Vibration isolation

[jhitesma]

I was under the impression that some of the errors in the prints in #13 were due to the resin moving during the printing (creating intentionally by bumping the printer to see what kind of effect it would have.)

I'm sure there are dampening issues with the mirrors which are being worked out, but I was thinking more along the lines of how to keep the resin stable since it appeared that the resin moving during the printing was creating some of the errors as well.

Perhaps I'm misunderstanding and the only issue is the mirror dampening in which case isolating the printer itself wouldn't make much of a difference (but still seems it couldn't hurt as external vibrations could still be passed through.)

[martinf1977]

@Martin:
Have you been at the Form1 userforum? The Form1 uses similar galvos, and Formlabs have had a lot of trubble with them. The printers start out printing really high resolution, but degrade after a while... Some users have had their printers replaced 3 times......

Johan

No I havent.... I have to admit that I would be kinda pissed off, if I payed almost 3000Euro for a printer and they used 100euro galvo's as the key component in them.
but I can see myself building a printer along the principles close to the peachy, but with 100 pound galvos - spending a total of 150 to 200 pounds for a printer. and then maybe living with sometimes needing to replace a galvo. For 3000 I would expect a higher quality overall......

Cheers
Martin

[Pete]

These cheap galvos are an interesting quality. I bought some similar to this and the casings and mounts are great but the electronics and feedback leave a lot to be desired. Unlike the peachy homebuilt galvos which are open loop these are closed loop and rely on a PID controller and reasonable feedback. Unfortunately the feedback in the galvos that I received are optical, there are two light sensors, an LED and a piece of glued cardboard on the spindle, the position is apparently sensed by comparison of the two optical sensors and the cardboard baffle moves and changes the proportion. I can't believe that the accuracy of these is actually any better than the stock peachy galvos (although they will be faster but they do burn significant power).
Also if anyone out there does purchase any of these to play with then I strongly urge you to use your own power supply. The questionable quality of the PSU I've received vs the energy you can get from mains is just not worth the risk.

[martinf1977]

<snip> Unfortunately the feedback in the galvos that I received are optical, there are two light sensors, an LED and a piece of glued cardboard on the spindle, the position is apparently sensed by comparison of the two optical sensors and the cardboard baffle moves and changes the proportion. I can't believe that the accuracy of these is actually any better than the stock peachy galvos (although they will be faster but they do burn significant power).<snip>.

Sounds like it's possible (maybe easy even) to improve the optical feedback to the PID and thereby improving these drastically - Getting closed loop servo's on the printer, should (if the sensor works properly) guarantee repeatability of the printer.
Since you have access to these kind of galvo's,(if you still have them) would it be possible for you to take some pictures of this feedback loop? I'm very curious!

Kind regards
Martin

[Anuvin]

Actually I don't think so... How much would be left of the existing printer, once you put in the galvo set? - isn't that most of the build?
The way I see it, a set like this, and an audio amp, to get to more ideal levels input for the galvo's....
Maybe can be done for around 150 instead of the 100, but I think you would avoid a lot of trouble. Sometimes we can go to far to save a few bucks, compared to how many compromises are needed....

Good point, I hadn't thought of that. Truthfully though? There is still a lot of printer left. The laser, the circuit board, and the valve. Much reduced though, if you end up getting one of these, I will certainly be interested in your findings. $100 is not prohibitively expensive.

would it help to put a second set of magnets on the bottom of the galvo with a second coil (basically mirror the top of the galvo system) and use the equalization of the magnetism cancel out most of the vibration and then instead of a little flag with some oil to cause drag use a full disk that the acetate arrow slips through the middle of, on further reflection perhaps the acetate is to flexible so maybe they should switch to a styrene for the arrows, my only other suggestion would be to add "wings" to the arrows (same principle as a longer see-saw) it would slow the print speed a bit but would dampen any vibrations or "jumps" in the mirrors.

Maaaaaybe. There is already a second magnet for the purposes to equalization and centering. Still jitters too much. I like the idea of a full ring! I would love to try it, I will see what I can cook up.

[Anuvin]

I was under the impression that some of the errors in the prints in #13 were due to the resin moving during the printing (creating intentionally by bumping the printer to see what kind of effect it would have.)

I'm sure there are dampening issues with the mirrors which are being worked out, but I was thinking more along the lines of how to keep the resin stable since it appeared that the resin moving during the printing was creating some of the errors as well.

Perhaps I'm misunderstanding and the only issue is the mirror dampening in which case isolating the printer itself wouldn't make much of a difference (but still seems it couldn't hurt as external vibrations could still be passed through.)

No, I misunderstood, really. I had dampening on the mind and you used that word and my mind went there. Isolation is a great idea IF you have need for it. I can set my peachy on an adjacent desk that receives 0 vibration. Even when I have it on my own desk and move around and occasionally bump the desk, the resin only ripples or sloshes for a moment, too little time to mess up the print. Still, anyone who does a lot of printing may want some kind of isolation. So please post your designs!

The issue in update 13 is from a funny issue that I have noticed. PP28 had a little wiggle to it, not as rigid as PP29. This meant that if you whacked the desk hard, it would physically change the positioning of the hardware!



I tell you this not to discourage you, but rather in attempt to illustrate what that shot is about. This issue could absolutely be solved by your inner tube idea, so keep working on it!

[Compro01]

The issue in update 13 is from a funny issue that I have noticed. PP28 had a little wiggle to it, not as rigid as PP29. This meant that if you whacked the desk hard, it would physically change the positioning of the hardware!



I tell you this not to discourage you, but rather in attempt to illustrate what that shot is about. This issue could absolutely be solved by your inner tube idea, so keep working on it!

Yeah, the wiggle there was from working on a rickety table and kicking it a few times, among other things.

[3dpaftermarket]

We produce lasercut vibration dampeners out of cork. They're precisely cut to dampen vibrations from stepper motors. It's inexpensive and worth a shot with your issue. Cork used is industrial cork, not hobby-grade cork.
http://www.ebay.com/itm/Stepper-Moto...item4ad1b19c11

[jhitesma]

Well, I'm not working on anything yet since I couldn't afford to be a beta tester But I was in the first delivery tier for the final printers so hope to be experimenting before all of them are out of the door I'm hopeful that they ship on time...but would rather they be late and improved than on time and in need of a lot of extra work. Either way I can't wait for mine to get here so I can start to play. Just hope it does get here close to the expected date since summer is when I'm inside and can play with this kind of thing while winter is my outside time due to living in the desert