PLA printing

Hi. I have been succesfully printing my first objects and I started to wonder what might be the best settings for pla printing. My machine is mendel90 from Think3DPrint3D and printng surface is glass.

For heatbed all layers I have been using are 80 degrees. About hotend 175 degrees for first layer and 170 for others. Results have been very promising for my first prints. And I have a cooler for hotend.

Now here I have plenty of questions about pla printing and reasons for that.

I guess the easiest is why cooler is neccessarry? Also what part of hotend cooler should cool?

I am intrested to know should I try to print even lower temperatures on hotend? I have been reading plenty of manuals and all of them recommend of using more high temperatures on heatbed and hotend. However is that right or just beginers tip?

What I have noticed is if I lower heatbed temperature to 75 degrees pla simply don't stick at all. Would it be better for quality of print if I lower bed temperature and increase hotends?

Also what is the reason for having higher temperatures for first layers? Is that neccessarry? Should I decrease or increase temperatures on bed and hotend?

PLA is generally extruded at 185C but it does vary and even the colour of the filament can make a difference. However, 185C is a good ballpark figure. You shouldn't really need 80C for the heatbed, 60C is a pretty good number.
The cooling fan is not meant to cool the hotend but rather the part you are printing - small parts in PLA are prone to distortion from heat without it.
If you are having trouble getting your prints to stick make sure your glass is spotlessly clean, your nozzle gap is 0.1mm max all over (a piece of copy paper should drag lightly under the nozzzle in the homed position) and set the bed to 60C. The hot-end should be fine at 185C throughout the print.

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Waitaki 3D Printer

What are the negative sides of overheated heatbed?

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What are the negative sides of overheated heatbed?

For PLA, if you exceed 65c...
Your first layer will actually blister and create areas in your first layer that are no longer stuck to the bed. Next layer (2nd layer) will scrape the blistering and can actually dislodge your print from the bed.

Typically 55c - 60c is perfect.

One other note about PLA. Many j-head users use a small fan pointed at the body of the hot end when printing PLA. This does not need to be a large fan. Its duty is not so much to cool as it is to break up convection rising from the hot end. Not everybody needs this, but people have reported frequent jams with PLA without it