Automated and 3D printed ski and snowboard Ptex/HDPE repair

[yoshimitsuspeed]

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.

[o_lampe]

@yoshimitsuspeed If you'd be able to scan the surface continuosly, you'd probably find all the scratches.
But how do you know their profile (depths and shape) ? IMHO it's impossible to calculate the right amount of extrusion.

[droftarts]

@yoshimitsuspeed I'm usually the first to endorse build a complicated, single-use contraption, but I'm struggling to see the advantage over doing ptex repairs manually. To be fair it's been a while since I did my own ski repair (kids have limited the amount of skiing I get to do, so renting is a more sensible option for the 2 weeks a year I get to do now), but I don't think the technology has changed much. I remember setting fire to ptex sticks, then letting the melting plastic drip into areas for repair.

I can see the merit in using a 'glue gun' rather than the burning method, and that would make sense in a rental/repair shop, but there's so many other processes that are involved in base repair (trimming back loose ptex, edge repair, epoxy for really deep gouges into the ski structure before ptex, trimming/smoothing the added ptex, then all the waxing, and finally edge grind/sharpening) that I think a machine is going to struggle to implement and improve over the Mk1 eyeball and a not-even-very-skilled ski technician.

That said, I'd imagine you'd want to scan the whole ski at high resolution. Probably Lidar would give a sufficient point cloud. Then you'd need a machine that could run the length of the ski, with the ski clamped down. You might perhaps be able to run the ski through a machine; you can clip guides and runners to skis that go through base grinding machines, so you don't have to remove the bindings. Perhaps even have the ptex extruder as part of the base grinding machine (I hated having my skis base ground, they thin the edges and make them weak), so it runs through to scan, reverses and runs through to extrude ptex, reverses and base grinds the repair before waxing. But I may be out of touch with the processes involved, nowadays!

Ian

[mikeabuilder]

Interesting problem to solve. I read the intro messages with a different assumption than @droftarts - I assumed you are trying to repair gouges in the PTEX, not dressing the whole base of the ski/snowboard, and my thought was that rather than try to map a gouge, why not have a two step system. Position the "gadget" over the gouge and clamp it to the ski/snowboard. Select one of many pre-defined "patch" shapes. Insert tool #1 in the gadget. Tool 1 is a Dremel tool (or similar and routes a patch to a predefined depth. Then insert tool 2- the PTEX extruder which fills the shape the first tool routed. I can also imagine "custom patch shapes" could be created from a photo of the gouged surface.

[yoshimitsuspeed]

@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.

[yoshimitsuspeed]

@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.

[droftarts]

@yoshimitsuspeed said in Automated and 3D printed ski and snowboard Ptex/HDPE repair:

@droftarts

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

You need a reputation of at least two to post links. It stops the spam posts.

That's BS. The drip method is very far from ideal in many ways.

I never said it was the best way, just how I remember doing it as a DiYer. I said a glue gun method would be better. I don’t know what repair shops currently use.

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 still don’t like them! If I still had my own skis, I’d want them to last as long as possible. When hiring skis, you’re more likely to damage the ski if the edge is thinner, which causes wasted time and usually an insurance claim.

Ian