[BlairM]

Hi Guys,

I am in the same position as everyone starting out in the CNC Hobby game gets to at one time or another. What size motor.

I worked my way through here off and on for weeks and are still as confused.

Essentially I have a custom wood made Router with 1605 lead screws on all axis.

With router attached it will be about 30kg sitting above the bottom axis with gantry and Z axis etc. I have about 600mm x 450mm x 130mm travel on the machine

I don't know how fast I need to go, I dont know the cutting forces of the material I want to cut. Mostly ply and custom wood, but I would like to cut some sheet Ali as well. I cant find a really clear beginners guide to motor selection and have been tossing up between Nema 23 270 oz-in and 425 oz-in

I was planning to run them on 48V as the drivers I plant to use DQ542MA or CW5035 from Aliexpress stores will handle up to 50v. If the supply I get has a pot I may de-rate it a little to be a little safer.

If I go with the 425 oz-in units could I be to big? One of the models I have found has 6.8 inductance rather than 9 so that must help speed a little if using 48 volts if the formula I have used to select optimum voltage is correct.

Sorry really just another of those what size posts, but just really struggling to decipher the vast amount of information in these forums.

Regards Blair

[UUU]

Have you got your gantry moved by one motor, or two?

[BlairM]

Just 1 central motor

[ger21]

In a lot of cases, no, bigger is definitely not better. But that typically comes into play with large Nema 34 motors.
In this case, it's not that the 425's are too big, but rather they are a poor match for your lead screws.
1605's are not the best choice for a mid sized router. Ideally, you'd like to see speeds of close to 400ipm, or about 10m/min. This would require the screw to spin at 2000rpm. Most steppers are usually only usable up to around 800-1200 rpm. This is largely determined by the motor's inductance and the power supply voltage. For max performance, the voltage should be 32 x sq.rt of the inductance rating of the motor. If you use this formula, you'll see that you need to use about 130 (guessing) volts to get max performance. Since you'll only be using 50v, you'll barely be using 30% of the motors capabilities. This is why the 425's are usually a poor choice for routers.

Your best choice would be to get a Gecko G540 drive and low inductance 387 oz motors. They'll give you the best performance you can get out of those screws your using. You can get them from Homann designs in Australia.

[BlairM]

Thanks Gerry,

I had picked up on the lower inductance the better idea and had seen 387 motors mentioned, but did not realize the inductance was that low. For an Australian company the price looks very good. I think thats the motors I will get.

I would love the Gecko Drives, but just don't think the budget will stretch. Maybe I need to save up for a while longer :-( as I have seen all the talk about Chinese controllers. With that in mind I was looking at the more expensive and higher current DQ542MA or CW5035 as there seems less trouble talk in the forum on these units.

Anyone have "Good" experiences with them?

Regards Blair

[H500]

I can't tell from the specs whether the DQ542MA can be ran at 50v, or if that is the absolute max limit before destruction. Without further information, I would go no higher than 40v or so.