Resonance Damper

[yngndrw]

Hi guys,

I know that threads about resonance dampers have been done to death on here, but I have an idea which I haven't seen before in order to make them quiet.

First let's look at how I see the "rattlers" working. Yes, "centrifugal force" does not really exist but I will treat it as a real force in this as it fits well.

Let's look at a single hole in the rattler:

Here you can see the metal pin inside of it's oversized hole. As the damper spins, the "centrifugal force" forces the pin outwards in the same way that a spring would. The pin centers in the hole to rest in it's natural position.

When a change in angular velocity happens, (I.e. It speeds up or slows down.) inertia forces the pin either to the left or the right. As the "centrifugal force" still exists pushing the pin outwards, the sideways force must overcome the outwards force in order to follow the curve of the hole and move sideways. This wastes some of the sideways force, dampening it:


If we were to represent this as a spring-mass, it would look something like this:


So the first method to make it quiet would be to turn it into the spring-mass system shown above, but this would be harder to make. This is actually very simelar to the split-flywheel separated by rubber method which I've also seen on these forums.

So how can we make the pin-based rattlers quiet ? Well first of all let's look at the hole. We don't need the hole to be round as the pin, when the damper is turning, should never be pulled inwards past the half-way mark. With this in mind we can change the cutout to be this shape:


The second thing that we can do is to line the inside of the cutout with a thin piece of rubber. This can be a thin-walled tube which has been put in a cutout of the correct size.

Is this idea new or has it been done before ?

Finally, as a bit of an aside - If I were to get a 60mm diameter bar of Delrin and cut a 30mm thick chunk from it, what would be the best way to clamp it to my CNC Router ? I only have a T-Slot table on it.

Thanks,
-Andrew.

[CarveOne]

Might be worth trying, and it seems to have merit. I haven't seen one like this so far. You could even add oil in the cavity for grins if you can seal it well enough. Different viscosity oils will have an effect on how it operates.

CarveOne

[yngndrw]

Originally Posted by CarveOne Might be worth trying, and it seems to have merit. I haven't seen one like this so far. You could even add oil in the cavity for grins if you can seal it well enough. Different viscosity oils will have an effect on how it operates. CarveOne

I will be sure to try making them if I get the right setup, but the clamping is holding me back on that right now. (I could get a sheet of 25mm thick Delrin and machine them out of that, but I wanted to use the full length of the second shaft and hence make them 30mm thick. I couldn't find any sheet thicker than 25mm so for 30mm I'd have to cut it from a bar.)

The oil may do wonders in terms of quieting it, but I'm not sure what it would do in terms of performance. (I.e. Resonance removal.) To seal it you could just put a rubber o-ring around each cutout - Quite a bit of extra work but if it's being done on a CNC it shouldn't be a problem to get right.

If anybody is in a position to quickly and easily try making a prototype of this that would be really awesome.

[ger21]

Why not try making Greg's silent dampers.
My take on a stepper damper

[SScnc]

Originally Posted by ger21 Why not try making Greg's silent dampers. My take on a stepper damper

I have my 4x5 CNC router about 99% done and it is making things, I have 1/2-13 lead screws on the X and Y and the original X lead screw from my X2 on the Z. I had planned to upgrade to ACME screws but instead will go with R&P on the X and Y soon.

It appears I'm suffering from the resonance problem on the Y axis as at times it will suddenly stop and growl very loud unless going at 30 IPM or lower. The lead screws do have some wobble to them even though I tried to straighten them. I have single shaft nema 23's on the router so I will swap with the double shaft steppers that are on my X2 and I want to make Greg's silent dampers. I didn't find where he posted his results though. I'd like to know how they ended up working for him, any idea ?

I'll post some pics of my rig soon, I didn't have a clue as to what was causing my problem at higher IPMs until I read about it here a few days ago, the Zone to the rescue again, thanks !

Steve

[ger21]

I didn't find where he posted his results though. I'd like to know how they ended up working for him, any idea ?

Did you read the last line of his post?

Mine aren't silent, but might be easier to make.
My take on a stepper damper
My take on a stepper damper

[yngndrw]

Originally Posted by ger21 Why not try making Greg's silent dampers. My take on a stepper damper

While they are a great idea, I'm not sure it would be so easy for me to make them. It's a lot easier for me to work with wood or plastic, but as the outer part of them is the mass really they need to be metal. Having said that, the more I see them the more I think "Maybe I could make them ...".

Originally Posted by SScnc I didn't find where he posted his results though. I'd like to know how they ended up working for him, any idea ?

A lot of people seem to be happy with the improvement that their guestimates have made and hence don't have a need to do any additional trials and comparisons. I think that any design which follows the general "spring-mass" idea should work well.

Originally Posted by ger21 Mine aren't silent, but might be easier to make. My take on a stepper damper My take on a stepper damper

That design would be a lot easier for me to make, it also gives me a solution to my thickness problem - Make the body out of 25mm thick Delrin then glue in a longer hub.

The only thing that I have against the design is the hub - I'm not a fan of setscrews as they mark the shaft. I prefer the split clamp so would probably change that: Thanks.

[SScnc]

Originally Posted by ger21 Did you read the last line of his post? Mine aren't silent, but might be easier to make. My take on a stepper damper My take on a stepper damper

Wow, I guess that I saw it but it didn't sink in as my eyes were drawn to the pics, easily distracted you know thanks. Yeah, I saw yours, they look good and it was your video that really made me realize I had the same problem.

I already have the urethane and I have some 2" steel rod to turn them out of, I don't have a knurling tool so I think I'll just turn some grooves into the center part and make some grooves perpendicular to those.

I know he said the dimensions were a guess, I hope 2" OD will be good (?) His looks like they may be 2-1/2" dia.

Originally Posted by yngndrw A lot of people seem to be happy with the improvement that their guestimates have made and hence don't have a need to do any additional trials and comparisons. I think that any design which follows the general "spring-mass" idea should work well.

I hope you're right about that in my case too. We'll see.

[yngndrw]

Good luck !

Don't forget to post about the results and any changes you make.