I am proposing to build this part in ABS, and I am completely new to this game.
What sort of support structures do I need to add to support it during the build?
I was thinking of several small snap off pegs on the bottom face to allow for the projection.
That’s going to be difficult to print. Also this drawing is very complicated and I think still has some ambiguities, although I’m not well versed in mechanical drafting. But here’s some discussion:
Options in order I think is best (whatever that’s worth)
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Split the part into subassemblies, join after printing with mechanical fastener or adhesive. Perhaps mold in bosses to aid in assembly.
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Print on the side with internal and external supports. Will need continuous support, you cannot print over thin air and you cannot bridge between supports with any consistency as they skip a layer so they don’t adhere well. Also the long thin piece won’t print well in a sideways orientation due to the small bed adhesion zone with the tall aspect ratio.
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Model supports directly into the part as something that can be broken away and cleaned up by sanding off. This would allow bridging, but keep the bridges short. Still has issues with the cavity, and will certainly have poor surface finish resulting in significant post processing cleanup if you care about aesthetics.
Overall it seems this part was not designed specifically to be printable (which is to be expected, that’s no problem as you learn more about additive manufacturing). If this was my part I would redesign such that there are large flat areas that can adhere to the bed, minimal overhangs, and then assemble after.
For example, the circular area would be printed best as a vertical cylinder. It looks like there’s already mechanical fasteners present in it. So print it in the vertical orientation and bolt it together.
At some point the complexity of this will necessitate slicing in Cura, Prusaslicer, or something more capable than Luban. Support placement, type of supports (tree supports or rectangles, size, density, etc) may need more ‘power’ than Luban has to offer.
Also reviewing the generated gcode will be essential to ensure nothing starts printing over thin air. Get in the habit of reviewing each layer of the print layer by layer and ensure there are no significant overhangs and no filament being extruded over nothing as that will guarantee a failed print. Slicers will happily generate programs guaranteed to fail if you accidentally miss a support placement or the auto place routine does a poor job.
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Thanks for your thoughts on this Brent.
I did think of not moulding the large slope on the left hand end and the boss detail on the base and machining those afterwards. I could then mould it in a vertical position which would only have over hangs where the hex holes change to round and the left hand ramp surface in the slot and the 8mm bore hole.
I could change the transition from hex to round hole to a 45 degree slope which would go some way to alleviating that overhang.
I could drill and counterbore the 8mm hole after moulding.
A simple shallow indent to locate the centres of the 8mm bore hole and the almost semi circular boss would help in the machining positions of those features.
Arthur.
If it wasn’t for the pin that extends below the body, I think it wouldn’t be too difficult. Given the size, you would probably need some supports touching everywhere, and there would some surface finish issues. You’d have a hard time cleaning the supports out that horizontal bore, but nothing that a bit of elbow grease can’t fix. Especially if you have a part that’s going to sit in that horizontal bore, just inserting it and working it around will do a lot of cleanup. If the part was smaller, I think the bore would print without supports, but it’s unlikely to work at this size.
I think printing on High Quality alleviates some of the concerns that brent113 mentioned, like the surface finish issues when printing on supports. The smaller layer height makes gap between the support and wall less of an issue, allowing new surfaces to bridge the supports better.
You generally don’t want to drill into a printed part without a lot of extra work during modeling. Most slicers default the interior volume to be infill, not solid. You generally don’t want the interior solid. It really increases your print time, and you can usually dial in the structural strength you need by making the infill more dense. Luban doesn’t give you the option to change the infill type, just the density, but other Slicers do. If the 8mm hole w/ 10mm counter isn’t under a lot of stress in any direction (or compression), that might be fine. If you’re expending any sheer or compression force on it, you might have issues. The model could be worked to force the slicer to print that volume solid, and the rest as infill, but that’s beyond my modeling skill level. I know I’ve accidentally created interior defects that caused interior fill walls to be printed. But I’ve never set out to do it on purpose.
Here’s the cool thing about 3D printing though: It’s cheap and easy to print a prototype and try it out. In fact, you’ll probably need a few attempts to get it right, as the Snapmaker has a history of making negative cylinders a bit too small.
Regarding the drawing, I see a few missing measurements. I don’t see a total width. I believe I could calculate it from the sub-width dimensions, but there would be a few interpretations. There is a depth and height. I assume the left angle is 45º, but it’s not marked. The depth of the larger pin (center bottom) view is unspecified even though the smaller pin is labeled. That’s what I noticed, but a few more things might turn up once I started modelling.
BTW, I design models the same way. I draft the part (usually freehand though, I don’t need to get out the Tsquare). Then I build the 3D model from the draft.
Thanks Craig,
The block around the 8mm hole is under compression with an 8M bolt through it clamping the part in place.
The semi half round boss on the base is in shear along the long axis of the part which is why I want to mould it in place rather than add it as an insert. Having said that if I made a circular cavity about 5mm deep I could machine that boss from aluminium and insert it after the moulding. But then I have the problem of the overhang of that cavity to deal with. Maybe I could machine that cavity into the part after moulding. I will probably only be making 2 or 3 of these so I am not looking at time cost issues.
A large spring sits around the boss in the horizontal cavity and 4 M3 bolts go through the corner holes into nyloc lock nuts in the Hex cavities. There is a 3mm thick aluminium pressure plate mounted on the ends of the 4 M3 bolts that presses against the spring and the large boss is the back stop for the action. The bore does not have to be particularly clean as long as the large spring can be compressed.