DC Servos and SnapAmp

[Courier250]

Another newbie here, so please forgive me for the elementary questions. The purpose of my project is not only to have a CNC mill, but also to learn about building the system with Dynomotion products. Decision 1: SnapAmp or Kanalog? Use the existing DC servos or switch to AC an Kanalog?

I have a knee mill with Anilam Crusader II CNC that is going to get upgraded. The DC Brushed servos and power supply function and I would like to reuse them. The power supply AC input is stepped down from 110V to 80VAC, and that gives a predictable 111VDC supply. SnapAmp voltage limit is 80V.

Do I want to change the DC power supply to 80V? The net effect limits max speed and torque. SEM servo is MT-30M4-59, data plate voltage is 142. My theory is that 80V will limit speed and torque too much and I won't get a usable machine. Any input is greatly appreciated.

[TomKerekes]

Hi Courier250,

The DC Brushed servos and power supply function and I would like to reuse them. The power supply AC input is stepped down from 110V to 80VAC, and that gives a predictable 111VDC supply. SnapAmp voltage limit is 80V.

It might be simplest to keep the existing analog Amplifiers, motors, power supply. In that case you would use KFLOP+Kanalog. You might do this simple test to check the amplifiers.

Do I want to change the DC power supply to 80V? The net effect limits max speed and torque. SEM servo is MT-30M4-59, data plate voltage is 142. My theory is that 80V will limit speed and torque too much and I won't get a usable machine. Any input is greatly appreciated.

If you want to drive those motors with SnapAmp instead of the existing amplifiers you would need to reduce the power supply voltage to 80V max. This would reduce the max speed but not so much the max torque.

[Courier250]

Thanks Tom. I tested the servo drivers as the link instructed, no action what so ever. Information and parts for this Anilam Crusader system are scarce. I think it's good to replace it with something current and serviceable.

[TomKerekes]

Hi Courier250,

Maybe the amplifiers were simply not enabled?

But in that case you will need to decide whether to keep the existing (brushed?) motors. Or go with something else. Also what Drivers you will want to use.

[Courier250]

I don't know, Tom. What drivers should I want to use? The servos are brush type SEM MT-30M4-59, data plate indicates they are 142 volt and 30 "pulse amp" limited. I hadn't got to the driver question yet, still contemplating a suitable power supply for the 2 servos with room to add a third later for Z-axis.

After surfing Google a few time and asking some local people, I have no clue as to the nominal power consumption of the SEM servos. I have learned that pulse amps are much greater than actual power consumption. Kind of like a DoAll blade welder that draws 30 amps, but runs on a 20 amp circuit with 12ga wire. The duration is short and does not pose a risk to safety for NEMA code. While I understand the concept, I haven't found any info leading to a recommendation for watts in a PSU. Anyone have any suggestions? Above 1500 watts, things start to get expensive. I would even consider 3 individual PSU's instead of one big one.

[TomKerekes]

Hi Courier250,

Well its hard to say without knowing many details. I'd suggest using our SnapAmp and a 1KW 80V Switching power supply. If you search around you should be able to find a switching 1KW 80V supply for < $200. Here is one. 1KW is well over 1HP of power. You might even start with one supply for all 3 motors. Power will determine maximum acceleration and Voltage will determine maximum speed. It should be guaranteed to work but at some accelerations and speeds. If you need more acceleration go to multiple or bigger supplies. If you need more speed you will need to go to different Drives. One nice thing about SnapAmp is that it monitors Power Supply voltage so you can see if the Supply is maintaining voltage.

[Courier250]

Thanks, Tom, that's great info. I have found several 1 - 1.5Kw power supplies for around $200.

Previously, you asked about servo drivers. I am open to suggestions. Is there anything to look for specifically? Any manufacturers that perform better with Dynomotion products?

[TomKerekes]

Hi Courier250,

Well as I said you might consider using SnapAmp as a Driver if 80V would provide enough speed.

Otherwise you might select some Step/Dir or +/-10V analog Drive. AMC makes excellent drives of all types.