Tag: 3dprint

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.

Someone asked how to change some settings halfway through a print. If you use Cura, this is pretty easy to do.

Cura is pretty powerful, right out of the box. It’s my go to software for print slicing. I’ve tried others, but I always come back to Cura because of the capability that it provides.

However, sometimes even Cura doesn’t have the functionality that’s needed. Thankfully, many people in the community have created different extensions that offer capability for the gaps in Cura’s capabilities.

One of these is the Post Processing Script extension. One of the options inside of the extension is to change a setting at a specific Z height. You have the ability to change speed, retraction settings, temperature, etc. If you haven’t experimented with it, it’s definitely worth checking out.

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.

I switched filaments. I’ve been meaning to change my nozzle, so while I was in there I did that too. When I printed a test print to make sure everything was good my first layer had holes in it.

Here is what I had to do to fix it.

  • my new nozzle doesn’t necessarily have the same height as my old one, so I releveled the bed and reestablished my mesh bed leveling.
  • my new nozzle probably doesn’t have the same heating characteristics as the one that I replaced, so I tuned PID.
  • my new filament may not feed in quite the same way as the old one, so I updated my e-steps.

Sometimes, you just can’t get the part quality that you want. For whatever reason, your machine just is not capable. Whether it is because your overhangs cause you to have to use a lot of supports which leave ugly marks on the surface, or your machine just doesn’t have the resolution to leave a good finish. There are a few things you can do.

  • Tune your machine. Make sure that 25mm commanded in the gcode results in 25mm of material printed.
  • Split your model into pieces. I print a lot of figurines for my kids. The hands and arms prove to be particularly difficult, as they need to be supported and they are small. When I cut the arms off and print them separately, I have much better results, then I just glue the arms onto the model.
  • Primer/paint. A little paint covers a multitude of imperfections. 

The final intent of the part is going to drive a lot of decisions in the 3d printing process. 3d printed parts have become very useful in improving prototyping and developing new products. However, as the cost of 3d printers has come down significantly over the past decade, or so, many hobbyists (like me) have also started buying 3d printers. I’m sure I’m not alone in this, but I use my 3d printer for all kinds of stuff. I make figurines for my kids’ games. My wife wants a new decoration for her curtains and can’t find any that she likes in the store, 3d printer to the rescue. I also use if for functional parts.

End use drives many decisions, such as:

  • material selection: for functional parts, I tend to use ABS. For the figurines that I create for my kids or decorative items that I make for my wife, I tend to use PLA
  • layer height: for decorative parts especially, I like to use a very small layer height to allow my components to be as smooth as possible in the Z direction. If I’m just creating a quick prototype and don’t care if there are obvious stair steps on the model, I might increase the layer height
  • speed: in my experience, higher speed = more vibrations, and more vibrations = lower part quality. There are a few things that you can do to dampen vibrations in your printer, but you will need to adjust your speed based on the final use of the part

 

 

I’ve run across a couple of posts where people are having trouble with different things. Upon digging into it a little bit, I have found that they are using the wrong temperatures for the materials that they are trying to print with.

My post today is pretty simple, use the temperatures for the filament that you are using. If you are using PLA, use temperatures in the PLA temperature range. If you are using ABS, use temperatures in the ABS temperature range. Most manufacturers provide their recommended temperatures on the side of each roll of filament.

The optimal temperature will vary some and will depend upon your setup and your ambient environment, but you can’t run PLA at 260 degrees and expect a successful print.