Bottom of prints melting

I attempted to print emmetts gear bearing [www.thingiverse.com] and the bottom of the print is fused together.

I printed this in PLA with the bed temp set to 60c and I am printing on glass.

I have also noticed on other things it seems like the bottom of the print gets mushroomed out on the sides like it's melting.

What suggestions does anyone have to help with this? I was getting prints not sticking when I tried with the bed heater off. I am afraid if I turn off the bed heater after the print starts it will come loose. Would a raft help?

I am going to experiment more but if anyone can suggest something it would be great.

Edited 1 time(s). Last edit at 07/09/2015 11:29PM by msaeger.

A photo showing the problem would help. If the bottom of the print really is melting, then it sounds to me that your firmware may not be correctly configured for the bed thermistor you are using, so that the bed temperature is higher than reported. So I suggest you check the temperature calibration.

If you are sure you have the correct thermistor configuration, then try reducing the bed temperature by 10C. Most slicers also allow you to set a lower temperature after the first layer. 60C is above the glass transition temperature of PLA, however if you are printing on glass then the temperature on the glass surface will be at least 5C lower than the indicated temperature.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I do have to wonder why you would use the heated bed to print PLA....

Quote
Downunder35m
I do have to wonder why you would use the heated bed to print PLA....

When I had it off the prints wouldn't stick and I read to turn it on. That's why I am asking should I have it on or should I be doing something else?

Here's the bottom of the print.

[goo.gl]

So after trying to free it up with an xacto it cut the outer gear ring. I was able to pop free the inner gears with a pliers. Then I found with all five inner gears in there I am unable to get the cut in the outer gear to line up. I am going to try it again with the tolerance set higher to try and get some bigger gaps between the gears.

Printing PLA on a cold bed is possible using certain print surfaces such as painters tape, but if you have a heated bed it is better to use it. When the bed cools, the print usually comes off easily.

Having now seen the photo, I still think the bed temperature is too high, probably a higher than the 60C that you set.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Trying to print it again this time I set the tolerance higher and only did 4 planets. I set the bed temp to 50c vs 60c when I check it with the IR thermometer it reads about 45c but who knows how accurate that is.

I tried with the bed at 50 and the print came loose about 1/3 way through. Then I tried 60 and lowered it to 50 after the first few layers and it came loose again.

I am trying something else now that won't matter if the bottom melts :-)

I run PLA at 60 for the first, 55 subsequent and have zero deformation. Any chance that either your Z calibration or first layer extrusion os wrong? Over extrusion or too low will mushroom the first layer as well.

- Tim

60/55 is what I do as well for PLA. As tadawson has suggested, it might be your first layer extrusion, or perhaps you are a bit too low on the Z axis. Some degree of smashing the first layer is desired - to help with adhesion - but not to the point of deformation.

I think you guys are right about it being something with the Z height. I moved the bed up a little with the levelers and it seems to have fixed the issue. On the things I have tried anyway. Haven't tried the gear bearing again yet.

I also measured the filament diameter and put that in. It measured 1.72 and I had 1.75 in there.

Edited 1 time(s). Last edit at 07/12/2015 03:06PM by msaeger.