CNC_0017

BUY: Shop Equipment - CNC - Workstation - Servomotors w/ Brakes & Encoders - Electro-Craft - E242

Usage (Proposed):

1 w/o brake. For Y-axis, with long 404 linear slide and with one of the 5:1 planetary reducers.

1 with brake. For Z-axis, with short 404 linear slide.

1 w/o brake. For A-axis, with one of the 5:1 planetary reducers.

A better idea will probably to leave the brakes on all three motors. Two or all 3 brakes release when the system is turned on and all three will brake if the E-stop is actuated.

Information:

Purchased 1 on ebay 7547158794

Purchased 2 more on ebay 7556357513

There are 3 wire groups. The center one, for the brake consists of 2 wires with gages that are smaller than those going to the motor but larger than those going to the encoder. Should they be removed, and can they be removed seeing that the attempt on one to remove the encoder did not work. Perhaps the one for the Z-axis should be left on and used. Perhaps all should be left on and used with the E-stop.

Servomotor:

Electro-Craft. Reliance Electric
Model No. E242

Part No.	242-027-0142	242-025-0142	242-025-0142
Serial No.	G000134	G000068	G000180
Description:	Was w/ flange	Was w/ cylinder	Was w/ cylinder
Additional Information:			IEC 34-1 S-1 Duty 45 VDC MAX 4.5 AMPS
Initial Testing:
Volts:	24.5
Amps:	3.74
Note:	Brake is probably partially on.	Brake is on. No rotation.	Brake is on. No rotation.

RPM: 5000 max. ??

45VDC ??

4.5 A ???

Looks like NEMA 23 spacing, but the slots look smaller. 1/8" wide.

Looks like the shaft is 8mm. or 5/16", not the 1/4" of NEMA 23.

Considering for fuse ~ MDL Slow Blow Fuses (6.3 x 30mm) 4.0 Amp, Model MDL-4A-2

Consider 2 ohm, 10W to lower the voltage from the power source.

Testing: The following notes are copied from the large motor and must be modified for this motor.

The power supply outputs 52.6VDC (rated at 48VDC)

A 2.2Ω 10W resistor was added in series with the motor. The voltage across the motor was 50.0V and across the resistor it was 0.9V. The current was 0.45A and the speed was? The resistance in the motor would be 50.0V / 0.45A = 111.1 Ω The power consumed by the resistor would be 0.9V * 0.45A = 0.41W. The resistor was not checked for temperature.

Four 2.2Ω 10W resistors (total of 8.8 Ω) were added in series with the motor. The voltage across the motor was 47.4V and across the resistor it was 3.7V. The current was 0.43A and the speed was? The resistance in the motor would be 47.4V / 0.43A = 110.2 Ω The power consumed by the 4 resistors would be 3.7V * 0.43A = 1.59W. The resistor was not checked for temperature.

At the assumed motor's rated current of 4.5A the power consumed by the resistor would be 3.7V * 4.5A = 16.7W, which is too high for a 10W resistor. However the resistor could be replaced by 2 * 4Ω 10W resistor and the voltage to the motor may be acceptable and the power consumption at the resistor will be OK, if mounted on heatsink.

Since it is not detrimental to run the motors at up to 5% over rated voltage, the assumed 45V * 1.05 = 47.25VDC the above may be OK. These 3 motors are not intended to run very fast therefore might a smaller or no fuse be acceptable?

Brake:

2-wires. Look like 20 AWG. 2-pin connector

Testing:

5VDC had no effect, but 12VDC caused the brakes to 'click' open and so did 15VDC. The 'clicking' should indicate that the solinoid is fully seated. Should the intended operating voltage be higher, say at 18 VDC? See the bottom of this page.

Motor Serial No.	G000134	G000068	G000180
Electrical Resistance:⁽¹⁾	315 Ω	89 Ω	85 Ω
Manual turning of shaft with brake open.	Shaft turns stiffly.	Shaft turns freely.	Shaft turns stiffly.
Operation w/ 12 VDC on brake and 24 VDC on motor ⁽¹⁾	Appears to operate well.	Appears to operate well.	Appears to be a little noisy and rough. ⁽²⁾
I checked the current under no load on all motor, at 24 VDC.	0.35 A ⁽³⁾	0.32 A	0.35 A
I checked the current under no load on all motor, at 12 VDC. ⁽⁴⁾	38 mA	142 mA	145 mA

(1) Why are the resistances so different?

(2) I turned all the shafts by hand when the brakes were off. G000180 feels a little rough. Could this be the bearings, encoder or brake?

(3) This result is out of sync with the value below and with the equation A = V / Ω. Why?

(4) The amperages on this line are in sync with the equation A = V / Ω.

The CNC4PC Mini Power Supply only puts out 1 amp per voltage channel. It appears that one channel should be able to power all 3 (or 4) brakes. The three require a total of 325 mA. The 3 relays for the brakes is be 50.1 mA and the 3 relays for 6 motors will be 225 mA, for a total of 275.1 mA. Therefore all can be powered by 1 voltage channel.

Encoder:

The connector is loose on A-axis encoder.

Renco Encoders Inc. showing on all three cover

Inside the encoder is a label that says P/N77678-266 and D/C 0016
Inside the encoder is a label that says P/N77678-266 and D/C 9816
Inside the encoder is a label that says P/N77678-266 and D/C9734 X9743

All three have the round cable CA18.

Pinout, Motor Serial No. G000134, G000068 & G000180: Round cable DB-9 connector.

Pin nbr:	Signal:	Wire color:
1	+VCC	Red
2	GND	Black
3	CH A	White
4	CH A NOT	Yellow
5	CH B	Green
6	CH B NOT	Blue
7	INDEX	Orange
8	INDEX NOT	Brown
	SHIELD	Drain (thick)

This appears to be the closest specifications to the encoders on the three motors. RM21 Modular 2.1 Inch Encoder Have hard copy in binder.

The above is also the sequence of the wire colors in the bar connector inside the encoder cover, of all three encoders. All three encoders look identical with the exception of the color of one very small part, which is different on the G000134 (Y-axis) from the other two.

For view of DB-9 connector with pin numbers see OTHER: CNC Work Station - Electrical - Cables & Connectors, Etc.

For color of wires used see; OTHER: CNC Work Station - Controller - Internal Wiring ~ Encoder

______________________________

This is how I have connected the Encoder's wires to the DB-9 male connector;

	Pin nbr:	Wire color:
	1	Red
	2	Black
	3	White
	4	Yellow
	5	Green
	6	Blue
	7
	8
	9
		Unconnected:
		Orange
		Brown
		Shield probably

______________________________

This is how I have connected the Controller wires from the Geckos to the DB-9 female connector, all encoder inputs;

Pin nbr:	Gecko Label	Wire color:
1	ENC+	Red
2	ENC-	Black
3
4	PHASE A	White
5	PHASE B	Green
6
7
8
9

Some additional information inside the front cover of 'Electrical' binder.

This pdf file has drawings and data on a number of Electro-Craft. Reliance Electric motors. Unfortunately, not this one . Might the motors all be equipped with tachometers? I don't think so. http://supportbbs.ra.rockwell.com/motion/ec/Motomatc.pdf

The G240 series may have a commonality with the E240 series. Have printed 2 pages and stapled them to one of the E242 ebay pages.

http://www.electrocraft.com/cust_demand/marketing/electrocraft/forms/CatalogEC-001April2005.pdf

Comparison of Electro-Craft - Model #E240 to #G240 to see if #G242 Specifications might be used for the purchased 3 E242's;

	Model #E240	Model #G240	Model #G242	Model #E242
Peak Torque:	1.7 Nm	169.5 Ncm	247.2 Ncm
Stall Torque:	0.22 Nm	20.5 Ncm	35.3 Ncm
Peak Current:	24.5 Amps	31 ~ 24 ~ 13.9 Amps	31 ~ 24 ~ 19 Amps
Stall Current:	3.1 Amps	3.8 ~ 3 ~ 1.9 Amps	4.2 ~ 3.4 ~ 2.7 Amps
Max Speed:	4700 RPM	5000 RPM	5000 RPM
Max Voltage:	48 Vdc	60 Vdc	60 Vdc
Radial Load:	4.5 kg	4.5 kg	4.5 kg
Axial Load:	2.3 kg	-----	------
Voltage Const:	7.8 V/kRPM	5.7 ~ 7.1 ~ 14.2 V/kRPM	8.7 ~ 10.9 ~ 13.9 V/kRPM
Weight:	1.1 kg	1.0 kg	1.0 kg

The 3 values are related to Winding Designator; A, B & C.

The brake voltages for the G-series motors are; 12 VDC, 24 VDC, 90 VDC, custom.

In the G-series (at least) the first two numbers identify the motor's diameter and the last number identify the motor's length.

I also compared the E722 to the G722 and they are a long way apart.

Electro-Craft E286 servo motor and tachometer with electrically released brake. May be of some value. Perhaps re brake voltage.
KEY MOTOR SPECS
Torque Constant ..... 7.68 oz-in/A
Voltage Constant ..... 5.12-6.26 v/krpm
Max terminal voltage ..... 28 volts DC
Max cont speed (no load) ..... 5900 rpm
Max peak torque ..... 240 oz-in
Max peak current ..... 4.7 amps
Inertia ..... 0.0052 oz-in sec2

TACH SPECS
Voltage Constant ..... 12.5-15.4 v/krpm
Resistance ..... 600-800 ohms

BRAKE SPECS
Voltage ..... 18 Volts DC

Motor Specs May be of some value.

Electro Craft Model Number: E643

Frame Size: Nema 34

Continuous Stall Torque: 155 oz-in

No Load Speed: 4800 RPM

Max Bus Voltage: 60 VDC

Max Continuous Current: 10.2 Amps

Demag Current: 43 Amps

Kt: 16.8 oz-in/Amp

Ke: 13.7 V/kRPM

Shaft Diameter: 0.500"

Encoder: Renco 1000 PPR Optical Disc Differential Incremental Encoder

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Last Revised: June 10, 2006