Best posts made by theruttmeister

@zapta Thermocouples are accurate to +/- 3C (at room temp). That accuracy will degrade over time because the construction inherintly suffers from galvanic corrosion.

RTD's, like a PT100 or PT1000, at the lowest class, are accurate to +/-0.5C at around 250C.

Which is a long way to say: RTD's are significantly more accurate than thermocouples.
Although both are much more accurate than thermistors (which I have seen be +/-20C at 250C).

RTD's have a longer service life, use normal wiring and are less prone to electrical noise than thermocouples. Basically you use thermocouples when you need to measure very high temps or a very wide range. Otherwise RTD's are the better choice. Thermistors are for low temps and really low costs.

*is printing a multi part file...

One of the parts as apparently on a blob of oil or some nonsense, is going to fail and probably ruin the whole print.

Pause print. Sigh.

Remember that the g-code viewer has a cancel part function.

upload version 3.2 of DWC.
enable Gcode Viewer plugin.
cancel the failing part.

RESUME PRINT!

ALL. OF. THE. WINNING.

Like seriously, epic epic feature to have.

@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...

@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

It can also be motor resonance. Stepper motors will move more smoothly at certain speeds. You can try just changing the speed to see if that helps.

Printing a tower that changes speed by ~5mm/s every 5mm is a nice way to see if that is what is causing the artifact.

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!

@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!

Other people have covered it but...

220VAC is not the issue, all of Europe uses that voltage without everyone suddenly bursting into flames
But I'm guessing that your heater is not just a couple of hundred watts.

The rule of thumb is, either design your heated bed to be able to withstand the max temp it will reach if just set to 100% for an indefinite period of time.
Or add a fail-safe device like a thermal fuse.
And make sure the fuse is either inside the heater (if you can get it made that way) or mounted somewhere that its going to be the first thing that overheats.

Grounding the bed is excessive, a silicone heater should be double insulated, if its shorted to the bed its because you have drilled through the bed, or some other nonsense.

@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.

Silicone encapsulated wire heaters are double insulated (making them suitable for use in Class II electrical devices) and as such do not need to be earthed.

A short to the metal bed would require something catastrophic, like the entire heater catching fire, or someone running a drill bit through the bed and the heater.

If you are going to earth the bed, you also MUST earth the frame, the hotend, basically everything metal on the machine. Those earth bonds should be appropriately sized (so that the fuse for the device, 30A, blows before the earth bond(s) burn out).
You should also probably implement an annual in-service inspection and testing protocol. The UK standard is PAT-testing and is terribly dull and mostly involves cutting the plug off of devices that can't be correctly identified by the technician.
Like kettles.
/s

Personally I'd be more worried about the plug. US 30A plugs are garbage and a fire waiting to happen.
(Ok, all American plugs are a fire waiting to happen).

@vistalert said in Requirements to have a 1000x1000 aluminium build plate:

Could anybody please tell me the required thickness of an aluminium plate sized at 1000x1000 which would have the smallest possible "reasonable deflection" due to it's own weight, support at three point like a triple Z kinematic bed support.

And, does anybody have any experiences of building a printer with this build area. Were any alternatives such as a glass build plate (minus any aluminium plate beneath) considered?

Thanks!
Chris
@slimshader said in Requirements to have a 1000x1000 aluminium build plate:
@vistalert I've built several large format machines although not quite as large as 1m square.

My experience has shown that getting large, perfectly flat sheets of aluminium for this purpose is not as straightforward as it sounds. For one, most sheet metal suppliers...

Sheet =/= plate.

@vistalert
You need to contact a local aluminium supplier and ask about sourcing some MIC6 plate. That is cast aluminium that will be reasonably flat.
Typically 1/4" is the minimum thickness that will stay 'flat' at around 12" square. If you want to go to 1000mm, you'll either need to be able to adjust the bed with many many supports to take out any curve (there are a couple of commercial printers with beds like that) just from sag, or you'll probably need something like 3/4 to 1 inch thickness. Maybe both.
Taking to a local supplier is a very effective way to find out who can supply something suitable. The first people you call might not be able to help, but they will usually be able to suggest the right people to call.

There are plenty of companies out there that supply large pieces of MIC6 for things like injection molding tools, its just expensive.

Glass is not a reasonable alternative, a piece that large is going to be either very thick or very fragile. Either way people expect glass to be much much flatter that it actually is (float glass is smooth, not especially flat or of consistent thickness, at least compared to other things, like MIC6).

If you want properly flat aluminium, you'll want at least 1 inch thick and then get it surface ground. Although that will be expensive given the size.
The old joke in engineering: How do you make 8mm expensive? 8.0, 8.00, 8.000...
Getting MIC6 in stock form will probably be just fine, getting it ground to be really flat could be quite expensive (and the company doing the grinding might want a really really thick piece to start from).

@jens55 said in Requirements to have a 1000x1000 aluminium build plate:

@vistalert, If you look at the build plate in isolation I am sure that this is possible but maybe not in a conventional 'just increase thickness' approach.
One could for example drastically reduce the weight of that build plate by milling out a support structure that is part of the bed but with all unnecessary parts milled away. IE a drastic reduction in weight with very little reduction in strength.
Doing so is well beyond my capabilities but someone good at FEA could sort this out without too much effort.

That would greatly increase the cost and adds the risk of deforming the plate. If you really really really wanted to do something like this (which also complicates heating the bed) you would use a custom casting and then just grind the top surface flat.
It would be insanely expensive though.

Thermal expansion also needs to taken into account. A piece that large will expand by ~2mm when heated to 100C. If the bed is rigidly mounted you'll get quite a bow in the surface at that point.

You could also just make the bed from a granite surface plate. Granite works really well as a build surface. Takes FOREVER to heat up, but I never had PET chip it the way it does to glass. And its thermal expansion is so low that 100C is nothing.
Kinda heavy.
I seem to remember that you can get granite surface plates fairly cheaply these days though.

@o_lampe said in Requirements to have a 1000x1000 aluminium build plate:

@phaedrux said in Requirements to have a 1000x1000 aluminium build plate:

At 1sq meter maybe plywood and a coating of self-leveling cement? Embed a floor heating coil in the cement?

I like the idea! How flat would that cement be?

So long as you use the right 'cement', good enough for NASA.

Seriously, self-leveling compounds are used to make large reference surfaces and can be flat to unreasonable numbers of decimal places.

There's a ton of information out there. Look at polymer concrete and epoxy granite. Both are cheap and if done for a self-leveling finish, can be very very flat.
Just needs to be the right material and finished in the right way (materials that shrink are not going to produce a level surface).

@jbergene said in external motor: speed be reduced more by adding more motors?:

Good evening

Im testing a Clearpath Nema23 on a Ballscrew with 10mm lead.

Initially I set the Input resolution in the software to 6400/revolution.
And 640 steps/mm in the Duet Config file.

Its running very slow.
To get it up at full speed (36000mm/min) I need to reduce the resolution to 2000/rev and X200steps/mm in duet.

Thus the question: If I add 2 more of the same motors, and program them at 2000/rev & 200steps/mm. Will the duet 2 wifi have trouble handling it or how will that be?

Best regards
John Henrik Bergene

I assume you are are asking if you are hitting the CPU limit?
Probably.

The fact that dropping the resolution enabled you to hit your target speed certainly seems to indicate that.

I also assume that you are asking if adding additional motors will increase the load on the CPU, meaning that a 3 axis move can't be stepped as fast as a single axis?
I don't know enough about the control loop to know, hopefully @dc42 will stop by and be able to answer that question.

@barbarossa-cologne

An SSR is just a switch. The control side only needs to be 24V (actually anything from 3-48V is common, the SSR will be marked), the PSU is powering just the switching of the SSR, which uses a very small amount of power.
The whole point of using an SSR is that the other side of the switch can be for much higher voltages and can carry lots of current.

So your wall socket can supply up to 13A, your SSR can carry 25A and the bed only draws 11A. Everything is good.

The PSU is not powering the bed in any way at all. Its just controlling the switch.

@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.

@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.

@hebigt

https://duet3d.dozuki.com/Wiki/Gcode#Section_M571_Set_output_on_extrude

No need for post processing.

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.