First Proper CNC Router

[Voicecoil]

Just spotting I have the fuse on the zero volt side of the psu!

Maybe because you've used brown for 0V and blue for +68V & hence thought the fuse was in the "live" side?? I tend to try to keep blue and brown for mains N and L and use other pairs of colours e.g. red/black or orange/violet for other power rails, helps to know what's what if the wiring gets "busy". As it's AC and floating it really doesn't matter anyway!

[Doddy]

<deleted - thought I was replying to a recent post about wooden enclosures... >

[diycnc]

That's exactly what I was planning on doing, but at some point I managed to wire brown to + and blue to 0! Not really sure how.
When it comes to the finally wiring I'm definaltly planning on using other colours to differentiate. Is there a standard when it comes to control panel wiring?

[diycnc]

All three drivers tested and working perfectly. Thanks for everyone's help with this!

Iv got a feeling it might be a while before I make any more progress on this. Some genius (me ) decided to start decorating three rooms at the same time, so that has to take priority now or the missis won't be too happy if it ain't finished before Christmas

[Kitwn]

Think on the bright side: You may be able to lose the cost of a tin of Hammerite in the housekeeping paint budget

[diycnc]

Found a little bit of time to wire up the motor on X axis (side to side one on the gantry) to see something moving.
I very quickly seamed to find the limit of these motors+drivers+screws at between 4000 and 5000mm/min (800-1000RPM at the motor). I was hoping for a little more than this. Acceleration is down at 20mm/sec2.
Do these sound like reasonable numbers when compared to other similar machines? Im a little more used to deal with lightweight 3D printers which are happy fly around at 150mm/sec+ all day. Guess a heavy CNC is a totally different animal though.

Spec is; 3.1Nm Nema 23 wired in parallel, 3.08A peak driver current, 68Vac, 1600 steps per rev (1/8th micro stepping), 1:1 belt drive, 1605 screw.

I know 1610 would be much more appropriate, but 1605 was sooooo much cheaper!
Motors are rated to 4.2A, so I could push the peak current upto 3.77A. Would heat dissipation become an issue running at 90% the rated current?
A quick google seams to suggest around 1000RPM is the limit before torque starts to drop of significantly, so im starting to think this is the genuine limit of the motors.

Its bloody loud too! Was expecting digital divers to be nice and quiet! I know increasing microstepping would help. What microstep settings do other people use?

[Neale]

My machine is a very similar size, and also with 1605 driven 1-1 from a NEMA23/3Nm. I get around 5000mm/min as well, although I haven't really tried winding it up much more as that is about as much as the long axis will take anyway. That was my design goal in any case as, as you say, that is about the corner speed of those motors when they start to lose torque. Can't remember the acceleration I'm using - I'll try to check next time I fire it up.

Brian's law of motor current tuning is - "keep winding it up until it starts to get about as hot as you can comfortably hold when it's been running for a while." I'm not sure how accurately those driver current limit numbers are given that they are averaging a pulse output, and the motor current ratings are RMS? Peak? Who knows - the only issue is whether or not they get too hot in practice! Stepper motors are designed to run hot and mine have run using that adjustment technique for a few years now with no apparent ill effect. As for noise - that one's very difficult to judge!

[Kitwn]

I know 1610 would be much more appropriate, but 1605 was sooooo much cheaper!

I'd be interested to know where you found cheaper 1605 ballscrews. A quick scan of Fred's BST Automation's site has 1000mm long ballscrew sets of 5 and 10mm pitch at $148 AUD and $135 respectively, including delivery to Australia. Interestingly he also has 1616 screws for those wanting an ultra-fast machine.

[diycnc]

Ebay.
850mm 1605 screws are just £30, and are delivered from the UK so no need to worry about getting stung with import tax.
To my in experienced eye they seem ok. Were packaged well, and dont appear to be to bent.

[AndyUK]

That might be why things are sounding loud. Are they lubricated well?