Flex 3401 vs. Rupes Mille/Makita P5000C, for those that are wondering.

[WRAPT C5Z06]

Thank for your input, Todd.

[Philips146]

wow thats a lot of important info. Thanks Todd!

[RSW]

Todd,

Thanks for that explanation.



Isn't that why Rupes makes their pads thinner and stiffer? And why a long nap wool pad on a random orbital doesn't work well - the fiber of the wool flexes and reduces the amount of movement between the pad and the paint.

Also, it occurs to me that when a random orbital is run with the edge of the pad against a surface and the spin stops, the drop in performance is because that movement at the edge of the pad isn't a full orbit. instead of the full 21mm per orbit which is, Pi X 21mm X 2000RPMs and creates 131,880 mm of movement. you get at the very edge where there is no spin 21mm X 2000RPMs for 42,000 mm of movement - a dramatic drop because the pad is moving back and forth at the edge, not in a full circle. The lack of spin most certainly hurts it that case, but when the pad is flat against a surface it's not the same because even though the pad is stalled, the edges are still getting the full 21mm of movement.



RSW

My math was wrong when it came to the mm of movement of the pad at the edge by a factor of 2. It should have been 21mm X 2000 rpms X 2 for 84,000 mm. Still a lot less movement.

Some of the other comments were interesting as well. I'm going to get back to them but I thought I'd better correct my mistake first.

RSW

[RSW]

I'm not sure what kind of ego trip RSW is on, but the Mark II has more rotational spinning power and that's a FACT. I'm sure they wouldn't have bothered increasing rotational power if it didn't improve correct performance. Unless, the strictly wanted to satisfy the masses...lol


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I'm not on some ego trip, i just prefer it when answers to my questions are just that. I read the Rupes materials and they listed a lot of advantages for that machine but I didn't see increased spin mentioned anywhere. There are a lot of people who make claims about machines both negative and positive but manufacturers themselves are in the best position to say why they did what they did when it comes to the machines they produce.

There was another answer from Todd, who obviously knows what he's talking about responding to my comments regarding pad thickness and stiffness along with binding of the bearing and how those things effect efficiency of transferring movement from the backing plate through the pad to the paint, as well as spin.

Todd: "If we lock the bearing, the orbital speed and the rotational speed are fixed as one. This means 4000 OPM would also equal 4000 RPM. The effect would be like an offset pad on a rotary polisher. As slip is introduced into system, the bearing allows the pad to spin slower than the eccentric speed is orbiting, creating the random orbital movement. Too much friction in the bearing can over rotate the pad and also create the motor to stall as more of the load is directly transferred to eccentric set (and then to the motor). Too loose of a bearing will reduce the ability of the motor to "drive" orbital movement and create too much pad stall."

RSW: I found that interesting, particularly regarding how the friction of the bearing creating forced rotation. It would be possible to introduce a lot of forced rotation by making putting some friction into the interface between the backing plate and the shaft. It would be possible to introduce enough friction to really force the rotation but it would get hot enough to melt everything into one piece without some serious, serious heatsink. Still, an interesting thing to think about even if it's technically not likely.

Todd: A more powerful motor, that spins at the same speed, with no additional friction in the bearing will not allow for more pad rotation. However, a more powerful motor, with a carefully tuned bearing, will allow that motor to drive more of the movement (instead of relying on things like centripetal force and inertia alone).

RSW: I've read the explanation of centripetal force a few times and I must be missing something. The claim seems to be that the shaft moving in an orbit throws the outside edge of the pad in the direction of travel of the orbit. My confusion comes from not understanding why if a pad is moved in any direction from the center would the force effect one side of the pad less than the other? Any movement from the center looks to me like it effects the entire pad at the same time and in the same direction so the movement of one side would be countered by the exact same movement on the other side of the pad.

Anyway, I think it's fair to say that the most important difference between machines is rpms and orbit. More of either makes more movement and increases cut. As far as the class of machines - random orbital - is concerned.

RSW

[Mike@ShineStruck]

I 100% percent agree with the following points

A) You should always be a student - I am so lucky to be surrounded by the engineers at RUPES, to be involved in technical discussions, and to have Jason Rose as a mentor. I have also had the benefit of working alongside some educational powerhouses, including one Mike Phillips for a number of years at PBMG and of course before then too

B) I also don't believe in experts, per say. My focus, because of the people I am surrounded by, the company I work for, and my title as a Techincal Sales Manager for North (and South) America have forced me to ramp up my technical understanding of all things paint polishing. I am far from an expert and as the saying goes, "The more I know the more I realize I don't."

C) I agree that losing rotation is going to have, in almost every conceivable circumstance, a negative impact on polishing performance. However, over rotation can also have a negative impact. With a random orbital DA, there is a sweet spot between pad rotation, friction, orbital action, etc. Over rotation of the pad can reduce cut and reduce the cross-hatching movement a random orbital produces, leading to less-than-homogenous surface.


This part I may not agree with so much "RUPES is lucky to have you" lol. However I do my best. Looking forward to seeing you tomorrow old friend (and mentor).

Is it safe to Call the Rupes Mille the Little foot? lol


and since I cant correct my original post on specs ...

Mille
clockwise
5.18mm Stroke
7,490 OPM
14 orbits per rotation at 535 RPM
900 watts
motor amps ???
6.17lbs

PO5000C
Counter Clockwise
5.5mm stroke
6800 OPM
Math comes out to 8.608 orbits per 790 rpm
900 watts
7.8 amp
6.2lbs

3401
counter clockwise
8mm stroke
4800 OPM
10 orbits at 480 RPM
900 watts
9amp
5.73lbs

[WRAPT C5Z06]

Is it safe to Call the Rupes Mille the Little foot? lol


[/B][/B][/B]

I wouldn't call it little as far as correcting ability. I've "heard" it will outcut the 21 MK II.



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[Mike@ShineStruck]

I wouldn't call it little as far as correcting ability. I've "heard" it will outcut the 21 MK II.



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yeah read the same..just referring to short stroke :-D

[Todd@RUPES]

"RSW: I found that interesting, particularly regarding how the friction of the bearing creating forced rotation. It would be possible to introduce a lot of forced rotation by making putting some friction into the interface between the backing plate and the shaft. It would be possible to introduce enough friction to really force the rotation but it would get hot enough to melt everything into one piece without some serious, serious heatsink. Still, an interesting thing to think about even if it's technically not likely. "

Yes, you can theoretically "drive" the backing plate with a tighter bearing by reducing the slippage, almost like releasing a clutch. At some point, depending how much you drive the backing plate, it becomes far more efficient to use a gear-drive, for some of the reasons you touched on.

The problem with a gear-drive is that you loose the random rotation of the pad, and thus begin to scribe a similar, repeating pattern across the paint which makes it easier to achieve a hologram effect. In addition, you loose the cross-hatch that occurs when the orbital movement and the rotation are in the same direction.

"RSW: I've read the explanation of centripetal force a few times and I must be missing something. The claim seems to be that the shaft moving in an orbit throws the outside edge of the pad in the direction of travel of the orbit. My confusion comes from not understanding why if a pad is moved in any direction from the center would the force effect one side of the pad less than the other? Any movement from the center looks to me like it effects the entire pad at the same time and in the same direction so the movement of one side would be countered by the exact same movement on the other side of the pad. "

This is frankly where my lack of education in this specific type of engineering and physics is quite visible. The movement of the pad off axis creates inertia (technically it creates a lack of centripetal force if my education is to be trusted) which should act to help keep a spinning pad spinning. I don't believe it would create spin in-and-of-itself, nor should it make a difference on the direction of the spin.

It was explained to me this way by somebody with a doctorate in physics from an IVY league school, who works as a high-level mechanical engineer.

If you took a random orbital into the vacuum of space, and there is absolutely zero friction in the bearing, and turned it on, the tool would orbit but there would be absolutely no pad rotation. It would continue to face in the same direction, such as north.

[Eldorado2k]

@Todd@RUPES. Happy belated Birthday.

[RSW]

"RSW:

Yes, you can theoretically "drive" the backing plate with a tighter bearing by reducing the slippage, almost like releasing a clutch. At some point, depending how much you drive the backing plate, it becomes far more efficient to use a gear-drive, for some of the reasons you touched on.

The problem with a gear-drive is that you loose the random rotation of the pad, and thus begin to scribe a similar, repeating pattern across the paint which makes it easier to achieve a hologram effect. In addition, you loose the cross-hatch that occurs when the orbital movement and the rotation are in the same direction.


It was explained to me this way by somebody with a doctorate in physics from an IVY league school, who works as a high-level mechanical engineer.

If you took a random orbital into the vacuum of space, and there is absolutely zero friction in the bearing, and turned it on, the tool would orbit but there would be absolutely no pad rotation. It would continue to face in the same direction, such as north.

Thanks for the response.

Last thing first, The model of the machine running in space without any friction in the bearing is exactly what I've been saying. The force applied to the pad from the center is applied to every molecule in the pad at exactly the same time in exactly the same direction so if one side of the pad moves the other side moves in the same direction and, because they balance each other out there is no spin at all. Instead of drawing a line on the outside of the pad draw overlapping circles all over the pad.

I know forced rotation machines aren't random, but I think the movement of the entire machine can provide enough variation to overcome that problem. I think, though I'd like some feedback, that forced rotation machines have an advantage in the way the abrasives interact with the paint. Because the pad is moving in generally the same direction all the time the abrasives don't rock back and forth so they cut more consistently and that makes for a higher gloss. It could be that there's just more raw movement between the pad and the paint as well but in any case, it's been my experience that I can get a higher gloss given the same products and time. And of course, I can get really close to edges and on things like window moldings without having to change machines.

The new Rupes machine is pretty much exactly what I was advocating for when I talked to your designer at the Rupes booth at SEMA, the only difference is, I asked for 800 rpms. I'm sure you're all looking forward to selling that machine the way I described in my response about direction of spin regarding Makita's new machine.

Oh yeah, Happy Birthday!

RSW