[IQChallenged]

http://www.youtube.com/user/4287765

I recently posted a rough prototype of a solution I came up with for dust control. I've redesigned it and I believe it's much better now. I wanted a "shoe" which would follow beneath the router yet not apply any pressure on the router as the brush bristles pole-vaulted when changing direction. Furthermore I didn't want the torque from the vacuum hose to push on the floating shoe. I ended up with a shoe that is free to move up and down as the bristles pole-vault without affecting the router. I made a telescoping vacuum connection so that there's actually an air gap between the inner tube and the outer tube. The vacuum hose is attached to the rigidly mounted outer tube. The inner tube is oblivious to the torque of the hose. The vacuum was so contained that I had to open up the inlet in the top of the shoe (where the router goes through) to keep it from being sucked down on the table. I put up a little video on YouTube. The quality is terrible but hopefully you'll be able to get the idea. I'll appreciate any suggestions on reducing the buzzing noises in my machine. It varies a lot depending on my motor configs.

http://ProjectCNC.wordpress.com

[txcowdog]

That is pretty cool. What is the shoe attached to and where? Does it just float free under the suction line?

[IQChallenged]

That is pretty cool. What is the shoe attached to and where? Does it just float free under the suction line?

The shoe (the plexi plate with the brushes) moves with the router. The two metal rods that connect the shoe to the router plates allow it to move up and down. You can see a very large hole where the router passes through the shoe. That hole was much smaller. I had to enlarge it to reduce the vacuum effect which was pulling the shoe smack down on the project! It worked too good. You can also see a small round hole where the square inner tube is welded to the shoe. Initially I was going to use a short piece of PVC. I decided it was too heavy so I made a lightweight square tube. I'll eventually hog out the hole with a grinder making it square. The inner tube moves up and down inside the outer tube which does not actually contact the inner tube. A brown strip of felt around the inner tube helps to reduce leaks thought it is not necessary. The outer tube is bolted to the router so that the torque in the vacuum hose will not move it. When the machine is not in use I lift the shoe off the table to protect the bristles from bending. The plastic screws get turned in against the hardened rods to hold it.

http://www.ProjectCNC.wordpress.com

[Steve-Tee]

Wow, that has got to be one of the neatest solutions I have seen.
I would surely give this a try when my machine finally begins to draw breath.


The buzzing sounds that you mentioned, sound a fair bit like resonance.
Perhaps you could try the resonance dampers that have been invented by folks on this forum.
There are a few little videos around too. These dampers provide a remarkable improvement in stepper motor performance.
When you view those videos, you'll see, and hear, what I mean .

Thanks again for sharing such a fine example of innovation in dust extraction.

Best wishes,
Steve-tee.

[IQChallenged]

The buzzing sounds that you mentioned, sound a fair bit like resonance. Perhaps you could try the resonance dampers that have been invented by folks on this forum.

Thanks for your compliments. I suspect resonance too but I didn't want to "lead the witness". I've never seen the dampers you speak of. I'll do a search. On certain settings I can get my motors to be a quiet as can be. But when I slow them down with f250 or something like that they start buzzing. I suspect it's all related to my direct drive rack and pinion. The thing develops so much gantry speed with so few RPM that I have to keep my feed down low. The lack of reduction gearing is probably the culprit. All suggestions are appreciated.

http://ProjectCNC.wordpress.com

[txcowdog]

This is the thread that ran recently concerning the dampers for the stepper motors. http://www.cnczone.com/forums/showthread.php?t=32284 It turns out to be a simple and easy to build fix.

[IQChallenged]

Before reading the responses to my post I already knew a teeny tiny bit about resonance. I knew nothing about these dampers. Having researched them just a bit it's easy to get the impression that is nothing but a chunk of mass that somehow reorganizes the energy. But I'm sure there's more to it than that so I'll look further. One thing's for sure though I'm very excited at the prospect of being able to get rid of this dreadful sound and palpable vibration. When I put my hand almost anywhere on my machine (depending on the motor settings at the time) it feels like something really destructive is going on.

[Steve-Tee]

Howdy IQchallenged,

That resonance thing had me quite baffled also. I had a motor sitting on the bench. As I altered its speed, it would exhibit all sorts of parasitic oscillations. Naturally, I suspected the electronics. Nope, not there. Although there were some odd waveforms, it became apparent that those were being generated by variations in the back EMF of the motor, during resonance.

The damper assembly that is shown on this grand site, is surely the answer.
While a standard flywheel can offer some assistance, all it seems to do is lower the frequency at which resonance becomes an issue.
The damper works on a wonderfully simple principal.
My hat is off to the inventor.
By having a number of individual masses, each reacting at slightly different moments in time to the motor's steps, the prospect of resonance is eliminated.
The maths behind this is not all that clear to me, but I sure can relate to how this wonderful device works.

When you see the videos that have been put up by the makers of these, you'll be a convert .

Here's hoping you'll get rid of those unwanted vibrations.


Best wishes,
Steve-tee.

[IQChallenged]

I've only found a couple of videos. They show before and after performance which is, of course, dramatic. One example uses a quickly tossed together device made of shop scraps. The other is apparently a commercially made device. I still don't have any idea how to go about getting one (or more) or how to make my own.

[IQChallenged]

My bad. It was there all along.

[Steve-Tee]

Howdy IQChallenged,


Yup I plan to make some like these soon.
First, I need to add a shaft to the rear of my motors, as these are the single shafted variety, and there is no room elsewhere for the damper unit.
I found that I can bore into the existing shaft and then press fit a home made shaft extension into the rear end of it.
That was lucky .




Hehehe, I was just waiting for this comment .

My bad. It was there all along.