RE: [CAD_CAM_EDM_DRO] re-selection of motors....avoiding another rathole

Hi Eric -

I've caught only bits and pieces of this thread, but I don't
understand why a simple belt drive won't work? It's pretty cheap,
no backlash, takes the place of expensive couplings, and is a
common method for good reasons. I think 10 or 20x reduction with
the gearhead approach is going to be way too much reduction, and
will introduce substantial backlash. Am I missing something?

Regards,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: etauch [mailto:erictauch@...]
Sent: Friday, June 13, 2003 7:56 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] re-selection of motors....avoiding
another rathole

Greetings,

Recently I posted on the overheating servo drive issue. I have
decided that instead of moving to belt and pulley, I would try
a "gearhead" servo motor in the 160-500 rpm range. This is
for running direct drive thru helical beam shaft couplers. I will
calculate the exact RPM I need based on my leadsrews (10:1) I
believe
and desired IPM and pulse rate of my current PC.

As this is my second attempt (current setup caused motors to
get hot due to running of servos at low speed constantly), I am
hoping to get some feedback on my motor selection.

I dont forsee any problems, but does anyone have any input or
comments. Thanks in advance...

Here are my choices:

1)
160 RPM Dunkermotoren, #88442/88851. This is a high quality German
made gearmotor with opitcal encoder. The input voltage is rated at
24 VDC @ 2.7 amp. The gearbox ratio is 20.25:1 Tested on 24 VDC
the
no load speed is 178 rpm @ 0.6 amp. With a 100 oz in lad the rpm
is
173 with a current input of 1.1 amp. We estimated that the motor
rpm
with a 300 oz in load will be approx. 160 rpm @ 2.7 amp. The motor
and gearbox have ball bearings. Shaft: 12mm dia X 7/8" long. The
shaft has a 3mm cross-drilled hole located approx. 5/16" from the
shaft end. The encoder is Hewlett Packard modular device (series
9100) with an output of 500 counts per revolution. The encoder
produces TTL compatible quadrature outputs. Encoder input voltage
is
5 VDC @ 40 mA max. The motor has 6" long flexible lead wires. The
front of the motor gearbox has a removable mounting plate that has
four tapped mounting holes. The tapped holes are 4mm X 0.7mm
pitch.
Dimensions: 2 1/2" dia. (max) X 7 3/16" long (excluding shaft but
including encoder). Stock #DCGME2201 $59.95


2)
210 to 550 RPM JAPAN SERVO CO. MOTOR #DME60, GEARBOX #6H9F-H46. 24
VDC gearhead motor with encoder and drive electronics. Gear ratio
9:1 Encoder: Hewlett Packard HEDS-5600 with 100 counts output per
revolution. As shipped the motor/encoder/electronics will give a
variable speed between 210 and 550 rpm. Speed is set via on-board
trimpot. As shipped the motor is set for 380 rpm. A 24 VDC input,
no
load current is 280 mA. At a 6 in-lb load the motor rpm will be
380
rpm. Motor current will be approx. 4 amps. The motor rotation can
be
reversed by swapping the leads connecting the motor to the drive
electronics. As shipped the motor rotates CCW. The drive motor is
permanent magnet type rated 24 VDC, and has ball bearings. The
gearbox has sleeve bearings. Shaft: 8mm dia. x 1-3/4" long. Motor
shaft has a cross-drilled hole with pin plus a plastic cog pulley.
The pulley is approx. 1/8" or 3mm pitch with 20 teeth. This pulley
is easily removed. Dimensions: motor 2-3/8" sq. x 6" long
(excluding
shaft). Drive electronics board 3-3/16" wide x 2-5/8" deep x
1-5/8"
high. Stock #DCGME9650 $47.50


Number 1) may require a pulse multiplier due to 500cpr encoder and
~29to1 gear ratio. I think the 500cpr will be for the motor shaft
and not the output shaft (I think).

Choice 2) looks good, but from the description they talk about
reversing the motor leads to reverse the direction...not sure why.
I would think all these motors would be "reversible". I am
leaning
towards this choice as I think I can get away with NO pulse
multiplier here.

This is from candhsales.com. They also have shaft couplers
(spider type) for 2.95 or 10 at 2.50 each. These have 1/4 shaft
and set screw. I will probably pick up a few.

Thanks,

Eric







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