Baja i3 Rework Working with Files and Printing

From Roaddog Labs Docs

Introduction | Bill of Materials | Y-axis Assembly | X-axis Assembly | Connecting X-axis and Z-axis | Motor Installation | X and Y-Axis Motion | Heated Bed Assembly | Extruder Installation | Electronics and Wiring | Firmware Configuration | Validation and Testing | Working with Files and Printing

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Preparing for Your First Print

Now that you've made it this far you're ready to make your first calibration print. We use three objects to calibrate and commision the printer. These files have been prepared and are available to download at YouMagine.

It's a good practice to have some sort of organization for your files. In the lab we have them grouped into like folders. For example calibration files for each machine have are grouped together in folders for each machine type. Managing your files is essential to having an organized workflow.

Loading the First File

Open your print host and connect your computer to the printer. If you need to refresh your memory have a look at the connection instructions. Once the printer host and computer are connected load the file thinwall.gcode from your computer. The file load buttion is in the upper right portion of the host window. Click it and a dialog will appear from which you'll be able to navigate to the folder with your test files. Once the file loads there will be an outline of the object on the print area display in the print host.

Priming the Hot End

Before we start we want to check the extruder motor and prime the hot end. You may need to adjust the stepper controller current using the method described when we commissioned your printer.

Loading Filament

Before we can print we need to load some material into the extruder. For the complete kits we provide a bit of filament to make sure the machine works. We use PLA in this exercise as a means to test the machine.

To load filament remove the screws that compress the extruder idler to the extruder. Feed the material down the hole into the hot end To best feed the material cut it at an angle as this will help when feeding down through the hot end. You'll want to get the material as far down into the hot end as possible. Typically you can feed it down through the heat break to the heater block. That's around 40-50 mm into the extruder body. When you are done replace the extruder spring screws and lightly tension the idler.

(pic of feeding)

Moving the Extruder

To move the extruder motor you use the printer host in the same way you use it to move the axis of the machine. The difference with the extruder is that you are going to tell it how much material to extrude. For the extruder to move the hot end will need to be at the target temp. There is a feature in your printer firmware that prevents what is called "cold extrusion" where the extruder motor is disabled if the temperature is not within a specified window.

To heat the extruder you need to set the target temp in the printer host software. It's in the lower left of the panel.

(pic of temps drop down)

There are usually a couple of pre-configured options in the temp drop down but we'll enter a value of 200* C. The temp is at the upper end of what is usually required to extrude PLA but a good starting point to prime your hot end. Once the hot end reaches the target temp you need to tell the machine how much you want to extrude. The input box for this is right below where you set the temp. The unit of measure for the extrusion is in millimeters. I find that 30 mm is a good setting. You'll have to feed 30 mm through a couple of times when you add a new roll of filament or change colors. With the hotend at temp and a value set for the extrusion hit the extrude button in the printer host. Once the hot end is primed, usually 3 or 4 cycles of the extrude button, you should be betting smooth, consistent extrusion. If not check your idler tension and make sure the filament isn't catching on anything that would hamper the feed into the extruder.

Printing the Thinwall Object

Before we print our first object make sure the print bed glass is clean that the area around the machine is clear front to back to allow movement of the print bed. To clean the bed an ammonia based glass cleaner like Windex brand or the equivalent works well. It's easier to get the first layer to stick by using some sort of adhesion promoter. For PLA I use Aqua Net hairspray and for ABS I use UHU glue stick. It's possible to get good PLA prints using the clean glass of the heated bed alone. Still others use either polyimide tape or blue painters masking tape.

First Layer, Skirts, Brims

I can't stress how important the first layer is to a good print. That will be one of the areas you'll want to focus on when you are learning. There are a few approaches to insuring a good first layer. Some use a bit thinner first layer. For example a 2.5 mm first layer on an object with 3 mm layers. Others use a bit thicker first layer so the first layer smashes down more to the print bed to improve first layer adhesion. In the example of the thin wall object, the first layer is 2.5 mm with all other layers 3 mm. While a better surface finish can be had with thinner layers it's best to learn on thicker layers like 3 mm until you get the hang of it. Different slicers offer different options for first layers and what works for some objects with some slicers may not work for all objects with all slicers. The varying algorithms in each slicer package are the reason for the variance that can be seen between the results of the different slicers.


The print starts with what is called a skirt. A skirt is material printed to the bed, away from the object to be printed and offset from the object by a determined amount, usually 5-10mm or so. The purpose of the skirt is to get the filament flowing and equalize the pressure in the hot end so you get consistent extrusion. Skirt paths around the object are called "loops" and are set in the slicing software. I usually do three loops but in larger objects or sets of smaller objects being printed at the same time (also called "plates") using less than 3 loops will work to get the hot end primed.


Brims are an outline directly around and attached to the object being printed. The purpose of the brim is to assist in the adhesion of the object to the print bed. Brims also provide to reduce warping of objects, particularly in the corner of an object by holding the edge down to the print bed. A brim width is specified in the slicer. The brim can also be more than one layer tall. This would be advantageous with a complex object that has bed adhesion issues. I typically use a 5 mm wide brim, one layer high. Note that not all slicers implement brims in the same fashion of even allow for skirts and brims both to be used on the same object.


To print the file hit the print button in the upper right side of the printer host. Check the "watch" checkbox to watch a graph of the printer temps. The bed will warm to the target temp set in the slicing profile. in this case 50* C. When the bed warns all three axis of the machine home. Depending on your slicer configuration the Z axis may home, then raise 10 mm or so. This is a method some (including me) use in case the nozzle is a bit hot and "drools" the material can expand off the end of the nozzle. Once the axis are homed the hot end starts to heat. When the hot end has stabilized at target temp the machine will start the print.

Once the printer starts printing, watch the first layer to gauge how well it is doing. Check to see there is adhesion and the ends don't curl. This is an area where practice makes perfect. After you gain more experience you'll be able to tell in many cases if the first layer prints well enough for a successful print. In no time you should be able to tell by looking at the skirt and the first few loops of the brim to see if the print is likely to stick. Right now watch the print as it builds to familiarize yourself with how the machine works. The thinwall should take about 4-5 minutes to print.

(pic of thinwall complete)

Removing the Object

When the print is finished the X axis will home out of the way and your print will be complete. the next step is removing the print from the bed. Wait a few minutes for the print to cool. On the thinwall object it's not such a concern but on other larger, more detailed objects the plastic may be soft, particularly in the area most recently printed. Handling the object prematurely can distort or damage the object as it cools.

It's also more difficult to remove a just printed object from the print bed. With objects with more surface area attached to the print bed you'll be able to hear the object loosen from the bed as it cools. What happens is that as the object cools, it contracts. As it contracts the object produces a slight popping or cracking sound as the material unbinds from the print bed. When the bed has cooled to room temperature for 5 minutes or so many prints come right off. if you you are using an adhesion promoter you may need some mechanical help to remove the prints.

Use care when removing stuck or stubborn prints. You can break the print or in more extreme cases crack the heated bed glass when attempting to remove the print. To minimize this use a bare utility knife blade. Start by sliding the blade under one corner then working it around the object until it pops loose. Be careful as you may lose control of the blade due to the part coming lose sooner than expected. With a sharp blade that presents an opportunity for injury or damage.