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.
Since the last post I have worked hard in the design and build of the Wood/Plastic clock. I have made a lot of changes in the original design, and I think that the final result is really a very nice clock!
It even has a name thanks to my sister! The time Transparency Clock:
Acrylic is difficult to work in the CNC with small diameter end mill bits. I used a 1/16” 2 Flute carbide end mill for the wheel teeth. After damaging several plastic stock and 2 end mill I learned:
Use new and sharp bit or a sharp bit that has been used only in plastic. If you used a bit to cut wood, forget to use it later in plastic.
You need to remove very little material each pass :.
24,000 RPM spindle speed and 10 inches/minute feed rate.
Keep the bit cool with compressed air.
For the internal cuts I used a 1/8” 1 Flute end mill. You also need a new and sharp bit or a sharp bit that has been used only in plastic but feed and RPM are different: 15,125 RPM, 16.1 Inches/minute feed rate and .004” maximum step down per pass.
With the above settings, and with lots of patient it is possible to get a very nice and clean cut. Below a video showing the internal cut with 1/8” end mill:
The other complicated thing is to bond brass and acrylic. After several test I ended using 2 part transparent epoxy.
Here is a video showing several details of the clock.
This is an old book! but a very good book for those who want to start building interesting things in wood.
To practice and learn how to use and simulate mechanism in Fusion 360 I modeled all the projects in the book except two.
What I found during this exercises is that Fusion is really friendly and essay to use for and also very powerful. It has some limitations with advance features like motion simulation and contact sets but for general design this things are not very important.
I am an experienced 3D drafter. In my day to day work I use AutoCAD, Invertor and SOLIDWORKS. I can switch from one to other without major effort. These programs are all very good and well recognized but at the same time very expensive for personal use. All these programs require to have a computer (powerful) loaded and with the licenses. For big projects you need a server to work on collaboration mode and the price of the license per user is several thousands of dollars a year if you need to keep the software up today.
I have tested many open source 3D drafting programs and also Google SketchUp; some of them pc residents and some cloud based. I did not feel confortable or productive with any of them.
This weekend I downloaded the demo version of Autodesk Fusion 360 and after a couple of hours I registered it and I I fell in love with it. I transferred some of my clocks models to Fusion 360 and started to play around. Then I decided to make a first full drawing of a part, in this case a RC Servo that I will use in a clock. Knowing Inventor the learning process was a piece of cake.
The other good news is that Autodesk Fusion 360 has a very interesting offer: A free 1-year startup license is also available for hobbyists, enthusiasts, makers, and emerging businesses that make less than US$100,000 in revenue per year. At the end of 1 year, you can reselect the startup entitlement or transition to a commercial entitlement.
After finishing the drawing it is necessary to use a program for generate the CAM to be able to mill or fabricate the parts. Mastercam is an excellent program but too expensive for personal use. I don’t know any good machine shop that does not use Mastercam. This program is the standard.
I use BobCad-Cam V26 as CAM postprocessor because I bought it during an offer they had last year at a reasonable price, but I need to convert my work to DWG or STEP in order to run BobCad. The CAD part of BobCad V26 is not as good and flexible as other programs. I know they made a lot of changes in version 27 and probably is much better now but I am not willing to pay more for something I use for hobby and not for work.
Fusion 360 has CAM as part of the package and also has the postprocessor for MACH3 that is the software I use to drive my small CNC. Now the work will be straightforward: Model – CAM – Mill with the same platform.
The next step will be to create a model of a sprocket or wheel and run the cam to learn and test the results with my small CNC machine.
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.
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.
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.
Yesterday night I worked with the electronics and a little bit of programing. The Pythagoras mechanism is making tic tock for the first time.
Here is a video of the first tick tock:
I learned a lot of things:
I used a simple fade up / fade down routine but the response of the solenoid is not linear with the voltage
I need to work on the mechanism:
Add weigh to the stopper lever
Polish the surface of the escapement wheel’s teeth in contact with the pull lever as in some positions it get stock when returning
polish the arbor of the escapement wheel and reduce the play as it is too loose in the arbor and some times it touches the third wheel. I placed some washers but I thin I will need to mill a new escapement.
Polish the rest of the arbors and teeth of all the wheels
This is a lot of work pending that will be done after I return from my business trip and find some time.
I made some provisional fixes and modified the program non linear analog output to smooth the solenoid action and added some weight to the stopper and the results were promising:
I am very exited with this project this will be a fantastic clock!
Today after work I worked in my garage to finish all the rest of the wheels in the CNC router: The hours wheel, the intermediate wheel. the intermediate pinion.
I also worked a little in the lathe to make the small cannon. I could not wait to see all assembled in the frame and the result is stunning
This is a close up of the cannon spacer. Still need to make the hole for the fastener:
And this is a close up of the Intermediate wheel, the spacer and the intermediate pinion:
I am really happy that everything fitted perfectly and all the wheel turns with almost no blockage. Anyway I need to disassemble all the clock to make all the wood finishing work and polish all the arbors.
Now I will not be able to go back to my garage for the next 10 days due to business travel.
Next step will be the electrical assemble an testing testing Everything arrived today so the only thing I need is time…
Yesterday I finished the third wheel and the pinion and made some tests of the escapement system using a manual push button.
I am very happy with my .0625” 2 flute bit. I really makes a a good work and at reasonable speed. It would be impossible make these tiny parts without it.
I also made the spacers and stoppers. I made a jig for my drill press and now I can make a perfect centered hole in wood rods
This is how Pythagoras looks with its 3rd wheel installed:
I tested the escapement with a 5 VDC power supply and a push button but the solenoid engages really fast and the lever pushes so fast that wheel advances several teeth. I need to modulate the the motion.
I have a test program already written fir the Arduino but I need a power transistor to handle +1 ampere of the solenoid.
Unfortunately with Radioshack out of business now I need to buy the parts online… I will save a lot as Radioshack was expensive but it was very handy and near home. Now I have to wait a couple of days (thanks to Amazon Prime) to get my parts!
Many things have happened since my last post!
I made the frame 2 times more as I was not very happy with the first one. First the mistake in the holes and second the feed rates and speeds.
Wood is not easy and with end mills bits that in general are not designed for wood there is a lot of trial an errors. Searching in the Internet did not help a lot until a found a very good software with the most important characteristics:
Full of data including wood feed and speed calculations
Easy to use
The software is G-Wizard Calculator and I should say that any hobbyist with a CNC should use this software. Since I started to use de G-Wizard No more broken bits and 200% quality and milling speed improvement. I really recommend the G-Wizard!
This is a print screen of the speed/feeds window of this great software:
This is the final frame with the quality and speed I like:
Below the CNC milling the base:
The base and the frame looks really nice!!!
And with the help of the G-Wizard I found the right speed and feed rate for a new .0625” 2 Flute end mill bit to make all these small parts and gears from the escapement with precision and quality:
I used one of the bad frames to test the escapement system and it looks beautiful even with the unfinished wood!
Next step is to write the program for the Arduino Nano to activate the solenoid exactly each to seconds. One thing I will use is a pulse modulated output to control the speed for solenoid to make a controlled engage and disengage. In this way this clock will be both very precise and quiet.