I have wondered why someone hasn't created a balancing wheel for many tools, such as bench grinders, and routers, and essentially ANYTHING that spins quickly and has a tendency to become slightly out of balance for any given reason.

These CENTRAMATIC balancing wheels are used on wheels of vehicles and motorcycles. They are a flat plate with a circular tube. Inside of the tube are tiny ceramic balls that move freely around the interior of the circular ring. They work well to balance loads, since an unbalanced load has speed differentials between the segments that rotate faster (around a larger orbital path) and those segments that follow a smaller orbital path. The beads move around inside and gravitate to the slower areas, thus balancing the wheel.

I use DYNABEADS on my motorcycle tires and trailer tires. They are awesome for maintaining the balance of wheels through their lifetime. As the tire wears, or a rock takes out a chunk of rubber for example, the beads move around inside of the tire to compensate for that change in the centrifugal force of that small segment of the wheel, replacing the weight of the rubber chunk that was removed.

I suppose a balancing wheel COULD be made for a router spindle, and I am guessing that it would improve the performance of the router, if someone would only INVENT the dang thing!

Here is the company that makes the balancing wheels.

Joe

http://www.centramatic.com/balancers.rhtml?customer_id=546-629-9909&gclsrc=3p.ds

 

 

I am a big believer in DYNABEADS.

 

I've heard about dynabeads or similar products. Cool demo video. A self-balancing flywheel might be easy to spec, though I'm not sure whether it's necessary in this case. Interesting question. Note that routers are moving a lot faster than tires, I don't know how that would change the math (i.e. bead size or shape, maybe?).

 

I am not an engineer, and I do not play one on TV.

Joe

 

I want to learn more about this kind of balancing, I wonder if it works well with liquid or if you want the particles to "lock in" to some degree. I imagine particle size, shape, density, and total quantity might all have some contribution. I realize also I was calling this dynamic balancing, but that really means something else.
Regards,
Keith

 

Wouldn't anything that anything that adds mass to the spindle be bad, since it must change directions quickly and precisely?

 

As noted: it's very little net weight, though yes that will change responsiveness, roughly equivalent to putting a bigger bit in your spindle.
What's important to a flywheel is energy storage, and that's only indirectly related to net weight. Spindles are often spinning very fast, which is flywheel heaven, lots of energy storage. That will make the entire assembly resistant to rotation (precessional motion blah blah), but it won't effect translation (normal x-y-z movement).

 

How are you handling your E-Stop..... you'd need to incorporate a mechanical break. Now you have account for that mass at dynamic load on your gantry.... assuming your using a AC motor.....which then gives very little control over speed and torque.


Next idea.....

 

We're talking about a small flywheel. Yes, it will slow down acceleration: start up, stopping, and changing speeds. How much does that matter? Given a material and a bit, how often are we changing speed? Why do we care about the E-stop, if it takes an additional second? We're talking about weight equivalent to a slightly larger bit.
In terms of added weight: I'm guessing an ounce or two, not a lot of weight. The trick with flywheels is diameter and speed, total weight isn't exactly a helpful way to think about them generally (but see below).
Such an arrangement won't interfere with translational movement, except in the "total weight" sense, so if total weight is a very small proportion of the current weight of whatever is being moved (either router/z-carriage, entire z-axis, or z+x-axis, I think): in all cases I'm not sure how much difference a few grams would make?

 

I few grams makes a ton of difference, you're not talking about a static load, it's moving under load as well.

I don't know maybe my 30 years designing machinery is kicking in, but have you looked at the consumer and industrial woodworking machine market lately??? We've got saw that detector skin and within a millisecond the blade is safely out of the users way. If you look at any CE, UL, or OSHA machine safety regulations you have less than a second to safely stop all motion on any machine when the e-stop is pressed.
If you want to build something for your personal use, that's cool. But to even consider this as a commercially available item all this stuff has to be considered.

 

There's also a chance, btw, that there's much less leeway in sizing this for it to work properly than I've assumed. That is, it might only help when designed specifically for the material/feeds/speeds of a particular situation. Which might make it less helpful, or not.

I don't really expect this. I think bigger will be better, wrt to cutter stability/cut quality & capacity improvements, as long as it doesn't bog down the spindle. But I could be wrong on this point. There's even another possibility, that building a little damping in to the flywheel through construction & materials, could make a difference.

I feel like all of this ought to be a discussion in a 1930's machining manual, but I can't find any reference to it. But I might not know where to look. I'm not trying to reinvent the wheel... haha. Sorta literally.

 

Electrical/electronic engineer here. The armature of the motor (universal motor for router or high frequency induction for a spindle) has a significant mass anyway and effectively functions as a flywheel. Both styles of motor operate reasonably smoothly and with minimal vibration unless the user installs something that is out of balance. Adding something with a significant potential to be out of balance, and canterlevered beyond the bearings, then trying to operate the system at between 10000 and 30000RPM is more likely to create issues than solve them.
Do you have access to a dynamic balancer that can handle that sort of speed range and can be configured to drive the entire system at that speed? If you do, your day job probably involves design, development or maintenance of jet engines, if you don't how are you going to balance the system? That is the only way to be sure that the components you add are balanced to the tolerances required.

 

Electrical/electronic engineer here. The armature of the motor (universal motor for router or high frequency induction for a spindle) has a significant mass anyway and effectively functions as a flywheel. Both styles of motor operate reasonably smoothly and with minimal vibration unless the user installs something that is out of balance. Adding something with a significant potential to be out of balance, and canterlevered beyond the bearings, then trying to operate the system at between 10000 and 30000RPM is more likely to create issues than solve them.
Do you have access to a dynamic balancer that can handle that sort of speed range and can be configured to drive the entire system at that speed? If you do, your day job probably involves design, development or maintenance of jet engines, if you don't how are you going to balance the system? That is the only way to be sure that the components you add are balanced to the tolerances required.

Remember that all this is about chatter. Which is sort of by definition out of balance dynamic forces. Yes the armature (including shaft, and all moving parts of the motor) are acting like a flywheel. If I bolted on a bigger (higher rotational inertia at least) motor, would you expect smoother cutting? Or not at all? With no other changes to system rigidity? My guess is yes, but am I wrong?

 

The solution to chatter arising from the cutter face impacting the material is to judiciously control the extent of that impact, via selecting feed rates, depth/width of cut, and the number of cutting faces on the cutter to find a sweet spot where economical material removal rate and required finish quality meet. My guess is that if you add a perfectly balanced mass (theoretical flywheel) between the bearing and the cutter, then start hogging material out, the motor speed will not be influenced by tooth engagement in the interrupted cut, but the bit may move in the collet.
The flywheel on an engine is there to 'bank' and smooth torque because the engine produces a series of torque pulses as cylinders fire. As a secondary effect, the inertia of the flywheel can be taylered to provide additional motive power depending on application. For example, race car flywheels are often significantly lighter than for a road car using the same engine base, simply to allow the engine to accelerate and decelerate more readily because the flywheel has less inertia. Similarly large trucks and earthmoving equipment have huge flywheels to a. smooth the more massive torque pulses occuring at each firing, b. provide a torque bank to assist in getting vehicles moving, and c. provide a lot of face surface area for clutch contact to transmit immense torque.

 

Yes, exactly.
Barring experimental data, I'm increasingly confident that the flywheel would change feeds & speeds to the degree that they were power-limited, which may be fairly common. The Feeds & Speeds wiki page makes that clear, sort of.
In the case of the router, we're closer to a large truck than a race car, in terms of speed variation of the spindle. It's interesting, b/c a properly proportioned flywheel will have far less translational inertia, but may actually further stabilize cutting even through translation due to gyroscopic forces. That is separate from my main point.
I think when you mentioned the bit slipping in the collet, the presumption is the flywheel is on the motor shaft. It could of course be on the bit shank alternatively... or even built in to the bit.