Reducing the space in my garage.

[Rich]

Per an earlier post, I’d run through ‘Gecko: Step Motor Basics’ and put the details into a spreadsheet, the results reflect the numbers quoted by Jazz. As the basics of building a dedicated PSU have been clearly stated, I will give it a go.

I will follow the PSU circuit provided by Irving, except for the safety circuit, which will be adjusted to include things I already have hanging around:

- NVR Switch, removed from a 240v hobby router table
- Zig CF-8 charging and distribution unit 12v http://www.zig-electronics.co.uk/products.htm#
- 240vac, 25 amp Consumer Unit
- STAC, AC voltage regulator, ST500W (Type D) http://stac-japan.jp/portable/

Zig unit will be used in the safety circuit, in place of the 24vdc transformer. The NVR switch is an option, but more probably a 12v momentary push button switch.

The Consumer Unit can be used as the primary switch (C or D rated MCB). The AC regulator can be wired into the safety circuit, using a third relay. It will take power from the 240v garage supply. I’m assuming I can break into the cable between the mains and the unit, so the unit and the spindle will be isolated when the e-stop button is pressed.

I'm still roughing things out and will need someone to review the completed PSU before I turn it on?

[Jonathan]

The methods described in your link from Oriental Motors are essentially the same as my script here. Mine is a bit more detailed in some areas, for what it's worth...It's also to get a qualitative feeling for the system.

If you don't have the torque speed curve for a particular stepper motor, a reasonable assumption is that it outputs 2/3rds of the rated holding torque up to the corner speed, then assume constant power from that point. This is essentially the method used in Irving's spreadsheet. This is of course an assumption, so it's safest to design for just below the corner speed, unless you're very confident about what you're doing. I guess I could add a plot of the stepper motor torque speed curve and machine torque requirement to my scrip, then look for the intersection to find the maximum speed... but nobody seems interested.

[Rich]

​Thanks Jonathan, I will run the script and see what I am able to do. Irving's spreadsheet was a good place to start. Although my machine doesn't quite fit the profile the sheet expects, I was able to gain a sense of what factors where critical to the design/specifications of the machine.

Should you do decide to write the additional script, it would be interesting to see the distinction between the projected and real world examples. This is v.1, so knowing the maximum top speed at which the machine is able to provide sufficient torque to cut particular materials would help with v.2. The gear ratio on v.1 is just an informed guess and now the holes are drilled, there's no way back! ​

[JAZZCNC]

​This is v.1, so knowing the maximum top speed at which the machine is able to provide sufficient torque to cut particular materials would help with v.2. The gear ratio on v.1 is just an informed guess and now the holes are drilled, there's no way back! ​

The speed/torque of the stepper motors won't be the limiting factor regards cutting speeds.? It will be Spindle power and machine stiffness/build quality.!!

[Rich]

Yes but, no but, yes but, no but, yes but ......... )

And I did include the phrase 'distinction between projected and real world', covering all my bases! You're just being selective.

[EddyCurrent]

This might explain better; http://www.mycncuk.com/threads/2148-...2975#post62975

[Rich]

Jazz, I get the point. Using a spreadsheet doesn't distract from the issue of build quality. If the error rate between projected and real world is 20% and I've used all the right parts (as detailed clearly within the forum), then the figures will tell me I can't build a thing worth a damn. My issue, the things I need to be realistic about. I haven't used all the right parts, but then I'm a novic and likely to break, bend and drop things. So I design with this in mind. I have two key issue to resolve within this design. The first is to learn everything I can from it, the second it to buy the electronic responsibly so that don't end up dumped in a foreign country. If I do it right, the worst thing that will happen is the aluminium rail with travel 5 miles to the local smelter.

BTW: I've not quite finished reading all your posts )

[JAZZCNC]

You're just being selective.

No it's called being realistic.!!