Building a 3D printer vs. Buying one

Nozzel size and build quality have some effect but the fundamental characteristics of the equipment will set the bottom level possible. Step angle (.9 vs 1.8, etc) and microstepping capability in the controllers will define the finest detail threshold and tuning can only close onthat ideal threshold.

Kirk

I do agree with you Kalani that step angle and microstepping along with the other equipment used will define the highest possible resolution you can get.  I have had numerous people come to me saying, “I have a printer that should be giving me higher resolution prints but it’s not, why is that.”  Almost all the time it’s that they have problems with the extruder setup and the print height isn’t to where it should be.  That’s why I would say in the end, the print height along with your extruder setup ultimately defines the resolution you achieve.

Nate

Thank you both for the information, I'm sure it will come in handy when I build my own 3D printer. Do any of you know how large of a print area I can build with the printer controller I want to use? I'm sure that the controller can only handle a certain sized motor and the size of that motor will limit how big I can make my print area. Im just not sure how big of a motor I can use without burning out the controller. The 20'' by 20'' I mentioned in the first post would be nice but could I go with say 48'' by 48'' or larger? Possibly a 4' by 8' print area? I am not sure that I will be needing anything that large but I would like to build it as big as I can.

The particular controller's firmware might have a maximum step value based on the precision of its variable definition, but otherwise you will not overload the motors by size of the printer's build space alone. A stepper motor tracking the X or Y translation of the print head's position will step the cable/tooth belt/brainded line/etc for 10 steps as well as 10,000 until the weight of the entire structure starts to near the failure loading of the motor. Z axis load can become problematic with a larger build volume and item weight depending on the design (if the Z axis has to lift/drop the build plate as in Morgan RepRaps or Makerbot Replicators, then the object's weight will limit the maximum capacity of the Z-axis motors, etc) but if you use a fixed bed and lift only the extruder, then build scale should not affect your maximum size - the rigidity of your structure will constrain that more fully. If the span of your gantry is too long, the transition of the extruder can cause it to bend slightly at the middle, sagging due to the weight. When your print layers are only .1mm, that sag can shift across multiple layers of the extrusion.

Really large RepRaps have been built (http://www.grassrootsengineering.com/blog/mymachine) but you can see that the structural framework had to be increased to support the increased span, which then requires larger motors, higher-amperage motor controllers, and a larger power source since it's all tied together. Some of concrete 3D printers being developed to print hourses are several yards aross each axis, with the increased framework accordingly. The control circuitry can be the same as for smaller builds, as long as the rest is increased in power and capacity to match, or can be entirely custom designed from articulated robotic arms and other mechanisms for accessing the entire build volume desired. The MendelMax uses an extruded aluminum 80/20 framework, so can resist flex along a longer span than the earlier threaded-rod construction of the original Mendel, but if you used wooden beams instead of aluminum, you would just need to adjust for the greater mass in movement and inertia during fabrication.

Kirk

The particular controller's firmware might have a maximum step value based on the precision of its variable definition, but otherwise you will not overload the motors by size of the printer's build space alone. A stepper motor tracking the X or Y translation of the print head's position will step the cable/tooth belt/brainded line/etc for 10 steps as well as 10,000 until the weight of the entire structure starts to near the failure loading of the motor. Z axis load can become problematic with a larger build volume and item weight depending on the design (if the Z axis has to lift/drop the build plate as in Morgan RepRaps or Makerbot Replicators, then the object's weight will limit the maximum capacity of the Z-axis motors, etc) but if you use a fixed bed and lift only the extruder, then build scale should not affect your maximum size - the rigidity of your structure will constrain that more fully. If the span of your gantry is too long, the transition of the extruder can cause it to bend slightly at the middle, sagging due to the weight. When your print layers are only .1mm, that sag can shift across multiple layers of the extrusion.

Really large RepRaps have been built (http://www.grassrootsengineering.com/blog/mymachine) but you can see that the structural framework had to be increased to support the increased span, which then requires larger motors, higher-amperage motor controllers, and a larger power source since it's all tied together. Some of concrete 3D printers being developed to print hourses are several yards aross each axis, with the increased framework accordingly. The control circuitry can be the same as for smaller builds, as long as the rest is increased in power and capacity to match, or can be entirely custom designed from articulated robotic arms and other mechanisms for accessing the entire build volume desired. The MendelMax uses an extruded aluminum 80/20 framework, so can resist flex along a longer span than the earlier threaded-rod construction of the original Mendel, but if you used wooden beams instead of aluminum, you would just need to adjust for the greater mass in movement and inertia during fabrication.

Kirk

Kalani hit it right on the head.  Having a print area of 4'x8' will have some problems you will have to overcome.  One will be the print time.  Printing even a 4'x4' object would take days.  Increasing the print speed will help  but  inversely effects print resolution.  You will also have to deal with warping and bed leveling issues.  I'm not saying it can't be done but make sure you are aware of these.

Nate

I figured that it would be much harder to build something on that scal, and I will probably not build somehting like this. I was more so seeing how larg I could thereticly go.  I will most likely build one with a print size of around 24'' by 24'' by (not sure yet).  But thank you both for the information. Very helpful.