Building a 3D printer vs. Buying one

Hey Kristopher

The printrboard will work with a larger printer as long as you scale up the x,y,z values to match your print area.  Below is shown in the marlin firmware.

#define X_MAX_POS 130
#define X_MIN_POS 0
#define Y_MAX_POS 130
#define Y_MIN_POS 0
#define Z_MAX_POS 107
#define Z_MIN_POS 0

If your looking to print at the scale your talking about then i would recommend you use the mendelmax type design.  This design uses extruded alumninum tubing helping with the rigidity problems associated with others.

Nate

I figured that all I had to do is change a couple peramiters but now I know for sure, thank you.  I have decided to buy the printrbot simple so that I can get a few ideas about how everything works together and if I have any problems with the one I want to build I can look to that to help me out.  Also I will check out the mendelmax design as you said and hopefully I can get a few more ideas on how I want to build mine.

Do you by chance know what the typical resolution of a home made 3D printer is? I want to achieve the .1mm that most of the 3D printers have. I assume that it is just a matter of build quality and how much "slop" you have in your movements.

It would be hard to put a number to the typical resolution but, if setup right, should have no problem reaching the .1mm resolution.  The build quality does have some effect on resolution along with print speed, was the machine calibrated, nozzle size but most of it is from the extruder and print height used.

Nate

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

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.

It all depends on the acuracy and quality of the printed object. Have a look at the video http://uk.news.yahoo.com/video/african-inventor-makes-3d-printer-094104530.html at a printer built out of scaps.