rotary to linear converter 13

[nelsonk11]

I need a way to convert rotary motion to linear motion just like a rack and pinion, but it can't be a rack and pinion or a ballscrew. Anybody have any ideas.

 

[gt6racer2]

How proportional must the control be, and what is the variable being controlled ?

 

[nelsonk11]

No, this is most certainly not a school project--it is an actual life support device controlling low pressure flow of gas. I am experimenting with a linear motor currently, and a voice coil is also a possible choice.

 

[nelsonk11]

Overall control needs to be to position to .001" and hold against varying pressures.

 

[unclesyd]

Out of the box,
Could you use an arragement like the tatoo machines. I know they can recipitate .250. Don't know about your requirement. If applicable you could use the needle as the piston.

http://unimaxsupply.com/tatmch/1swash1.htm

http://unimaxsupply.com/tatmch/1swiss.htm

If you didn;t need the dwell time you use a cheap PM dc with a larger shaft and an offset crank pin.

We have some production machinery that uses small PM DC motors to provide oscillating movement to a wire.They buy $1.39 motors, original $.39. All I know about them is that they tell me the're are operating on AC. I called the inventor of this system and asked him about your problem. His response was that his design would not work due to speed requirements.

 

[sreid]

I'm with alansimpsom, a voice coil-servo drive is the only way to get those speeds and accuracy. There are some quite small linear optical encoders available today for position feedback. A flexure mechanism can be used for the linear motion and would also provide the spring return to the unpowered position.

Let me add that voice coils and magnet housings are easy to design and easily built in-house. I say this because purchased voice coil actuators are insanely expensive.

I can supply all the details you might need if you should elect to try this option.

 

[IRstuff]

Or, just rip them out of a hard drive:

http://en.wikipedia.org/wiki/Seek_time

A 2.5-in HD's platter is 0.9 inches across the annulus, which is traversed in no more than 15 ms, so about 0.4 inches in less than 10 ms

TTFN

FAQ731-376

 

[sreid]

0.4 inch in 20 ms is about +/-12 G with a peak velocity of about 20 in/sec. Most of the accelerated mass will be in the straight line flexure and voice coil Voice coil bobbin aluminum, flexure EDMed titanium (low mass, high strength, good fatigue resistance). To keep the voice coil cool, ferrofluid in the voice coil-magnet housing gap.

Renishaw just came out with a self calibrating linear encoder.

 

[nelsonk11]

Thanks for all the suggestions and good ideas! The voice coil is one of the leaders. I have a valve company quoting on a custom product. I don't know if I mentioned it but it has to control air and oxygen up to 100% oxygen at room temp. I experimented with a linear motor today and got some very surprising result--great control and ultra fast speed. I also have proposed a butterfly valve design which I built to a valve mfr who is considering a custom version for us. Thanks for the concentration of brain-power on my challenge.

 

[sreid]

Renishaw TONiC Encoder.

http://www.renishaw.com/en/10187.aspx

 

[MarkUMSU]

Can you use a piezo actuator?

 

[nelsonk11]

Piezos won't work because they don't release upon power loss.