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Printing PLA on a Thing-O-Matic Mk7

Posted by Luke Chilson on

THIS IS NOW A LEGACY POST:

For more in-depth, up-to-date content, please see this post:Thing-O-Matic MK7 PLA Set-Up and Troubleshooting (Likely MK8).

Printing PLA on a makerbot is a question that OFTEN comes up among Cupcake and Thing-O-Matic owners. I mean, it sounds like a great material, nice smell, natural glossy finish and the potential for VERY fast printing. When I started printing with Makerbots new MK7 I gave PLA a try to see if makerbot had managed to work some kinks out of their extruders. I'm happy to say that yes, you too can be printing with PLA in no time.

There are a few points to remember when attempting to print in any new material, especially PLA.

Happy printers have level beds: A poorly leveled bed can create many problems that are not obvious to pinpoint. Take your time, level your bed.

  • Use 3(!) screws to hold your bed down NOT 4. If you use more than 3 screws you are incredibly likely to warp your bed. 3 screws also means you never have to adjust more than 2. If you put springs (Hardware Store) between your Heater PCB and the carriage it will make leveling dead simple.
  • Jog just to the side of a screw and use the control panel (NOT YOUR HAND) to move the extruder nozzle as close to the bed as you can while still having the tiniest bit of visible space between it and the bed. I like kapton for leveling as I can use the reflection of the nozzle to help me see if the bed is sloping one way or the other. Jog to your other screw, observe the difference in spacing between the two, change your jog distance to 50mm and move your nozzle up 100mm if you have the space. Adjust your screw and Jog Z Down 100mm to where you were, using the control panel instead of your hand should guarantee that the nozzle stops at the same height. Do this until the height of the bed by the second screw is the same as the first and then repeat for the third screw.

Find a Good Z Height: Luckily PLA on a Heated bed is more forgiving than ABS. If your used to smashing your first layer into the build surface you could probably let up. PLA will stick much better than ABS and can survive with a Z height that is close to or even a little greater than your layer thickness.

Find your operating Temperatures: The temperature your extruder reports is NOT the temperature your plastic is when it leaves your nozzle. The actual temperature of your plastic is based on a number of variables, the most applicable of which is how fast you are pulling the filament into your extruder. High Flow-Rates require higher temperatures; lower Flow-Rates, lower temperatures. Too high extruder temperature and your plastic will get soft where it is driven and strip away, to low and it won't get hot enough by the time it reaches the nozzle and you will clog. This also means that we need to watch any plugin in skeinforge that can slow down our flowrate throwing off our balance. These are Raft, Cool, and Speed. If you are just starting to print with PLA you may find it useful to keep your first layer feed and flow rate ratios above (.8), turn off cool, and make sure your perimeter feedrate is the same as your operating feedrate in the Speed plugin. As you get more comfortable you can start tweaking these back to where you want them. If your stuck about finding a temperature to start from, 200C is a worthwhile place to start, going as cool as possible to reduce stringing without clogging. It can be difficult to know if your too hot or too cold as they both cause your filament to strip but if your stepper controller is set right then hopeful you can identify too cool from skipped extruder steps and to hot by straight stripping of your filament...as always though, your mileage may vary.

Find a good Starting Profile: It always helps to have a base to jump from. Here's what I use for printing PLA on the MK7

MK7 pt2 PLA - Download This!

Unzip this file and place it with your other profiles in skeinforge. I changed the start and end gcode to match the newer and more standard versions of replicatorg so there shouldn't be any problems but let me know if there are. Here are the highlights:

  • Extruder - 200C
  • Bed - 50C
  • Layer Thickness - .2mm (I can't say I have any profiles thicker than this, with a level bed you really should be printing at this or lower, feel free to ask for help in the comments if your having trouble getting to .2mm on your printer)
  • Width - .4mm
  • FeedRate - 35mm/s

Please give it a try and let me know how it works so I can tweak it to make it usable to more people. We're printing with ABS, PLA, Polycarbonate, and several other plastics over here and enjoy getting botters up and running on new things.

THIS IS NOW A LEGACY POST:

For more in-depth, up-to-date content, please see this post:Thing-O-Matic MK7 PLA Set-Up and Troubleshooting (Likely MK8).

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