I had the exact same issues when I got my printer. The issues causing this were:
1) The right print head was plugged badly when it came from the “factory”. A soldering iron and “E” guitar string, or piano wire (0.04mm) work great to clean them up… make sure you use a vise or pliars, they get hot.
2) The PTFE 2mmx3mm tubes in the hotend were missing, causing the filament to melt into a 3.5mm glob, completely filling the feed tube.
3) The plastic extruder assembly was over-tightened to the stepper motor, and full of brown goo. Carefully disassemble it, and clean the inside. The 2 halves are pressure fit together, rotate them slightly until the small plastic “peg” on the top comes out. Take pictures, so you can put it back together in the proper orientation.
Also, after you have had the hotend apart, add a drop of vegetable oil on the filament when loading it; it works down to the ptfe tube, and helps prevent jams.
CTC is selling these printers as new, but they are clearly returns with several hundred hours on them.
The non-adjustable plastic extruder will wear down quickly, and stop being able to grip any filament. I would recommend investing in a metal spring-loaded one.
Other issues I have encountered with this printer:
With both extruders, the carriage is too heavy to print with any reasonable speed (80mm/s) without excessive (3mm+) backlash. Personally, I removed the left head and wires, and print at 50mm/s… that yields nearly perfect prints. The attached picture is an RPI case printing in ABS; which proves that this printer is capable of decent prints, with a bit of love.
No feed system, causes the filament to jump off of the spool and get bound up… In a pinch, 5" of 2mm x 4mm PTFT and 2 cable ties on the back of the printer will solve this. (it keeps the moving print head from feeding filament back down past the edges of the spool.
The 6.5mm holes in the wood (Chinese bearings?) for the 5mm Z axis rods had way too much play in them; printed 4 new ones with a 4.9mm hole, and pressed the rods into them while they were hot. (You have to remove the chinese mightyboard to replace the bottom right one)
Half of the screws/nuts/washers were missing, quarter of them were loose in the box, and the other quarter were loose.
If you print ABS, Kapton tape and hair spray work great… and personally, I have been using automotive high-temp grease on the axis rods with great success. DO NOT get hair spray on the Y axis rods.
The 5mm Y axis rods (the ones in the top front and back corners) flex considerably. At 80mm/s, they flex 12mm in the center… consider printing 4 pillowblocks and putting a 5x11x4mm bearing on each corner.
V/r,
Mike
