Reducing the space in my garage.

[Rich]

Thanks Eddy, that helps with my working out.

At 8 microsteps the resolution using a pinion with a pitch diameter of 23.87mm is 0.0149mm, and that is good enough for me ) But the holding torque is reduced to 19.5% peak value, per the linked paper. However, with a gear ratio 2.8, holding torque is increased to 54.6% peak value. It seems to follow when the gear ratio is include that 4 microsteps provide a resolution of 0.0106mm, with no loss of holding torque.

[JAZZCNC]

At 8 microsteps the resolution using a pinion with a pitch diameter of 23.87mm is 0.0149mm, and that is good enough for me )

Nope you forgot the to include mr Pie.!! . . . .23.87*pi=74.989 /1600=0.0468

Also you shouldn't really think of Micro stepping in terms of increasing resolution. It has more affect making motors smoother.
If you need resolution then best to achive it by lowering the pitch.

Regards voltage then you can easily run those motors above the guide given on Gecko site. They easily run at 68Vdc without any trouble and the extra voltage gives that bit more torque and speed.
The amp you'll require will depend slightly on the type of PSU used. With Unregulated toroidal supply you'll only need aprox 60%-70% of total rated motor amps. IE: 4 x 4.2a=16.8 / 65%=10.92A

[Rich]

Thanks for those three points Jazz, they help a lot!

I've corrected my calculations and marked them down as 'guidance only'. The main issue I was focused upon within the calculation was the effect of microstepping on the available holding torque. It appears with a 2.8 gear ratio, set at 4 microsteps, the machine retains 100% peak holding torque.

Having used your original recommendation as a starting point for the research, I now see that I have the option to spec the machine according to what is required, circa 1.5Nm Nema 23 low inductance or over spec the machine and carry the electronics forward. More reading to be done!

[EddyCurrent]

Don't forget to take into account the screw pitch, it's the resolution at the tool you want to calculate

[Rich]

On the z-axis using a TR12x3, resolution will be 0.015mm at 1 microstep. This assumes no backlash, deflection of the carriage or issues with the table. If I'm out by a factor of 10, then the starting point would be 0.15mm. As the majority of any variation will arise as a result of deflection, the option to gear the z-axis is on hold.

The z and y axis are belt driven, the gear ratio is 2.8, so the starting point for mechanical resolution at 1 microstep is 0.1339mm. I will have issues with positional accuracy when cutting longer lengths, but I can compensate within Mach 3.

I'm guessing you started you build with better figures?

[EddyCurrent]

I'm guessing you started you build with better figures?

I didn't calculate them as such but obviously had an idea of what I needed. I used the best components I could and the best design I could build myself with the tools at hand. Having plenty of engineering experience I knew it would be achievable, but having no experience with cnc, I initially relied heavily on the advice from members of this forum on the mechanical side.

The actual figures after the machine was finished are here; http://www.mycncuk.com/threads/7155-...6572#post56572
that is with a 200N force applied as described.

[Rich]

Great number Eddy. Your log is one of many logs I have been reading )

So after further research I found this website:

http://www.orientalmotor.com/support/motor-sizing.html

The numbers offer a guide to the amount of torque required to move at specific feedrates.

The issue now is what will the available torque curve will actually look like. I am unable to get hold of the torque curve for the motors I have in mind ( This is fine, as the torque curve is stepper specific ... so I have read.

On the X-axis – if I remember correctly, I have a theoretical ratio of 1:10, required v’s available. In practice, when testing the X-axis using an oversized drive pulley and a poorly tensioned section of belt, one side worked really well, the other was satisfactory. As the belt was being held in palce without correct tension this was a good result. A confidence builder! Once the pulleys and belts are in place, I can run a second test, adjust etc and then attach a line and weight to the gantry and let gravity tell me how much force is required to move the gantry, in particular the friction coefficient.

Steppers, after bit more reading, I realised this isn’t the place to start when thinking about building the circuit ) I need to be thinking in terms of ripple, electrical noise, and clean/dirty sides of a circuit.

http://www.mycncuk.com/threads/6696-...machine-wiring

http://www.mycncuk.com/threads/7450-...ical-behaviour

Stripping back on some of the technical detail, I think I need to focus on segregation, shielding, filtering and then follow best practice, as detailed within the document and many of the build logs. I will write something up, best way to avoid mistakes.

As per the second link, it looks like Leadshine is ‘the’ brand and they offer an anti stall feature, which is important feature when slaving motors on such a light rail.

Next steps, take the frame apart and PU the mdf. Order a few non-essential elements, write up the outline for the electrical circuit, order the pulleys and belt.