what to upgrade? lead screw or control

[Rat]

I'm looking at options to upgrade my cnc router. Now i have 5/16-18 all thread for lead screws, hobby cnc controller and linuxcnc. I can get around 25 inches per minute but would like to get up to 45-60 ipm for jogging.

I'm considering going to a gecko g540 or an acme screw. Rough estimate the cost would be similar either way but the acme screws would be a much bigger overhaul/redesign so im leaning towards the gecko. Any thoughts or experiences making similar upgrades?

Thanks

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[SteveWill]

I would go to a 1/2-13 all thread for lead screws. That should get to you 35 ipm. Do you have the most power supply that you can use with the current driver that you have? I have 1/2-13 all thread on my cnc, it will run up to 120 ipm where it starts losing steps so I feel safe at 60 ipm. I am using these driver Slowing 69.16.243.61&c=1&t=42892.81103125 . I am surprised that you can not run faster with the 5/16-18 all thread.

[louieatienza]

Easily ACME screw and anti-backlash lead nuts. You'll gain speed and accuracy. There are threads here with tips on how to turn down the ends, this way you can use the beatings you currently havr. Everything else, you can CNC!

[NIC 77]

5/16-18??

Am I reading this correctly? I'm not experienced with lead screws. The only one I've used came already assembled as part of a linear slide, and that one had a lead of 0.25". So that's 18 treads per inch, single start? Or 1.4mm per rev?

If so, that there is your biggest problem! Steppers deliver most torque at slower speeds. You might think a lower pitch is better, but when the machine is moving faster, the stepper is now also moving faster and will have less power as a result.

I've recently done analysis including inertial effects for my own build with ballscrews. I was surprised to see how much better the 10mm pitch out performed the 5mm pitch in the speed range I want to use. And you're using 1.4mm pitch? Or is that a misunderstanding on my part?

[louieatienza]

5/16-18??

Am I reading this correctly? I'm not experienced with lead screws. The only one I've used came already assembled as part of a linear slide, and that one had a lead of 0.25". So that's 18 treads per inch, single start? Or 1.4mm per rev?

If so, that there is your biggest problem! Steppers deliver most torque at slower speeds. You might think a lower pitch is better, but when the machine is moving faster, the stepper is now also moving faster and will have less power as a result.

I've recently done analysis including inertial effects for my own build with ballscrews. I was surprised to see how much better the 10mm pitch out performed the 5mm pitch in the speed range I want to use. And you're using 1.4mm pitch? Or is that a misunderstanding on my part?

Many folks, for their first build, use inexpensive hardware store threaded rod because of its availability and price.

[ger21]

2 start 1/2"-8 acme and a 36V power supply should get you close to 200ipm, depending on your motors.

[Biggs427]

+1 for leadscrew but evaluate your cnc as a whole system and make sure that the rest will follow.

My very first build was using the same exact threaded rod.

I was able to run Nema17 stepper at 45 IPM but as soon as I switched to Acme leadscrews, the nema 17 weren't strong enough because of the increased pitch from 1.411 mm/turn to 8mm.

I had to switch to nema 23, PS from 12v to 24v, better drives etc.

I'm not saying that you need to upgrade everything but this needs to be analyzed when upgrading only one part of a system.

[Rat]

I am maxed out with voltage. Thats impressive speed. I was expecting faster with mine, i keep reading about midband resonance and think that may be my issue.

[Rat]

thats a great idea to turn down the screw, i was dreading replacing all the bearings and adapters.

[Rat]

+1 for leadscrew but evaluate your cnc as a whole system and make sure that the rest will follow.

My very first build was using the same exact threaded rod.

I was able to run Nema17 stepper at 45 IPM but as soon as I switched to Acme leadscrews, the nema 17 weren't strong enough because of the increased pitch from 1.411 mm/turn to 8mm.

I had to switch to nema 23, PS from 12v to 24v, better drives etc.

I'm not saying that you need to upgrade everything but this needs to be analyzed when upgrading only one part of a system.

This makes me think i do have a driver issue. I'm already running Nema 23 motors at 36 volts and can only get about half the speed you were.

[NIC 77]

I'm not saying that you need to upgrade everything but this needs to be analyzed when upgrading only one part of a system.

I absolutely agree with you on that. The entire system should be looked at as a whole when doing upgrades.

This makes me think i do have a driver issue. I'm already running Nema 23 motors at 36 volts and can only get about half the speed you were.

What motors and drivers do you have? Links? What are the amps per phase of the motors, and what is the amp output of the drivers? 36V power supply, you already mentioned that. Pics of your build? Acceleration settings? Gantry weight?

[louieatienza]

This makes me think i do have a driver issue. I'm already running Nema 23 motors at 36 volts and can only get about half the speed you were.

NEMA17 steppers can usually attain higher RPMs [than NEMA23], and one reason why they're usually paired with finer pitched screws. The NEMA23 motors will max out power output at a lower speed generally. Since the all-thread is a cut form, and not hardened (ACME screws are essentially forged from the rolling process) it is more prone to wear, so in the long run, spinning them at high RPMs through whatever nut you choose will introduce backlash a lot faster than ACME screws with a less-fine pitch.