Common print faults
Copied from Tony's blogpost at http://rapmanv3.blogspot.com/2009/05/print-problems.html and edited and expanded"
Potential print problems
The filament looks like it is wiry with strands that pop up from the raft, inter layer adhesion is poor or non-existent.
This is harder to diagnose, you might find you can build the object completely especially if the object is small. Generally speaking the characteristic of to high temperature is the layers melt into one another too much, fine detail in the shape is hard to maintain and the object is likely to exhibit more warping. The easiest way to diagnose this is to print a test object that has a fine stem, like the wine glass.
Print speed greater then Extrusion rate
This pulls the filament thinner, if you intend to run like this you must make allowance for it in Skienforge, set the layer thickness to a lower value in direct proportion.
Print speed less than Extrusion rate
This is used to good effect on the base layer of the raft, more material is pumped out thickening the filament. As above if you wish to maintain dimensional accuracy in the main body of the print you must make allowance for it in Skienforge, set the layer thickness to a higher value in direct proportion.
Running 16mm/s at 40rpm with ABS is good for small objects but starts to cause problems the larger the object gets. By the time any dimension is > 50mm warping is a significant effect. I have done some experimentation recently and found warping can be reduced if the print speed is reduced. Try 8mm/sec at 20rpm, this has produced objects > 100mm long with minimal warping, the obvious down side is the build time is doubled. Another option is to warm the print table or blow hot air round the print, both methods have been used to good effect.
Is the mug round or very slightly oval? You may need to run a large circular object to be sure of this. If there is any ovality it should be aligned with either the X or Y axis. Take the small diameter and note the axis that is running undersized. Check the belt on that axis is tight enough.
The photo shows good prints top and bottom, left and right are slightly oval.
Material Feed fault
This otherwise good print was spoilt by the material feed, the plastic reel was too stiff on its axle, the extra drag was too much for the extruder and it slipped a few times during build. The drum was remounted on bearings and the next print was fine.
If the threaded rods used on the Z axis are bent slightly it makes the table wobble as it moves up and down. The question is "what is the tolerance for the bend?" is 0.5mm OK and 2mm too much. The answer is the bend is too much when the resulting print quality bothers you.
Look at the head print very closely and you can make out a repeating horizontal pattern, very regular and repeating all the way up the print every few layers. The cause of this pattern is due to a slight bend in the threaded rods, if measured you will find that the vertical pitch of the lines matches the pitch of the thread. The head print is a very mild case and its probably not worth stripping to fix, but the photo is so good and enlarged, it shows the effect.
Look for this pattern on your prints, if its bad enough to do something about, straighten the rods.
Have a good look at the finished object. The minimug is quite strong, it should be very hard to break it. If it does fracture along the layers then try a slightly higher temperature.
Are the sides of the mug good quality, with no hanging filaments on the outside, it may have slight imperfections due to Z moves. Inside will have a few hairs, this is normal.
The minimug is a good starting point, but it will not allow the fine tuning required to run off some of the more demanding objects, so for now, try a series of minimugs, play with the settings and observe the results, you will soon start to get a feel for the machine and how the material behaves.
Continue until you can reliably produce a good mug.
Changes on the fly
With firmware 1.0.5 (unreleased) it is possible to change the extrusion rpm and the set temperature during a print run. You can use the four axis buttons (+X-X+Y-Y) to increase or decrease the settings as required.
X RPM Adjust the extruder RPM Y Temperature Adjust the heater temperature
Once you start printing you can use the buttons to do any fine adjustment and immediately observe the result in the print. This is also a real help when testing new materials, it can save much card swapping. When you see the result you want, make a note of the settings and edit the G_Code file to suit.
Play with the feature and learn what changes can be made to the print quality. Take care when you run down to the lower temperatures for the material.