The strongest way to glue PLA

If you are trying to print a large model on a small printer, you will come to a point that you need to attache the pieces to each other. Plastic epoxy and super glue are usually the first two that you would go to for this. Unfortunately, both of these options leave much to be desired when it comes to bonding strength. In all cases, even with special care to prep and sanding, the bond broke at the joint.

Because the end result is going into a new printer, it had to be stronger than what could be achieved with epoxy or glue. I have found the strongest way to bond PLA is with a solvent glue. This dissolves part of the print, which then hardens when the solvent evaporates fully. The resulting bond is so strong that the layers separate before the joint breaks. This is as strong as you can get, and hopefully the result will be strong enough to withstand the forces during printing. The solvent that I used is Weld-On #4.

The resulting bond. You can see that the layers separated above the joint itself.
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Weld on #4.
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Auto Bed Levelling

One of the most tedious tasks owning a 3D printer is leveling the bed. The nozzle must be level with the bed surface at all points, within about 0.1mm. It can be done by hand, and must be done every time you remove the nozzle or bump the bed too hard. If you get it wrong, your print will not stick.

To fix this, I added a capacitive proximity sensor to my printer. It is adjustable and once it is set up the printer will measure the distance of the bed every time. There is still some calibration when removing the nozzle but it is a much simpler process and only needs done when the nozzle is changed. One problem I ran into was the sensor ran on 6V – 36V, but the microcontroller for the printer runs on 5V. Sending the sensor less than 6V didn’t work, but sending a signal to the microcontroller over 5V would break it. I ended up making a connector that had a voltage divider built in. The sensor then ran of the 12V that the heater, stepper motors, and hot end run off of, but sent the signal back through the voltage divider to the microcontroller. The end result is just under 5V at the microcontroller and a working bed leveling.

Here is the printer leveling the bed using the new sensor.

Here is the voltage divider in the adapter I made, large enough to see the resistor values of 10k and 15k.
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Sometimes you ignore the errors

Mistakes or errors happen often when printing. How you recover from them is just as important. Sometimes you can let it just keep on going and get a partial success, especially when you are making many duplicates of something. For my new printer I am trying to make it out of mostly printed parts. This includes the beams that make up the shape of the printer.

Often tall slender objects will fail because they lose contact with the build plate. The leverage the nozzle has against the holding surface only increases as the parts grow taller. In this picture one of the beams had come loose from the surface about halfway through. It took it 6 hours to get this far, with another 3 to go. In this case it was better to just let it finish, having 5 successful beams instead of 6.

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A printer of my own making

After learning so much about 3d printer, I am excited to continue. My current printer can make some pretty nice things, but it is limited in the size that it can make. There are many things that I would like to print that it just isn’t quite big enough. After doing some research of printer designs, I have decided to build me a CoreXY style printer. The first step was to design the XY section. There will be two stepper motors with two belts and pulleys to control the XY motion. I am building it out of 2020 extruded shapes but instead of using aluminum I am trying to do it with all printed pieces. This may not work, but it is worth a try.

The first corner assembled.
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All corners assembled, motors go in the bottom, pulleys in the top.
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Making more struts. One failed, but with several like this removing the failed one will allow the others to finish. It takes hours to print, so the loss of one is worth trying to continue anyways.
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Mistakes happen

Throughout the learning process more often than not you will end up with a blob of plastic. Maybe the settings weren’t right for the model, or it was too difficult for the printer to print. In this case, it was a model I had modified for the corner of a new printer and it had an error in it. The printer didn’t care that it was impossible to print, it tried anyways. The result was the mess you see here.

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My own designs

After downloading many objects that were already made, I have started learning how to modify designs and make my own. I am now at the level where I can measure basic objects and duplicate them with my printer.

I designed these clips to hold the glass. They take up much less space than the binder clips I had been using.
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This plug was an existing design that I modified. I purchased a plug on Amazon, measured it, and modified the mount to fit. Worked perfectly the first time.
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Print all the things!

In it’s new location I continued to improve and print as many things as I could find. Not many more improvements were made to the printer directly as it had now reached a point where it was reliably finishing prints without too much issue. Not going to label each picture here, but these were among the things I have made recently.

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Printers new location

Now that the printer was in good working order, I have moved it to my my office. The first order of business is to build replacement parts. Parts break all the time so I want to have extras on hand. If a part ever breaks, I should be able to put a replacement part on and then immediately create a new replacement. This is one of the X carriage ends.

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A new nozzle, and the evolution of a mini

One of the things I would like to do with the printer is to make gaming miniatures. It turns out that making small detailed objects is a fairly difficult task for a 3d printer to do. It takes very good heat control to avoid making a blob. To get enough control I had to change the nozzle to a different design, as well as add an additional cooling fan. This had the negative side effect of making the printer fairly loud. On the plus side, it made the printer much more accurate for smaller objects.

The first attempts. The feet slowly went from puddles to the beginnings of legs.
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Some fine tuning and I eventually came up with this blob like figure. The first that was able to complete to the end.
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The new nozzle and fan ducts printing the figure.
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The result, something that looks much nicer!
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More parts being made

Making some of the final parts before moving the printer off the table. My girlfriend was very tolerant of the huge mess that I made on the table for the several weeks that it took waiting for parts and getting it running.

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