designing mechanism for axis adjustment of a shaft 1

[abnabb]

A shaft is attached with the help of bearings fixed in 2 blocks (70 mm X 70mm) from both sides

I want to design a mechanisum to adjust the hight of horizental axis of a shaft withim a 3 mm range.

The main requiremnt is that the positioning should be highly Precise and rigid.

Positioning resulution at least 0.1 mm

The current mechanisum is based on two screws in both side block. A manual and equal tightning of cecrews is required to adjust the height. This solution is not satisfectory to meet the precision, rigidity and long term Performance.

I would really appreciate to get some ideas

Shaft specifications:
Dia = 30 mm
Length = 400 mm
weight ca 5 Kg
Load in the middle of the shaft 8-10 Kg
Material: Steel

Thanks in advance

 

[bithkits]

Is it not possible to connect the two "adjusting" screws using a chain?

Because, if I understand correctly, the only problem here is that the screws are manually adjusted and do not move by the exact same amount resulting in a shaft that is rotated/not level.

Then they will move simultaneously and remain level if properly calibrated.

Adriaan.
I am an Engineer/part time student (Mechatronics) from South Africa.
Advice from lecturer: "Be warned - when you go into industry your boss will give you a thousand things to do and he wants them done yesterday!" So far he is right...

 

[MadMango]

Can you add an external thread to the shaft and use a threaded collar?

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[abnabb]

Thanks for the useful suggessions
The independent tightning of both screws would be good but it is not the only problem. The mechanisum have issues of stable performance in long run. I am loking for an alternative mechanisum (more stable, stiff, precise and rigid)
Thanks

 

[williedawg]

If space will allow, how about cams on a common shaft, with incremental markings ?

Existing bearing blocks may have to have an area faced off for a common dimension.

One or both cam faces slotted for lock-down screws....or small clamps to hold cam in position.

Another method might be to use a (one-piece) forked adjuster frame that is moved by only one screw; the forks pushing on the bearing blocks.

 

[Tmoose]

Is it adjusted and then left alone for a while?
Must it be adjusted "on the fly"?

"stable, stiff, precise and rigid"
I'd use a clamp or gib arrangement as used on machine tools that must be loosened before adjusting

http://image.made-in-china.com/2f0j00yhtTjsEKaaVH/Drilling-Milling-Machine-ZAY7045FG-.jpg

If stiff really means stiff then the rubber portion of this device would have to be removed.

http://product-image.tradeindia.com/00096573/b/0/Wedge-Mount-Series-DB-Bolt-on-.jpg

I'd think about mounting both blocks on a common plane, then using a large hinge to allow a single adjusting screw.

http://www.hardwarestore.com/media/product/506634_front200.jpg

similar to the way car alternators pivot to adjust belt tension

http://www.mgfcar.de/alternator/belt.jpg

 

[abnabb]

Thanks Tmoose,
I am working on one screw mounting as you suggested.
I have designed a CAM as "williedawg" suggested. A picture is attached. After adjusting, the CAM may be fixed tight with help of 2 screws from sided and one from top.
Would it be a stable, rigid and stiff solution?

Thanks

 

[abnabb]

Problem with the single screw monting is:

Actually I have to change the load on shaft axis quite often. For that reason, I use to take one side block out of shaft quite often. Thus single screw mounting may not be feasible.

CAM Mechanismus have slip free designing and fine polar adjustment issues.

some other ideas?
Thanks