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| Pete W.:
Hi there, all, This may be a touch :offtopic: but here goes anyway: Some modern microscopes have plastic gear in the focus mechanism. These fail soon after the microscopes get into the amateur community (presumably, professional users can afford their service contractors' charge to replace the gear). There has been some discussion on the Yahoo Microscopes group as to whether 3D printing is capable of making replacement gears with the necessary precision. My reading of the various posts, pro and con, is that the jury is still out. Having said that, the various posters aren't usually very specific about how much they've paid for their 3D printer. It may be that top-end machines can do it but the cheapies can't. |
| Joules:
Don't ignore PLA as an engineering material, it is much underestimated in what it can do as long as you keep its operating temperature below 50℃ Those ring gears are 62mm diameter and I printed them for destructive testing, mix the pinions and see where colours get transferred to improve the design if needed. These are going to be for an experimental extruder for another 3D printer. I use a lot of parts like this for prototyping and maintenance, PLA is very unreactive to solvents and oils. The printer these were made on cost £470. It's a Createbot Mini, however what makes this machine a gem is its welded steel chassis and direct drive extruder. All the cheap machines in the Prusa i3 vane suffer from rigidity problems and this in turn appears as lines and blobs on your prints where the machine is RINGING as it prints. You want something with a sturdy chassis and good quality bearings, not bushes if you expect any sort of life from it. I use this machine daily in my business and hobby applications, got through about 6kgs of PLA so far, or about 2.1km of filament so very happy with the extruder mechanism on this one. http://www.technologyoutlet.co.uk/collections/3d-printers/products/3d-printer-mini-by-technologyoutlet-2015-model This is my machine. The downside is the lousy electronics it used, BUT even that is not insurmountable as they are pretty bog standard and can be replaced by off the shelf parts available in the UK. |
| picclock:
@ Joules The gears look impressive although the surface finish looks a bit rough. This is one of the aspects I am concerned about, because as parts get smaller the roughness becomes a greater percentage of the part. Like the idea of using the different colours for a visual mesh check. At £400 your printer seems a very reasonable choice. Which software package did you use to design the parts? The mechanics of the Prusa kit seem fairly OK. It has 10 linear ball races used with precision ground rod (0.03mm) and a water jet cut aluminium frame, which to me looks pretty good. I don't think they could get the head position accuracy figures otherwise. The only part that concerns me is that the vertical metal plate (gantry) attaches to the base with just two nuts and washers to keep it vertical. To be fair there is no load to move it from vertical but the dynamic loads caused by the movement of the head may cause some accuracy issues here. If I go ahead with the purchase I will measure the repeat accuracy with a gauge and anything that I find which reduces it I will stiffen up with custom mods. It looks like just mounting it on a known flat surface with brackets at right angles to the gantry (vertical plate) would sort it. There is a computer generated assembly video which seems quite well done (and entertaining :-) ) : Best Regards picclock |
| Joules:
Don't be fooled by the surface reflections, that roughness is about 0.1mm that being the layer height. This is a close up of the pinion you can see the layers, the plastic is very slippy so little friction. Most prints can be treated as precision castings, PLA machines quite nicely and can be wet sanded with fine emory and then lacquered for a tough finish. The parts were designed in Rhino, and output as STL files I then used in Simplify3D, but you could use (Free) Cura for this. The Prusa is a bold claim considering they are using tie wraped pipe as couplings onto unsupported hardware store threaded rod. If you plan on building tall models, you aren't going to see 25 micron accuracy ! My software has rounding errors for Z so expect >0.1mm in say 50mm. I use the printing in association with my lathe and mill for precision parts, just like you would a casting. What is the smallest size gear you are trying to make ? By swapping to a 0.2mm nozzle you could expect a blob of accuracy 0.25mm x 0.25mm in X,Y even if your Z does 50micron steps. The blob size dictates your minimum detail, if that makes sense. |
| Arbalist:
Not suitable for parts like gears but I understand the surface finish can be improved cosmetically on some materials by giving them a wipe over with some type of solvent. Plastic gears are often the weak link in some products. Two for no particular reason spring to mind and those are telescopic sights and milling machines! |
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