Print Quality Issues

Finally got my printer up and running, not quite getting the quality of print I would like.

I am running Marlin and Pronterface software. The program I have been trying to test run is the 20cube_export file that is included with Marlin. The machine has a 90W 240V heated nozzle with a 0.5 orifice and is running 3mm ABS. Heated bed with 4x 400W 240V elements.

The nozzle dribbles a lot when not printing, even when the filament is reversed from the nozzle.

I was having thermistor issues originally as I didn't realise the 100k thermistors I was using were only rated to 125degC and I was destroying them. I'm now using an EPCOS B57560G104F thermistor but to get the nozzle close to 230degC I have to tell the software to reach 285degC. I have double checked the actual temperature of the nozzle using an engine exhaust thermocouple I have and with a digital laser temperature gauge. At room temperature the EPCOS thermistor appears to be giving a correct temperature but gets exponentially further from the actual teperature as the nozzle temperature rises. Is there a simple rate modification value to change in the firmware like there is for the axes stepper values?


I've attached a picture of the print as it first turned out. I'm not too sure what to change from here, any help is much appreciated.

I think the plastic is extruding too fast as halfway through the print the nozzle starts hitting the printed part.

I'm going to buy a roll of kapton tape today as the parts start sliding on the bed as the weight of the printed part builds up.





Edited 1 time(s). Last edit at 01/06/2013 06:28PM by Nigel_NZ.

I am not to familiar with the thermister settings in the firmware but I would recommend you start a print and lower your temp about 5 or 10 degrees every couple of layers until you get to a point that it appears it can not extrude properly, you will see dots instead of a line. When that happens, start raising the temp 5 or 10 degrees at a time until you are extruding well. Whatever the degrees C comes up, will be your magic number for that filament. I had issues with the same sort of thing on pla and i was increasing the temp when i first started printing to try to get a good print. The issue I had was actually that I needed to change my e steps to extrude less. I am not saying you have that issue but I would start my finding your magic number and see if that helps with your temp. Different manufactures/colors/ ...... can very quite a bit on temp settings. some filaments melt cooler than others. Good luck and let us know when you figure it out. P.S. i was running my PLA at 210 to try to get good prints and i ended up at 188 for my magic number on the same filament.

John

Nigel,

In the firmware did make sure to select the proper thermestor value first? If so the next step you can do is called PID tuning. This is really simple. First go into your firmware and right under the section where you select your thermister there should be a section on PID. Make sure that "#define PIDTEMP" is not commented out, upload to printer and you are set to PID tune.

Next you will want go into your host software and send M303 commend to the printer. This will start the PID tuning sequence by heating up your hot end to around 150 (I believe) then cycle it for 6-8 times. There will be a message in the communications box indicating that the test is complete and give you values for kp, ki, and kd. Take these values back into your firmware (make sure to uncomment one of the hot end profiles you wish to use), and enter in the three values. Try a temp comparison again and see how well it works.