Motor type selection for door actuator

[RyreInc]

We are looking for an electric actuator to replace a pneumatic valve. This will be used to open and close a door in horizontal and vertical orientations, about 20lb mass. Max speed up to 20 in/s is desired. The door will cycle typically every 30 seconds, but possibly as little as 10 seconds. If possible I would like to power the motor from a 24VDC supply.

We are looking at belt/pulley, rack & pinion, and ball screw actuators.

I've been looking at various motor options, and a DC/universal motor seems like a good choice. Simple to control, fairly straightforward to reverse, appropriate torque/speed relationship. Downsides I see are: no direct control over speed/accel/decel; need for sensors to detect when in retract & extend positions to avoid overheating; asymmetrical up/down speeds when door is vertical; brush wear and associated maintenance.

Another option I've looked at is a stepper motor--this has the opposite problems of the DC motor, e.g. more expensive control system but precise speed & positional control, no overheating issues, no brush wear.

What other motor types would be a good candidate for this application?

Would the brush wear on a DC motor be of great concern considering the intermittent duty? Should I focus more on wound field or permanent magnet motors?

Thanks!

 

[ScottyUK]

Bitter experience rules out ballscrew in my eyes. Self-contained electro-hydraulic is worth looking at, especially for high duty cycle applications.

 

[jraef]

Are you looking to get into the linear actuator business from scratch, or to solve a problem with opening a door? If you want to solve a door opening problem, look at electrical linear actuators that are already made and self-contained. I wouldn't fuss with the motor type, sensing issues, etc. etc. Put out a performance and durability spec and let the best supplier win, but get backup information from other users as to reliability, responsiveness etc.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[JSPRINGS]

Servo Motors.

Costly but effective.

 

[RyreInc]

Thanks for the replies!

We really just want to open a door, and want to get rid of the pneumatics that we currently use.

Unfortunately expense is a concern so servo motors are out.

I'll look into the EHAs, but I'm anxious that this would not play nicely in a clean room environment, which is one potential area this could be utilized. EHAs also seem more suited to high force/power applications.

Why would we NOT want to use a DC motor?

 

[controlsdude]

I would not use any motor size less than 1HP if 3 phase is available. Use a VFD type motor with a VFD. Since your using a motor you need 2 limits switches for each position.
inner limit switch on door is that the door is approaching open or close position. When the door is between the inner limit switches the motor is a max speed.
Door between inner and outer limit switch = slow or creep speed.
Outer limit switch on door is that the door is stop, its either fully closed or open.

Used to with pallet conveying with a transfer cart. Also used this with freezer doors where the pallet is going from production to freezer storage.

Gearing i have no idea.

 

[RyreInc]

1 HP seems like gross overkill for a 20lb door. I didn't specify the door size, but it is about 18" square.

 

[controlsdude]

try this 24v linier actuator

just a google away, i am sure you can google some more

http://www.duffnorton.com/products.aspx?id=7841&gclid=CMuei96f8cUCFQaTaQodm4cApw

LT Series
27 to 225 lbs.
(120 to 1,000 N)

can use the same idea with limit or prox switches to do same thing.

 

[jraef]

Why would we NOT want to use a DC motor?

If you are thinking of a cheap DC motor or a universal motor, you will have brushes, so brush / commutator wear with the associated maintenance and in a clean room environment, you are potentially adding contaminants. So if you go with PMDC and have to add travel sensing, you may as well go with stepper or servo.

I've used these guys in the past, they have a clean room qualified linear slider that will handle 19 lbs. They also have very low cost belt drive LAs as well.

http://www.intelligentactuator.com/pdf/ISDA_CJ0085-2-UST-2A.pdf

"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington