Category: Troubleshooting

A couple of days ago, I wrote about calibrating your extruder with Klipper. Today, I would like to talk about how to calibrate your extruder e-steps with Marlin firmware. Here is how I do it:

  • Move printhead to center of bed and about 150mm off the bed
  • Mark a spot (I use tape) on the filament about 125mm down from the bottom of the extruder
  • Use calipers to measure actual value of tape from extruder. We’ll call this “A” and say we have 126mm for this example
  • M503 – read current values and make a note of the current E value. We’ll call this value “B” and say we have a current E value of 400 for this example
  • M83 – enable relative mode on extruder
  • G1 E100 F100 – feed 100mm of filament at 100mm per minute
  • Let it finish the extrusion and measure the distance between the bottom of the extruder and the tape that we marked. We’ll call this value “C” and say that we have a current value of 24 for this example. If everything were already calibrated correctly it would be 126 – 100, or 26mm.
  • Calculate our new E-Steps value. 100 * B(A-C) is the formula. Substituting our values from this example we get 100 * 400/(126-24) = 392.16.
  • Update our esteps on our machine with M92 E392.16
  • Save our new value with M500

A lot of people push for Capricorn Tubing on their Bowden system. In fact, I have it myself. I recently found out about an issue that surprised me, but it makes sense when I think about it a little bit more. Capricorn is known for having high precision, tight fitting tubing to connect the extruder to the hotend. Using Capricorn tubing solves a lot of feed issues and ensures consistent prints, or does it?

What happens when you have a high precision tube that fits around filament with significant width variation? That’s what some printers are experiencing. The solution? Printers are finding that they either need to switch to more precise filament, or that they need to switch to a larger diameter Bowden tube.

If frequency were the only indicator, you would guess that printing different versions of the Venom Symbiote was my favorite thing to print. I’ve printed green ones, black ones, and in this case, I printed a transparent one.

I had to completely rebuild my hotend after this one, over a very simple mistake.

I had purchased a new hotend (complete) to replace one that I was having problems with. I put it on my printer and started printing and you can see the results for yourself.

What I forgot to do is “hot tightening.” When assembling the hotend together (at room temperature) you screw in the nozzle and the heat break until they touch. My heat sink also has some setscrews that need to be tightened. At room temperature, everything is tight. However, when things heat up and expand, little gaps in between each of the components will occur. The solution to this is to heat up your hotend to around 20 degrees beyond what you intend to print at, and then finish tightening the components.

At times, I get lost in the minutia of 3d printing. Dialing in the bed leveling, fixing my first layer and getting it just right, getting exactly the right PID and retraction settings.

Sometimes, it’s nice to just step back and remember what this hobby allows me to do. My brother-in-law is a big fan of “A Christmas Story.” He watches it every year several times and quotes the movie all year long. I thought it would be fun to make him the lamp from the movie, so I’ve been working on it and just finished it.

 

 

 

After trying to print a QR code over the weekend, I decided to tune in my retraction settings. Step 1, I printed a retraction tower. I printed a tower with different levels, with retraction distance set at 0mm, 2mm, 4mm, 6mm, 8mm, and 10mm.

2mm of retraction was a clear winner for my machine, so I decided to dial it in more. I printed another tower at 1mm, 1.5mm, 2mm, 2.5mm, 3mm, and 3.5mm. 2mm was again the clear winner for my machine, so next I decided to play with the retraction speed settings. Most source recommend a retraction speed of 35-40mm/s. I printed a retraction tower with speeds of 30mm/s, 35mm/s, 40mm/s, 45mm/s, 50mm/s, 55mm/s. 40 and 45 both looked pretty good so I printed another one that ranged from 39mm/s – 44mm/s.

Judging from the towers that I printed, my optimal settings are 2mm at 42mm/s.

My daughter makes handcrafted little dolls and sells them. We thought it would be fun to 3d print little boxes with her business information on them. As a part of the box, I designed a box lid that contains a QR code that people can scan that takes them to her online store.

It was more difficult than I, at first, thought it would be. Mainly, I didn’t realize my settings were so far off. The most important setting that I needed to tune were retraction settings. My retraction settings are “pretty good,” but in this case I needed them to be perfect. You see, the little nubs that are left on the parts get picked up by the camera and messes up the QR code, so I had to clean them all up by hand. Fortunately, I had the foresight to create the box in pieces, with the plan to glue the QR code to the rest of the box instead of creating it all at once. 

Learn from my mistake, run a retraction tower and update your settings. This should be done each time you change filament types.

The topic of first layer adhesion comes up often in 3d printing. Sometimes, the footprint of the part itself is not enough to keep the print stuck to the bed. I’ll go through some of the bed adhesion options below.

Priming Line: One of the main reasons for making an extrusion before you start on the part is to make sure that there is filament in the nozzle. A priming does this and nothing else. I don’t use this option much, but using a 50mm priming line accomplishes the purpose of filling up the nozzle.

Skirt: Your printer will create a quick circle all the way around the perimeter of the part. I use this option frequently. It accomplishes a couple of things for you.

  • A skirt fills the nozzle with filament
  • A skirt goes all the way around the perimeter of the part, confirming that your part will fit on the bed
  • By going all the way around the part, you also ensure that your bed level is accurate, just in case you have doubts about it

Brim: I use this option for tall, skinny parts. A brim is actually attached to the part, whereas a priming line or skirt are not. A brim provides more of a base for your part that is pretty easy to remove when you are done printing.

Raft: Every option is a compromise between robustness and printability. A raft leans heavily towards the robust side of the scale, but the cost is a longer print time and the fact that you will have to remove the raft from the print later. A raft creates a base for your print to build off of, rather than printing directly on the bed.

Someone on a forum had a question about why horizontal lines might be showing up on their 3d prints. Someone else suggested that maybe their infill was showing through and that increasing the number of walls from 2 to 3 thicknesses might fix it. That’s a good place to start and I thought that was the solution to the problem.

Well, it didn’t fix it. It turns out that they had to go through their whole 3d printer. Their z rod had just a little bit of play in it. Once they adjusted that, the horizontal lines went away.

Every once in a while, I am asked by someone about what their acceleration should be set at. My answer, as in so many cases, is “it varies.”

If you go too low, you won’t necessarily hurt anything, but your prints will take forever. If you set acceleration too high your belts will jerk abruptly each time the axis changes direction and you risk skipping teeth on the belts and getting layer shift.

I’ve run tuning test towers, and I know that my printer starts to have problems around 2,500 or 3,000 mm/s². It skips teeth and my layers end up all over the place.

Unless you want to do a tuning tower for each print (not practical) you are better off doing a little educated guessing based on what you are printing. 

For small, intricate, parts I set my acceleration low. Somewhere around 500 mm/s². For larger parts that don’t have a lot of detail, I might set at 2,000 or 2,500.

Maybe this is an unpopular opinion, but I don’t think it matters a whole lot for small parts. When you do a 3-point turn in your car, your acceleration doesn’t matter much. You are changing direction too frequently for it to even matter. I don’t have scientific data to back this up, but I would guess that it takes a Ferrari about the same amount of time to do a 3-point turn as my Dodge Dakota. If someone has a Ferrari they want to let me borrow to do that test, I’m game. The same is true on your 3d printer when you print small parts, so your acceleration doesn’t matter a whole lot.

As the temperature outside gets lower, I’m seeing an increased number of asking on forums why their prints aren’t sticking to the bed properly. In addition to all the normal reasons why your print might not stick to the bed, cold weather presents a few additional challenges.

 

For starters, most homes aren’t airtight and many have drafts. A sudden burst of unexpected cold air on your print can cause it to shrink away from the bed and lift off. 

 

Be careful of where you have placed your printer. Is it in front of a HVAC vent?

 

Your heater has to work harder to get up to temperature and maintain temperature. Make sure you have done your PID tuning and I usually increase my temperatures by a couple of degrees.

 

As a more generic principle, consider how you might be able to keep more heat in. I usually put my enclosure around my printer this time of year. It’s not terribly complicated and doesn’t need to be watertight. I found some brackets on Thingiverse and printed them, then connected them to make a frame with 2×2’s. I bought some acrylic and hinges to make a door and I have an enclosure. It’s not the most beautiful enclosure on the planet, but it works well enough.