Printing with PLA

Rick Pollack

<img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/PLA_nozzle_assembly.jpg?1263854867' alt='' /> I recently posted this photo in the MakerBot Google Group <a href="http://groups.google.com/group/makerbot/browse_thread/thread/a29a9bf3fdb486a9">discussion</a> about PLA. I created this funky nozzle to demonstrate how to print with PLA and how to lower the print temperatures (from the temps being reported by most MakerBotters currently printing with PLA.) When I was trying to get PLA type 4042D working I found experimentally that in order to get it to extrude continuously using a standard MakerBot style extruder, the temperature at the top of the heater barrel needed to be at least 150C. 150C also happens to be the melting point of 4042D. (I didn’t realize at the time the melting temp for 4042D was 150C as I’d misread the spec sheet and thought the melting temp was 130C.) If the temp at the top of the barrel drops below 150C (even by a few degrees) the filament will eventually stall or if I pause the motor a hard PLA plug forms at the barrel entrance and the filament strips when restarting the motor. Since gooey (not fully melted) PLA is very sticky and hard to push, the goal is to get it melted in a quick and orderly fashion. 4042D melts at 150C and 4032D melts at 160C. So, if a 150C barrel entry temp works for 4042D then I’d speculate that 160C will work for 4032D. So, before doing anything crazy, just try placing a thermistor at the top of your heater barrel. You can mount one using a ring terminal connector. (We’ve just started adding high-temp ring terminal connectors to the Operators Packs and Ceramic Heater Kits). <img width="500px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/terminal_connectors.jpg?1263854867' alt='' /> The photo contains a ring terminal connector demonstrating the placement of the thermistor (of course, the thermistor needs to be mounted so that the leads don’t short). A fork terminal connector is also shown. So, why am I able to print at lower temperatures with this design? Because I’m measuring the temperature at the top of the barrel rather than at the end of the nozzle! The thermistor is mounted on a ring terminal connector located between the M8 nut and the the upper piece of PTFE. The reason botters are reporting higher temps is that they are measuring the temp at the end of the nozzle. In other words, you need to measure 220C near the tip of your nozzle to get 150C at the entrance to the barrel. Kind of like driving a car using a rear-view mirror?!? (FYI – the M8 nut has a small brass insert and that is how it fits on an M6 barrel.) It is not necessary to use a nozzle assembly like the one at the top of the page. I just like to try out different designs and see what I can learn…there is no need to try this unless you just want to tinker as well. Though I will say that after having built dozens of nozzle assemblies with the nichrome wrapped directly on the barrel, I’m now a huge fan of our ceramic coated heater cores!!! <img width="500px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/ring_terminal_mounted.jpg?1263874979' alt='' /> Getting PLA or even ABS into the insulator threads does not matter unless it is causing a problem. For the most part it is just one of those things. I’ve found that the larger nozzles (more metal) do a better job extruding (especially when working with smaller diameter openings). The design I use here puts plenty of metal at the key points (barrel entry and nozzle) but since there is only one thermistor, only one of the points is actively regulated and I chose to focus on barrel entry. The unregulated nozzle ends up at about ~190C and works great. Here is an approach using standard MakerBot equipment that I know works for 4042D at 220C and, at least, I was able to print a 608 pulley using 4032D at 235C (4032D just came out so testing is quite limited so far): <img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/full_assembly.jpg?1264697430' alt='' /> **Important Note: The nozzle assembly explained here is for a standard MakerBot style plastruder (like in this photo) and is unrelated to the photo at the top of the page. 1) Put your nozzle on nice and tight with barrel in either direction – I prefer to mount the smooth side in the nozzle. <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/tighten_nozzle.jpg?1264725662' alt='' /> 2) Wrap your nichrome in one nice and tight layer starting at the nozzle and going up while staying in the grooves – you are looking for good contact. You don’t need to double back, one layer will get plenty of heat to the nozzle. Getting the nichrome wrapped correctly is the most important step. I use a straight 250mm length. I only measure the ohms to be sure nothing wacky (like a short) is happening – and it probably won’t be 6 ohms…maybe a little more, maybe less. Wrap it nice and tight with a couple of layers of Kapton tape. <img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/single_wrap.jpg?1264005396' alt='' /> <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/kapton_wrapped.jpg?1264725012' alt='' /> 3) Place your thermistor within a couple mm of the end of the hex surface (towards the tip). And, UPDATE your thermistor table to match your thermistor – this is the second most important step. For the 1mm table I’ve been using the Zach 1 table (see below). <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/thermistor_attached.jpg?1264725455' alt='' /> 4) Put your washer and M6 nut on, I use a full size M6 nut. Also, the washer can act as a heat sink which you really don’t want it to do here so try to keep it from direct contact with the M6 barrel. It will still get hot but the less heat it conducts, the better. <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/hex_probe.jpg?1264724989' alt='' /> 5) Screw your PTFE on so that is just tight with the brass. I use a small hex wrench to probe the junction between brass and PTFE – a very small gap is not a problem as long as the barrel is at the right temp. You should be able to smoothly push filament through. A slight lip at the junction is also not a problem as long as your temp is right. 6) Place your ceramic insulation around the nozzle and nichrome and slowly heat it up. Good luck! and let me know how it goes… <hr /> Zach 1 table: //generated with T0:25 and T:220 // Thermistor lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts) // Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py) // ./createTemperatureLookup.py —r0=100000 —t0=25 —r1=0 —r2=4700 —beta=4198 —max-adc=1023 // r0: 100000 // t0: 25 // r1: 0 // r2: 4700 // beta: 4198 // max adc: 1023 #define NUMTEMPS 20 short temptable[NUMTEMPS]<a href="#fn2">2</a> = { {1, 752}, {54, 242}, {107, 199}, {160, 176}, {213, 160}, {266, 147}, {319, 137}, {372, 128}, {425, 119}, {478, 112}, {531, 105}, {584, 98}, {637, 91}, {690, 84}, {743, 76}, {796, 68}, {849, 59}, {902, 49}, {955, 34}, {1008, 3} };

2010-01-18T17:45:47-05:00

printing-with-pla 3756192

2010-01-18T23:58:37-05:00

307372

Printing with PLA 2010-01-30T00:34:53-05:00 <img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/PLA_nozzle_assembly.jpg?1263854867' alt='' /> I recently posted this photo in the MakerBot Google Group "discussion":http://groups.google.com/group/makerbot/browse_thread/thread/a29a9bf3fdb486a9 about PLA. I created this funky nozzle to demonstrate how to print with PLA and how to lower the print temperatures (from the temps being reported by most MakerBotters currently printing with PLA.) When I was trying to get PLA type 4042D working I found experimentally that in order to get it to extrude continuously using a standard MakerBot style extruder, the temperature at the top of the heater barrel needed to be at least 150C. 150C also happens to be the melting point of 4042D. (I didn't realize at the time the melting temp for 4042D was 150C as I'd misread the spec sheet and thought the melting temp was 130C.) If the temp at the top of the barrel drops below 150C (even by a few degrees) the filament will eventually stall or if I pause the motor a hard PLA plug forms at the barrel entrance and the filament strips when restarting the motor. Since gooey (not fully melted) PLA is very sticky and hard to push, the goal is to get it melted in a quick and orderly fashion. 4042D melts at 150C and 4032D melts at 160C. So, if a 150C barrel entry temp works for 4042D then I'd speculate that 160C will work for 4032D. So, before doing anything crazy, just try placing a thermistor at the top of your heater barrel. You can mount one using a ring terminal connector. (We've just started adding high-temp ring terminal connectors to the Operators Packs and Ceramic Heater Kits). <img width="500px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/terminal_connectors.jpg?1263854867' alt='' /> The photo contains a ring terminal connector demonstrating the placement of the thermistor (of course, the thermistor needs to be mounted so that the leads don't short). A fork terminal connector is also shown. So, why am I able to print at lower temperatures with this design? Because I'm measuring the temperature at the top of the barrel rather than at the end of the nozzle! The thermistor is mounted on a ring terminal connector located between the M8 nut and the the upper piece of PTFE. The reason botters are reporting higher temps is that they are measuring the temp at the end of the nozzle. In other words, you need to measure 220C near the tip of your nozzle to get 150C at the entrance to the barrel. Kind of like driving a car using a rear-view mirror?!? (FYI - the M8 nut has a small brass insert and that is how it fits on an M6 barrel.) It is not necessary to use a nozzle assembly like the one at the top of the page. I just like to try out different designs and see what I can learn...there is no need to try this unless you just want to tinker as well. Though I will say that after having built dozens of nozzle assemblies with the nichrome wrapped directly on the barrel, I'm now a huge fan of our ceramic coated heater cores!!! <img width="500px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/ring_terminal_mounted.jpg?1263874979' alt='' /> Getting PLA or even ABS into the insulator threads does not matter unless it is causing a problem. For the most part it is just one of those things. I've found that the larger nozzles (more metal) do a better job extruding (especially when working with smaller diameter openings). The design I use here puts plenty of metal at the key points (barrel entry and nozzle) but since there is only one thermistor, only one of the points is actively regulated and I chose to focus on barrel entry. The unregulated nozzle ends up at about ~190C and works great. Here is an approach using standard MakerBot equipment that I know works for 4042D at 220C and, at least, I was able to print a 608 pulley using 4032D at 235C (4032D just came out so testing is quite limited so far): <img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/full_assembly.jpg?1264697430' alt='' /> **Important Note: The nozzle assembly explained here is for a standard MakerBot style plastruder (like in this photo) and is unrelated to the photo at the top of the page. 1) Put your nozzle on nice and tight with barrel in either direction - I prefer to mount the smooth side in the nozzle. <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/tighten_nozzle.jpg?1264725662' alt='' /> 2) Wrap your nichrome in one nice and tight layer starting at the nozzle and going up while staying in the grooves - you are looking for good contact. You don't need to double back, one layer will get plenty of heat to the nozzle. Getting the nichrome wrapped correctly is the most important step. I use a straight 250mm length. I only measure the ohms to be sure nothing wacky (like a short) is happening - and it probably won't be 6 ohms...maybe a little more, maybe less. Wrap it nice and tight with a couple of layers of Kapton tape. <img width="575px" src='http://cdn.shopify.com/s/files/1/0030/7372/files/single_wrap.jpg?1264005396' alt='' /> <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/kapton_wrapped.jpg?1264725012' alt='' /> 3) Place your thermistor within a couple mm of the end of the hex surface (towards the tip). And, UPDATE your thermistor table to match your thermistor - this is the second most important step. For the 1mm table I've been using the Zach 1 table (see below). <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/thermistor_attached.jpg?1264725455' alt='' /> 4) Put your washer and M6 nut on, I use a full size M6 nut. Also, the washer can act as a heat sink which you really don't want it to do here so try to keep it from direct contact with the M6 barrel. It will still get hot but the less heat it conducts, the better. <img src='http://cdn.shopify.com/s/files/1/0030/7372/files/hex_probe.jpg?1264724989' alt='' /> 5) Screw your PTFE on so that is just tight with the brass. I use a small hex wrench to probe the junction between brass and PTFE - a very small gap is not a problem as long as the barrel is at the right temp. You should be able to smoothly push filament through. A slight lip at the junction is also not a problem as long as your temp is right. 6) Place your ceramic insulation around the nozzle and nichrome and slowly heat it up. Good luck! and let me know how it goes... --- Zach 1 table: //generated with T0:25 and T:220 // Thermistor lookup table for RepRap Temperature Sensor Boards (http://make.rrrf.org/ts) // Made with createTemperatureLookup.py (http://svn.reprap.org/trunk/reprap/firmware/Arduino/utilities/createTemperatureLookup.py) // ./createTemperatureLookup.py --r0=100000 --t0=25 --r1=0 --r2=4700 --beta=4198 --max-adc=1023 // r0: 100000 // t0: 25 // r1: 0 // r2: 4700 // beta: 4198 // max adc: 1023 #define NUMTEMPS 20 short temptable[NUMTEMPS][2] = { {1, 752}, {54, 242}, {107, 199}, {160, 176}, {213, 160}, {266, 147}, {319, 137}, {372, 128}, {425, 119}, {478, 112}, {531, 105}, {584, 98}, {637, 91}, {690, 84}, {743, 76}, {796, 68}, {849, 59}, {902, 49}, {955, 34}, {1008, 3} };