RepRap Squad’s Tips N Tricks

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Getting Rid Of Devil Horns (Print edges that lift)

Testing out all kinds of different methods, we found that a combination of skirt and brim within Repetier do the job. Depending on the specific part you are printing deturmines the actual settings required. The best way is to just dive into it to find what works best for you. We usually set it so our skirt ends where our brim starts as this helps to anchor the part being printed.

We typically set it for 3 or more loops and sometimes more for smaller prints. This gives us a chance to get our z axis height perfect as well as make sure the extruder is extruding correctly. What we do is level the bed much as you normally would. Then we make sure the z axis homing switch is pretty close to where it should be. Manually adjusting the two z axis couplers by hand as it lays down the first few loops. Once you have done this enough, you will know exactly how high to set it.

Due to variations in the print bed, sometimes I will raise one side a tiny bit more than the other. You will also get really good at turning both z couplers in unison. Practicing this has helped me to know what to look for if a print isnt going the right direction. Mastering this allows for very short setup time as well as the bottom of my prints coming out flawlessly.

Standard EIA Color Code Table:
We put this table on here so you can use it as a quick reference guide for your resisters. I refer to it from time to time and it always comes in handy.
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Here is a chart to give you an idea of what it takes from start to finish 3D printing:
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Make your large prints warp-free:

You probably also have the same problem when you print large objects using a 3D printer like Makerbot or Reprap, that it warps when it is cooled down. The reason is that the thin layer of plastic is laid down one at a time. Before the second layer is laid down the first layer cools already down. So the second layer pulls the edges of part toward the center and the part is bowed.

Jamie Mantzel wanted to make some 20cm+ long parts but he had also encountered this problem. After several experiments he found a solution. He changed his design so it causes less stress on the parts. First of all he added alternating voids to a layer between the raft and the actual parts. This release the stress from the first layer. Then he made holes in the main body of the part to avoid the edges of part to warp. He adviced that the holes was not necessarily as big as he did, just big enough to break up the layers.

Using Paint to Perfect Your Print:
I recently found a post where a fellow reprapper has used Valspar frosted spray paint to put a finished look on his prints. It also will remove any marks made by sanding your print. This has always been an issue in the past but, its a problem of the past with this paint. The pictures below will show reference to different methods and their results. Its great little tricks like these that keep our product looking great.

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Also another effect you can get by using a sparkle spray paint.
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How To Remove Prints From Your Bed

Problem: “I can’t remove my part from the build platform.”

Sometimes, a part can be stuck to the print surface really well and you’re unable to get good leverage to pop it off. When printing a pyramid shape, it’s even difficult to get at it with conventional tools.

Here are a few tips:
● Bring the temperature of the heat bed up (or down) to about 60C for ABS.
● Wrap the jaws of a pair pliers with a rag and try to get some leverage somewhere on your part.
● Wrap the end of a chisel with some tape and carefully work at a corner of your part. The tape just protects your Kapton or other printing surface from getting scratched.
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Combat Warping By Printing Pads
Sometimes, when you’re printing a large flat object, such as a simple box container, or a very long thin feature, like a stick, you may see warping at the corners or extremities. One trick is to add little pads to your part where the warping would occur. These can be any size & shape you’d like, but generally, diameter 10mm cylinders that are 1-2 layers thick work well. After the part is printed, just trim them off. Here are two techniques to add pads to your part:
Add pads to your 3D data. Use this method if you plan on printing several parts over time.
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Add pads to your part in Repetier (or your GUI of choice). This is a great trick (thanks Charles H.!) for quickly adding pads to parts that you might not be able to easily modify (i.e. STL files, SCAD files, etc.). Just create a pad shape in your CAD package of choice, save as an STL, and add it to your build tray. Quickly add as many as you want and easily move them around!

Repair An STL File Using NetFabb

Problem: “I’m getting unexpected (bad) results from slicing my STL file.”

When slicing an STL file, sometimes the result you get are not what you expected (i.e. features missing, different geometry, etc.). This is often due to the actual STL data not being “perfect” in the eyes of the slicing engine. Most times, it’s difficult to see where the actual “bad” portion is located. Other times, it’s just downright too time-consuming to troubleshoot. The best method, as a first line of defense, is to use the powerful and free STL repair tool by netfabb. The free version is called netfabb Studio Basic and you can get it here.
Here are a few quick steps to follow once you load your part into netfabb:
● Go to “Extras -> Repair Part”
● Click “Automatic Repair” (bottom right) and Execute the “Default Repair”
● Click “Apply Repair” (bottom right)
● Right click on your part in the file tree (right side) and export it as an STL to your preferred location.
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ABS Glue
ABS glue is a great addition to any 3D printer operator’s tool box. This slurry of acetone and ABS has many practical uses such as:
○ Bonding small parts together to create larger or more intricate ones (it’s just a bit easier to apply than straight acetone)
○ Improving the surface finish of your part (simply paint it on or dip your part into it)
○ Mending cracks in your parts (if you don’t feel like reprinting/redesigning them)

How to make ABS glue:
○ Use a small glass jar with an air tight lid. (You can find these at most hobby shops.)
○ Empty nail polish bottles work too, but they’re kind of small.
○ Fill about half way with straight acetone (or however much you’d like if you’re using a larger jar).
○ Add ABS. ABS takes time to completely dissolve in acetone, so the smaller bits you use the quicker the results. We like to simply print a 1-layer thick square sheet (or just start any print and stop it after the first layer), and then cut it into pieces. Snipping small pieces off the end of your filament works too, but it’ll just take more time to dissolve.
○ Wait and stir. Repeat until all the ABS is dissolved.
○ There’s no perfect ratio of ABS to acetone. Just use less ABS to make a thinner solution (great for surface finishing) or more ABS for a thicker solution (great for bonding or mending parts).

Cracking On Taller Prints

Problem: “There are layer cracks on the sides of my taller prints.”

This cracking phenomenon can occur with taller prints. The reason is because at higher layers (say from ~30mm on a typical Reprap), the part cools quicker and has less “help” from the heated bed. Therefore, subsequent layers cool down faster and faster which causes poor layer adhesion. Try increasing the extruder temperature by about 10C. Also, try increasing the bed temperature between 5-10C.

Slicer Save Problem

Problem: “My Slic3r setting changes are not being saved even after I click ‘save.'”

This is commonly a problem for Repetier installs on Windows 7 PC’s. In Repetier, make sure the “Work Directory” (Config -> Repetier General Settings) is not in your “Program Files” folder (usually C:\Program Files). In short, Repetier creates and/or writes into a log file every time slice settings are changed and there is some issue with permissions.
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My X or Y Dimensions Out Of Spec

Problem: “The dimension of my part in X (or Y) is suddenly under-spec.” -or- “The sides of my round object are flat.”

If your printer was known to be printing with dimensions within tolerance (meaning the settings in the firmware are good) and all of sudden parts are measuring smaller, check the tension of your drive belt. Loose belts will require the motor pulley to need to take up this little bit of slack before the extruder/print bed gets moved. This results in parts being undersized. If for some reason you have difficulties tightening your belt, try printing and attaching one of these nifty little S-clips (Thing:10082).
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Warping

Problem: “The base of my part is warping.” Try these tips:

● Is your heat bed hot enough? For ABS, this is generally set between 100-110C.
● Is there a breeze or draft blowing across your printing area? Turn off that ceiling fan, or build some make-shift walls to surround your printer.
● Do you have a good connection between your bed thermistor to the actual bed? (ensure that the thermal paste is still effective, i.e not dried up)
● If printing with ABS, is your Kapton tape surface clean? Try occasionally wiping it down with acetone and/or rubbing alcohol.
● Are you printing very wide or thin features? Try adding little pads to the corners of your 3D data to use as anchors (Check out the tip “COMBAT WARPING WITH PADS”).
● Do you have enough 1st layer squish? Insufficient squishing of the first layer can cause poor adhesion, leading to a warped base.
● Are you printing your first layer too fast? Trying slowing down your first layer speed to around 30mm/s.
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Making your own belt mounts with hot glue

Timing belts are useful for all sorts of synchronous motion. They can be used to connect a rotary encoder to a lathe spindle or to provide linear positioning on a 3D printer. They have little stretch or flex and can accurately transmit rotational motion. One of the challenges with using timing belts is mounting them in your projects. This is especially true when you want to use timing belts to convert rotational motion of a computer controlled stepper motor into positionally accurate linear motion on a project like my 3D printer build. Here’s a fast and easy way to make yourself a timing belt clamp and mount for your project. The clamp shown in this post will function as the y axis mount on my DIY 3D printer.

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First you need to make a mounting block for use as a substrate from your material of choice. Aluminum in this case. I machined the part to fit onto my 3D printer’s y-axis structural cross member. I cut a small scrap of XL series timing belt to fit the groove. This is why it is always good to hold onto things like a scrap bit of timing belt. It may be hard to see in the picture above but I drilled a series of 6 shallow holes into the timing belt slot to allow the molten hot glue to seep in and form mechanical interlocks. It’s best not to rely on the adhesive strength of the hot glue, mechanical interlocking features for the polymer to mold into provide good shear resistance.

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Pre-heat the substrate. You could use a project toaster oven, heat gun, 500w lamp, etc. I used the woodstove. If you try this with a cold substrate the hot glue will cool too quickly to mold to the features of the timing belt. You want the substrate warm so it does not pull heat out of the molten polymer before we can mold it to the timing belt.

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Quickly take your preheated substrate from your heat source, put it on a nonflamable surface (leather glove in this case) and fill both sides with hot glue quickly. Use a bit more then you think you need, it will seep out the ends if there is too much in the slot.

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Then clamp down the timing belt into the molten plastic with the screw. I used a long screw to provide alignment and a nut to make clamping easier and faster. It is also acceptable to just squish it down with your fingers. Put the hot assembly into cold water to quickly cool the hot melted plastic before it can seep out of the cavity.

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Let it cool completely before disassemble. I’ve never had any issue with the hot glue sticking to the timing belt enough to be a problem. Usually it is possible to remove the Timing Belt used to mold the plastic with fingers. If it is a bit stubborn in coming free use a small pair of pliers to get a grip on the bit of timing belt and slowly pull it up and away.

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When disassembled, trim up any of the plastic that seeped out with a sharp exacto knife or chisel. As you can see you get a perfectly molded Timing Belt clamp that can be used for your project.

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Wipes To Clean Your Print Surface
I found these when looking through an old catch all spot in the shop. After looking on the back to see what was in them I had an, “aawwe haa!” moment. I could use these to clean my printbed before each print. The primary active ingredient is iso alcohol which is used for cleaning off oil and buildup on my bed. The original use for these is to clean eye glass lenses. They also contain an anti-static formula. I’ve tested them out and they work great. The best part is the fact that they are biodegradable and easily desposed of.

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