB1 output spec. If a mosfet might find it has a commutatinf diode built in, otherwise place a 1N4001 across the coil, cathode to 24v line, anode to ground