@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!

@ziggymanpopo said in Max wattage for extuder heater:

So here is my concern
At 12v and @ a 60w. Heater that converts to 5amps.
Since 5amps is max or 100% for the heater output, It makes me wonder if a ssr is needed considering continuous load.. by elecrical standards we can only load up to 80% of full load current if used for more than two hours.
In my book this would be considered a continuous load. Do i need to take precautions to protect the board by using a ssr. Second what can i do to prevent the possable runaway scenario if the ssr. Were to short closed i plan on using a thermaly controlled over temp sensor in line for the bed heat but this is upractical for the hotend i believe the firmware protects against a runnaway extruder heater.. but will that still work when a ssr. Shorts closed .. with out some sort of secondary input the duet would be able to fault.. but not stop the runnaway heater. any input and ideas would be appreciated...🤔

A 60W heater, on most normal printheads, if run at 100% duty cycle for 2 hours, hopefully will have triggered an over-temp shutting off the board, and if you are not using a well designed all metal hotend... might well have melted something important.

An extruder heater is not a 100% duty cycle, continuous load. It is PWM controlled and will run well below 100% duty cycle for the majority of the time.

There are ways to design fail-safe setups that would cut off the power to the board in the event of the type of failure you describe...
That said, based on my experience the way to deal with this is to size your heater correctly and have an extruder that will not melt.
A failure of the board is rare enough that its not worth the trouble to build in a fail-safe if you have an extruder that can withstand the temps of a thermal runaway.
PTFE has no place in a hotend

@whopping-pochard

What you have designed, because its floating on 3 points (which is elegant), runs the risk of not running true to ANY of the linear constraints... you could end up with a bed that translates and rotates relative to all three axies as it moves in Z.
To prevent that, you would need to precisely align 3 rails on three separate planes, which themselves need to be precisely aligned to be at least parallel.
Possible, but a lot of work.
You also now have the issue of CPE in the screws compounding (only an issue if you buy cheap leadscrews though).

The advantage of reducing the number of rails, is that you greatly reduce the challenge of aligning those rails relative to each other.
Lots of commercial printers use just 2 linear constraints and a single screw because of the need for a simple (hence cheap) assembly process. They then rely on the bed/frame stiffness to compensate for the cantilever.
The big advantage of rails on extrusions is that they can handle very high side-loads which means you can have just 2 rails and a large cantilever. Do that right and you only have to align 2 rails on the same piece of extrusion.
And given that good quality rails are expensive... fewer is generally better.

All of which is probably academic, in an FDM printer, especially a home built one.

And for custom leadscrews. Misumi. Not cheap, but very high quality.

The number 1 issue I normally see is beds that are not tightly enough constrained in the x/y plane, so things move about and cause vertical ripples.

Identical g-code run on machines with significantly different accleration settings can have quite dramatic differences in print time, for the reasons already described. There are lots of machines out there that claim huge print speeds but can't actually deliver. And even if your printer really can hit 600mm/s within its own travel, printing huge thick layers at low feed rates will always be faster than thin layers at high speeds.

The deep details of print speeds and slicer settings are not widely understood, that often even includes the people writing the software.

I'm fairly certain that both Cura and S3D still don't actually calculate extrusion volumes correctly...

@dgrat said in To rigidify or not to rigidify? - vibration issues:

Have you enabled interpolation on your machine? I have the feel, that dampening 800 Hz vibrations is also not that easy. There are too many Alu parts which can resonate, even if you add endless weight.

Its not about adding endless weight. Its about adding the right kind of weight.
Metals like aluminum are essentially great big crystals, that propagate vibration really well.

CNC machines traditionally use cast iron, not steel, because its actually much more of a granular structure. Because the vibrations are having to cross lots of boundaries between the grains, the materials soak up a lot of the energy. Epoxy granite is used a lot because it has this property, its a mix of aggregate, with epoxy as a binder. Its almost all boundaries between rocks and epoxy, so its really good at absorbing vibration (plus you don't have to wait weeks for it to fully harden like cast iron, and you don't need a foundry).
Regular concrete isn't quite as good as cast iron or epoxy granite, but its still much better than aluminum, and its so cheap and easy compared to those others...
There are lots of people out there building cnc machines using steel or aluminum bonded into concrete or epoxy granite, its a very effective.
Will there still be bits that vibrate or resonate? Probably, but this is a test that will cost tens of dollars and is fun. And based on what the machining world has been doing for over a century, its probably going to work.

@deckingman said in What do you think about Dragon Hotend:

@theruttmeister As I'm being talked about, I thought it best to respond.

The main thing for me is solving the problem.

Best place to start.

And as a designer and I once started saying, if an engineer points out issues on your project... It's because he cares.

@CaLviNx said in What do you think about Dragon Hotend:

@deckingman

And as a designer and I once started saying, if an engineer points out issues on your project... It's because he cares.

I must remember this analogy, as when I point out the issues with a project at work I usually get called a "difficult cu*t"

I used to get that. Thankfully I'm now an overvalued 'expert' so they listen (and just think it instead).

The original version was actually 'if an engineer starts telling you what you did wrong...' The really good engineers will respond by explaining why they did it that way and why you are wrong about it. Which can start some great friendships!

What @thwe said.
Aligning two rails on the same plane (assuming you align the frame well), is much much easier.
Oddly one of the very interesting bits of design feedback I've heard, is put the rails under the extrusions, not on top. That way they don't collect dust.
Seems silly, but its actually really nice.

Not using coreXY would be more rigid. Don't get me wrong, H-bot (or a weird monstrosity I designed) would be less stiff.
Basically, with the type of bearings, mounts (I'm assuming metal) and frame you've selected, all of your lack of rigidity will be from belt stretch. Two ways to minimize that stretch are to reduce the length of belt and increase its width. CoreXY uses a longer belt than you would have on a conventional cartesian/flying X motor. The flying X motor adds more weight and wiring complexity, so it might outweigh any advantage...
TLDR:
Wider belts is the easiest way to get more stiffness.
Its also really important to design in a way to adjust the belt tension!

2
I wouldn't.
Having the bed be structural and heated is a big challenge. If you are going to heat that bed (which will take lots of power, look at an SSR) then you want to both mechanically and thermally isolate it from a separate frame that is the actual Z stage. I've had great results just using nylon foam as a structural spacer. It can be glued, is a great insulator and rigid enough to work well mechanically. Its still a foam though and will happily absorb any expansion of the bed.
Screws and rails in-axis, its theoretically better, I think your bigger issue is that you seem to be relying on the motors own bearings to carry all the vertical load. They are not designed to do that, you should think about including a thrust washer.

3
How much does that gantry weigh? I'm guessing 450g for the extrusion. Plus the weight of the rail, rotational mass of the motors etc, if you are worried about the weight of the pulleys, don't be. If you mean the extruder? Its more significant, but the difference is going to be small compared to the mass of everything else, at least for acceleration not involving X.
If you really want to get higher speeds use bigger motors. NEMA23's are not much more expensive and produce vastly more torque. I don't know why everyone is so fixated on NEMA17's...

4
How fast do you need to go? 24V, 32 tooth GT2 pulleys and NEMA23's get me up over 500mm/s... Which given the huge mass of my extruder, is quite scary.
More voltage is better for speed... And you can always just use the Duet3's heated bed circuit to drive your extruder and only supply 24V to it.
You shouldn't need to actively cool the steppers if they are big enough. People tend to have to when they undersize the motors, overdrive them to get enough torque, then discover they get crazy hot (although good steppers will run hot enough to burn you without being damaged themselves).
You could also get an external relay or SSR to drive an extruder heater, although I'd try and avoid that myself. There is also the Toolboard 1LC if you can get one.
I'd suggest trying 24V at first.

5
How are you actually connecting your uprights to the crossbars? I don't see anything for that. But there are lots of easy ways to do that. If you haven't already go look through Misumi's website and see the millions of options. Including getting them to machine stuff into the ends of the extrusions.
The rest seems fine, although I wouldn't use u-channel for the gantry. If you change it the way @thwe suggests you can use flat brackets, which is way easier.

And to echo what @whopping-pochard said, if you move (in fact you can probably just remove completely) the 'front' crossmember, you get a much better view of the printhead/nozzle.
Similar theme, with the extruder mounted on top of the gantry, you have very little space around it for things like fans for cooling prints. Or fans to cool the extruder itself.

Don't forget to plan for filament mounting, and electronics!

@N3XT3D said in Very loud stepper motors:

Would it make sense to buy motors with different specifications?

If you can hit the speeds you want with the lower current, no.
Motors with different current rating will also have different torque etc. Its not unusual to have a current rating higher than you are actually setting for the driver.

Also, your steps-per-mm in X and Y... seem odd. Are you running printed pulleys or something? I would expect with a coreXY machine that they would be identical (and unless you are running MXL belts, whole numbers).

If you are looking to increase speed, going to larger diameter pulleys is the most effective choice. I don't believe anyone is getting even close to the precision that 200 steps/mm is promising.

@campeancalin
Looking at the pictures, either you are over-extruding or your first layer is too low (which means you are trying to fit too much material in too little space). That causes material to push up higher than it should, and if the nozzle runs into those lumps it tends to cause layer shifts.

And if you don't have one already, get a filament drier, CF filled filaments absorb moisture like crazy and need to be dried. If you look closely you might be able to see the filament bubbling as it comes out of the nozzle. Drying the filament for at least 24 hours will make a huge difference to both print quality and material strength.

@peterartechno said

My question: I have a signal and ground cable for a sensor fitted next to the nozzle. Where do I put which cable AND what do I write in my configuration.g? I do not want to avoid the board with the optocouplers, just working with those cables.

Kind regards

You only have 2 cables? 1x Signal 1x ground?
Most normal induction sensors require 3 wire connections... 1x power (12-36v is common) 1x signal 1x ground.
How are the other sensors wired? Do they have an additional power connection?

@Phaedrux said in Heatbed with SSR with maximum on time:

Ah I see, in the context of your application it makes more sense on what you're asking for.

You could perhaps reduce the PWM power factor (M307 S0.5). Or reduce the PWM frequency (M950 Q) to something slow like 1 second.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M950_Create_heater_fan_or_GPIO_servo_pin

https://duet3d.dozuki.com/Wiki/Gcode#Section_M307_Set_or_report_heating_process_parameters

Just some ideas until someone with a better grasp comes along.

Those are a good start! With 10kW of load, switching losses could be quite significant, I would expect the SSR (or maybe SSR's) to need at least a large heatsink. PWM'ing 10kW would be very lossy, probably noisy too!
Or maybe switch to IGBT's, which tend to have much lower thermal losses.

@Argiros-Apostolos

10kW is a huge load... I suspect more than enough to melt your aluminium bed. I'm curious why you need so much power?
And RRF isn't really designed to deal with really big delays in the thermal loop. Is there a reason why you can't have a bed heater that is less likely incinerate itself? You could also look at connecting your sensors very close to or even directly to the resistors.
But it sounds like you are trying to power a golf cart with a jet engine...

@ziggymanpopo said in Max wattage for extuder heater:

So here is my concern
At 12v and @ a 60w. Heater that converts to 5amps.
Since 5amps is max or 100% for the heater output, It makes me wonder if a ssr is needed considering continuous load.. by elecrical standards we can only load up to 80% of full load current if used for more than two hours.
In my book this would be considered a continuous load. Do i need to take precautions to protect the board by using a ssr. Second what can i do to prevent the possable runaway scenario if the ssr. Were to short closed i plan on using a thermaly controlled over temp sensor in line for the bed heat but this is upractical for the hotend i believe the firmware protects against a runnaway extruder heater.. but will that still work when a ssr. Shorts closed .. with out some sort of secondary input the duet would be able to fault.. but not stop the runnaway heater. any input and ideas would be appreciated...🤔

A 60W heater, on most normal printheads, if run at 100% duty cycle for 2 hours, hopefully will have triggered an over-temp shutting off the board, and if you are not using a well designed all metal hotend... might well have melted something important.

An extruder heater is not a 100% duty cycle, continuous load. It is PWM controlled and will run well below 100% duty cycle for the majority of the time.

There are ways to design fail-safe setups that would cut off the power to the board in the event of the type of failure you describe...
That said, based on my experience the way to deal with this is to size your heater correctly and have an extruder that will not melt.
A failure of the board is rare enough that its not worth the trouble to build in a fail-safe if you have an extruder that can withstand the temps of a thermal runaway.
PTFE has no place in a hotend

@tony73

Interpolation gives you a smoother wave-form, but you don't need to generate the extra steps (you'll have to imagine a 1/256th wave that is really smooth!)

Its mostly a benefit for noise, although for some applications you might actually be able to see that the motion is more smooth.

First:
Line 24: M350 X64 Y64 Z16 E16 I1
By setting X and Y to 1/64th stepping, it prevents those drivers from using interpolation.
There's not really any practical benefit to running 1/64th stepping anyway, as you are highly unlikely to actually get that mechanical resolution. Most people run 1/16th, and the interpolation just smooths the motion.

But your question:
The motors are whining because they are resonating (different motor windings will do that at different frequencies). The drivers try and avoid this with a clever thing called 'SpreadCycle', which is on by default. You can try playing with that setting by adding the command M569 Pnn Dnn
For example: M569 P0 D2 sets the X driver to SpreadCycle. M569 P1 D1 will set the Y drive to random off time.

For more info:
https://duet3d.dozuki.com/Wiki/Gcode#Section_M569_Set_motor_driver_direction_enable_polarity_and_step_pulse_timing

Remember you can just put the commands into the console to see their impact before you edit config.g

If you are really desperate for silence, try 'StealthChop' but be aware that it drops the torque by a huge amount.
If you want to know more about StealthChop and SpreadCycle, check out Trinamic's documentation.

Out of stainless?

Might be a little bit overkill

Also, retaining rings for the bearings? Or are you planning on them being a press-fit?

@Phaedrux
Clearly we have had very different experiences of the Palette... I've build multi-input heads, and I've used multiple generations of the Palette.
The development units had some issues. But I have found the production units to be reliable. I'd certainly pick one over any multi-input design I've ever seen.

You've lost me?

@sebkritikel said

Hilariously Misumi put out a blog post to talk about some of the differences, but frankly they did a bad job at it: https://blog.misumiusa.com/youve-got-the-power-mr-vs-gt/

They are different! [proceed to not explain the differences at all]

Thanks Misumi!