What about lube and those carbon rods?

Bambu Lab P1 Series General Discussions
41

No! You have no idea how crazy that sounds to me :crazy_face:
Normal composite parts laminated in a negative mold.
The same way they make boats (typically fiberglass), wings and fuselages for GA and RC planes or gliders or even custom car parts and bike frames.

Edit: Googled you an example. It even includes 3d printing along the way in this example…

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42

I wonder how bad that dust is for us.

43

Carbon fiber dust is terrible

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44

it smells very good though :upside_down_face:

45

@Nebur Any update? Did your redesign work the way you hoped it would?

46

Sorry, no updates.
Other life & work & summer related priorities/activities managed to slow things down.

Maybe an interesting detail: In the context of the cad work and measuring the original parts, I found a design error. The belt paths on the x-axis are offset in y by exactly the amount they should be offset in the opposite direction. So the belt spans between the cf rods don’t run exactly parallel as they should.

Also I side-projected into experiments in precision grinding pultruded CF tubes. Idea was to basically build the x-axis from scratch instead of trying to free the original tubes from the side parts. But maybe more so curiosity being a bit of a machining nut ;-)…

Long story short: The p1s is currently out of order and shelved in its box. To be continued around November when it’s dark and cold…

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47

Why make them from scratch if you can buy 10mm rods for cheap in any well sorted KITE shop ? :wink:

48

Because we are talking about precision parts and not random CF tubes for kites.

The original ones are within 1-2/100mm diameter variation along the whole length and absolutely straight (at least on my specimen).

Also I’m of course not pultruding my own tubes from scratch. ‘Just’ trying to find a suitable process to grind and/or diamond lap regular commercially available tubes to the same tolerance without de-lamination or splitting.

When I wrote ‘from scratch’ I just meant it in the sense of not re-using any parts of the original x axis, apart from the toolhead assembly.

49

Like it or not: Those tubes are not really random.
They have to into tight fitting and very precise connectors, in my case brass or stainless steel for my big kites.
Those rods are available in several standard ID/OD combinations, depending on the required strength and weight limitations.

I measured one of my in use 10mm rods over the entire 73cm length.
The OD had a variation from 10.12 to 10.48mm.
However: My rods come with a protective and abrasion resistant coating, the ends that go into the connectors have to stripped of this coating in order to fit.
There the 14 rod ends (IN USE ONES!) had a variation ranging from 9.86 to 10.02mm depending on their level of wear.
Don’t know, but for the few bucks they cost well worth trying.
And if need much greater precision and strength check out modern carbon fibre arrow shafts :wink:
They cost a bit more in those diameters than kit rods but you can’t beat their precision as a base for custom rods.
Just saying, knowing that in some parts of the world access to precision parts can be easier than where I am…

50

I guess you are just not familiar with the tolerances required to make an overconstrained linear axis for this application actually work at all, let alone nicely…

Even those 6/100mm variation would be like
Untitled

Edit: And again - I have cf tubes! I’m not going to laminate my own. Just machining them to the required tolerances.

51

@user_3026326371 What kind of coating is it that confers the protection and abrasion resistance? What effect does it have on the friction?

52

I don’t know about other rods but mine came with a hard PU based resin coating.
The resin itself softens with Acetone and can then be scraped off the rods if, for example you would have to fix a broken rod.
In terms of friction I never tested or worried about it as it is not something affecting things for a kite.
All I know is that using connectors large enough to allow for the use of the rods without removing the coating requires constant pressure to keep them in.
Even with a near air tight fit they just slide out.
A abrasion protection is I think more for the fabric.
Standard acrylic based coatings tend to crack with the constant bending and the nylon fabric of the kite quickly wears the coating of contact areas.

I think the main problem with our carbon rods are those over-simplified bushings the head runs on.
So far I encountered three main types of carbon rods.

  1. Just spun carbon fibre strands.
    Easy to identified if uncoated or clear coated as you can see the nice woven pattern.
    They are produce by winding the strands in meaningful patterns around a dowel of sorts.
    A coating prevents the resin to bind with it for better removal.
  2. Fibre core with spun outer layer.
    Similar process only that the strands are woven around a rod made by vacuum forming and baking a blend of resin, different lengths of fibres and carbon particles.
  3. Plain carbon rods with a smooth or linear finish.
    These are usually high precision rods for specific applications, like abusing them as linear rails.
    With the linear finish you can see how rather long and well aligned fibres were used.
    For the smooth finish it is either just the outer layer or entire rod that is made out of blend of mainly short fibres and particle sizes optimised for the intended usage of the rods.

They all come with their own benefits and drawbacks.
Take machining rods with orientated fibres - near impossible to prevent chipping then, ripping them out and to a get an actually smooth surface.
On the other hand you can machine a smooth carbon with great precision and a good surface finish if you do it right.
Either way the main problem is the created dust and sharp fibres filling the air.
Not all wet lubricants/coolants can be used and using suction for the dust while the tool runs dry can quickly created excessive heat and certainly wears our most tools quickly.

If you ask me then a compromise would be ideal.
Stick with carbon rods to save weight but pre-tension them and given then a tough hardcoat that is thick enough to be machined down to the required tolerances.
Like that and even with the additional wire to tension the rods the weight would be still be lower as thinner walls can be used.
If you then would replace those flimsy sliding rods in the head with a set of PU rollers neither friction nor wear and tear would be an issue.

53

Well, friction might well be an issue with PU. I had chatgpt do a comparison between POM wheels and PU wheels for 3D printing. It was quite long, so I won’t copy/paste all of it here, but the friction section was telling:

Friction and Smoothness of Motion:

  • POM Wheels:
    • Low Friction: POM has a naturally low coefficient of friction, which allows for smooth, quiet motion along V-slot or linear rails without the need for lubrication.
    • Precision Movement: The smooth motion of POM wheels ensures precise layer alignment, reducing the chance of surface artifacts in prints.
  • Polyurethane Wheels:
    • Higher Friction: Polyurethane has a higher friction coefficient than POM, which can make it less smooth in linear rail systems. This increased friction can lead to more wear on the wheels and rails over time.
    • Grip: Polyurethane provides better grip compared to POM, which can be useful in traction applications but is generally less desirable in sliding or rolling motion systems where low friction is preferred.

I haven’t vetted these claims, but at least on its face, if nothing else, it explains why 3D printers typically come with POM wheels and not PU wheels, and the higher friction throws some doubt as to whether PU would actually be a good coating for carbon rods if they are to be used in a X1C type setup.