Best posts made by DaBit

@smece said in mellow nf crazy hotend:

I used e3d X nozzle for this test, first time I tried X nozzle, they are support to have some polyfobic coating that makes plastic not stick to them ... well ..

I am running an E3D NozzleX in my v6 heaterblock, mainly because crashing a brass nozzle into something tends to deform the nozzle enough to throw off the alignment of the dual nozzles on the Chimera. And although these are quite pricey when compared to a brass nozzle, they are still a fairly cheap way to ensure that things will keep on working the same for a reasonable amount of time.

So far I am happy. PETG stringing makes little to no mess, have not yet seen those dreaded black blobs in a print that occur when the nozzle picks up stringing and drops it on the print when buildup has passed a critical amount. Whatever sticks to the nozzle is easy to remove.

Regarding cheap clones of whatever: you may get less than what you pay for, but you will never get more. Accurate machining and good quality base materials are often not required to make parts perform well initially, but accurate machining keeps parts performing well day in, day out. Compare a Papst fan with Chinesium. Day 1 both work well. Day 100 the Chinesium fan makes a lot of noise or stops working, the Papst keeps on humming like it did on day 1.

Frustration continues after the joy of saving a few bucks is long forgotten. In the end buying decent quality stuff saves money overall. Higher initial expense, but less money spent on failures and replacements, higher resale value, less headaches.

@dc42 said in RepRapFirmware road map as at 15 February 2020:

True; but we value our users!

And I am grateful for that!
I have become quite fond of the Duet controller in short time. Bought the Duet2Wifi out of curiosity. Toy with it, see what it is all about, sell it. Never even thought it would really be a decent contender to LinuxCNC with it's endless possibilities to make things work the way I want them to work. And the first experience was indeed like a naked plunge in subfreezing water. No conditional G-code, a weird way to use homeswitches not exactly at the end of travel, blah. But here we are, a few months later, and the water is nice and warm. Not considering moving back. Mainly because of you, your insane drive to move forward and efforts put in RRF3, and the insanely quick fixing of issues.

[rant] Also I get disgusted with kit that ceases to be fully functional because the manufacturer can't be bothered to update the firmware.

As a consumer I totally agree. Not only the software, also the actual technical life and irrepairability of 'modern stuff'. After a few years it becomes hard to get parts. Kept my old xperia X10 phone running for a bit over 6 years, cannot do that anymore it seems. Bought 10 year old motorcycles and ran them until they were 20 years old, then only sold them because I longed for something else. Not sure I can do that with my shiny new KTM; I highly doubt that the TFT screen they use for dashboard lasts that long, and build quality is more optimized towards cost and weight instead of durability.

As one of the designers at an electronics company I am not so convinced. IMHO the worst thing you can do for customers is going out of business or having to find other sources of money which lowers the amount of resources that can be put into the original product line. Given the fact that development time is a limited resource there is a point where the hours spent on maintaining compatibility is preventing staying ahead of the rest on the new hardware and just costing money. It often makes sense to create a 'light' version of the more current hardware or lower pricing on the full version a little. Which you can since you save money elsewhere. A bit on the increased volume, a bit on the development, a bit on the support. It adds up.
Also, the Duet is not a PC, phone or PVR where 3rd party software stops working due to the system being too old. If I stop updating today the Duet will happily keep printing for the next decade just like it does today. Many of your users are probably not updating the software anyway. If it ain't broken....

All this is personal opinion only, of course.

Also, Duet 3 is expensive and overkill for most 3D printing applications.

Yes, you have chosen nice and expensive motor drivers that almost no 3D printer needs. I bet a large part of the additional cost come from those
I did not check the BOM, but a Duet3 with 5x TMC2660 instead of the 5160's should not cost that much more than Duet2 to produce, and more alike platforms usually means faster development and less issues. However, I am aware that initial cost for a new board is high.

Anyway, I love what you are doing, and I am happy to get to use all the useful new stuff with a click on the 'upload system files' button.

Not much of a braincrunching project (which is usually most of the fun), but a decent option to texture 3D prints could be hydro-dipping:

It can do wood grain nicely.

Requires a suitable inkjet printer, hydrodipping sheets, activator and a bucket of water. I never actually did it, but maybe I might someday.

@weed2all said in Where's the Duet Wifi 3?:

@dc42 but we need Duet3 6hc with WIFI for cnc use case!

No, you don't. Really, you think you want Wifi, but you don't.

I have seen countless of issues with USB/WiFi and CNC machines. Mostly that is due to less than stellar wiring and insufficient use of supply filters in front of the frequency inverter or brushed universal spindle motor, but that is often the way it is and only a good electrical engineer is able to slay those gremlins. I know how to do it, I tried using an USB Pokeys57 for my lathe control panel, worked fine until the spindle servo starts to deliver more than a few Watts of mechanical output power, and no shielding, supply filtering or CM-choking the USB could stop that. Switched to Ethernet, never had a single issue since.

Second problem: if the Wifi connection drops, the CNC keeps doing it's thing, including the spindle. And you will encounter the mill pulling the workpiece out of it's clamps or simply loading up. Try to stop it using the normal interface, realise it won't work, hitting the (hardware) emergency stop, and that is 5 seconds wasted. I had a big dent in my garage door due to those precious seconds. There is a lot of energy in even a few grams of material spinning at 10000+rpm.

At least you want a very reliable stop and feed-% knob; the last one saved more endmills and workpieces than any other knob or button on my machine. Ethernet is a very reliable data transport mechanism with a robust physical layer, it's failure rate is so low you could consider that 'never', and latency is low too. USB and WiFi are not that reliable, not even close.

Most of my contacts come either directly from Wurth, or from Farnell/Digikey/Mouser.

But oh well, every crimp tool needs a bit of feeling and a bit of exercise, I am probably just not doing it enough and the Iwiss is simply more idiotproof. I suspect most people here crimped an RJ45 to CAT5 at least once. Remember how long it took before you got the first one correct?

Another sound here. I am very happy with the speed of progress. Many new releases bring features I can actually use on my quite nothing special printer.

Regarding the effort: last week I set up a Duet2 for testing a motion stage. I needed RRF3+ for that so I could use while loops to iterate the same movement tens of thousands of times. Zip-zap-zip-zap, all day long, all night long. It took me about 20 minutes going from plugging in the USB cable in a freshly arrived board to a WiFi-connected testbed that was exercising the motors running RRF 3.2. The process took upgrading the FW to 3.0, then to 3.2 (somehow going directly from 2.x to 3.2 would not work but I did not spend time on figuring out why), configuring the controller and writing a few lines of G-code.
I am very comfortable with LinuxCNC, I can do the Arduino+stepper drive stuff too, but there is no single piece of kit that allowed me to get up and running THAT fast. Which is exactly why I chose a completely-overkill Duet for the task.

Whatever you buy, you need to learn how to operate and maintain it or find someone who does it for you. Software is not different.

@dc42 said in Enhancing pressure advance:

Ideally we would measure the pressure within the melt chamber, but that's hard to do.

In what ballpark is the nozzle pressure anyway? I might have access to temperature resistant pressure sensors with an extremely small sensing head soon, and milling a hole in the nozzle to accept one would be easy. But these are for a fullscale range of 400 bar and absolute accuracy is not that high. Resolution is higher, which is probably what is needed most.

Would the curve change much between extruder brands? Would an E3D hotend with Bondtech display a different shaped curve than, for example, a DyzeXtruder?

Regarding small segments; how many segments can a Duet2+RRF3 process per second as long as no acceleration/speed limits are hit? And Duet3?

If you use cast tooling plate it won't bend as long as it can expand freely, and as a bonus it is quite flat on at least one side. If you use rolled plate it will twist or bend slightly over time.

I am using a 300x300x10mm aluminium plate with 600W Keenovo silicone heater. Absolutely no issue reaching and maintaining 150C, never tried 180C but that should be no issue; the heater is not operating near full power at 150C. Your surface is 2.8x as large, with 2kW the power density is higher.

My plate is mounted on a carrier structure with 3 PTFE spacers and stainless screws. One is fixed, one spacer moves in a slot (and thus constrained to a single axis), one can move freely in the XY plane but not in Z. This allows expansion but constrains free movement.
A couple of images can be found in this forum topic. Dutch, unfortunately.
Although I must say that the kinematic mount using a couple of balls is quite charming too.

PTFE tends to creep over time when under a constant load. I do not expect many issues with that though, and I did not yet want to spend some of my limited supply of PEEK on those spacers.

OK, granted

@Danal said in Adding a 24V safety relay for the heaters, any thoughts?:

Could you expand on that? It would seem a sprinkler requires a water supply, and it is hard to see how that is cheaper.

I think that is more applicable to my situation. Machines in the garage, and there is a water supply available.
For the price of one AFO fireball one can buy a lot of pipe and mounting clamps, and the sprinkler heads themselves are not very expensive either.

In my situation it might be a good idea. The 3D printer is not the only machine.

@deckingman said in Adding a 24V safety relay for the heaters, any thoughts?:

Better still, use a clean agent fire extinguisher as I mentioned above - much kinder to the electronics than water (or foam).

I will look into that.
I am also wondering: how effective are one-shot devices when the power is not killed? Water would sooner or later trip the ground fault interrupter, and it keeps flowing (which might be a 'small' disadvantage also)

@arhi said in Adding a 24V safety relay for the heaters, any thoughts?:

I have 750W, 1000W and 2500W silicone heaters here on some aluminium beds ... never tested how far they can go but they get up to 100C in seconds, I would never allow them to run without meltable fuse for security. Running low power beds that would settle at max power around 100-150C is safe but I don't run those and more and more printers are made/upgraded with high power beds.

Mine is a 600W heater on a 300x300x10mm aluminium plate. They can become way hotter than needed, but it lacks the power needed to reach autoignition-hot. I think the remaining risk after taking into account the overheating prevention of the Duet in combination with the regular SSR and relay is acceptably small. Can it be better? Sure.

It is not an issue for me. I suspect the large amount of short segments simply choking the Duet. When using gcode with sane segment length the Duet hums along fine.
But still, it should slow down to a crawl, but not hang.

One caveat with the sensor close to the top: during warmup there is 10's of degrees temperature differential between the silicone heater core temperature and the top of the build plate. If you really intend to go to 150-180C plate temperature you might end up in a situation where the top is not yet at the intended temperature, but the silicone heater is hot enough to break down the adhesive backing.

I have drilled the hole for an extra sensor, but I am still using the sensor in the mat itself for this reason after a friend of mine kept having issues with silicone heaters coming loose. I just allow a couple of minutes extra heat soak time. After all the heat must soak through the glass plate also. Usually turning on the bed heater before exporting STL/slicing/preparing gives plenty of time for the bed to stabilise.

The best solution would be to use two sensors, the one in the mat to put a cap on the maximum temperature there, and another close to the top of the build plate for control. Not sure how to do this with Duet though, maybe with some creative use of themostatic fan control.

Someone stretching his neck to create an optimal RRF post for F360, and you guys start a date notation discussion?

@DaBit thank you for an interesting reflection on what I assume has been your journey into low cost CNC and the motion control limitations and issues.

Personally I converted a BF20 (G0704) mill to CNC, designed and built my own CNC-mill, converted an Emco lathe to CNC and designed&built my 3D printer. On top of that I have helped out many people with machines varying in size, 'professional-ness' and control.

I started out with LinuxCNC, and sticked with it. The flexibility offered to make things work the way I want them to work is unparallelled. The 'smart PC, dumb hardware' concept is powerful, especially when combined with the ease of LinuxCNC HAL.

On my CNC-machine I am running a mix of -10..10V analog servo's and steppers, 1um resolution linear scales for compensation of positioning errors and a Danfoss VLT5008 inverter controlled over RS485, a small compensation for the angle between Z and Y not being exactly 90 degrees, etcetera. No way I could have done all that with Mach3/4, EdingCNC, PlanetCNC, or Duet.

User interface is a second thing. In LinuxCNC it is very easy to add a panel for control of your vision camera, probe, flux capacitor, whatever.

There is an ongoing shift away from 'industrial' closed loop AC servo drives for light duty machines because of cost. We see Leadshine respond to that with various hybrids of stepper and servo. These are quite good ideas - combine the low cost of laminated pole stepper motors and the ability to avoid a backlash-inducing gearhead or reduction gearing, with refined drives and 4000 tic/rev position feedback. Add step/direction interfacing which still dominates the low end of CNC and automation.

My personal opinion is that step/dir is a less than optimal choice for servo control. A servo driven by step/dir is always running with a positioning error since it is always behind. A missed step (no communication channel is error-free) is never corrected. Actually, the control has no idea at all what the actuators are doing.

With my (analog-driven, torque-mode) servo's I can feed-forward acceleration and speed. The trajectory planner knows that it wants to accelerate or decelerate an axis, which can be translated into an instantaneous request for extra torque. Makes accurately following the programmed path so much easier. Keeping the stepper-driven Z position synchronous with the servo-driven XY within 10um was a royal pain in the ass; stepper motors need to build up a load angle for a given torque, and you cannot send a multi-MHz stepping pulse train into the average drive to quickly build up load angle.
Closed-loop steppers (those were not available at that time anyway) do not solve this; many of them function as open-loop drives as long as the positioning error is smaller than 2 steps or so.

Crimps and screws are OK. If I had that much power loss at the heater connector it would burn out anyway, but loosening and retightening the screws was one of the first things I did. Maybe there is something wrong in the (factory) wire towards the cartridge; I did not measure it's resistance.

Thermistor seems fine; idle temperatures are OK and the temperature reported when the inactive heater block picks up some heat from it's active neighbor seems to match too.

I guess that just ordering a new cartridge is the easiest thing to do. I would like to have a bit more heater power to accelerate tool changes anyway.

I think I spent around 100 liters of petrol and many Teamviewer sessions helping people to get the Duet2Wifi in their printer working after a network change or relocation of the printer. In my garage I had to place an extra access point to make the Duet2Wifi (and Pi, for that matter) work. All in all the Wifi on the Duet2 series is not great, and from a developer point of view it is quite hard to improve a lot. ESP32 Wifi is not that great either.

And then there is setup. For 'us computer wizards' it is a piece of cake, for many people just wanting to print whatever they download from Grabcad & co it is not.

With Ethernet: plug a cable into the router, open up a browser, go to http://<printername>.local, and it works. Want to add Wifi? That 20-euro TP-Link thing sounds good. Usually TP-link makes decent stuff, so I bet it works a lot better than Duet2Wifi builtin client. At least the antenna does not end up between a steel table and aluminium build plate, really close to some aluminium extrusion.

I think delegating Wifi to a 3rd party device is a good choice, but that's just me.

In case that's really an issue it is quite easy to add a small bit of silver braze. That's how I connected surgical tubing directly to brass nozzles in my DIY hotend (heatbreak and nozzle were one part in that design).

@dc42 said in Duet 2/3 for CNC vs other controllers:

RRF was changed a few versions ago so as to use smaller segments than that when moving slowly, specifically at the request of CNC users. If it's still a problem, I'm sure we can fix it.

In metals and hard plastics such as POM deviations and banding far below 'fingernail-detectable' are already visible. In reality this means that the segments must be short enough to become blended into a continuous curve by the mechanical lowpass action of the motion system.

My fairly heavy (gantry+Z weights 125kg or so) LinuxCNC-driven mill has a cutoff at ~20Hz (I actually ran sine sweeps through the motion system), but interpolating at less than 500Hz becomes visible. I am running at 7kHz 'servo-thread' which does the interpolation, but the servo thread being that high has another reason.

Therefore I would say that a fresh linear segment must be generated every 2ms or faster.

For good surface finish and decent endmill life there is also not such a thing as 'slow milling'. Endmills are like babies; you have to feed them enough otherwise they start crying.
Regarding cutting speed: there is a heavily disproportional relation between cutting force and cutting speed; at higher speeds relatively little force is required to shear off a chip. For aluminium, at 1m/min cutter speed it takes force X to shear off a chip, at 200m/min it takes 5X or so. Numbers are fictional but not that far off, real graphs can be googled.

Regarding feed: the chips carry away the heat. If you feed too little, the cutter rubs, a welded edge builds up, and cutter life is low. And even though the bulk of the cutter itself might not become very hot, that is not the case for the actual cutting edge.

Also, carbide cutters hate shocks. Thus, it is necessary to keep the speed constant as much as possible, and in the process window. Consistent force, consistent loading, consistent deflection, consistent shiny mirrorlike finish.

In what way(s) do those drivers run the motors "far better"? Assuming you are not just referring to maximum voltage and current.

More silent, less vibrations, less torque dropoff at higher RPM, higher sustainable RPM.

That really has to be experienced, some things cannot be captured in words well. If you never did so, I can highly recommend to grab a genuine Leadshine DM442 or so off Ebay, make sure you (auto)tune it with the motor mounted, and try it. There is some magic inside that TI DSP they use.

I once built my own drives using a dsPIC33F, nice PI phase current control, 80kHz PWM rate, phase advance to keep a 90-degree relation between winding current and rotor electrical position, notch filters to cope with midband resonance, morphing to fullstep operation, blah.
They were decent, but not as good as Leadshine DM drives.

Not sure about 2D toolpaths, but when using 3D toolpaths most CAM-tools including f360 create a polygon mesh under the hood and uses that for toolpath and rest machining generation. It is computationally so much easier to intersect a polygon mesh with a ray or another mesh than intersecting a BRep model...

To prevent a gazillion G1 segments, f360 allows you to optimize the toolpath with a given precision. I suspect they do some arc fitting and segment joinery there. I suppose they give you the same option when doing additive.

All in all they have everything building block they need now. If rest machining can see where there is still material to remove, the inverse is also true. If they can determine whether the machining tool and holder intersects with the stock and possibly work around that, they can also do so for a printhead. And so on.
What is left is handling the 'wet noodle' (in case of plastic). For that they can either buy the technology, or have a good look at the available codes and re-implement those.

My LC has arrived too.

Package is complete; all cables and things are in:

Looks OK on the outside:

Screw thread for the pillars is M6.

Heatbreak is a one-piece thing, or so it seems (did not pull it out).

3 of the 4 screws hold the aluminium cooling block in place. Guess which one does not

The inside:

Slave drivewheel runs directly in the plastic lever, I don't like that. Bearings are the cheap ones that go crunchy quickly. Oh well, it is built for a price.

Gears are metal, well formed teeth, with neither too little or too much grease applied:

Heatbreak could have been extended a bit more towards the drive wheel:

But oh well, this probably works OK too.

It will take a while before I can actually test it, but the first impression is quite positive.