Extruder pushing down on print

Hi, I started with ABS, I got the prints to stick but a few mm into the print it looked like the extruder was pushing down onto the print. I spoke with Jeff/Tesseract (very helpful) and switched to PLA.

I modelled a 5mm square as the first print. With a cold bed it would not stick, even with hairspray, but it sticks well with a heated bed (I set it to 70* for the first layer and 0* thereafter). The print started find but I noticed as it builds the extruder seems to go up, then adjust down onto the layer. I thought maybe I was imagining it or the piece was too soft and couldn't withstand the pressure of the extruded PLA, but then right at the end of the print the extruder moved down 2 or 3 mm and squished the print (which wasn't looking too great to begin with). It was doing the same thing with ABS, which is supposed to cool faster, so I'm not blaming the heat of the print.

The following pictures show what I ended up with. Keep in mind this is a solid 5mm square. The first is it on the bed, the second shows the bottom.

So far all the prints I've attempted have resulted in the same thing, they start out fine, then look as though the extruder is pushing down on them or adjusting too low and swiping across the top few layers spreading the whole print wider.

Any suggestions?

 

I'm having the same issue.

 

For ABS, you can't print with a cold bed as ABS is well known for warping. So, you should heat the bed up to 100°C and extruder temp should be around 220°C. Even with this you might be forced to use raft or brim to make it stick better on edges and prevent warping.

 

I was heating the bed with ABS, but switched to PLA.

 

are you using the Robo settings? your own custom settings? the settings Jeff or someone else on the forum gave you?

 

Jerry, thanks, makes sense that the small print would not give the PLA time to harden, that is pretty much what it looks like. Can I slow down the print if I'm wanting to do just one or two small items?

However there is still the second problem of the extruder pushing down on the print at the end. It just lowered on the z axis and moved away instead of lifting and moving away.

I will print a number of them as you suggest and report back here.

 

Thanks Jerry.

I noticed something else, I was printing a couple of small items that Jeff/Tesseract sent me and instead of printing a layer on each and going back and forth, it printed the first four or five layers of the first item (where I stopped the print), which seemed odd. Anyone know any reason for that?

 

I've checked the gcode, mainly looking for at the z axis. I noticed that it's lifting it to 2.30mm and then lowering it to .30mm, which seems about right. However there's a bazillion lines and it doesn't seem to show when the job was stopped, which would help in identifying when the problem occured.

Any advice on what to look for?

Thanks.