@George_Allen that was just a example of the difference between direct and reduction.
Having reduction will still work but at some point, you will run into rpm speed limit with reduction. I don’t know what it will be with your motors. If your not cutting plywood and composites than it probably won’t be a issue.
But I thought feedrate needed to be rather quick
@George_Allen cutting steel and ferrous will require lower spindle rpm. There are feed/speed tables for optimum aluminum cutting. I put in 2500rpm, 2 flutes, diameter and it gives me back feed.
@Jim_Fong Yes, I plan on cutting some aluminum with this eventually…part of the reason for building this monster. No steel or ferrous metals though. I think I should be ok so long as I limit the depth of cut.
I also go use climb instead of conventional cut
@Jim_Fong the RPM I can manage. The rest of the metric units you’re using I am not in the mood to convert into US customary units. Well I did convert the pitch to decimal inches. I run a pitch close to twice as tight as 5mm. 5mm is 0.1968" I run 0.1" or 10 TPI leads. 10 is a nice round number, don’t you agree? Metric uses such oddball numbers. Five is not a round number. Although I suppose it is a half of a centimeter, so in that respect it is round then. 1/2cm There may be hope for the metric system yet. It just needs more fractions. The units themselves are hopeless though. A centimeter is what, a half assed third of an inch? Something like that. We don’t really use thirds of inches. 3/8s of an inch is popular though. A cm is close to that. When you use our 3/8s drive what do you call it? I know half inch drive is called 13mm. Another one of those not round numbers. Metric is so clumsy mechanically. It is no wonder the rest of the world has not gotten to the Moon. What with being saddled with the effete metric system and all. Some foreign sports cars are still OK though. Like this Ferrari 512BB model https://www.youtube.com/watch?v=RvV3nn_de2k
@George_Allen just limit your depth of cuts. I have a 2.2kw spindle on the gantry router. I’ve cut aluminum before but it’s hard on the small spindle bearings. Better for the Big mill to do it instead.
I like to run 3.5m/minute when cutting plywood on the router.
For a 10mm pitch ballscrew, that’s 350rpm. No problem for a direct drive stepper motor.
With 15:1 reduction, will require the stepper motor to spin 5250rpm. That not going to happen.
If your happy with your machines current maximum feedrate, then keep the reduction in.
@Jim_Fong the RPM of stepper motors is limited by inductive reluctance. So if you can run high enough voltage you can run a stepper motor pretty fast. I have seen torque curves out past 4,000 RPM at 80V So 5250 RPM is not completely out of the realm of reason for a stepper motor to go. Because they do make 130V motor drives too.
@Paul_Frederick yes I have some Parker AC stepper drivers. They can spin motors fast. I’ve spun steppers 8krpm. There is no useful torque at 4k rpm with any standard $40 Chinese stepper motor.
We already know the OP is using 24volt supply with DM542’s. You are not going to get high speed with that combination.
@Jim_Fong I have run TB6560 drives at 24V up to 2,500 RPM. That seemed to be an upper limit there to me. I had a bit better than $40 Chinese stepper motors perhaps though?
@Paul_Frederick that’s probably no load. Put it under actual leadscrew friction load and tell me how fast it goes.
At that speed, there is just enough motor torque to overcome its own bearing friction and not much else.
I can make a nema17 spin 6k rpm, so what. Gecko@24volts. Unless the motor can actually move something, it’s just a useless number.
@Jim_Fong nah it ran strong. Gobs of torque. It’d tear a brick wall down I tell ya.
@Paul_Frederick I truly would like to see a video of that happening.
Nema23 stepper motor spinning at 2500rpm @24volts moving a cnc axis with a tb6560. BS
What model number motor is that? If I could find a motor that can do as you say, there wouldn’t be a need ever to recommend any better stepper driver than a cheap TB or motor and 24volt PS.
I can point to this thread and say Paul uses this and says it works great. It goes 2500rpm and will make your cnc super fast.
@Jim_Fong Jim Fong, I need some sagely wisdom. I’ve just about completed my build, but I’m unable to get my motors properly tuned. I am trying to calculate steps per unit to input that into Mach3. Almost all tutorials shown use inches and TPI when calculating steps per unit. Since I’m using RM ballscrews on all axes. It’s not a difficult calculation, but I must be missing something because I either get stuttering or fast rotation when doing a g0 move. I will give you an overview of my hardware and settings and see if my calculations are ballpark with the correct value, so I can troubleshoot elsewhere.
I’m using mm as my native unit. And, I realize 1 inch = 25.4 mm.
To run the table (I call my Y axis) I use 2, RM 2010 (10 mm pitch/20mm diameter) ballscrews with 2 425 Oz-in NEMA 23s with 1.8 step angle at 200 steps per revolution. The ballscrews are driven with TB6600 drivers. I intend to adjust the micro stepping after I get all my motors calibrated and I am sure I have a handle of setting them, but not initially.
My X axis is now driven by a NEMA 23 Stepper (without the gear reducer) direct drive. 1.8 step angle, 200 steps per revolution. THIS BALLSCREW is RM1605 (16mm Diameter/5 mm pitch). This ballscrew is driven by my DM542T Stepper Driver with the dip switches set for 400 pulses/revolution (the lowest operating level of pulses/rev allowed for this driver and set a full current. I’m not always certain the ideal setting for the dip switches authorizing the amount of peak current, but my Steppers have a max current rating between 2.8 A and 5.5A, so I usually set it at least 2.8 to 3.5 or 4 Amps.
My Z axis is driven by a NEMA 34 also with a step angle of 1.8 and 200 steps per revolution. This Stepper is driven by my 201 gecko driver and I’ll have to check the resistor I installed to determine its settings. This motor drives an RM 1204 ballscrew (12 mm diameter/4 mm pitch).
All of the drivers are powered with a meanwell 24v 350 watt PSU with a max current capacity of about 14 amps.
If you could give me some ballpark #s so I can compare with my values, I’d certainly appreciate it. I’m excited to begin running my machine, but there’s always hurdles.
@George_Allen I’m at work right now. I’ll respond later tonight when I can give you a proper response on how to figure out step per mm for Mach3
@Jim_Fong Thanks Jim! I certainly appreciate it!
Y axis
RM2010 10mm pitch
TB6600 Drive
To calculate steps per unit, need to know the microstep resolution. I always use atleast 8. So set your drive to 8 microstep.
Steps per 1 revolution is
200full steps * 8 = 1600 steps/rev
We know the ballscrew moves 10mm per full revolution.
Steps per mm calculation
1600/10mm = 160steps/mm
Set Y axis steps per unit to 160
X axis
RM1605 5mm pitch
DM542 set at 400steps/rev
400/5mm = 80steps/mm
Set x axis steps per unit to 80
Z axis
RM1204 4mm pitch
Gecko201. All 201 drives are 10microstep resolution
Steps per Revolution
200*10microstep = 2000steps/rev
2000/4mm = 500steps/mm
Set Z axis steps per unit to 500
@Jim_Fong Thanks so much Jim! You’re my hero!
