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Building a Sunhokey Prusa i3 3D Printer Kit


Sunhokey Prusa i3 3D Printer Kit

If you can assemble children’s toys on Christmas Eve, you can build a 3D printer kit. And it will probably work fine. But remember this: a 3D printer kit is not a finished product. You are buying a proven design, a box of parts, and assembly instructions. There will be bumps in the road. Here is the story of my ride.

The order was placed. The price was paid. A few weeks later, the box arrived. The 3D printer kit was well packed and complete. Obviously, the folks at Sunhokey had made an effort to “get it right”.

Two issues were discovered during unpacking. First, the power cord had a European standard plug, not usable in North America. This was easily replaced. Second, one of the smooth rods for the Y-axis was slightly bowed. An easy way to test a rod for straightness is simply to roll it across a flat surface, like a desk. A slightly bowed rod will rumble rather than roll smoothly. The vendor told me that “some bow is allowed”. We will see.

Other than these two points, everything was correct. None of the 49 pieces in the acrylic frame was damaged. This might seem daunting at first. But each piece had its unique shape and markings. It was easy to tell one part from another, and which part went where.

A 3D printer kit is generally assembled using metric screws with round hex heads. It is important not to over-tighten these fasteners or you might crack the acrylic. All of the hardware was packaged in plastic bags and labeled. There were lots of spares.

Assembly instructions were included in a series of fourteen short videos on a DVD. The disc also contained software, as well as some pictures showing the proper software settings. The control board for this 3D printer kit contained the equivalent of an Arduino Mega and RAMPS 1.4 board, as well as driver modules for the stepper motors. The videos showed you how to assemble the various modules and piece the entire 3D printer kit together. All of the required tools were provided in the kit.

The videos were great. They had no sound track, just a video of a person putting things together. The camera was over his left shoulder. Each video started with a description of the pieces you would need for that step, and then showed a person completing the step. The approach I used was to spread all of the acrylic and other parts across a large surface and then pick out what I needed. After watching the technician perform the work, it was easy to duplicate.

Since I had previously researched this model, I knew roughly what to expect. The assembly process was easy. It took about eight hours. I was not in any hurry. Even if I had not prepared, the work would still rate as moderately easy for someone with basic assembly skills. Since the acrylic frame was well designed, there were few opportunities to make serious mistakes. Basic rules such as “measure twice, cut once” and “don’t over-tighten the hardware” were all that was needed to go with the videos. This was not really any harder than some children’s toys I have had to assemble on Christmas Eve.

The electronic wiring was also straightforward. Most of the wiring was pre-assembled with connectors. There was not a video for the wiring harness, however. Rather, there was a picture on the DVD showing which wires should attach to which connectors on the control board. After completing the wiring and checking it twice, I powered up and the machine came to life. The final video showed a very basic approach to level the print bed on the 3D printer kit.

Overall, well done to the folks at Sunhokey on putting this kit together. From what I have read in the various user groups, I think most builders would agree. There is something very fulfilling with hands-on an assembly. You feel confident that you know every part, what it is for, how it should work, and where to start if something needs fixing or changing.

A Few Problems with 3D Printer Kit

To be fair, though, I need to describe the problems experienced with this 3D printer. These are things you might expect with a low cost kit. None are deal breakers.

  • The first was a complete lack of after sale service. Part of this might be language-related. I could tell this from my written e-mail exchanges, and unfortunately, I don’t speak Chinese. Part of this might be due to price. There is not much room in their pricing to provide service. And when you are dealing with a kit rather than a product, there are perhaps too many uncertainties to deal with. My advice is not to expect any service and you won’t be disappointed. If you buy a 3D printer kit and all the pieces arrive in working order, expect to be on your own after that. And given the price point of these Chinese kits, that’s probably okay.
  • The second problem, already mentioned, was the bent smooth rod for the Y-axis. They would not replace this. It worked, but I could tell that the bed was not traveling smoothly. I replaced the part with a length of O1 5/16 inch drill rod from my local Metal Supermarket for $8. While I am not sure that drill rod will stand up over time, for now the print bed moves much more smoothly and quietly. Incidentally, I discovered that drill rod is quite easy to cut with a hack saw. Before you cut, do some experiments to ensure that you are preserving the length of rod that rolls most smoothly.
  • The third problem was the mysterious death of my controller board, the MKS GEN V1.1. It stopped working about a month after I built the machine. No idea why. After wasting a month going back and forth with Sunhokey, it became clear they were not going to replace it. So, I hooked up an Arduino Mega and RAMPS 1.4 board as a temporary replacement, and ordered a new MKS controller from a supplier on ebay. That cost around $40. Judging by what I have read on the user groups for this 3D printer kit, spending an extra $50-$100 above the purchase price for replacement parts is not unusual.
  • Forth is the issue of calibration. Remember, the Sunhokey Prusa i3 is a KIT, not a finished product. In a finished product, you would expect it to already be fully calibrated. In a 3D printer kit, you know that you probably have to calibrate it yourself. This would be true even what all the parts fully met their specifications. A 3D printer needs to be finely tuned to work properly, just as you would expect to give your car’s engine a tune up. The heart of the problem was that the way Sunhokey configured the firmware, they made it impossible for the kit builder to calibrate the machine in any real way. More about that in my next article on this 3D printer.

The bottom line is that the RepRap Prusa i3 3D printer kit is a good design that can work well when calibrated. The Sunhokey kit is a good value and well regarded by its users. It’s easy to build and easy to run with a little help from the owner’s groups on Thingiverse and Facebook.

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