looking to design a automatic backlash checker for gearbox

[cliff turnell]

Hi Group,

I am in the beginning stages of designing an automatic backlash checker for small gearboxes (Nema 17 and Nema 23, possibly as large as 34) and wanted to bounce my ideas off this group. the basic idea is to have a stepper motor w/ encoder mounted to the input of the gearhead, "lock" the gearhead output shaft in place, apply a CW torque of X IN-LBS and record encoder count, apply a CCW torque of X IN-LBS and record encoder count, compare those readings to obtain angular backlash, "unlock" gearhead output shaft, rotate gearhead output shaft 90 degrees ( by virtue of stepper motor and whatever ratio I am testing) and repeat process. I plan on controlling the process via PLC (should be a fairly straightforward program). Where I am getting hung up is finding a way of securing the output shaft. I am trying to find a thru bore brake or some sort of air powered clamping mechanism for a .500" diameter output shaft that I can engage via PLC signal. My first thought was to a have a motor/brake combo coupled to the output shaft but I am not sure if I will be able to back drive the motor coupled to the output shaft. If anyone has any ideas as to how I might accomplish this I would love to hear any/and or all ideas! Thank you for your time and have a great day!

Regards,
Cliff

 

[hendersdc]

The first thing that comes to mind is a pneumatic collet closer like this one [URL unfurl="true"]https://www.mscdirect.com/product/details/90867292[/url]. You can get a 1/2" collet to go along with it. Could work with other size shafts as well with different collets.

from your description, I understand that whatever locks the shaft in place is fixed and you are applying the set torque to the stepper motor body, is that right?

 

[cliff turnell]

Attached is a 3D PDF of the concept (minus whatever will be used to secure gearhead output shaft). The motor will be mounted to the gearhead and then that entire assembly will be secured on to the mounting plate (light gray is gearhead and dark gray is motor). On the side of the mounting plate opposite the gearhead will be the device that will "brake and hold" the output shaft while the motor shaft does it's CW/CCW check (that setup is not etched in stone but that is the basic idea). Hopefully this makes it a little clearer...

 

[hendersdc]

I still think a pneumatic collet closer would work, found a cheaper one that works better with your orientation: [URL unfurl="true"]https://www.mscdirect.com/product/details/09148255[/url]

There are also pneumatic or hydraulic 3-jaw clamps out there but they are probably going to be more expensive: [URL unfurl="true"]https://www.spreitzer.de/en/clamping-technology/dbf-p-three-jaw-chucks/[/url]

 

[btrueblood]

Your pdf is a blank page. Can you not couple a relatively cheap electric clutch to the output shaft?

https://ogura-clutch.com/industrial-intro.php

 

[hendersdc]

btrueblood, it will show up if you give it a minute, I thought it was blank at first too. All it shows is an axial gear stepper motor mounted directly to a plate with the shaft extending through the plate.

 

[cliff turnell]

Did you "enable 3d content" at top ( I have noticed that if that is not clicked it will come up blank but with content enabled should come through, I have attached a 2D PDF with this response. The electric clutch idea definitely looks like a viable option!

 

[cliff turnell]

It looks like both the pneumatic collet closer or clutch would work for what I am trying to do. Thank you so much for the input, this has been a tremendous help and if there are any other ideas out there I would love to hear them!

 

[MintJulep]

If the shaft lock doesn't need to be automated:

http://www.fennerdrives.com/trantorque/_/Trantorque-Mini-1/2/?=

This could be actuated by an air cylinder pretty easily:

https://www.fixtureworks.net/store/pc/Shaft-Locking-Clamp-QSC-Series-c826.htm

This is ready for air off the shelf:

https://www.imao.biz/en/products/quick-shaft-clamp-en.html

 

[cliff turnell]

For the amount of torque I am needing to hold the "off the shelf" pneumatic version of the holding clamp would probably work although I would need to machine a sleeve to interface between the bore of the clamp and my .500" diameter shaft ( not that big of a deal, we utilize sleeves like that all the time), great ideas and thank you!

 

[btrueblood]

I'd think you could roll your own version of the pneumatic clamp that Mint pointed you to. See the views of the product in the catalog (link below) and also notice they have different sizes, all metric though.

https://imao.meclib.jp/sw002e/book/...11360-726890254.1584111360#target/page_no=102

 

[btrueblood]

Just noticed the name of the company is LMAO...sheesh.

 

[MintJulep]

I guess that a 12 mm version could be pretty easily reemed up to work for a 1/2" shaft.