I have been thinking about this idea to fix ski and snowboard ptex with 3D printing.
Last year I made a little manual repair tool out of a hot end with a base and spring setup where I could push the hot end down into scratches, then feed PE repair filament by hand as I moved the repair tool by hand.
This was a pretty cool proof of concept and I think my results were probably at least as good as traditional methods but still not perfect.

I could make a simple working prototype for flatter areas by making something pretty close to a traditional 3D printer that mounts to the surface and prints a small flat area but this doesn't address the curved areas so I would love to make a working prototype that at least started to show something could work on non flat geometry.
One idea was wheels that roll along the surface and a pressure wheel that rolls along the back (or really top) side. Even this has challenges with the width changing and some skis and snowboards having non flat top sides. Along with wanting to be able to print right up to the edge of the board.

The other big challenge if this is recognizing the gouges, assigning them a coordinate system, and then slicing and printing.
I could do this by doing something like mounting a printer, 3D scanning the surface with some reference points on the printer I can use to assign coordinates, then do some mesh work to fill the void and create a solid object to put into a slicer. This again works easier for flat areas.

More ideal would be to be able to scan the surface from the 3D print head. If you had an axis that rolled along the curved surface and say a laser scanner or something that scanned perpendicular to that axis it could then basically interpolate the scan as a flat surface.
I have been wondering if there is anything that could be done easily that could take advantage of existing bed leveling firmware.
Would it be possible to do this with a capacitive sensor or is there anything similar that could easily work mostly off existing tech and firmware?

Then the next question would be whether you would need to send the scan to other software. I expect the answer is yes but I have been wondering how hard it would be to take that "bed mapping" determine a best fit surface, detect any imperfections say more than .1mm deep by a couple mm squared, create a watertight geometry of the scratch/gouge, generate a simple slicing profile for that geometry and fill it in.
I recognize this would be a good ways beyond your average bed leveling gcode but I am curious if it would be possible to achieve with a reasonable amount of work.
Otherwise we could do something like send scan to a mesh editor, create 3D geometry, send to slicer, generate Gcode, then back to the printer.

Another thought i had the other day was using a robot arm to do this. This eliminates the issue of trying to get a 3 axis machine to track a non flat surface. I imagine it would add a good bit of complexity in other ways though. A quick search makes it look like at least some development is going into getting Duet to run a robotic arm.
This could allow the arm to be mounted separately. If the arm scanned the surface the scan would be tied to it's coordinate system. Then it is just that matter of creating geometry for the voids, slicing, and sending back to the machine.

I know this would be a pretty big undertaking.
If a finished product could be delivered for the right price I think there could be some interest in the ski industry. If it was dialed in I suspect there are even some hobbyists would would be interested in building their own.

@droftarts

Welp can't post links so here it my response with them removed. That's BS.

The drip method is very far from ideal in many ways. The typical material is a softer more low density PE.
Burning it means inconsistent heat with at least some being heated above ideal temp. You are adding contaminants from the burning process. You also have very sub optimal control over temps and bonding between old and new material.
From a thermoplastics sciences perspective this method is horrible. It just happens it has worked well enough to be considered acceptable for DIYers.

This is a much better solution which is basically a manual form of doing what I am trying to do in a more automated and controlled process.

The more you do these kind of repairs the better the results and you can get pretty good results but it is also possible for someone less experienced to get a lot of air voids, poor adhesion, etc.
Then you want to build up above the surface, and then cut back down. Oftentimes having little pockets that you come back and fill again. None of this is particularly hard but I think I would be pretty awesome to have something automated that filled the hole to a consistent say 0.05-0.1 above the surface that could be quickly lapped down.
An automated process gives far more control over temp, the ability to keep it in the optimal ranges for material properties and adhesion. Once set up it could even save time and might even have a place in pro repair shops if refined and developed enough.

Yes there are similar scanners in existence already that mount to CNC machines. These systems are often designed to replicate. So they would scan a 3D object, convert it to geometry that it could then machine. This would basically just add the step of creating a volume out of the negative volume which could be easily extracted through best fit simple geometry. Or to start just through manually creating closed volumes over any gouges big enough to bother with.

I was trying to find an example of the older CNC scanners I was thinking of and came across this which is exactly what I want to do. Just on a lower budget level lol.

Here is an example of the older style I was thinking.

Base grinding is primarily for getting the edges sharp again. Or for those of us who ride rocks as much as snow at least trying to get back some semblance of an edge lol.
You can generally get quite a few grinds before it's just too thin and or compromised. But at some point any board or skis reaches the end of it's practical lifespan.

I have been playing with this for the last week or so and I have to say even in it's current state it is a game changer.
I think there is a lot that could be done with the idea that would make it infinitely better but I also see that there are challenges in how to implement that with existing firmware, hardware, memory, etc.

For ages I have had printing profiles in Prusa for both print settings and filament settings in about 10C increments ranging from 10-20C below to at least 20C above recommended settings for various printing speeds, part sizes, etc.

I think the current implementation can take me down to about two for most filaments which is awesome.

TPU is an example where I have configurations that go all the way down to 180C for printing tiny, super low volumetric flow rate things. And admittedly probably not with the driest filament because I can print perfectly dried filament at those speeds and higher temps without issues.

As I suspected I think the biggest evolution from here would be to use a nominal temp and printing speed in the middle somewhere and then run hotter for faster, cooler for slower.

I also think more look ahead is probably the other biggest gain that could be had.
I think something like a 2-3 second look ahead would be a massive improvement. More than that I think would still show some improvement but from there definitely at a rate of diminishing returns.

It is good enough that I am pretty sold and expect to be using this for the large majority of my printing as is. I also hope it can keep evolving and would especially love to see it switched to starting at a mid point heat, and trying to get as much look ahead as possible.

On the note of look ahead I have set to 50ms on my 3HC and 5+ and they seem to be running just fine at that.
Is there any way we could get it running higher values?

@mikeabuilder
Yes that is at least the starting goal.
The thought of removing material might have some merit if scanning and creating a volume from the gouges was too prohibitive but I don't think it should be too hard to do.

The one big issue is that once you hit the core a proper repair takes a bit more work and generally you want to keep the exposed core as minimal as possible. I suppose you could do a manual fill of the core shots and then an automated cut and fill of the top layer but then you are kind of doing some work the way it is currently done and could just fill the whole thing at that point.
The original base material is also harder, tougher, and slicker than the fill material so again ideal is to keep as much of the original material as possible. Having a slightly expanded fill area isn't a big deal but is definitely something to factor as much as possible.

Since my second thread trying to discuss proper use and documentation once again degraded into people trying to troubleshoot my setups I am going to try this again.

I would like to have a thread devoted specifically to proper use. Something that could be a reference for any users and hopefully something that could be turned into useful documentation.

I'll try to outline what I mean and my thoughts with what I know but recognizing the optimal workflow and documentation might look much different if there are things I am missing.

Step 1?
We want esteps to be calibrated and this will likely be a lower value than running without Nonlinear Extrusion (NLE)
Without NLE you would generally want to tune esteps somewhere in the middle of your typical extrusion rate.

It seems the current best practice way to tune this for NLE is to tune your esteps at the lowest practical extrusion rate.
Then NLE will add the multiplier for all rates above that.
This does have the unfortunate result of needing to run NLE since without it you will always be under extruding anywhere above that min rate. I would imagine a more ideal solution would use your standard Esteps as a mid point, then subtract below that and add above that. But maybe that is too complicated?

Step 2?
I assume next we want to test extrusion at a range of rates.
Presumably at the rate Esteps were tuned at we should see 100% extrusion. If you ask it to extrude 100mm of filament it should extrude 100mm of filament.

Most people seem to recommend what I have been calling static extrusion where the Z axis is raised and then you tell the printer to extrude a given length of filament at a given rate.
Has this been demonstrated to be accurate enough to compensate during actual printing?
Actual pressures will likely be notably higher especially for example if you are printing low layer heights and especially layer widths notably wider than your nozzle diameter.

Test at a range of flow rates.
How many?
How high?
What is a good rule of thumb for max flow, max deviation, max correction?
Is that different for diffrent matierials like say hard filaments vs 95A TPU, vs 50A TPU?

So now we have our extrusion tests done. I'll make up some results to use as an example. Let's say TPU because this is where NLE has the most benefit. And let's say tested up to 10mm/s just to give some nice round numbers.
Test is extruding 100mm and measuring to compare requested to extruded
So say
1mm/s 100mm
2mm/s 99.8
3mm/s 99.5
4mm/s 99
5mm/s 98.2
6mm/s 97.2
7mm/s 96
8mm/s 94.2
9mm/s 92
10mm/s 89

Step 3?
Calculate M592 A and B values
Now how do we do the math? Or preferably what calculator should we use to enter these values into? Preferably an official Duet calculator known to work.

Step 4?
test extrusion
My understanding is that the only way to test this is during a print move. So the test needs to include XY moves.
Is there any way we could put DWC into a testing mode where we can just use the extrude function and have it apply our M592 multiplier?
Otherwise can we come up with an official Gcode file that people can use that should give reliable results?
If we used the static test above then it seems logical to test again with the same test.
Today I have been testing with this. IDK if it's ideal but it seems to be working at least at lower speeds.
I know the faster the speeds the more we need to worry about things like acceleration.
G28
G0 X100Y0 F20000
G1 F60 x100 y100 e100 F60

If we use the 10mm/s example above I imagine it should be plenty to test at 1mm/s, 5mm/s, and 10mm/s.

If it appears to be extruding 100mm at all three points it should be a pretty good curve everywhere else. I would think.

Step 5
I think it would still be ideal to have some sort of dynamic test. This does bring in a lot more variables, especially for your first few layers where you are impacted by first layer height. So you would probably want a test that prints a few mm high.
One thought might be a few rows probably at least three layer widths wide so you can look for under/over extrusion between them. You could have three or more different lines so it prints the first series of lines at your min test, the next series at midpoint, and the last series at max flow rate.
It would be nice to make it easy to change a couple variables like layer height and width to see if those impact your extrusion.

Does this look like about the proper workflow?
If so can we get answers on things like the best way to do the calculations?
Or even better can Duet give us a known to work calculator that we can just enter our variables into? A plugin for DWC would be awesome.

I have been playing with this for the last week or so and I have to say even in it's current state it is a game changer.
I think there is a lot that could be done with the idea that would make it infinitely better but I also see that there are challenges in how to implement that with existing firmware, hardware, memory, etc.

For ages I have had printing profiles in Prusa for both print settings and filament settings in about 10C increments ranging from 10-20C below to at least 20C above recommended settings for various printing speeds, part sizes, etc.

I think the current implementation can take me down to about two for most filaments which is awesome.

TPU is an example where I have configurations that go all the way down to 180C for printing tiny, super low volumetric flow rate things. And admittedly probably not with the driest filament because I can print perfectly dried filament at those speeds and higher temps without issues.

As I suspected I think the biggest evolution from here would be to use a nominal temp and printing speed in the middle somewhere and then run hotter for faster, cooler for slower.

I also think more look ahead is probably the other biggest gain that could be had.
I think something like a 2-3 second look ahead would be a massive improvement. More than that I think would still show some improvement but from there definitely at a rate of diminishing returns.

It is good enough that I am pretty sold and expect to be using this for the large majority of my printing as is. I also hope it can keep evolving and would especially love to see it switched to starting at a mid point heat, and trying to get as much look ahead as possible.

On the note of look ahead I have set to 50ms on my 3HC and 5+ and they seem to be running just fine at that.
Is there any way we could get it running higher values?

@dc42

Did you see the results of my first test above?
If I am learning to read the filament sensor output correctly it doesn't seem like NLE is really doing anything at all.

I have a lot more data from tests yesterday but I need to go through it and test some things. I was testing TPU and had more drag on my filament before the extruder than is ideal. That might be causing under extrusion but in a test today I don't think it was really skewing results of NLE notably.

If all my results are accurate and like the results above it seems like NLE isn't really having any impact at all.

On the subject of reading the filament sensor data. Am I correct in my assessment that something in that 24.8-25.3 range is nominal and that higher numbers equate to less linear filament passing through and lower numbers mean more filament passing through?

So for example if 25.3 is what I get on a low speed test and 25.8 on a high speed test that would equate to 98/100 mm of filament passing through correct?

@dc42
The last set is using the calculator I have which already happened to be at 98 for 12mm/s3 so I tried that.

But according to the filament sensor it doesn't appear to have had any change compared to NLE A0 B0

@dc42

So I finally installed my mag filament sensor since it seems like the best tool I have to try to move forward with this and to measure filament usage.

I think I understand how it works.
Most the documentation and threads seem to say 24.80mm/rev is default for the sensor but @timschneider came to 25.3 in his thread which is pretty much exactly what I am getting with my extruder set to manufacturer recommended specs.
So I set L as 25.3 but I don't really understand what that does since the output of M592 D0 seems to be the same regardless of what that number is or if I manually have an L value entered at all.

From what I can tell we are looking for deviation in the mm/rev output and it appears to me as though a higher value means less extrusion.
So if I get 25.26mm/rev at 1mm/s and we assume that is nominal, and 25.8mm/rev at 5mm/s then I am taking that to mean 98% extrusion or if I ask for 100mm it is pushing 98mm. Correct?

I then did a number of tests using this Gcode to have an XY move included.
M592 D0 A-0.000317 B0.000187
G28
G0 X100Y0 F20000
G92 E0.0
G1 F300 x100 y100 e100 F60

Here are the results from those tests. I think you should be able to understand the changes by the file names.

Extrusion test 1mm/s NLE0
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 130 agc 79, measured 25.26mm/rev, min 97% max 102% over 99.4mm

Extrusion test 5mm/s NLE0
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 130 agc 77, measured 25.80mm/rev, min 95% max 104% over 99.5mm

extrusiontest-1mms-nle- M592 D0 A0.01 B0
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 128 agc 75, measured 25.25mm/rev, min 96% max 104% over 99.7mm

extrusiontest-5mms-nle- M592 D0 A0.01 B0
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 131 agc 77, measured 25.87mm/rev, min 97% max 103% over 104.8mm

extrusiontest-1mms-nle-M592 D0 A0 B0.01
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 132 agc 77, measured 25.26mm/rev, min 97% max 103% over 99.4mm

extrusiontest-5mms-nle-M592 D0 A0 B0.01
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 128 agc 75, measured 26.37mm/rev, min 96% max 104% over 119.2mm

extrusiontest-1mms-nle-M592 D0 A-0.000317 B0.000187
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 129 agc 79, measured 25.28mm/rev, min 97% max 103% over 99.5mm

extrusiontest-5mms-nle-M592 D0 A-0.000317 B0.000187
Duet3D magnetic filament monitor v4 on pin io3.in, enabled when SD printing, 25.30mm/rev, allow 60% to 160%, check printing moves every 3.0mm, mag 131 agc 79, measured 25.81mm/rev, min 97% max 104% over 100.0mm

Since my second thread trying to discuss proper use and documentation once again degraded into people trying to troubleshoot my setups I am going to try this again.

I would like to have a thread devoted specifically to proper use. Something that could be a reference for any users and hopefully something that could be turned into useful documentation.

I'll try to outline what I mean and my thoughts with what I know but recognizing the optimal workflow and documentation might look much different if there are things I am missing.

Step 1?
We want esteps to be calibrated and this will likely be a lower value than running without Nonlinear Extrusion (NLE)
Without NLE you would generally want to tune esteps somewhere in the middle of your typical extrusion rate.

It seems the current best practice way to tune this for NLE is to tune your esteps at the lowest practical extrusion rate.
Then NLE will add the multiplier for all rates above that.
This does have the unfortunate result of needing to run NLE since without it you will always be under extruding anywhere above that min rate. I would imagine a more ideal solution would use your standard Esteps as a mid point, then subtract below that and add above that. But maybe that is too complicated?

Step 2?
I assume next we want to test extrusion at a range of rates.
Presumably at the rate Esteps were tuned at we should see 100% extrusion. If you ask it to extrude 100mm of filament it should extrude 100mm of filament.

Most people seem to recommend what I have been calling static extrusion where the Z axis is raised and then you tell the printer to extrude a given length of filament at a given rate.
Has this been demonstrated to be accurate enough to compensate during actual printing?
Actual pressures will likely be notably higher especially for example if you are printing low layer heights and especially layer widths notably wider than your nozzle diameter.

Test at a range of flow rates.
How many?
How high?
What is a good rule of thumb for max flow, max deviation, max correction?
Is that different for diffrent matierials like say hard filaments vs 95A TPU, vs 50A TPU?

So now we have our extrusion tests done. I'll make up some results to use as an example. Let's say TPU because this is where NLE has the most benefit. And let's say tested up to 10mm/s just to give some nice round numbers.
Test is extruding 100mm and measuring to compare requested to extruded
So say
1mm/s 100mm
2mm/s 99.8
3mm/s 99.5
4mm/s 99
5mm/s 98.2
6mm/s 97.2
7mm/s 96
8mm/s 94.2
9mm/s 92
10mm/s 89

Step 3?
Calculate M592 A and B values
Now how do we do the math? Or preferably what calculator should we use to enter these values into? Preferably an official Duet calculator known to work.

Step 4?
test extrusion
My understanding is that the only way to test this is during a print move. So the test needs to include XY moves.
Is there any way we could put DWC into a testing mode where we can just use the extrude function and have it apply our M592 multiplier?
Otherwise can we come up with an official Gcode file that people can use that should give reliable results?
If we used the static test above then it seems logical to test again with the same test.
Today I have been testing with this. IDK if it's ideal but it seems to be working at least at lower speeds.
I know the faster the speeds the more we need to worry about things like acceleration.
G28
G0 X100Y0 F20000
G1 F60 x100 y100 e100 F60

If we use the 10mm/s example above I imagine it should be plenty to test at 1mm/s, 5mm/s, and 10mm/s.

If it appears to be extruding 100mm at all three points it should be a pretty good curve everywhere else. I would think.

Step 5
I think it would still be ideal to have some sort of dynamic test. This does bring in a lot more variables, especially for your first few layers where you are impacted by first layer height. So you would probably want a test that prints a few mm high.
One thought might be a few rows probably at least three layer widths wide so you can look for under/over extrusion between them. You could have three or more different lines so it prints the first series of lines at your min test, the next series at midpoint, and the last series at max flow rate.
It would be nice to make it easy to change a couple variables like layer height and width to see if those impact your extrusion.

Does this look like about the proper workflow?
If so can we get answers on things like the best way to do the calculations?
Or even better can Duet give us a known to work calculator that we can just enter our variables into? A plugin for DWC would be awesome.

Also I have to point out how I specifically asked that this thread be about documentation for proper use for this feature and not about troubleshooting my specific setup and all it has turned into is people trying to troubleshoot my specific setup.

@dc42
DWC 3.5.4

I also assume I will need to do this test as a print move with some kind of XY motion to make M592 work right?

@dc42

Do you want me to do this test with my estep settings as tuned without NLE, or the Estep settings I have found work best with NLE?

Out of curiosity if I started playing with this is there an easy way to make the target temp the middle of the range with heating for faster and cooling for slower than x rate? Or is there no easy way to do that?

I am so stoked to see this being implemented. I have been wanting this for years now but deff didn't have the need or drive to try to develop something on my own.

I will admit I quickly skimmed a lot of the more recent posts.
Reading through my first thought was that I would greatly prefer something that aimed for the middle of a filaments range instead of starting at the low end then ramping up.
Let's say a manufacturer recommends 230-250 printing temps I would want to set the printing temp in my slicer at 240.
Then I think it would be awesome to have a min and max from there. Either deviation say +20-15 from that or just actual temp min 225 max 260 .

Then reading about the discussion on how far to look ahead I think the above strategy would largely solve the issue of a longer look ahead because you are starting in the middle of the acceptable printing range instead of way too low for most print speeds.
Using the above example if the printer is just sitting there at 240 it shouldn't really be cooking the filament and could start printing slowly or pretty fast.
Then if you had a 6 second look ahead it wouldn't need to wait 6 seconds to start. It just starts at 240, starts printing, and starts looking forward as soon as it does.

I also assume there must be some sort of averaging or smoothing on how it does that?
If it looks ahead 6 seconds and just averages flow rate over that 6 seconds then it should basically be processing real time and as soon as you hit start it just adjusts to the average for the next 6 seconds.

I would think setting the target temp in the middle would eliminate the need to wait before starting to print but it might be nice to be able to change that look ahead time depending on our machine, needs, etc, especially if there is any tradeoff. My nozzles change temp pretty fast so I don't think I would need 6 but I think being able to go into that few second range would be a lot better than 50ms.

Also right now thinking of how even typical starts take a while. Moving from the home position, pause position, etc usually takes a second or two. Print head temp could have already changed a few degrees by the time is starts pushing filament and with that inertia already heating or cooling.

I basically do this when I'm printing with my IDEX printer. I don't have it pause to heat. Have standby temp for say 215 so it doesn't cook the filament. Then by the time extruder one parks and extruder two starts pushing filament it's at 220. By the time the filaments that has been sitting nice and hot in the nozzle is pushed out it's up to 225 and a few seconds later 230.