Pressure angle: Pressure angle in relation to gear teeth, also known as the angle of obliquity, is the angle between the tooth face and the gear wheel tangent. It is more precisely the angle at a pitch point between the line of pressure (which is normal to the tooth surface) and the plane tangent to the pitch surface. The pressure angle gives the direction normal to the tooth profile.

Lower the pressure angle higher will be power transmission( in terms of pressure angle). But higher pressure angle will give good loading ability(Torque) and increase the stress as well.

Power = 55%

Speed = 15 mm/s

First one :

I gave dimensions same as mdf sheet to test. (0.5 mm additional).

Sun gear : 60.5 mm
planet gear : 30.5 mm
Ring gear : 119.5 mm

second one :

(1 mm additional)

Sun gear : 61 mm
planet gear : 31 mm
Ring gear : 119 mm

Third one :

Sun gear : 60.5 mm
planet gear : 30.5 mm
Ring gear : 119 mm

dowels

So if I wanted to use one axle, I need to use taper dowels in which, Wedge Action will help to Fix the Bearings with the help of Friction. Click here to know about Wedge Action. My dowels have varying Diameter from 18 to 21 mm.

Creating CNC Files

After fixing my dowel Dimensions around 20 mm (in the center), I started designing for the Main gear files for CNC cut. My CNC file is also parametric. so I can have good flexibility in design changes. Below are the Parameters and the relations I gave on Desing. the design procedure is the same as I explained in prototype file. Here I used pitch circles as references , according to it I am going to generate gear profiles.

I want to cut the output disk later, if sun and ring gear will work perfectly after assembly and able to load after I will cut it, reason I put disk there is to make sure of some space.

Parameters

Below are independent parameters

Outer Diameter of ring gear : ring1

Clearance : c. Clearance I gave from the original size is 30 mm from one size.

Width of the material sheet : widthouter

Length of the material sheet : lengthouter

parametric GIF

So as I decided both the frame and the planet gear assembly will change accordingly.

Deciding the inner diameter for Planet gears

So for planet gears, I have to decide the inner diameter, I have a bearing diameter(outer) of 47 mm so I have to check which inner diameter of the planet gear will be good. since I have to check for the holder also I did some experiment cuts to know which dimensions will be good for assembly, since Dowels are tapers, I can't have an exact idea which dimension will work properly.

So I cut some and found the exact one, I generated a code file on partworks 3.5.

For now, I made some conclusions about inner diameters.

Inner diameter of Ring gear : 47.5 mm

Diameter for the Holders : 19.5 mm

Design in Fusion-360

After knowing the pitch diameter I generated a gear profile on fusion-360. The process of generating the gear profile is the same as I mentioned above in prototyping. after generating profiles and manual check on the cad I generated DXF files for each type of gear.

Here I didn't generate the inner diameter of gears, that part I can do in Autodesk after generating .DXF files.

Back to autodesk

After then I arranged profiles according to the sheet. The reason I pit small holes around profiles is for screws, I noticed in CNC we spent much time in mounting the sheet and it is a tedious job, sometimes we need to mount screws in between the sheets. but the main problem is screws can be in way of our toolpath and we never know exactly how far it is from the main tool path, I saw some screws are cut from the tool so far.

So the solution I came with is to use Pockets. I was going to cut Pockets in a sheet of 1 or 2 mm and place the screws there. so I can have a perfect location where can I put the screws and the main advantage is if I have to change the location of the profile I will know where to put the new profile exactly.

One can Download the CNC bed file from the sidebar.

using Reusable sheets

In the lab, I found we have one sheet which I can use for my sun, ring and axle and it will help me to know about cutting clearance, if I have to give the component the kerf or not. so I went to cut these three profiles. after making these cutting files separate I went for a cut on CNC.

I uploaded files in .dxf 2004 version.

Partworks

Partworks is a software solution for cutting and creating different shapes in CNC. Partworks can help to generate 3d patterns with profiles, Pockets, Drills. with the partworks-3D user can able to do 2.5D cut or 3D milling.

Click here to see 3d milling in Partworks 3D in Week 10. Click here to know more about partworks.

partworks

In part works before importing the sketch, we have to give Bad size - cutting sheet size. to do that click create a new file.

bad size

There is a small issue between our CNC and partworks software, they have a different orientation. Axis orientation differs by 90 degree anticlockwise.

In our CNC,

X axis - Width : 1200 mm

Y axis - Length : 2400 mm

But since axis orientation is different in CNC and the partworks I have to interchange the values of Width and Length because they are differ by 90 degrees anticlock.

In Partworks

X axis - Lenth : 2400 mm

Y axis - Width: 1200 mm

Material thickness : 12 mm

Units : mm , Units should be the same with the software you exported files, otherwise it will scale up or scale down according to mm and inch scale.

Tools

create vectors: for test cut on the CNC, one can directly create profiles for cut

Edit vectors :  It is used to modify the curves, the bottom part of the section is for joining curves, suppose curves are not joined, it will join the curves if a curve is not joined machine will cut that line and arc as an individual curve and it may cause problems.

Align objects : it will align objects

Layers : It can help to orient the design files and separate two types of different operations.

Import files to partworks

Toolpaths

Click on the Toolpath on the side to generate toolpath.

Select tool

I used a 3 mm endmill milling bit for cutting.

Pass Depth : Pass depth determines how many phases you want to cut the material.

If I Put directly 12 mm here, it will go straight 12 mm down. it is not advisable because the tool will face very high forces than, so I decided to give 3 mm passes. each time tool will go 3 mm down after completing one cutting cycle and my material will be cut in 4 phases (12/3).

Spindle speed: it determines the RPM of the Spindle.

Feed rate: it determines the Feeding Force applied to the material.

Plunge Rate: Plunge rate is the speed at which the router bit is driven down into the material when starting a cut. if is too High it will break the tool or make a crack on the surface of the material.

Tabs

Tabs will hold the material on shit while cutting.

SAVE toolpath

I SAVE THIS FILE ON Shopbot (Inch) format.

On Shopbot software - spindle routine

After generating the Toolpath now its time for cutting operation. After opening the SHopbot it is good practice to level up the machine for a while and Run the Spindle worm up command. it will Re-circulate the oil on the Spindle assembly.

Then Import Tool path file.

Keypad

On the Control box, there is a Keypad box which can be used to move the spindle in 3 axis to set up origin. After setting up the origin click the zero axis button to make that point origin.

Emergency Switch

Setting up Milling Bit

Setting up the 3 mm bit on the Spindle. First Chuck is fixed on collet then collet is mounted on the spindle. After that bit is inserted on the chuck and tightened.

Cutting

Post processing

So accidentally I gave Tabs on teeth profile, and in some gear cut depth was not enough so I have to do some post process.

fixing Bearings

Now it was time to check the inner diameter again, and it was perfect Bearing fit perfectly

Axle

Assembley

Before going for outer ring gear I want to check manually if I Need to give more clearance to teeth or not, I had to take many iterations in the Laser prototype that's why I wanted to be sure. for that tab error, I cut more 3 gear so I can have better motion.

Ring Gear making

After checking that tolerance is good enough I went for cut ring gears and frames.

Toolpath making procedure is the same but this time I tried a 6 mm drilling bit. I want to try it for increasing cutting speed.

Feed rate : 1.5 inch / s

RPM: 14000 rpm

And I messed up!

2 flute spiral bit

I thought this is because of speed so I reduced it but no help from that, I think the tool diameter is too much for the teeth profile and that's what it burning the sheet by slowing down at edges. Then I tried 2 flute spiral bit 3 mm bit.

After that, I reduce the feed rate to 4.5 inch /sec and it was perfect!

Frames

These are my frames for ring gear which will hold the ring gear in assembly. I gave an I mm pocket in the inner diameter of the frame so planet gears can rotate freely.

Ready to assemble

Starting from Frames

I had different options in Fabrications

Could use Buiscuit joinery by making slots in frame

Use of glue for permanent fix

Use of Nails for Fast assembly and disassembly

Using biscuit type joinery: it would be good if I could use Biscuit type joinery and I intended to do that, but two frames should be concentric for that if not they will misalign and I will not able to fit my planetary assembly. I needed something which is good to change the joints position if frames can't align.

Using Glue: Glue would be a permanent solution, if I kept little bit misalignment it cants be fixable.

Use of nails: for my case, it was a solution, I could realign if there's some error in misalignment, it is easy to add and remove also. ao I choose nails.

Fixing secong Frame

Using araldite glue

Since friction force was not sufficient enough to move the sun gears, so I used Araldite glue.

FUll assembly

First try full assembly

Oops !!! Sun gear is not able to hold its place in a vertical position, it was my design fault I think, I should have to take care of back support in sun gears, I tried it on the Horizontal position Anyway.

Sub assembly working

I was very happy it was quite smooth but I don't know where it is h=giving problems! even the sub-assembly of planet gear and ring gear was quite smooth but when I integrate them it became too tight to rotate and sun gear can t handle that thrust for a long time. But it was rotating though, below is the video.

Full assembly Second try

But I enjoyed it from the start to the end! The end results were not as quiet as expected though but it helped me to develop some maker skills to use different tools and though how you can do things step by step! At this movement, Our Two instructers and the whole team were helping me to make this thing work for me! It was a very good experience, appreciated !

Group work

In computer cutting group work we as a group was going to try a different speed and feed rate on MDF and Plywood so we can have a conclusion in which speed and feed are giving better surface finish.

my role was to handle the machining process in group work, I and Samiul were trying different speeds and feed on the materials and checking cutting behaviors! Click here to redirect on the group Website.

conclusion

As I mentioned above CNC week was amazing from start to end. it gave me a feeling of being a maker which was one of the main reasons I wanted to Do fab academy!

In CNC week I learned much more about laser cutting moving assembly, Partworks software, Shopbot and very much new to me how to assemble things. The last was not perfect though. Still, a week was great!