Running a stepper motor continuously for years

Other Hardware Motors, Mechanics, Power and CNC
21

Slumpert:
To be honest, I would expect your 3D printed pump to self destruct long before a quality brushless motor would.

Did you consider just using a air lift pump. You could have the arduino monitor the ph and flow rate of the water that gets lifted and then the arduino simply controls a air solenoid to pump more or less out.

You likely already have an abundance of air pumps to tap off of.

That would be a great idea and I like the outside the box thinking. It's common practice for a saltwater aquarium to use a protein skimmer, which uses the principal of air lift. not so much as to pump water but to use the charged bubbles to attract particulates in the water and bind them to the bubbles so that they can be brought to the surface and collected in a cup. It's called chemical and biological filtration. The cup collects this nasty sludge. Using an air lift for a calcium reactor will create that sludge at the surface as well as increase pH (when you're trying to lower it).

22

MarkT:
I can't see any temperature ratings for the 17HS4401 motor in the datasheet I found - but its 1.7A at 1.5ohm
which is only 4.3W of dissipation. I've seen other NEMA17 motors rated for twice that power dissipation
(and 80 degC temperature rise), so I think that motor's going to be about 40 to 50 degC above ambient
in use.

Thanks Mark,

I just ordered the motor, and once I get that in, I will start to work on the design.

@Paul_KD7HB

What are some easy ways to determine actual motor revolution?

23

sisterlimonpot:
Thanks Mark,

I just ordered the motor, and once I get that in, I will start to work on the design.

@Paul_KD7HB

What are some easy ways to determine actual motor revolution?

Well, since you are already making the pump mechanism, make an addition to it. I guess the shape of the rotor is like a gear? Use a sensor to count the teeth by breaking a light beam. Or add a micro switch to ride on the teeth and count the switch operations. Or just use a leaf switch that will ride on the teeth.

Probably many other rotation sensors are possible. You really want to know the pump rotation, not just the motor.

Paul

24

sisterlimonpot:
Using an air lift for a calcium reactor will create that sludge at the surface as well as increase pH (when you're trying to lower it).

Further out of the box, use CO2 as the “air” for the lift..
Typical air lifts simply vent to outside, but in my mind if you submerge outflow into the reactor and add a container at the top that you recycle back into the lift with a “air pump”
Said top container would just need a high volume, low pressure regulator supplying CO2 as needed.

25

Just figured I'd come back and post the finished project:

This head had a 1.7" diameter.


Installed the motor and pump head

Installed the pivoting frame

Right now I'm simply using silicon tubing 6mm ID 9mm OD. In the future I plan to use a more durable tube.

Clamp it all down with the spring and nut

26

After verifying that it was going to work, I designed and cut out the pieces to make the box

Tapped all the holes

311×640 38 KB

Completed assembly

Now it's time to test how quickly I can move 500ml of water.

For the most part this was on the low setting about 1:30 in I ramp up the speed, so you can hear and see the difference that it made.

One of these 2 links should work.

I have to say, I was hoping for more participation from the folks here in the forum. I didn't enjoy the uphill battle trying to get the flow of ideas going. I guess I expected people to share their opinions of certain stepper motors to look at and which ones to stay away from. And the ardiuno coding to make this project over the top. But sadly, I didn't get much help. Hope those that are reading this can reflect and work to change this. Or not...

1 Like
27

Wow! Great job. Looks very professional. Hope you can make more and sell them to recoup the development expense.

By the way, may I suggest when all is ready to install, you put a dab of locktight on all screws and nuts.

Paul

1 Like
28

I'm a bit late into this discussion, however here's my take on the project.
For the utmost in reliability, the best solution I have found is redundancy.
For a given task, if you use two (or more) devices for a given task and one fails, the remaining item(s) can continue to provide for the task albeit at a reduced performance level.
Have a look at www.banggood.com and search for "peristaltic pumps". There are quite a few listed and prices ave very keen.
So maybe a second pump will provide the reliability you seek.

BTW Banggood, like a lot of other suppliers, have quite a range of gadgets including water/gas solenoids

29

Peristaltic pumps can fail by the tube wearing out and shredding/leaking, which means you'd need
isolation valves on the pump for any redudant pump to be able to take over.

I recommend preventative maintanence plus conservatively rated components as a good approach.

30

What I really want to know is what is the box made of and how did you cut and assemble it. In building Ards over the years I've found one of the hardest things to do is build a nice looking sturdy and easy to construct case.

I know this topic is a bit old but in searching for the exact same type of info as the OPs orig post - which never did actually get answered here did it ?

Here are some answers :

Stepper Motor Life

Based on this doc it seems most non-super cheap steppers last quite a long time - MTBF of 1 million hours ?

Lifetime depends on exactly what you would expect it to from a basic engineering standpoint - temp, bearing quality, insulation life, radial load water and dust intrusion etc.

There are some great charts in there on most of these.

For my application I need rotation 24/7/365 for a load of about 1 pound axially in an outdoor environment so I was worried about stepper service life. Looks like its not much of an issue for something rotating so slowly with a low mass.

Some other findings - grease selection for the bearings is a factor :

Stepper Motor Service Life

And this

Lifetime for a Stepper Motor

The typical lifetime for a stepper motor is 10,000 operating hours. This approximates to 4.8 years; given the stepper motor operates one eight-hour shift per day. The lifetime of a stepper motor may vary in regards to user application and how rigorous the stepper motor is run.

Required Maintenance for a Stepper Motor?

Since stepper motors are brushless, they require no maintenance for wear and tear on brushes and commutators.

Also they sell IP65 sealed motors for harsh environments (and other IP ratings too I'm sure).

For general use I would guess running continuously at fairly low rpm your looking at 5 to 10 year lifetime for a 'normal' off the shelf motor. And like many things probably cheaper and better from a statistical standpoint to plan ahead for motor failure - stocking a spare is usually a better approach then trying to buy/build the very highest quality motor.

You're welcome :slight_smile: