Rack and pionion brake system

[joostvsch]

I have an engineering challenge.
I am in the process of designing a pick and place machine with a table moving in the X and Y direction.
For the Z-direction, a gripper is placed on a moving arm above the table.

For speed and cycle time purposes, the table is driven by a rack-and-pinion system. Such as:

The drives that are used are NEMA17 stepper motors without gearboxes for X and Y. The Z-drive has a gearbox on it.

However: If the system is powered-down, The table needs to be stabilized so that it cannot move around anymore. Also, the gripper-arm must be held in position when the power is switched off.

I have been trying to find an easy electrical system to lock this in place, but I have been unable to find anything useful up until now.

Requirements for actuator/brake-system:

Power source available: 5 volts and 12 volts.
System must be fail-safe. If the power is switched off, the brakes must be engaged.

Things that I came across, have tested, but did not work:

1) Solenoid actuator, 12V. Disadvantage: The max. pull-force is only available at the end of the stroke.
2) Magnet, electrical. Disadvantage: The max. pull-force is only available at the end of the stroke.

Do you happen to have any recommendations on this aspect?
Thanks in advance,

 

[wayne440]

Try a search on the phrase "Permanent Magnet Electrically Released Brake", you might find some inspiration.

 

[TugboatEng]

There are shaft brakes that attach to the stepper motor.

https://www.omc-stepperonline.com/stepper-motor-brake/

You chose an unusual control voltage so you'll need to provide also a 12-24vdc converter.

 

[waross]

While you are adding a brake, consider also adding a 120V/24V transformer and a bridge rectifier.
Brake coils do a good job of self filtering.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[RedSnake]

Any particular reason why you haven't chosen a motor that includes a brake?

/A




“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[joostvsch]

Thanks for all the replies.

The reason I did not use NEMA17 motors with brakes is that I use a geared motor for the Z-drive (See picture below) A brake cannot be added. I was hoping on finding a simple solution that could be used on all drives.

The thing that I am exploring right now is to create a simple brake system myself for this. Use spring-load to generate friction between the moving part and the static part (rack).
The only thing that I cannot get my head around is to find an electrical actuator that is able to supply approximately 5 [N] of force with a stroke of +/- 5[mm] The simple types of solenoids (2nd picture in 1st post), they generate the force, but only at the end of their stroke and they cannot be activated 100% of the time.
If you happen to know of any principle / type of actuator to use for this, please let me know! Thanks in advance!

 

[TugboatEng]

Motor brakes usually replace the end cap of the motor opposite the drive end, or you can get a double ended motor. This is the correct solution for your application and you should adapt your application to allow for it.

 

[RedSnake]

Yes and even if Hanpose do not have that combination, gearbox and brake I am sure they can fix it.

It is easy and cheap to change things in your mind compared to do it after it's made. ;-)

/A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[srini1785]

Apart from all electrical solution so far proposed, if you have access to air pressure then a single acting (Spring return) cylinder, of suitable diameter and stroke, powered by a single solenoid valve would do the job of positive locking.

Power fails, valve resets and spring pushes the piston rod forward to engage positively with the table or gripper arm. Some designing has to be done but that's not a hard job.

 

[joostvsch]

Thanks for all the feedback! I did not find the nice NEMA17 motors with integrated brake myself as an assembled piece. The pneumatic option is the only option with an actuator that is feasible, I think, besides the on-motor brake.

 

[waross]

they cannot be activated 100% of the time.

Most AC solenoids may be actuated 100% of the time.
DC solenoids with an end of stroke limit switch and an economizer resistor or coil may be actuated 100% of the time.
Use a spring applied brake. Release the brake with a solenoid. You may design an "S" cam to apply the releasing force to the brake mechanism. The cam may be profiled to match the force/travel curve of the solenoid.
My favorite line in the Canadian Electrical Code;
"...may be accomplished by the exercise of ingenuity."

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[mc5w]

You can buy off the shelf electrically powered linear actuators that meet all your needs including a parking brake when powered off just the brakes in bridge cranes and elevators. You do not need to build them from scratch. You should try off the shelf first because that will be cheaper than designing and prototyping something.

Off the shelf solutions avoid reinventing the wheel.