To rigidify or not to rigidify? - vibration issues
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@Nxt-1
Perhaps a little bigger than I was imagining... but I don't see why they wouldn't work. Plus I bet they are cheap!Location and number of the bolts might be a variable.
And the rubber would help reduce the risk of deforming the extrusions to match the no doubt not flat or true concrete. -
@theruttmeister Since sleeping over it I am thinking about casting 7.5x15x145cm pillars myself (the extrusions are 15cm wide and 150cm high). It would cost me about €20 in concrete mix for all pillars instead of €40 a piece for of the shelf pillars (which I would need to cut to length as well)
I do wonder if my current approach of using M5 bolts and t-nut inserts will suffice to attach the concrete slabs to the towers. If not things start the get nasty real quick, as I'd need to drill larger holes straight through the extrusions
@Nxt-1 said in To rigidify or not to rigidify? - vibration issues:
@baird1fa said in To rigidify or not to rigidify? - vibration issues:
What about just adding isolation mounts to the Nema23 motors. They are the source of the vibration so if you isolate them it should be greatly reduced.
I already have (homemade) pieces of 2mm NBR between my motor mounts and the steppers, my plan is to try multiple sheets of those stacked and see what happens.
I just installed a total of 10mm of these NBR sheets and it improved the coupling a bit but not enough. I think a lot of the noise gets coupled via the bearings that support the shaft in the motor bracket I designed.
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@Nxt-1 The pics I have seen were of adding fishing line cross-bracing the upright frame members to act as triangular support segments so that the frame itself becomes more rigid. I don't have a picture on hand, but I'm sure if you google around you may find some implementations of that.
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@H2B
I wonder how applicable that technique is to the size of machine I have.@mrehorstdmd said in To rigidify or not to rigidify? - vibration issues:
How about a couple strap clamps?
I tried with the only strap clamp I could find and did not really notice a significant difference sadly, worth the try though.
@theruttmeister
I got myself four bag of ready to concrete mix and will play with it, hopefully in the coming days. Most likely I will go with the M5 bolt+t-slot nut approach as drilling holes trough the extrusions is just asking for troubles with all the interrupted cuts, at least with the tool I have at my disposal. I'll report my findings once I have something to report. -
@Nxt-1 said in To rigidify or not to rigidify? - vibration issues:
@H2B
I wonder how applicable that technique is to the size of machine I have.@mrehorstdmd said in To rigidify or not to rigidify? - vibration issues:
How about a couple strap clamps?
I tried with the only strap clamp I could find and did not really notice a significant difference sadly, worth the try though.
I suspect that right now, adding more rigidity is not going to do anything. In fact its probably just going to add things that can resonate.
@theruttmeister
I got myself four bag of ready to concrete mix and will play with it, hopefully in the coming days. Most likely I will go with the M5 bolt+t-slot nut approach as drilling holes trough the extrusions is just asking for troubles with all the interrupted cuts, at least with the tool I have at my disposal. I'll report my findings once I have something to report.That seems the most sensible path. You can use the same 3D printed mold technique you used for the base, and mold the through holes for bolts right into the concrete. Don't forget a draft angle!
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3 molds cut
2 molds assembled
1 mold filledIf the other sides of the concrete slab look anywhere near as nice as the top surface, I'll be real happy. Oh, and I added blue pigment to the mix
I plan to mix and pour the other two slabs as the extra pigment I ordered arrives. I also got myself a box of M8x80 bolts and matching t-slot nuts for attaching the slabs to the towers.
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@Nxt-1 I would install cement anchors as long as the cement is wet.
If you make new ones, I would suggest reinforcement steel inside and preproduced holes (filled with eg polystyrol), so you don't need to bore holes when the concrete is dry, with the risk of cracks. For a nice side, using molds from concrete formwork panel (screen printed plate, german Betonschalungsplatte) give a smooth surface.
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@JoergS5 Anchors would do me any good and there would be no way to screw a bolt into them once the slabs sit against the towers. As others suggested, I did think about printing some pieces to serve as bolt holes spacers (all the way through) but in the end I decided that I will drill the holes with a rotary hammer drill. If it gives me to much of a pain in the [redacted] I can still go that route for the two remaining slabs.
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@Nxt-1 I added some information to my post as suggestions. I wish you success, mixing blue color into it is a very good idea, this looks really great!
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I too would prefab the holes to reduce risk of cracking when drilling; fingers crossed!
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@JoergS5 I think all of you suggestions are good points, heck they might even be smarter to do. The reason I did not go for the betonplex wood (as it is called in Dutch) is simple, I had a large plate of this wood at hand and didn't feel like buying a fresh sheet of the smooth wood just for this
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@bearer @JoergS5 I have drill a few holes in concrete the last months, more than I'd like tbh, but never had cracking issues. Maybe I am naive but unless this slab is just to thin to resists cracking, I don't feel worried. * knocks on wood *
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@Nxt-1 To have a lot of experience increases the chances very much
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@Nxt-1 the only issue with that is the screws will still transmit vibration. True vibration mounts are isolated between the screws too. I had them on my CoreXY and it was much quieter than with out. The only issue I had was how they attached with some really long spacers and only two spots added some elasticity in the lotion that I disliked more than the noise.
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@baird1fa You are 100% correct. I have already placed an order for proper nema 23 dampers, but they will take a while to arrive.
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@baird1fa Thinking about this for a while longer, I expect the proper dampers to help but not really solve the issue. I believe a lot of the vibrations will still get coupled to the frame via the axle/bearings/belt combo. And I don't think there really is any way around that, except maybe making the whole motor mount of out tpu
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For a Delta it is not necessary to over regidify the frame. The mass of the print head in comparison to the printer is very low. There are no heavy axis which have be pushed. Print artifacts on Deltas seem generally more linked to exruder issues. Your built btw looks already relatively steady. All the work to make the printer more stable will very probably change nothing.
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@dgrat said in To rigidify or not to rigidify? - vibration issues:
For a Delta it is not necessary to over regidify the frame. The mass of the print head in comparison to the printer is very low. There are no heavy axis which have be pushed. Print artifacts on Deltas seem generally more linked to exruder issues. Your built btw looks already relatively steady. All the work to make the printer more stable will very probably change nothing.
While you might be right that extra rigidity will not help. At the same time we are not trying to make the frame more rigid with the concrete slabs. Just trying to increase the mass, which should reduce vibrations, or lower the resonant frequency of the frame to be precise.
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@Nxt-1 you would be surprised how much the proper mounts help. Belts don’t really transmit vibration as they are already vibration dampers. If you don’t have good linear bearings then that will cause vibrations but i suspect you do have good linear motion components.
If you are using aluminum extrusion filling it with something viscous (hydraulic oil or honey) would help in 2 ways. One it would dampen vibrations and it would also fill the resonance chamber with a fluid that would change the speed of the sound waves.
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@baird1fa said in To rigidify or not to rigidify? - vibration issues:
@Nxt-1 you would be surprised how much the proper mounts help. Belts don’t really transmit vibration as they are already vibration dampers. If you don’t have good linear bearings then that will cause vibrations but i suspect you do have good linear motion components.
I don't disagree that proper stepper damper can do wonders, I have actually used them with success in the first iteration of my printer (nema 17 that time). The issue here is that the motor rigidly connects to a 2nd shaft which holds the pulley. That shaft is supported by two bearings, which sit inside the whole bracket. So there is a rigid connection from the stepper to the axle through the bearings into the frame. What I said is that a damper will not solve that part of the problem.
I indeed use high quality THK SRS_WM rails, they will not be a source of significant vibrations.
If you are using aluminum extrusion filling it with something viscous (hydraulic oil or honey) would help in 2 ways. One it would dampen vibrations and it would also fill the resonance chamber with a fluid that would change the speed of the sound waves.
If I had not previously filled the towers with just pain sand, this would be a way easier solution. Right now, I don't have means of getting the sand out of the 1,5m long extrusions without turning the printer upside down, which I am definitely not doing unless it is my last resort.
