Need an ME for a rack and pinion design, what is needed from both of us

[faxibe]

TL;DR Summary

what should they do exactly for the job and what info do I need to provide?

I need a ME to design a rack and pinion system where both gears are plastic (type chosen through discussion) and rather small (5mm diameter for the pinion and 6mm length for the rack). The rack is moved by a spring loaded button press and the goal is to rotate an axle the pinion is attached to by X degrees.

I don't know what specs/requirements need to be provided to the ME for this job nor do I know what simulations I need to ask a ME to perform other than providing CAD drawings to verify the design will work (low likelyhood of physical damage from stress, durability to ensure long-lasting operation, amount of expected backlash, etc)

 

[jrmichler]

The ME needs a simple sketch of the total system that shows the button, gear, rack, and what the gear is connected to. For example, the gear and rack can be shown as a cylinder and a rectangle. There needs to be some idea of what maximum load will be, or at least enough of a description of what the gear will be driving so that the ME can estimate a maximum load.

(low likelyhood of physical damage from stress, durability to ensure long-lasting operation, amount of expected backlash, etc)

Focus on this, ask for simulations only if you want to pay extra for pretty pictures. Let the ME decide if simulations are needed.

How many will be built? If one or ten, parts may be machined or 3D printed. If 100,000, the parts may be injection molded.

How far do you want the ME to take the design? Do you want a proof of concept design, a paper design with dimensions and specified materials, or (for example) do you want the ME to work with an injection molder to build dies?

 

[DaveC426913]

You don't need an ME yet. You need a 3D prototyper.

I know this works because I did it myself (see my prototypes below).

Go on to a 3D printing site such as Shapeways. Ask for a designer. I got 4 or 5 offers. Describe your device. Have them design it and pay them for it. Have it printed and ensure it works to your satisfaction. Then take it to an ME.

I had only sketchbook drawings to start, and now I have a working prototype, which I tweak as-needed.

I was surprisingly cheap. I paid about $50 at a time for files. This will be both cheaper and more effective (because you can iterate your design until it does exactly what you want)

I can help you navigate the process if you'd like.

 

[gmax137]

Is this a "one shot" device? I mean, press button, axle turns, that's it? Or is there a reset? How does the spring get cocked, and if it needs to be, how does it get re-cocked?

 

[berkeman]

Is this a "one shot" device? I mean, press button, axle turns, that's it? Or is there a reset? How does the spring get cocked, and if it needs to be, how does it get re-cocked?

His previous thread with more details:

https://www.physicsforums.com/threa...tton-to-rotate-an-object.979011/#post-6247622

 

[DaveC426913]

Is this a "one shot" device? I mean, press button, axle turns, that's it? Or is there a reset? How does the spring get cocked, and if it needs to be, how does it get re-cocked?

In short: rotating head is slaved to button:

Press button: head rotates 10 degrees CCW.
Release button: head rotates 10 degrees CW.