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The parts of interest

A project log for Oasis 3DP

A powder and inkjet 3D printer based on HP45 inkjet technology

Yvo de HaasYvo de Haas 10/16/2018 at 20:050 Comments

Oasis is designed mostly around standard 3D printer parts. However due to some technical challenges with 3DP, there are a few specialty parts I cannot design around. In this log I hope to explain what they are, where I got them, and what alternatives are possible.

Spreader + motor

One of the most important parts of powder printing is the spreader, A round, smooth roller. It is also one of the more difficult parts to get, and possibly the biggest compromise I had to make to ease of getting the parts. In Plan B, first I did without, which did not work. Then I had to jump through a lot of hoops to make one anyway, that worked somewhat. Now I am blessed to work at a company that can order at Misumi. Misumi, is magical. They have everything. The spreader is a standard(ish) part at misumi, 'SSFRHQ20-200-F20-P5-T20-Q5'.

If you can buy at Misumi, do that. I have included a drawing of the spreader, 'OA-Y20-P13-00'. This is exactly what you buy at Misumi. If you have access to a lathe, you can make the spreader yourself. It does need to be concentric and smooth, but other than that should not be difficult.

To drive the spreader a motor is required. For this I am using a cheap 25mm gearmotor. I used 300 rpm @ 12V, which seems about right.

Between the motor and the spreader is a timing belt. I use GT2, and use a closed belt of 120mm long. They are available through the usual internet suspects. Timing pulleys can also be found here if you have trouble finding them. All used pulleys are GT2, 20T, 6mm width. The pulley on the spreader motor is 3D printed for 'pulley not being available' reasons. I advise against printing the other pulleys.

Encoder

The printhead and the motion driver are controlled by separate controllers. To synchronize them I use an encoder strip. These things are common in inkjet printers anyway, and are not that hard to get.

For the actual encoder I use a 'AVAGO HEDS-9740#150', a 150 lines per inch optical encoder head. Most component suppliers list them, but do not have them in stock. Places like ebay do sell them. The tape can also be found on Ebay. you'll need a matching 150 lines per inch tape.

Bearings

Oasis uses mostly standard 3D printer bearings (608, 624, 625, preferably ZZ, LM8UU). However, on some places special bearings are needed. The spreader takes 685-ZZ (685-2Z) bearings. I cannot easily provide a link, but ebay has them in bulk.

Aluminium extrusion

Oasis is built around aluminium extrusion profile. 2 types of profiles are used. 30x30 and 30x60. There is not much to the profiles. They need to be 30mm, have a groove of 8mm, and the hole in the middle of the profile needs to be able to take an M8 thread. Not all profiles will need M8, but some do. You'll also need 30x30 angles, and 60x60 (2x30 long) angles. The exact type of nut you'll use is unimportant, but I prefer profile nuts that can be inserted after assembly. 

I bought mine at Misumi because I was already ordering. I suggest finding a supplier near you. In the BOM, the Misumi name is given, but the number in the order number is the required length. You can use that to cut your profiles.

An example of the used profile. Bear in mind that not all holes need to be tapped M8.

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