Motor with lead screw - suggestions?

[CB123]

I am currently designing a mechanism which uses a leadscrew to drive apart two apposing arms. The leadscrew is the output shaft of a geared valeo motor unit. I think it is normally used as a seat adjuster in cars. Although this motor is fairly torquey, is begins to struggle as I increase the load on the mechanism. Does anyone know of another motor with an integral lead screw (I’ve become fairly attached to this motor/leadscrew combo) that has a high torque motor / output. I'm attempting to lift around 3000N; my current motor has a rating of 6Nm starting torque. I'm looking for a DC motor (12V - 24V). Any help would be appreciated as I'm running out of ideas.

 

[CB123]

the link to the motor I'm using at the moment....if this helps

http://www.valeo-swf-motoren.de/html/showmotor.php?id_artikel=1991&id_sprache=2

 

[unclesyd]

Here is one of many suppliers of DC actuators. You might look around as there are still some electric car jacks. Also there were a lot of actuators on the surplus market.

http://www.nookindustries.com/CCactuator/CCactuatorHome.cfm

 

[CB123]

Unfortunatly I'm very limited for space and I searched extensivly for an actuator that will do the job but to no avail. I have been able to fit a gas spring in but that is able to offer me a stoke that is more than 80% of the install height. Actuators only seem to be able to offer a max of aroung 60%.

 

[Barry1961]

How long of a stroke and how fast?

Barry1961

 

[CB123]

If I were to use an actuator, I would need a stoke of 175mm and a speed of around 4mm/sec at full load. The problem is the closed install height of the actuator can only be a max of 260mm (centre of fixings.

 

[djw2k3]

Once upon a time I looked at using a toroidal motor with the lead screw going through the center. This was quite a few years ago - 'Kollmorgen' I think were the crowd that made them.

Really not sure they would suit your application but throwing it out there

Dave

 

[Barry1961]

If you could use a rack and pinion instead of the lead screw you would get a lot more force out. Your screw may be only 50% efficient.

Just taking a wild guess you would need around a 900:1 reduction with a 50mm pinion. It would of course have to be a brake motor since the efficiency would be high. Brother makes some very small, high torque gearmotors but not using DC motors.

http://www.brother-usa.com/gearmotors/

I have done 12VDC applications in the past using converters which you can get for around $30.

http://www.dcacpowerinverters.com/12_volt_power_inverters.html

Barry1961

 

[zekeman]

You haven't mentioned a duty cycle. If the high loads are only intermittent, then it is possible to increase the DC voltage beyond the 24 volts to get the added torque, keeping in mind that overheating will be a problem if you exceed the manufacturer rated power for any length of time. I have done this on some occasions on permanent magnet motors.

 

[zekeman]

Just noticed . You would also have to look into the load capacity of the gearing and lead screw. If you want to experiment with one and risk losing it, it might be possible.

 

[israelkk]

Doesn't anyone uses calculationS any more? Why all the guess work? I have been tought in my engineering school and during my 32 years of aerospace engineer that calculations do the work and if I needed to learn the physics of a DC motor or a solenoid magnetic circuit I did it. The same about gearing design and calculations etc. Otherwise you will end up doing everything 10 times before you end up with a lame design instead of just one time ending up with a good robustic and safe design.

 

[ccw]

Hi BigMuma,
In addition to the excellent source posted by Unclesyd,
you might look at

http://www.duffnorton.com.

They also have free catalogs that are chocked full good eng. applic. data.

If you are attached to using the units that you have on hand, (acceptable closed length, acceptable cost) then try using two of them in parallel. This should take care of zekeman's mech. load concerns as well.

Your gas spring idea has merit, even if it does not have the optimum stroke/closed length aspect. Map your thrust required vs. stroke, and see if the gas spring will help you over the high thrust portion of the stroke with the remainder born by the original actuator alone.

 

[CB123]

Thanks for your help guys, there's a lot of leads there, hopefully one will ponit me in the right direction.

 

[unclesyd]

Here are two more sources of compact actuators and jacks. Look at the data as both have a product that I think will fill your requirements.

http://www.burractuators.com/index.html

http://www.joycedayton.com/jacks/jack_line_500lb.php

I have sone literature on a troidal motor as mentioned by djw2k3 if I can find it. If my memory is working these actuators were very expensive.