enough power?

[oneturboneeded]

I was wondering if any experts could help me deiced if this is enough power?
my gantry will weigh about 115 pounds. Will 906 oz inch nema 34 driven by gecko 203 (better than the 201x?) be enough to get to around 1100 ipm with out over working?
what size power supply will i need?
Should i step up to the 1200 oz inch? im kinda worried thees will weigh more and offer the same performance.
thanks all,
shawn

[jsheerin]

If you're using 2 of the Keling 906oz*in motors on a 115 pound gantry with a rack and pinion with a 1" pitch diameter pinion and gearing on the motor of between 1:1 to 1:2 (smaller gear on the motor), yes, that should work. I'd go with 1:2 on the gearing to get more force at lower speed and better resolution (around 0.0077" per full step). You would need about 12A at 60V for these two motors.

[oneturboneeded]

Thank you for the feed back.Yea more info would probably help.

My table is going to be 5X10 and i plan on using Cncrouterparts.com for the rack n pinion drive and linear motion on the X and Y axis. With a Dual X axis drive.

I have a Perske 2.2 hp spindle and will be using 8020 for the body.

[oneturboneeded]

Does each axis need its own power supply?
Should i get a regulated power supply or unregulated?

[chris-frm-fl]

just built cnc need help .the whole structure is all MDF ply with a 2' x 4' work area. i have the parts and screw setup for the y & z axis but im stumped on how to move the x axis.
the guys at probotix are awesome and they diddnt just try to sell me anything. im leaning towards a belt or chain drive system but ill need the parts and a clue. please help, where do i find these parts. Chris.

[ahren]

Shawn,
At 1100 IPM, you will be rotating at 1100/3.14 = 350 RPM at the gear. Through the 2:1 reduction on the Nema 34 R&P, that means a 700 RPM speed at the motor shaft. Check out your torque curve to get torque at that speed, but assuming you are using the Keling motor, it looks like the torque at 700 RPM (or 1400 ppm from their chart, since they used a half step driver), is about 5.75 Nm. Again due to the 2:1 reduction, this torque will be doubled at the gear to around 11.5 Nm. This translates to 101.74 lb*in of torque, which when divided by 0.5" radius to the gear mesh gives you 203.5 lbs of linear force per side driving your gantry, even at this high speed.

Translation -- your machine should be pretty much unstoppable . Happy building.

Ahren
www.cncrouterparts.com

[jsheerin]

You can use the same supply for all your motors if you like. That's what I do. It just needs to be big enough. You can use either regulated or unregulated supplies. I personally have a regulated supply and have had no problems. I've heard an unregulated supply is better in some cases though. I'm not an electrical expert, so I'll defer to others for the explanation as to why.

To add to Ahren's explanation, you should be able to set your acceleration pretty high with this setup as well - around 400in/s^2 could be possible (slightly over 1g). At that setting, you could probably let your gantry weight go up to about 200lbs before you ran into trouble (motor stalling). That would just be at the top speed. At lower speeds you should still have plenty of force available for cutting.

[oneturboneeded]

Thank you so much Jsheerin, and Ahren for your help. this makes me feel much better. i have 2 more questions now.
will the suggestion for a 12A at 60V power supply still hold up for all 4 axis?
and will this combo give good accuracy (i do know it depends on my machien but from a motor driver stand point.)?

[jsheerin]

I would say accuracy should be fine, although that depends on your definition of what is acceptable... If your resolution is 0.0077" per full step, then with 10x microstepping, you could theoretically see 0.00077" per pulse from your controller. From what I've read, how accurate the movement is in this range depends on the design of the motor - some motors are more accurate in their movement between full steps than others. I'd estimate conservatively you should be within a few thousands of an inch. Then depending on what the tolerance of your gear rack pitch is, you could be off a bit more. Any deflection of the cutter, machine frame, or drive mechanism during cutting could throw you off a bit more. However if you're really going for extreme accuracy, you could take a clean up pass with a light cutting load to reduce deflection. Any backlash in the system could also introduce some error, but since Ahren's r&p design removes backlash you should be okay and have relatively good precision (repeatability in positioning).

On the supply, a conservative route would be to have 6.1A available per motor (for that particular motor). So 4 motors would be ~24A. Typically you can undersize the supply a bit as not all motors will pull max current at the same time, but it could be possible that they would on a 3D move under full load.

[oneturboneeded]

Which power supply is better?
1. Unregulated Power Supply 1440W, 72VDC/20A ,120VAC or
230VAC
2.Unregulated Power Supply 1300W, 65VDC/20A , Input:
120VAC or 230VAC,

I'm leaning toward #2.
Thanks again
-Shawn

[ger21]

According to Gecko, your power supply only needs to supply 2/3 of the motors rated current. So just over 4 amps per motor, or about 17 amps.

Also, according to Gecko's formula for voltage, you want about a 58V power supply. 65V should be OK, but the motors will run a little hotter.