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All Springer/NP/PCP Air Gun Discussion General > 3D printing and files
Slim LDC
dan_house:
--- Quote from: subscriber on June 05, 2023, 06:08:18 PM ---Dan,
Printing short section of the design containing the critical dimension to measure helps a lot. Bob is an expert at that.
I have created short generic test prints that might be useful for general calibration: https://www.gatewaytoairguns.org/GTA/index.php?topic=204046.0
--- End quote ---
Oh man how did I miss that?? :)
Thank you sir!!
subscriber:
Thanks for the clarification, Dan
Obviously one can design one's own test prints that are closer to your design intent. Possibly with features stripped away that might be in the way for measurement - if simply cutting it short does not provide access.
Looking at my test print menu, the round on with the 8 mm diameter bore is probably most pertinent to the OP's needs; along with the next size up. It may be that more test print about that size are prudent.
Certainly, if one is printing threads that you intend to use without chasing, then having test prints for that would be useful. With Bob's help, I have developed a feel for how much clearance to add to threads in CAD.
That said, threads with a pitch smaller than 1 mm probably should be chased. Especially if the nominal diameter is below 12 mm. But then taps in the 3 to 12 mm diameter range are common and not expensive. Taps much over 1/2" can get expensive, if it is for one time use. And dies are much more expensive, but one could make a functional die to chase plastic thread from a steel nut. Many taps and dies can be ordered from China at more reasonable cost.
TorqueMaster:
--- Quote from: dan_house on June 05, 2023, 06:03:26 PM ---
--- Quote from: TorqueMaster on June 05, 2023, 05:34:59 PM ---
Key constraints as in key dimensions, or something else? Are you using Cura? Either way I can offer specific or generic suggestions if you're interested. Sometimes it is try, fail, modify, repeat...sometimes the first educated guess actually works!
--- End quote ---
Im interested..... Ive been using print/test/redraw for a long time, and if some or all of that could done in my slicer (Cura) then even better
--- End quote ---
Whoops, I meant to address this to OP, but should apply to Dan as well.
I've heard mostly good things about Prusaslicer, so it's probably fine. Most of these tips are generic.
Ok, you mentioned interior and exterior dimensions.
Exterior is all about printer calibration. On some printers, the XY steps/mm may need tweaking, but I've found on my cogged-belt driven printer, it's never needed adjusting. There is some unavoidable slop, but usually less than 0.1mm, so usually negligible. Next is making sure the extruder feeds exactly as much filament as requested-- call for 100mm, then 100mm should feed into the extruder. Some do it with the hot-end removed, some do it through the hot end, whichever, be consistent. Then tuning flow percent will help some -- I print a 2-line wide wall (0.4mm nozzle, 0.4mm linewidth), that should measure/average 0.80mm at it's topmost layers. Adjust flow % as needed to get there. That gets very close. Sometimes I print 10mm cubes until they have no measurable bulges or excess height to further gnat's @@@ the flow setting. I should say a calipers that does 0.01mm resolution is almost essential.
Once calibration is tweaked, interior dimensions should also be pretty close. The biggest exception is smaller interior holes, especially circles, printed in the XY plane. The filament tends to stick and create smaller holes than expected. The tinier the hole, the bigger the problem -- any under 0.5mm usually disappear completely. Designing hole diameters larger than needed (on the order of one-half-to-one nozzle size bigger) can get you close. Or plan on drilling to size. Or Cura has a "hole expansion" option that may fix them without munging other dimensions -- I haven't tried it. I also read somewhere that using hexagons or octagons instead of circles -- with straight rather than curved walls -- reduces this hole shrinkage issue. I haven't tested that yet.
Someone mentioned printing select slices of your object -- rather than the whole thing -- to test critical dimensions -- very useful and time saving. Chop it up in your cad, or I use tinkercad, to just that area. Also, Cura lets you place an object at negative Z relative to the print surface, so the layers you don't want are under the surface, and not printed, and then you can stop the print after 10-20 layers, and take measurements, adjust the design, reprint....
Hope this helps.
WobblyHand:
First shot through the LDC on my 2240 and it is quieter. No one is home, so I tried it without the LDC. I need to put the gun in a vise, and do a with and without for POI, but so far, so good. Simultaneously added an SSG. It's not dialed in, but it's functioning at some level. A good day.
WobblyHand:
--- Quote from: TorqueMaster on June 05, 2023, 07:05:45 PM ---
--- Quote from: dan_house on June 05, 2023, 06:03:26 PM ---
--- Quote from: TorqueMaster on June 05, 2023, 05:34:59 PM ---
Key constraints as in key dimensions, or something else? Are you using Cura? Either way I can offer specific or generic suggestions if you're interested. Sometimes it is try, fail, modify, repeat...sometimes the first educated guess actually works!
--- End quote ---
Im interested..... Ive been using print/test/redraw for a long time, and if some or all of that could done in my slicer (Cura) then even better
--- End quote ---
Whoops, I meant to address this to OP, but should apply to Dan as well.
I've heard mostly good things about Prusaslicer, so it's probably fine. Most of these tips are generic.
Ok, you mentioned interior and exterior dimensions.
Exterior is all about printer calibration. On some printers, the XY steps/mm may need tweaking, but I've found on my cogged-belt driven printer, it's never needed adjusting. There is some unavoidable slop, but usually less than 0.1mm, so usually negligible. Next is making sure the extruder feeds exactly as much filament as requested-- call for 100mm, then 100mm should feed into the extruder. Some do it with the hot-end removed, some do it through the hot end, whichever, be consistent. Then tuning flow percent will help some -- I print a 2-line wide wall (0.4mm nozzle, 0.4mm linewidth), that should measure/average 0.80mm at it's topmost layers. Adjust flow % as needed to get there. That gets very close. Sometimes I print 10mm cubes until they have no measurable bulges or excess height to further gnat's @@@ the flow setting. I should say a calipers that does 0.01mm resolution is almost essential.
Once calibration is tweaked, interior dimensions should also be pretty close. The biggest exception is smaller interior holes, especially circles, printed in the XY plane. The filament tends to stick and create smaller holes than expected. The tinier the hole, the bigger the problem -- any under 0.5mm usually disappear completely. Designing hole diameters larger than needed (on the order of one-half-to-one nozzle size bigger) can get you close. Or plan on drilling to size. Or Cura has a "hole expansion" option that may fix them without munging other dimensions -- I haven't tried it. I also read somewhere that using hexagons or octagons instead of circles -- with straight rather than curved walls -- reduces this hole shrinkage issue. I haven't tested that yet.
Someone mentioned printing select slices of your object -- rather than the whole thing -- to test critical dimensions -- very useful and time saving. Chop it up in your cad, or I use tinkercad, to just that area. Also, Cura lets you place an object at negative Z relative to the print surface, so the layers you don't want are under the surface, and not printed, and then you can stop the print after 10-20 layers, and take measurements, adjust the design, reprint....
Hope this helps.
--- End quote ---
Some of this is simply expectations. Since I can and do machine, I don't consider an error of 0.1mm to be good at all. Being off by 0.004" isn't very good, when I machine, I often do much better than that, especially on bores.
I do need to do further calibration. Actually, I need to level flatten the bed - which I have been putting off. I have the little nylock nuts, just need to figure out how to rig up a good dial indicator on the print head to measure the bed hot, to come up with settings.
Thanks for the tips on the hole size adjustment, that is helpful.
I've printed some stuff that didn't fit, particularly on inside dimensions. Made a DRO read head bracket that was shaped like a U, the read head was supposed to be a tight fit inside the U, and had a devil of a time fitting the read head in without excess slop. 3d printing is pretty cool, but the consumer stuff is somewhat limited.
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