First Layer Issues

After receiving our printer, the first few days were great. Almost no problems and prints were working pretty well. But after a few days, I started having several issues. Specifically, the outer loops and the first layers failed to stick, the extrusion didn't start immediately, and soon the extruder started dragging the print around and globbing around the hot end.
I am using the Slic3r settings recommended for PLA in the setup video settings, although tweaking the first layer parameters made little or no difference. The bed has been leveled and the extruder head is within .3mm of the bed at Z home.
Attached is a video of the start of the 5mm calibration cube print. It is clear the problems I'm having. Can anyone recommend a fix, or tell me what has gone wrong?
Thanks in advance.

 

In case it wasn't clear on my message above, The material is PLA, the bed temp is set to the recommended 0, the extruder temp is 200 for the first few layers and 190 thereafter. The bed is lined with 3M blue painter's tape.

 

Thanks, Tesseract. I have signed up for Skype and will contact you later this afternoon - after 2 PM your time.

 

Three big cheers to Tesseract for help with this issue!! After spending a couple hours trying to settle the printer down and get the bed leveled, he was finally able to educate me enough on the procedure for leveling the bed and adjusting the Z limit switch. Today, armed with that knowledge, I was able to make a few minor adjustments and get the printer to lay down a good (nay, perfect) track of PLA. It is now printing flawlessly.

Many thanks, again.

 

It had been working well, after my post above .... until yesterday. The problem now is that after 6 or 7 layers, the extruder starts dragging into the print. After I abort the print, I check the Z height and find that it has dropped.
When I start, the bed is level and the Z home height is perfect, but after I abort, the extruder is hard down on the bed.
The Z limit switch is oriented correctly and seems down firmly on the support tube.
I simply cannot see what is changing.
Anyone?

 

Lew, are you sure the Z axis nuts that the X carriage sits upon are fully within their enclosures? You should not be able to see them at all and when you press down on the left and right side right next to the threaded rods, you should not be able to cause the X carriage to move down.

 

There is ever so slight movement in the Z axis. However, the motion seems to be in the expansion and contraction of the couplings between the motors and the threaded rods. The nuts seem full home with no lost motion there.

 

I experience the same thing. I have a dial indicator set up that lays on the two rods for the x axis and when i get everything level and height set to .003" i zero the dial indicator. after a print the dial indicator does not come back to 0. i then have to level and reset the z switch. very frustating!

 

I noticed that the screw for my Z-level switch was very loose and had lots of thread play.
So I added a hex nut to the top and bottom of the screw.
When I got my Z-height set I just lock down the nuts and no more movement.
It's an extra pain to readjust, but I rarely have to now.

 

The Z-level switch on mine is plenty snug. But the problem seems to start when the Z axis is at around 1/2" high. It's like the Z axis slips (doesn't go higher) so it starts bumping in to the previous layers. Then when the home position is sought, the extruder is now too low. When I readjust things again, it starts all over on the next print.

 

OK, I have spent several days troubleshooting and solving problems.
The slipping Z-axis seems to have been solved by loosening one of the threaded rods from the coupler and removing a bunch of teflon tape which had not been put down into the coupler at all well. I replaced with new teflon tape and tightened the screws on the coupler.
I have also spent hours getting the bed leveled and printing with a perfect looking skirt. However, there is still a considerable difference in the extruder clearance across various parts of the bed. If the center is correct, a couple of the corners are too high (but not such that can be solved by adjusting the Z-axis threaded rods) so the extruder drags across the bed at those points.
My last (current) problem is that while printing in PLA, there is significant "stringing" whenever the extruder makes corners or lifts. I am assuming this has to do with extruder temperature. Sometimes it is so bad that the extruder bumps into those strings and actually knocks the print loose of the bed.
I'll continue to test various temperatures, but I'm open to any other suggestions.

 

Here is a great video showing what problems you are experiencing:

The following video shows what happens with no heat bed and no adhesive added to the glass. It depicts what can typically happen when printing on a non-sticky platform with no heat bed – Disaster!


Original source has a lot of vital information to getting a good print:
http://bootsindustries.com/portfolio-item/heat-bed-3d-printing/

 

Good information, Peter. But I'm still having stringing issues. I lowered the extruder temp to 190/185 (first/subsequent layers) and still seeing oozing and stringing. I didn't see anything on your recommended web site that addresses that issue, other than temps.