3D-Printing

Voorheen maakte ik mechanische onderdelen voor programmeer- en testjigs met een metaalfreesmachine, maar dat kostte veel tijd. Ik gebruik hiervoor nu een 3D-printer. Het grote voordeel hiervan is dat, als de onderdelen eenmaal goed zijn ontworpen, je de printer het werk kunt laten doen. Het printen kan ook best veel tijd kosten, maar ondertussen kun je iets anders gaan doen.

Although I use a 3D printer at work, I wanted my own for hobby projects. You can get low cost 3D printer kits from China. On Aliexpress I found a kit for around 160 euro, including shipping from Germany (no import duties to EU countries). It was fun to assemble, and I am impressed with its printing performance. In this article, I want to share my experience and a few tips and ideas for improvements.

The printer in question is an Infitary M508. Its design is based on the Prusa I3, this puts it in a popular and well regarded class of 3D printers. It uses the kind of hardware one likes to see in a 3D printer such as proper lead screws, aluminium couplers, an all metal extruder, a control panel with encoder button etc. It has a frame that will better prevent x axis wobble than some other budget printer kits.

 

The kit is very complete. For assembly, you don't strictly need any tools besides those already included in the kit, and besides a computer and a wall outlet, you really get everything needed to start 3D printing, including, for example, an SD card plus USB SD card reader, painter's tape and a reasonably sized roll of PLA. Some small hardware (screws and nuts) actually comes in more generous quantities than needed.

 

What is the difficulty level of such a kit? You do need to have some affinity with mechanical and electrical construction. This machine uses mains electricity and contains parts that get very hot, so correct assembly involves a safety concern. For example, you should be able to judge when the electrical terminal screws are correctly tightened. If you are not sure, get a technically experienced person to assist.

Results of building the kit

I needed about 10 hours to complete building the printer and was quite pleased with the result (apart, at first, from an issue with the power supply that I found out later on).

One of the first prints I did was from a test file on the included SD card. After 8 hours of printing this was the result:

In my opinion the print quality is comparable to that of the Ultimaker 2+ that I use at work. Not bad, considering that printer costs about 14 times as much.

Some issues and how to fix them

I did run into some issues. One was that the included power supply came with a non-functioning fan. After a little discussion, the seller properly resolved this by sending me a replacement power supply. Fortunately, I had another power supply at my disposal that I could use while it was underway.

Some other, smaller issues could be readily resolved, some by using the printer itself to print some additional parts (if anyone is interested, let me know if you want the OpenSCAD files).

* The electrical safety could be better. You may need tie wraps (included in the kit) to keep some overly loose covers of the switch and socket plugs in place. That done, in normal use of the printer you don't run the risk of electrical shock, but it remains possible to put your fingers in a place where you might touch live contacts or pull mains wires loose. I designed and printed some parts to better keep the mains switch in place, and an enclosed compartment that separates the mains wires from fingers and low-voltage wiring.

* At some point the extruder got clogged, and on disassembly of the hot end I found that the teflon tube did not extend all the way to the top of the nozzle. That would leave a chamber of maybe 2 mm height above the nozzle, filled with PLA that might not be effectively melted. I wound some 0.5 mm steel wire onto a 3mm drill bit, cut it to a short spiral and put it at the top in the metal tube, so it pushes down on the teflon tube. After flush cutting the teflon tube with a box cutter (see below picture for the result) the hot end could be reassembled. I'm not sure of the cause of clogging and whether this fixed it, but it definitely won't hurt.

* When reassembling the hot end it showed that the NTC was not properly fixated in the heat block, it was just held in place by a piece of tape around the NTC and heater wires. It can be a safety issue when the heater temperature is not properly measured, it may cause the temperature to get much too high. I used a piece of steel wire, attached with the little screw on the heater block, to fix this. It should also be checked whether the heater element is securely held in place.

* The carriage attachment points on both the X and Y toothbelts are a bit too high, so that the toothbelts do not run in a completely straight line. This may cause the belt tension to vary. It's unclear whether this may significantly affect printed object geometry or wear the belts down more quickly, in any case I designed and printed some small parts that can be used to correct this.

* I found that the dimensions of printed objects in the X and Y directions were about 0.5% too small (not too bad of a scaling error, actually). If accurate dimensions are important, you can compensate for this in the printer menu. These settings are not kept on switching the printer off, it should be possible to change that by recompiling and reinstalling the printer firmware.

Tips and tricks for assembly and use

  • If you insert the nuts into the nut slots, they fall out very easily. Much better if you stick them with the side to a piece of adhesive tape (e.g. the painter's tape included in the kit) and use that to  keep the nut in place while you put in the screw. A small magnet may also work for this.
  • Although the included screwdrivers will do, they are rather small and, for the many M3 screws, I preferred to use a Phillips #2 type instead. Also, a set of proper spanners may come in handy.
  • When assembling the main frame, screw the M3 screws in very loosely. Put the frame on a flat surface, making sure it stands firmly, then tighten the screws, but still only slightly. If tightened strongly, they will pull the frame to a parallellogram shape as viewed from above. In contrast, do tighten the nuts on the M8 screw rods strongly, this will keep the frame straight.
  • Mount the Y stepper with the cable exiting to the front, not to the bottom as shown in the manual/video. It fits better with the acrylic support part that way.
  • The screws that hold the idler pulleys in place in the X and Y tensioners should not be tightened, because that prevents the idler wheels to turn freely. But leaving them untightened they are bound to fall out after a while. I applied some rubber glue on both ends to prevent these screws coming loose.
  • The lead screws appear to be dry, it can't hurt to lubricate them with a small amount of mineral oil/grease. You could put some on the smooth bars as well.
  • Make sure you keep all the included tools with the printer, in case you need to refasten some screws or apply modifications.

Safety

The printer uses mains power, high temperature, and large electrical currents are involved. Safety is not to be taken lightly.

I can offer the following advice:

  • The PSU is not a double insulated type. Use the printer on an earthed wall socket.
  • The printer should not be operated unattended. It may not be practical to stay in the same room all the time while it is printing, but it should be switched off before going out or going to sleep.
  • Mount a smoke detector above the printer, especially when you are not continuously in the same room.
  • For more safety tips, google "3D printer safety"

A comparison with a much costlier 3D printer

The cost of the Ultimaker 2+ is about 14 times as high as this kit. In my opinion the printing quality is not much higher. However, depending on what you need it for, the Ultimaker 2+ has advantages that may justify its higher price, for instance:

  • It comes readily assembled
  • It has a reputation as a reliable and low-maintenance 3D printer
  • Its construction (lower mass x-y moving print head) enables higher printing speeds
  • Due to smaller dimensions of print head, it is better suited to printing multiple objects in one session
  • It takes up less space and is neatly designed
  • Operation is less noisy
  • Less hassle in case you need warranty

However, for a hobbyist this kit is attractive, because of e.g.

  • Low price
  • The fun of assembling your own 3D printer
  • More opportunity for tweaking and modification