# Thread: What should be material for T shape mechanism

1. ## What should be material for T shape mechanism

HI

My application -

I have an assembly as shown in figure.

RED - T shaped slider
BLUE - T shaped opening

A slider slides into a T shaped opening. The accuracy of sliding depends on the tolerance & the consistency depends on the material been used for the operation.

The life of the mechanism should be infinte so i am confused to select appropriate material for the same.

I have the following doubts -

1. Should both ( slider ) as well the T shaped assembly should be hardened. If yes, what should be the hardness value.

2. If we want to skip hardening ( to save manufacturing delays ) than which material should be used which is resistant to wear & tear & cheaper in cost.

Thanks
Zirok

2. ## What should be the acceleration when a object is pushed by hand ?

Hi

We all know that Force = Mass * Acceleration

The problem to me is that what should be the acceleration when a object is pushed by hand pressure ?

Thanks
Zirok

3. ## For infinite life & high accuracy ?

Hi

I am designing a assembly. A Slider slides into a Box type of Opening.

The requirment is that the sliding operation should be very accurate (with microns..Just like a machine) for a infinite lifetime.

So, I am confused about the sliding type to be used. Also there are some LM guideways i have heard of. Any recommendations about LM guideways ?

Any recommendation on the type of material & amount of accuracy in which it should be manufactured ?

Thanks
Zirok

4. Depends on how strong you are and how hard you push.

I don't really understand the question. Can you be a little more clear on what you want to know?

• Hi

A slider ( weighing 1 to 1.5 kg ) slides into a box type opening against a spring. The slider is pushed upto 10 mm only against the spring by hand feed.

Now, i am concerned for the Force harnessed by the mechanism for a distance of 1 mm.
As Force = Mass * Acceleration ( & we need to calculate acceleration to calculate the force )

After calculating the Force for 1 mm, i will multiply the force by 10mm(the stroke) so i will be able to calculate the correct force exerted on the spring.

I am in the stage of designing the SPRING.

Zirok

I hope rest is clear.

• Originally Posted by Zirok
Hi

The requirment is that the sliding operation should be very accurate (with microns..Just like a machine) for a infinite lifetime.

Thanks
Zirok

For a infinite lifetime and with micron accuracy.

First hurdle would be the infinite lifetime. This is an impossibility in the physical universe which we occupy. And no manner of wishful thinking is going to change that.

But with the proper design and maintenance you can get a very long lifetime, spanning decades even centuries.
An air pressure bearing has no real maintenance other than keeping it clean and fed with a possitive air pressure from a compressor, they can also be made to very high tolerances.
Electromagnetic fields can last a very very long time with minimal maintenance, all you need is an infinite supply of electricity. Maybe one of them free energy devices that seem to be all the rage with the young kids these days. Not too sure about the mechanical accuracy though...
As far as linear guides, some of them have a servicable lifespan meassured in kilometers provided they are used within their operating parameters. They can also be very accurate, but not maintenance free.

In either case you'd still need someone to maintain the assembly for infinity, which according to my old high school physics teacher is a very very very long time. Or atleast untill our sun runs out of fuel, swells up forming a red giant and engulfs our planet in ooh, lets say about 5 or 6 billion years.
And that brings us to cost... Paying someone for ever and ever and ever could potentially add infinite cost.
I'm no economist, but infinite cost sounds like a serious problem you need to overcome.

Suffice to say, if you walked up to any engineer with atleast some level of experience outside the protected confines of accademia and told them you want a sliding mechanism of unspecified lenght with infinite lifespan, micron precision and capable of supporting an unspecified weight or force they would laugh their ass off and walk away.

• Me thinks you are confusing acceleration with spring rate ie. K value.

Unless you are moving very large mass and or reaching high velocities acceleration is kind of meaningless in something powered by a human.

Contrary to the apparent current belief, CAD, FEA and the rest of the alphabet soup of virtual design software is not always the most efficient path to design something. Sometimes it is best to get out to the shop and build a crude prototype and try a bunch of different springs and see how they feel.

• Hi Guys,

I beat myself for using a Incorrect Word - "Infinite life"

Project -

1. A slider (weighing 1 to 1.5 kg) slides into a box type of opening (as shown in the figure). The slider pushes the spring by 10 mm, performs operation & then the slider reverts back (by the spring force).

2. The slider is moved by hand...(dont get confused...I dont mean feeding it by hand similar to what we do in lathe machine). I mean that the slider is pushed by the force exerted by fingers & palm.

3. This sliding operation is once in a day (24 hour). It actually provides a resting pad to the counterpart.

4. It is supposed to work in Normal Environmental conditions.

The Basic intention of saying precise accuracy is that it should not wear soon.

I hope I was not too confusing.
Thanks
Zirok

• Right then, that sounds more reasonable.

Sliding a 1 to 1.5 kg weight for an unspecified lenght once a day.

Yet again, wildly guessing here due to unsufficient information.
Let's say travel is less than the maximum lenght of any of the commonly available linear guides.

Based on that, it's probably safe to say that any of the linear guides over 12mm from this supplier would last for many many years.
http://www.nsk.com/products/precisio...e/linearguide/

Spare parts or equivalent replacement products from other suppliers shouldn't be a problem for several decades to come. Quite possibly for the rest of your natural life.

• As Andre'B said, force exerted on spring or by spring is k*the distance spring is compressed/extended (in your case 10 mm). Put a weight on the spring & see how much it depresses. Divide the weight (not mass) by amount of depression & you have your k (roughly). Of course assumption here is that spring is linear which may be reasonable.

• Try this: www.nelsonair.com

Dick Z

• Originally Posted by RICHARD ZASTROW
Try this:

Dick Z
Air bearings are certainly interesting, a while back I retrofitted a 36" rotary table that was A.B., the combined weight of the rotary table and the part was around 300lbs. At relatively low pressure.
Hopefully air will last a long time.
Al.

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