Introduction: DIY PCB Milling Machine - Part 2 - Linear Sliders
Hi Everyone. Welcome to another episode of this PCB Milling machine build. I am JCRP and this is Media Milan.
You are reading the second episode. If you want to watch the first episode where I built this frame then please click here. In this second episode I will be building the smooth rods on which the X-Axis and Y-Axis will slide.
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Step 1: Bearings and Some 3D Printing
I have bought these LM8UU linear bearings that go on 8mm smooth rod shafts. Now I have to design a holder for these and some blocks to hold the linear bearings. Lets dive in.
To 3D model the parts I use Fusion 360. The smooth rod holder needs to be about 30mm high so that it allows room for the motor to be placed beneath it. Here the walls of the holder is kept at 5mm for better strength. Then a solid block with a total height of 30mm given. This will be secured to the frame using M6 screws. So to accommodate the head of the screw I kept the base to be around 30mm wide. Then I can punch in two 6mm holes. I closed one side of the holder with 5mm thickness wall so that the rods does not slip out. This should be enough. But then it wouldn’t hurt to have some chamfer and fillet would it? There is no point in reinventing the wheel, so for the linear blocks I picked up this model from thingiverse. This model also has this washer. But for me it worked well just without it. All the models were sent to Simplify 3D where I set 80% infill for greater strength. Then I printed them.
The holes on the linear block had a very good tolerance. So with very little pressure I was able to push the linear bearing into the block. Rotating the block will apply even pressure on the bearing. The smooth rods that I bought on Ebay was oversized. With a thin cutting disc on the angle grinder I was able to cut it to size. The handle on the angle grinder helped greatly. All the parts were printed at .2mm layer height and with 80% infill. The chosen material was ABS because it is strong and can take some abuse.
Step 2: Bearing Placement and Why?
On a total I required 6 linear bearings. Now that all parts were ready I can quickly put it together. I remember seeing the Tech2C channel where he built the hypercube. In his x-axis he had four bearings. This gave him the binding problem while trying to move the bearings together. Then he finally decided to use a 3 bearing arrangement. Two on one shaft and one bearing in the other shaft. This way that problem was solved. I will link the video on the top right corner so you can check it out and understand what I mean.
Then when I took a look at my Prusa 3D printer the bed plate also had the same arrangement of bearings. So I just followed the same. Hence two bearings on one shaft and just one on the other.
Step 3: Fastening the Linear Slides
I have left the shaft loose because once I put the Y-axis plate I can move it and then screw them down. This way each axis will be perfectly parallel.
For the X-Axis I pretty much followed the same process. For the upper shaft two bearings were added and for the lower shaft one bearing. I aligned the top shaft to be flush with the first cross rod. This acts like a mark so I can do the same on the other side too. And this will also set the total height of the Z-Axis. Now I can loosely align the bottom shaft of the X-Axis. As I said this will have just one bearing .
Step 4: Conclusion
So all the smooth rods are in place. I haven’t decided the exact distance at which they have to screwed in. But we will come to know that when we design the X-Axis and Z-Axis in the third episode.
The Y-Axis motor and the belt bearing will be placed here in the middle. Thats why I had to keep the smooth rods high. Make sure you buy the Chrome plated smooth rods. 8mm rods are plenty strong and do not flex. Because its just 380mm long it can take the load even if I keep aluminium to engraving. I am sure that you might have some questions, write them down in the comments. If you feel that this video taught you something then please like the video. Sharing the video helps me a lot. The next video will be more 3D prints and a key point in this build. To not miss it subscribe to the channel. Thank you for taking time to read this. Until next time. Happy Learning.
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