3 Axis CNC router

[Clive S]

Certainly looking good Joe. Re the nema 24 I use one on the Z on my mill but on the router very similar to yours I use two 23's but Dean when using one belt for the two screws uses a nema 34 but no doubt he will confirm this for you.

[JAZZCNC]

Joe that 4nm 23 will struggle with 2 x 5mm pitch screws. It will turn them no problem but you'll have to sacrifice speed and with only 5mm pitch your already down on speed. I'd estimate you'll get around 4mtr/min Max rapid speed which isn't really enough for router. Idealy you'd want at least double this.

With 5mm pitch you'll struggle to get this with any single stepper motor 34 or 23 unless you go for larger motor and use ratio 1:2 ie Big pulley on motor small on screw. You need the larger motor becuase the ratio lowers torque not increases. Also you'll lose resolution but because you effectively have too much to start with this isn't problem.
My original machine ran with 6Nm with 2005mm pitch screws on 1:2 ratio running on 70Vdc and worked perfectly for well over 5yrs.

My advise is either change to 10mm pitch with small ratio if using 4nm 23 or go with twin motors.

To give you some idea I've just built 2 x 1250 x 750 sized machines that are using twin 2010 screws with no ratio applied running on single 4.5Nm 34 with 72Vdc using AM882 drives and they are tuned at 10mtr/min.

[JoeHarris]

Thanks Dean, I don't really want to have to replace the screws. This is what I mean about time passing - I based that decision on your old machine!! Would the larger mains voltage driver make a difference to speed? Are you saying a 4nm 23 could drive both of the screws if they were 2010? If so that would be a significant saving...

[JAZZCNC]

Would the larger mains voltage driver make a difference to speed?

Well yes it would but still you'll be limited mostly by the 5mm pitch. Simple maths really 1000rpm would give 5mtr/min but with 10mm that would be 10mtr/min for same RPM. The larger motors start to lose Torque quickly after 1000rpm so at best you'll get 1500rpm which is only 7500mtr/min.
Even then at 1500rpm your in the region where screw whip can start to become issue.

Are you saying a 4nm 23 could drive both of the screws if they were 2010? If so that would be a significant saving...

Yes it would, esp if 16mm dia but like I say you'll need ratio to increase torque. This will come at the cost of speed so you'll still be down in the 7500mtr/min area.

If it was me I'd go with 34 and run them on 70vdc and see what you get. 8nm should get you around 5-6mtr/min before saturation takes affect. Then if want little extra speed apply ratio to increase. 8nm will have enough spare power to handle the ratio.

[JoeHarris]

If it was me I'd go with 34 and run them on 70vdc and see what you get. 8nm should get you around 5-6mtr/min before saturation takes affect. Then if want little extra speed apply ratio to increase. 8nm will have enough spare power to handle the ratio.

Thanks for the patient explanation. Just so I'm clear are you saying 5-6m/min with 5mm or 10mm screws?

The things I have decided so far are:

> I want to use a csmio/ip-m
> I want to use it properly which means 3 motors and long belt on x
> I will use em806 drives on z and y with the 1605 screws I already have

The options are (all could be with or without ratio)

1. Stick with 2005 screws on x powered by 8nm nema 34 stepper and 240v drive
2. Stick with 2005 screws on x powered by 8nm nema 34 stepper and another em806
3. Swap screws for 2010 on x powered by 8nm nema 34 stepper and another em806

In order of preference I'm guessing you would say 3, 1, 2?

If I went with 2 as a starter I could see how it goes and swap out the screws in future... It's the only option which isn't insanely expensive!

[JAZZCNC]

Thanks for the patient explanation. Just so I'm clear are you saying 5-6m/min with 5mm or 10mm screws?

With 5mm pitch.

If I went with 2 as a starter I could see how it goes and swap out the screws in future... It's the only option which isn't insanely expensive!

This is why I'd go with the setup suggested. Easy to change up without costing the earth. If you make good job of alignment etc then you'll get 5-6mtr/min. Stick small ratio on and you'll get the speed up to point can cut most things.

[JoeHarris]

With 5mm pitch.



This is why I'd go with the setup suggested. Easy to change up without costing the earth. If you make good job of alignment etc then you'll get 5-6mtr/min. Stick small ratio on and you'll get the speed up to point can cut most things.

OK thanks Dean, sounds good. Tried to email chai to get best special price for some 2010s but email bounced... Wonder if he is still in business?!

Is 6mH inductance reasonable for a 8.7nm 34? i.e. this fella: https://www.cnc4you.co.uk/Stepper-Mo...15-4208-Nema34

[JAZZCNC]

OK thanks Dean, sounds good. Tried to email chai to get best special price for some 2010s but email bounced... Wonder if he is still in business?!

Is 6mH inductance reasonable for a 8.7nm 34? i.e. this fella: https://www.cnc4you.co.uk/Stepper-Mo...15-4208-Nema34

Drop Fred at BST automation on ali express message asking for quote. He's good guy to deal with.

Yes 6mH is ok for such large motor. I've used these and nice motors.

[JoeHarris]

I got my hiwin rails from Fred and yes agree he was very good. I'm working on a circuit diagram at the moment - hope to have that uploaded for scrutiny (a laugh at any rate) by you lot in a few days, so good to have that cleared up, cheers.

[JoeHarris]

Practice run for the next bit of aluminium routing. Pleased with my new Trend jig which should make pocketing for the motor mounts a lot easier.