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| PekkaNF:
Basically you want as light as possible structure, good 3d printer head must be able to accelerate and move relatively fast and fast stepper motors are small. Nevertheless should be rigid eneough, othervice printhead shakes all over the path. Pekka |
| Swarfing:
With the i3 we are only talking about the main static frame so weight does not come in to it. Yes it could be made from extrusion of course, but these days extrusion is a very hi cost in comparison to other materials. |
| picclock:
@swarfing Prusa I3 - I had already planned to s/s allthread for the m5 z axis because it always looks like the threads are better formed. I was under the opinion that they were still rolled - but if not what process is used to thread them ? IMHO this is one of the weak areas which may prove tricky to improve on - but as its only being made in plastic with all its dimensional issues (moisture absorbtion, high coefficicient of expansion etc.) it might just be good enough. The other axis of the machine are belt driven direct from a stepper motor. I suspect the reason for change on the Z axis was to improve the resolution to allow for thinner layers and achieve smoother finishes. @awemason The Velleman printer sold by Farnell and maplins uses an extruded frame - although it only uses one z motor which will likely lead to droop on the undriven side. Could probably be compensated for by bed levelling to some extent. http://www.maplin.co.uk/p/velleman-k8200-3d-printer-kit-n82qg ---------------------------------------------------------------------------------------------------------------------------------------------------- The frame (gantry) weight with the Prusa I3 design is irrelevant as it is a static part, so can be made very stiff, to allow good accuracy for head positioning in the X and Z axis. The Y axis will have to accurately achieve position with the weight of the heater bed and glass sheet plus the model weight and the cable drag. I think thats why the I3 design is a good one. Two out of three axis sorted for stiffness. Best Regards picclock |
| S. Heslop:
--- Quote from: Swarfing on August 04, 2015, 04:47:00 AM ---With the i3 we are only talking about the main static frame so weight does not come in to it. Yes it could be made from extrusion of course, but these days extrusion is a very hi cost in comparison to other materials. --- End quote --- http://www.valuframe.co.uk/ These kinds of extrusions seem very cheap if you're selling kits, since you can leave alot of the assembly and fitting to the guy buying it. Wonder how much the cost stacks up against paying for water jet/ laser cut plates though. |
| Swarfing:
Ha ha! yes is reasonable priced until you add delivery cost? It's all horses for courses, you choose your material of choice and go for it. Judging by the comments so far you can see people just have their preferences for different materials. I have used a lot of extrusion for my past CNC projects, in my final CNC router build I opted for welded Steel (Cheaper and stronger). The last lot of S/S threaded rod I bought looked too good to be rolled and I was under the opinion it must have been cut? I can't really comment on processes used. In general S/S rod just seem to present much cleaner threads and by virtue gives a lot less issues. You could opt for ballscrew but really a bit over the top for a small 3D printer unless you want that extra perfection? At some point I will build another for myself and again I would go for the birch ply approach. My friend is very pleased with the results he is getting. It is the 13 Laminate variety I used so is very stable especially with a coat of lacquer. I wish I had a pic which I'm sure would speak a thousand words. The overal advice I would give is to keep it simple and don't complicate it too much. With a working machine he has already remade some of the plastic parts to a much beafier spec. Hope that helps |
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