Z axis problem and filiment problems

For starters I have no experience in the following, electronics, 3d printers or programming. I'm leaning as I go. First things first, I preheat my bed and extruder before I do a job, I then home it. Once it a couple of degrees away from running temp, I run the job, it re-homes amd goes to print, but the z axis makes a grinding noise for 2 seconds then doesn't move. 2 to 5 minutes later it makes 2 seconds of more grinding noise and goes and prints. Why is it "jamming" up?

For the second thing, I printed a piece today with generally no problem other than adhesion and the jamming. When I go to to a second print I have very little filiment coming out of the extruder. Could this be caused by the motor feeding the filiment is overheating? Any ideas?

I'm using an melzi ardentissimo board with marlin and repitier host with slicer. Nema 17 for motors.

Keep the explanations in layman's terms, I can't brain today, I has the dumb.

First, make sure the Z asix moves well all the way from end to end with the printer powerd off.

Second, looking at the Melzi rep rap page it looks like there are pots for tuning the current to the motors. Check out this section from the RAMPS page about V-Ref. The same should apply. Me, I had to go a litter lower than recommend amount. Too little current and the motors miss steps, too much current and they run hot and perform improperly.

Quote
Dreadnaught426
For starters I have no experience in the following, electronics, 3d printers or programming. I'm leaning as I go. First things first, I preheat my bed and extruder before I do a job, I then home it. Once it a couple of degrees away from running temp, I run the job, it re-homes amd goes to print, but the z axis makes a grinding noise for 2 seconds then doesn't move. 2 to 5 minutes later it makes 2 seconds of more grinding noise and goes and prints. Why is it "jamming" up?

For the second thing, I printed a piece today with generally no problem other than adhesion and the jamming. When I go to to a second print I have very little filiment coming out of the extruder. Could this be caused by the motor feeding the filiment is overheating? Any ideas?

I'm using an melzi ardentissimo board with marlin and repitier host with slicer. Nema 17 for motors.

Keep the explanations in layman's terms, I can't brain today, I has the dumb.

Z axis moves freely while powered down. Z controls up down movement with two motors. They dont bind or fight each other, I did have to reverse them because repetier moved them in the opposite direction. I have no problems moving them with repitier, only when I go to run the job.

Mine worked fne in manual too. your z end stop works?

Yup, not a single problem with any of in in manual. Just when go to print.