how can I fix my 3d printer's printing problems?  <Morris County, NJ>

The first thing I ask when someone asks this question is "Did you calibrate your machine?".  Make sure the bed is level, extruder extruding the right amount of material,  Hotend is keeping a constant temp or even getting to correct temp.  Now if this is all set up then I would ask what filament are you using, where did you get if from and at what temp are you extruding it at.  Majority of the time if a printer is not printing correctly its that it was not truly calibrated or they are printing at to high of speeds.

Nate

First thing; yes the printer is calibrated, the bed is leveled, I was printing ABS at 225 and the bed is set to 80.

As for the filament, I do not recall where I bought it from, I do think it came from ebay (from Kbell Engineering in Hazelwood, MO). It starts printing good, about a 1/4" in z direction it starts getting spotty.

I'm going to take a wild guess here. If the failures only start to occur as your print gets taller, perhaps your nozzle is raising a fraction more per layer than it should, and after 1/4" there's too much air between the nozzle and the next layer, creating spotty results. My reasoning, if the plastic is sticking to the nozzle only after it gets about 1/4" high, then it's probably because the plastic isn't sticking to the lower layer. It might not be sticking to the lower layer because it's raising too high per layer.

Try this, use your software to raise the Z axis. Start homed in to the bed, tell the software to raise it 50mm, and then measure the height from the bed. If it's higher than 50mm, there's your problem.

No, it is correct in every axis, I homed it, then I zeroed my caliper and told it to go 50 mm in Y, X & Z and I measured each one and homed it each time. they all moved exactly the correct distance.... i am beginning to think that the board might be either broken and I can't see it or fried something....either way I'm considering trying to buy a smaller printer just to be able to make replacement parts, then rebuild it and get a new board. then see if that works.  Thank you for all the help

Not being able to see it directly it would be hard to determine exactly what's wrong but can give you some ideas of the likely cause.  I would say the likely hood that your board is bad is slim as you stated that smaller object print fine.  If you say that the machine is calibrated then I would go to say that it is your extruder/hotend  to blame.  It can either be getting plugged with dust that's on the filament or its melting to soon in the hotend causing the extruder start to slip on the filament.  If you could maybe post some more details or a video I could help you get this resolved.

Nate

Not being able to see it directly it would be hard to determine exactly what's wrong but can give you some ideas of the likely cause.  I would say the likely hood that your board is bad is slim as you stated that smaller object print fine.  If you say that the machine is calibrated then I would go to say that it is your extruder/hotend  to blame.  It can either be getting plugged with dust that's on the filament or its melting to soon in the hotend causing the extruder start to slip on the filament.  If you could maybe post some more details or a video I could help you get this resolved.

Nate