Here I'm sharing my learnings, projects and experiences with CNC 3040 router/milling/cutting machine I have in my garage. Here I will include all the projects I will make with the Arduino processor and accessories. You are welcome to comment, and share.
This clock will go to the hose of a very special person for me and I need it not only to be nice but also accurate. the Conical pendulum is very inaccurate and also has some noise problems. With the changes now the clock is quiet and very accurate.
I modified the clock to be driven by a 60 RPM synchronous motor.
I added a double sided contrate wheel and two crown wheels one driven by the motor and the other to drive the pendulum
The pendulum has also a inertial wheel. I embossed 12 weights to the wheel. I also added a new guide for the pendulum rod.
One of the things I love best from my profession and my hobby is when I can see in real life what I created in my mind. Technology is great for me because I don’t have the skills to draw by hand in paper so computers and CAD programs helped me to develop my creativity.
Combining technical knowledge with creativity has been the most important tool for my work and now my hobby.
The planetary clock was a challenge. The diameter ratio of the sun pinion to the planet wheels for 12:1 reduction and 8 teeth pinion is at the critical point. Too much play in the teeth can make the system to block as two planet gears can touch each other. Any eccentricity of the ring will block the system and if the teeth spacing is too tight the system will eventually lock itself.
I had to mill more than three times all the parts making small design adjustments to adapt everything to the tolerances for wood. It is almost impossible to obtain tolerances in the range 0 .1 mm with wood so I worked with .5 mm tolerances to allow space for the natural expansion/contraction of the wood temperature and humidity. I also made tests with hot and cool room temperature.
The picture below shows the three planet wheels, the sun pinion, the ring gear, the two ring covers
Below is a detail of the ring covers and the mill down of the sprocket area of .5 mm to allow some play of the planets in the axial direction. This also reduces the friction caused by expansion.
Next picture is detail of the planet gears support, all made form a single piece of wood milled and carved with the CNC to obtain the shape and exact position of the arbor holes.
Here a video of the the testing of the planetary gear: It works nice
Next was to make in the lathe the two circular bases, one is like a cup to hold the motor. The wood I used was so hard that I burned the small motor of the lathe. This is when a full replacement warranty is valuable!
Next finish the wood assemble and glue together everything and pray that it will work as before wood finish. I have found that the best finish for wooden clocks is to use Danish Oil. it is not sticky dries relatively fast it is very easy to apply.
The numbers and the seconds and minutes dashes are engraved in the dial ring:
Here us the clock finished (front view):
Here the back view of the finished clock:
Everything moves very slow in the clock so here are a couple of fast motion videos compressing 3 minutes to few seconds to show how it works:
One of the issues I always had with my small CNC 3040 was that I had to manually set the spindle speed in the frequency drive using a knob and chuting the speed with a tachometer. Each tool change or job type (rough or fine) requires different spindl;e speeds.
I found in EBay a small electronic board that converts Pulse Width Modulation to an Analog voltage. It is possible to set the Match 3 software (this is the software that controls my CNC) to output a PWM signal in one of the port pins. The frequency drive can also be set to use a 0 to 10 volts signal to set the motor speed.
It has some good information in how to calibrate the output.
Below is the small PC board as I installed in the control unit. The circuit needs 24 volts for power that are available in the control’s power supply.
The 0-10 volts output are should be connected to the analog input on the frequency drive:
The PWM input signal to the new circuit should be connected to one of the output pins. in my case I used the A axis on the CNC control board hat corresponds to the output pin 9.
On the mach 3 software it is necessary to adjust the following settings:
The last part is to set the frequency drive parameters to allow speed control via the analog input. The drive of my machine is a Chinese HUANYANG ELECTRIC
I spent a lot of time searching in the Internet for a manual until I found it in a Chinese site. Thanks to Google automatic page translate!
These are the parameters to change:
PD0000 set to 1 to be able to make changes
Pd002 set to 1 to use the external terminal
PD070 set to 0 to use 0-10V control
Once it is running it is necessary to calibrate the output using the potentiometer in the new circuit
The system works OK although it is not very linear but for milling plastics, wood and soft metals it is OK. I am very happy and it is working really good and helping me to avoid mistakes.
Before engaging in building a multilayer planetary gear clock I decided to go step by step and create a “light” version with only the 12:1 gear and driven by a 1 RPM motor.
I have a couple of timer motors the run at 1 RPM but the only problem is that the run counter clockwise and for this reason cannot be installed directly in the minute hand arbor.
I also have one motor that turns clockwise, but is big and when I draw the model the clock looked like a fan with a motor in the back.
In technology design and in many aspects I follow the concept of “Simple is beautiful” but some times adding some complexity to an an artistic kinetic device (that is what I think a wooden clock is), the complexity provides more visual action.
In this case I could use a couple of gears to invert the motion direction but it would be more or less the same as the motor will be exposed and the “magic” of the wooden clock will be diminished.
My solution is, using Clyton Boyer’s words” drive the clock wit a pawl and click gear. In other words: I cam lever with a ratchet or escarpment wheel.
In the back view you can see the motor hidden in one of the bases and the small cam wheel that will make the escapement to advance one tooth each motor turn.
Today I will start creating the CNC programs to mill all the gears.
I love gears. There are so many combinations and possibilities that allows millions of combinations.
This time I developed a clock wheel train based only on epicyclic gears.
I will use three sets of planetary gears connected in series as a sandwich. the input must be oration of one turn per second.
The clock will have the three hands: Hours, Minutes and Seconds.
For diving this clock I will use a timer synchronous motor. I have to options one that makes one turn per minute and one that makes 60 turns per minutes. I have not yet made any decision.
I already finished the 3D CAD model of the clock without the driving device and I think that this clock looks great!
This will not be a small clock! the diameter of the rings is 7.5”
A new challenging project with a lot of work in my garage
Projects need to be finished and this one is!. At the end is a very nice clock but not as quiet as I would like for a night table. It is quiet but still have a small hum as the coil is actuated with Pulse Width Modulation. I Could make it better but it would need a lot of electronics.
I will work in an alternative using a hobby RC servo motor, actually something like a robotic arm pushing the escapement! but this will be another history…
Sometimes I simply cannot sleep, this is not frequent but when it happens I need to be active. I can not stay in bed counting sheep ... When this happens I go to my garage and start working in something, I spent several nights of this week till late and the rewarding:
My Pythagoras clock is almost ready and working beautiful:
I still need some wood and electrical work:
Design and mill a new stop lever to hide an extra weight I added, now is a piece of rod glued to the lever
Finish retouch in some places
Make the final circuit and hide it inside the clock base
Now I am adjusting the Arduino program to obtain the precision.
Here is a short video of the clock and some function details:
This video was taken at night with no noise and the only sound was the tick tock of the clock.
Finally after a long wait trying to find an excuse to buy an accessory to for my small wood lathe that is more expensive than the lathe itself I got it!!
Got some reward cash back in a credit card and without thinking it twice I bought it.
Here is my new Barracuda Wood Lathe Chuck System that is a nice self centering chuck with a lot of accessories:
I just made a very small piece for my Pythagoras clock and now my I feel and understand the importance of a good chuck. I have several projects in mid with the lathe after I finish with my clock.
