Best posts made by Nxt-1

We have arrived at the moment of truth.

Friday I assembled the molds with, as you can see, the white pieces in there to make bolt holes and a piece of rebar in the center. Saturday I mixed up another 3 bags of concrete mix and did the pour. Then finally on Tuesday, I demolded the slabs and attached them to the printer. Before I go over the results, I'll share some more of my experiences and remarks.

Removing the wood mold pieces went very very easy just like last time. The white inserts for molding the bolt holes were not. From the 40 spread over the two slabs, just four came out with gentle percussive action. I did have a 1,5° taper angle on the pieces, but I ended up needing to use a drill to get rid of most of the plastic. The last cleanup was done using a hot air station at 200°C. The holes are not perfectly smooth around the edges, but no major issues.

Last time I noticed that the sides touching the mold wood were quite dusty and remained quite dusty no matter what I did. I did a quick google and assumed bad mixing was to blame for that. On the two new slabs I notice the same however, yet that could be due to me using the same mixing ratios. But actually I now believe it is due to the wood absorbing moisture from the concrete while it is still wet, thus effectively causing localized bad mixing. I figured this as I poured the excess concrete in a plastic bucket and after drying is was completely dust free. The wood absorbing moisture also explains why the top surface did not show the same issue.

I decided to add a piece of rebar in the center to give some added strength as the piece is quite thin compared to its length and did not want it cracking in half while working with it. The picture below shows how I suspended the rebar with some metal wire between the printed pieces. After demolding I noticed something interesting. In both slabs I can feel something moving quite distinctly when I jiggle a little with the slab upright. It really feels like the rebars are loosey goosey in there Don't ask my why, and I guess at this point it doesn't really matter that much either.

While playing with the first slab, I became clear that it did not sit perfectly straight against the tower. I got a piece of ~3mm rubber matting from a local home improvement store that sold it by the meter. I cut six pieces sized and holed correctly for the slab so I could double up on the thickness if needed. In the end I did end up just using one piece per tower, but oh well.

Now it is finally time for the moment of truth, attaching the slabs to the towers. At a little of 30kg a piece it was not trivial but I managed to get them one there. Some bolt holes are left open as one or two holes are badly located and do not line up well enough, or the t-nut fell down while playing with the bolt and I did not feel like removing the slab to put a t-nut back . Once I attached the first slab and even the second I did some test moves and was not really impressed with what I heard. But the third was the charm I guess, definitely an improvement. I can no longer feel any vibrations with my hands on the towers.

I must nuance the results a bit sadly. While the difference is certainly there and is quite noticeable, it's not perfect and not really acceptable even. I went from being able to hear the printer form all areas of the house to only audible in the next room. To combat the last noise I have some proper nema 23 dampers on order and I am most likely going to construct some sort of enclosure for the entire printer, that I line with sound dampening material.

Congrats to the people that made it this far down the wall of text, enjoy the pictures and drop an upvote if you think these longer post as worth the time Many thanks to all that pitched in with ideas and suggestions.

Just for the curious among us, this ended up costing my about €165, of which almost half went to the M8 t-nuts and the blue pigment.

@sneakyferret if it is of any use, I van provide a data point. My wiring to the smarteffector is a good 2m long and has been working for years without a hint of problems.

-Nxt

@Kolbi From own experience with the rubber isolation rings I can attest that they are more than rigid enough so that motor orientation is of no concern whatsoever. At least for sizes that I worked with (nema 17 and recently 23). What might be more of an issue is load tangential to the motor axis. About a year ago I actually removed these style isolation rings from my printer as my (high) belt tensions would cause the assembly to flex out of alignment. In recent months I circumvented this issue by adding an extra bearing to the stepper shaft, opposite of the pulley.

There style dampers are excellent at what they do however. Due to the fact that is no other path for vibrations to travel from the motor to a motor mount (except for through the shaft, but you can't everything rubber right ). The cock pads are in my experience worthless for that same reason. No matter how ideal there vibration absorption characteristics are, there will always be a direct path to the motor mount via the bolts.

The following threads that I started might all be of interest for you. Keep in mind most of these are quite long (and not always a pleasant read )and still ongoing.
https://forum.duet3d.com/topic/14674/external-bearings-for-stepper-shafts
https://forum.duet3d.com/topic/17513/to-rigidify-or-not-to-rigidify-vibration-issues
https://forum.duet3d.com/topic/17725/building-a-sound-dampening-enclosure

After further debating it with my machining guy, we ended up turning down the heatsink top shaft to 12mm diameter and not thread it at all. To be able to clamp it, a simple 10mm high spacer was machined to sit between the redish washer at the top of the pcb and the bottom of the screw in bowden connector. This way the bowden fitting effectively does the clamping.

@jrcl Since the new heater tuning model got implemented, tuning on large thermal mass beds has been known to take a while. As it happens I tuned my 2kW bed just last weekend and that took several hours.
So what you encountered might in fact be just normal behaviour.

@topenga I belive this should put you on the right track https://github.com/Duet3D/Duet-2-Hardware/tree/master/Duet2/Duet2v1.04

@phaedrux said in Duet2 connection interrupted: Let's get to the bottom of this:

@nxt-1 Would you be able to collect a wireshark trace?

1.pcapng.c
2.pcapng.c
3FullDataset.pcapng.c
Here you go, the .c extension needs to be removed abviously, the forum doesn't allow from .pcapng files The first two datasets were started when I notices warning popping up in dwc, so they are probabily missing the first pieces of vital information. The 3rd set contains everything from start to finish.

Note: all these traces were without the new v1.26 debug firmware as sugested by @chrishamm. I will install that now and report back.

@infidelprops Pluggin your exact question in the ol' google produced these:

• Duet 2
• Duet 3 Mini
• Duet 3 6HC

After 4,5 days of heating plastic, tearing it of and burning my hands, the mold is finally entirely removed. Some results/remarks can be made already, so it is time for an update again.

First, the center of the cast is not looking great, even though you one hopes for the best, this does not come as a surprise. While making the cast, the machine was placed on top of the empty mold and then the mold was filled from the sides. Therefore, the EG mix will not reach the upper-inner most edge of the mold without a large vibration insert or heavy duty compacting. Physics I guess This part of the mold is never visible to could be worse I guess.

The DIY threaded inserts I made work a treat and the rubber machine leveling feet screw in nicely.

The machine is now standing up again and looking solid. Before I stud it upright, I grabbed some scales to get a measurement on my craziness. On scale sat at the very top end a measured 13kg, the other one was placed at the other side about 20cm from the bottom plane of the printer, showing 95kg. Quick mafs leads to 98kg at this moment (this will still increase later on, keep reading ).

Up next is mainly cleanup and finishing work. At the edges of the mold and where different mold pieces interfaced, there were some epoxy ridges that I already removed with a rotary hammer (that was overkill for the job tbh). I still plan to further smooth rough edges with a flap wheel on an angle grinder, as sand paper on this material seems to be not exactly my definition of 'fun'. I am still debating whether I am going to buy and apply some kind of clear epoxy top coat to seal the whole deal (mainly the sides) and give it some more of that glossy finish.

I mentioned that the 98kg is still going to increase and that is because what got this party started in the 1st place is the cavities in the three main extrusions. At the moment, these are still hollow but will get filled with the same white sand that I used in the EG mix. I expect this will add an extra 5-10kg of fun to the machine.

Last, I think I might need to get rid of smurf evidences on my floor. If that's even possible, because it seems pretty well pigmented on there.

@Danal said in Delta proper endstop upgrade - advice welcome:

LOVE the custom pins, probably took you forever to get JUST enough iron oxide to act as a lubricant/traction interface without overwhelming the arc reactor. Microgram scale for weight/adjustment, no doubt.

You are correct getting the oxide layer just the right thickness and purity took several attempts and is not recommend for the faint of hearth. I am not sure when I started the process, but it might be over 20 years ago

A quick update on slab 1. After a little over 48h of curing, I demolded the slab and it looks great. The surface you see on the picture is actually the back side that was inside the mold and it is quite smooth, I'm happy. I will wait until tomorrow before I start drilling holes, that would bring the final cure to about 36 hours.

On thing I noticed it that especially the mold side surfaces are quite dusty. A quick google leads be to believe that this might be a mixing/moisture error, but I'll be the first to admit that I am not a concrete expert, not at all . I'm thinking that if it keeps being dusty, I might seal them with the same glossy sealer coat I used on the epoxy granite base of the printer. If the concrete is effective in what we want it to do that is.

More pigment for the other slabs and M8-tslot nuts should arrive tomorrow. So hopefully I can test effectiveness with one slab already by tomorrow and if successful, cast the other slabs by the end of the week.

As I said, yesterday and today was assembly/painting day. I applied one coat of primer on all surfaces just kind of seal the surfaces and make them dust free. All surfaces that I planned on actually paint in color got a second coat of primer. After that, I put a single coat of color on there. I chose what the manufacturer calls 'concrete' color, yet it does not look anything like concrete but whatever
Tomorrow, once its all dry, I'll see how good the result is with the single top coat. Assuming it's decent I will test fit the covers and see how it works out. I think I am going to wait with installing the sound dampening panels until the aluminium extrusion that the 4th axis rail attached to, arrives. And the 4th axis design I am working on is all finished up.

Oh and god I hate painting

For the past few months I have been battling sources of vibration and thus noise in my delta machine.

Video of the original noise levels

Intro

The journey started in this thread with trying to eliminate the vertical extrusions from resonating. After I felt the route of battling the source of the noise came to a dead end, I moved to simply trying to contain the noise inside of an enclosure. This is talked about in a second thread.

What is done already

A list of changes I did to the machine, with or without success, more or less in chronological order:

• Added heavy concrete slabs (dyed blue) to the vertical extrusions, effectively eliminating them from resonating.
• Added Astrosyn-like isolation dampers between the motors and their mounts. Somewhat effective, see later.
• Built a (heavy) wooden enclosure that bolts to the frame and is lined with sound dampening foam. While the enclosure doubles as heat insulation and a construction that the 4th axis rail attaches to, is its ineffective at sound isolation sadly.

Where we are at now

After being disappointed by the enclosure's performance I delved once again into battling the source of the problem. More or less by accident I found that a big part of the noise was actually as simple as the motors vibrating against the frame. The motor mounting is designed to that the motors sit practically flush in the corner against the vertical towers and the base plate. Yet the motor did not sit firmly pressed against the walls, leaving just enough room for loud vibrations.

This part of the issue was 'swiftly' resolved by adding some washers between the motor mount and the frame. Effectively distancing the motor far enough from parts it can rattle against. This eliminated a great bit of the noise, but were are not there yet.

@theruttmeister said in Battling sources of vibration and noise:

The shear loading on the rubber you have in that bracket seems less than optimal.

At the time you made your post, I was already printing the first bracket in this style. So I tried it out and you are definitely right, shear loads are not idea and in this case the loads were to large, causing unacceptable deflection.

Personally I'd be trying for something in-line similar to @Kolbi 's suggestion.

There are a couple difficulties I see with the soft dog-bone style. One, if you make to linkages, they need to be absolute same length, even under load. Otherwise the axle sits at an angle, in turn causing belt tracking problems. Two, I don't really have a good way of making rubber-ish shapes like that (except for printing them in tpu maybe), nor do I have a good source for rubber material that thick. Finally, and maybe most important of the three. If I understand the design correctly, you have a rigid bracket locating the bearings and that bracket is decoupled using the rubber-ish dog-bone links. This still allows for the bracket to vibrate and I believe that the bracket itself is emitting noise, not just coupling it further down the frame.

And @engikeneer 's suggestion of o-rings seems like both the easiest and best...

I agree, yet I had trouble sourcing o-rings (round or ideally square) in the size I need, especially the thickness proves to be and issue. And I am not a fan of doubling or even tripling up on thinner o-rings, because keeping them in place reliable becomes more difficult I think.

In the end I did more or less go the o-ring approach though I got myself some more of the type e dampers and cut them into pucks the thickness I need. Then I constructed a diy cork borer by sharpening a piece of metal tubing and printing an adapter so I could chuck in my drill. I used that device to drill the center holes, where the bearings sit and it worked surprisingly well.

After some more bracket redesigning I ended up with this. It's fairly compact, easy to install and tension and does what it is supposed to do.

This upgrade brought the noise levels down low enough that you can still hear the machine running on some moves from the next room if it is really quiet. So not perfect but we are definitely getting closer and closer. The next thing I have planned is to redesign the motor brackets to use this style of rubber washers as well. Even tough I have stated before that the upper bearing are not in play. I have some other changes I want to do to the brackets so why not squish the o-rings in there as well right.

It's about time for an update on this topic, perhaps even the final one.

I have received the stainess brackets a couple of weeks back and installed them right away. At first, with the stepper face right against the face of the bracket but that was not a success. The idea for that was that bolting the stepper to the bracket would form 1 rigid system with a larger mass and thus resulting in less vibrations. In reallity the bolted connection does not provide enough clamping force to form one rigid system, but rather the stepper vibrating against the bracket.

With that option scrapped I re-installed the stepper dampers I used before. This helped as expected a great deal and brought the noise levels down to that I was used to from the 3D-printed brackets, or lower. I never really did numerical measurements of sound pressure levels due to a lack quipement to do that properly. So it is quite hard to say whether the noise is lower that it was before with the plastic brackets, if so not by a whole lot.

For me this concludes this series of thread around the noise topic. I have exhausted all the things I wanted to try out in short to medium term and achieved decent results along the way. In the longer future I might experiment with different steppers and possibly another style enclosure.

You know it's going to fun when the simulation alone takes 1,5h to do

I think it would be a nice addition if we could select multiple g-code jobs from the list and simulate them all as a batch instead of doing each file separate. Especially when working with multiple larger printjobs, one could let the Duet simulate during off-time.

@arhi said in Delta stepper upgrade - advice welcome:

@Nxt-1 said in Delta stepper upgrade - advice welcome:

I was just complaining that the calc can't do it, even there is no way it could

yes, but like I said, you can see at that speed how much current will be supplied to the motor by using different current settings in the calculator ... and assuming some linear drop in torque with current is safe bet imo at those speeds

Ah, I understand now. Thanks for the insight.

For the nema 23 the current at which emf due to inductance becomes 24 V is just 920 mA (@200 mm/s). Assuming the linear relation between current and holding torque, that would leave me with 73.6 Ncm. That is still more then just about any nema 17 motor I have seen though. Leading me to believe that this is a non issue.

@danal I should have thought of the straight Z move, thanks for mentioning it.

As for the belt tensions, plucking them is kind of difficult since the only sit about 1 mm from the tower extrusions. I guess I keep using my gut feeling for now