Miniature Impact Hammer/Device for Delivery of Dynamic/Impulse Forces

Something like this might get you started; also look at mini vibrating massagers.

http://www.ebay.com/itm/Stainless-Steel-Oral-Vibrator-Pack-Tongue-Ring-Micro-Massager-Batteries-Included-/321002900413

He's looking for 60-120 cycles per minute, not second.

Yeah. I didn't even know those things existed.

It would be pretty easy to tear one apart though, and incorporate a dial to adjust the cycle time.

I think these vibrators just have a little motor inside with a off center weight. I doubt they could be slowed down and be very efficient.

Yeah. Probably more engineering involved than it's worth, but the little off center weight could probably drive a little piston.

Besides, I had never seen those, and I just wanted an excuse to post them.

I took an old cell phone apart that had one in it. It's a cute little thing but some most of the energy they make is due to inertia.

I've got a spectrum analyzer somewhere around here. I might could (probably won't) set it up and look at the amplitude vs frequency.

Not sure I could vary the frequency. I can't see well enough to work on tiny stuff.

These guys: HeatSync Labs are right down the street from my office. I could get them to do it. They're Geek Central.

If you have a smart phone (that you haven't taken apart), they have a built in accelerometer and there's an free app (Accelogger) that will plot frequency versus time and plot out a spectrum for you.

I just loaded it. You may have created a monster.

This will probably cause me to have a wreck.

Without knowing your budget, there's only so much we can do.

Impact Hammers - PCB Piezotronics

Manual hammers:
micro precision marking hammer - steelstamps.com

You could also do this with a pendulum and a calibrating sensor.This is how mechanical impact testing is done in the laboratory. (or, used to be anyway)

Your first task should be to study micro-impact hammers and then decide what your budget will tolerate.

Pendulum/sensor probably the way to go. Piezo impact sensors are inexpensive, and if you have an oscilloscope you could do this.

Impact Test - Zwick USA

ASTM D3420 - 08a is one test method.

Should find something here...

http://www.sinexvibrators.net/other-products1.htm

http://dry-bulk-material-flow-solutions.decavibrator.com/category/pneumatic-and-electric-impactors-hammers

http://www.vibco.com/docs/general-catalog/general-product-catalog.pdf

http://www.alibaba.com/impact-vibrator-suppliers.html

http://www.bksv.com/Products/transducers/vibration/impact-hammers/8203

http://www.altasol.com/products/AS-1220/AS-1220.html

You may be able to accomplish your experiments using a properly chosen or designed DC solenoid and its built-in its plunger to deliver needed force. The frequency of operation can be determined or adjusted by a variable DC power supply.

Dear Friends,

Thanks to everyone who contributed to the thread. It was very informative.

I have already got in touch with PCB electronics over their impulse hammer. Bruehl and Kjaer is yet to reply.

The rest of the descriptions are not exactly within my understanding - it may be possible technically, but not my cup of tea. :D

Alternately, can anybody suggest a place or a person who would be willing to take up this assignment for a customized product - at a minimum cost.

It looks to me that the requirement is pretty basic and since the dimensions of the device are small, it won't cost much to fabricate.

Look forward to your suggestions,

Best Regards,

Jigar.

For the frequency and force you specified, I can envision a hammer hinged at the end of its handle and lifted by a cam driven by a motor. Of course, you would need some kind of load cell sensor calibrated to read out in Newtons peak force. You would have to adjust the drop distance to allow for the maximum frequency and the weight of the hammer to get the forced required. I can't think of anything ready made that could be re-purposed for this.

I was thinking about your problem in the middle of the night. The diagram above is a plot of the force on a dropped mass as a function of position. As it falls, it acquires energy = weight x distance, the shaded area under the axis. If it strikes the target which compresses according to Hooke's law, the rebound force is equal to displacement x elasticity. In the diagram, elasticity is the slope of the force curve. The energy acquired through falling is transferred to the target and is equal to the shaded area above the axis. So when the shaded area above the axis is the same as the area below the axis, the maximum value of force will be the peak of the curve + the weight.
If the force versus displacement characteristics of the target does not follow Hooke's law, it could be determined experimentally.

Thanks everyone for your replies.

@Rixter - Please see your inbox! :)

Best Regards,

Jigar

A short remark: the force is not programmable since it depends on the resistance the plate and the body offer to the "hammer mass". You can only program the energy level by the amplitude at a given frequency.

I think you could be better served by an ad hoc device consisting of a long stroke DC solenoid + a spring and a simple function generator + curent (power) amplifier.

The best would be a double acting solenoid centered by 2 springs. This generates an oscillating system which frequency should be such that you can follow the frequencies you aim at. The force will be generated at contact and as mentioned above progressive.

The problem will be the choice of the solenoid which has to be done by a simulation of its dynamics if you want to avoid a long adjusting period. I would add that there are solutions to increase the force.

We could discuss more on the direct channel.

I like your idea. I've seen actuators advertised Ebay that would probably work and the driving voltage could be adjusted for the proper force.

Hi Guru,

Thanks for your reply. Apologies for the late reply.

If I understand it correctly, what you've mentioned is a combination of:

1) A miniature version of Long Stroke DC Solenoid, as depicted below:

http://www.youtube.com/watch?v=TKgRCIarczo

2) A function generator much simpler than the one below:

http://www.youtube.com/watch?v=YaI6LT233kA

Thanks for the suggestion, we can take this forward if this pathway works.

Best Regards,

Jigar

1- I wrote "long stroke" because usually strokes are quite small. You can find in the catalogue of MAGNET SCHULTZ the double acting solenoids you could use. The smallest size (040) Type G TU W could be enough for your experiment. You have only to measure the moving mass and compute the 2 springs you should provide. The armature has about 0.13 kg which you can accelerate the magnetic force going for instance from 21 to 83 N along the stroke of 8 mm. the time constant is around 6 ms which will allow you to use it at the frequencies you need.

As principle if you want to have a heavy impact you pull is and so charge the spring and commute to reverse so that magnetic forces and spring forces do sum. At 5% duty you can go as high as 54/190 N!

2- In your application it could be better to have a signal generator as the one you indicated since you have to change and optimize as well frequency as speed at impact and it is better to have a large variation possibility as pulse form.

The best solution would be to take off the rectifier bridge and build up a controlled loop with the DA solenoid as linear motor and with a stroke and speed feed back connected to a controller but this is over the possibilities you have.

If you have other questions feel free to ask.