We are continuously receiving emails from friends asking when we will publish the project.

We think next Monday (February, 23th) if all goes well (cross your fingers) you will see TwinTeeth.

Sorry because we are a bit delayed with respect to the plan but we didn’t stopped a second, just there was so much to do.

Last weeks we were: correcting small bugs on the software, redacting the web in English and Spanish, taking pictures of the robot, filming a video, mounting it, preparing the files with the blue-prints, circuits, software, etc.

Thank you very much for your interest.

Diyouware team.

Yes. We changed the name of the project to TwinTeeth. Why? Because we did not like MKII and also because that word inspired us in the robot designing. We don’t want to bore you now with the details so we will explain the full story when we will publish the project by january/february.

We have also coined a new term: PCB mini-factory. One year ago we had the vision of a robot which would help us to fabricate small PCB prototypes at home. During its development we though some possible definitions for this concept and now we think that mini-factory is the best.

More news: we tested the “professional-made” pickup’s driver PCB and the results are fantastic!!!

The electric noise has almost disappeared and we were able to focus with the IR diode very easily and without blurring the UV-film which was our primary goal. We were also able to turn on/off the red diode but we were a little afraid about destroying it, so in addition to the limiting resistor we also limited the diode intensity by firmware.

Take a look at some pics we took with a 20x microscope. They correspond to some details of the Pickup Driver PCB.

You can see on this one the 0.5mm pitch FPC connector tracks. It’s the small thing we have ever printed.

We will continue testing the printing quality but we can say that this stage has been almost surpassed.

Next stages: we have to 3D print some framework pieces we redesigned with improvements and then we will test the complete “mini-fabrication” process of a two-side PCB, including: designing, photoengraving, drilling, acid etching and dispensing solder paste on SMD pads. At the same time we will check usability and software functioning. We already tested the 3D printing toolhead but maybe we will also test it a little more. We would also like to test milling/carving on a soft material like expanded polystyrene or wax. For example it can be useful to make silicone moulds.

We hope the final functionality of the PCB mini-factory will be the following:

• Laser photoengraving – consists in drawing the PCB circuit on sensitive film or board using a UV or IR laser.
• Drilling – it allows drilling vias and holes using any mini-rotary tool like Dremel or Proxxon.
• Milling/Carving/Etching – using the same tool, it can also mill or carve soft materials or etch PCB copper with a v-bit.
• Solder paste dispensing – with a special syringe dispenser, it can deposit solder paste with precision on SMD PCBs pads.
• Plotting – if you prefer this method, you can plot the circuit with a permanent pen-maker.
• 3D printing – the mini-factory includes also a 3D printer so you can make knobs, boxes, front-panels, etc. with PLA or ABS. And also print circuits with conductive filament or graphene filament in the future!!
• And much more… because it is extendable and you can use any other tool you can install on it.

All of this functionality is supported by the robot firmware and a new user-friendly management console we have been developing this year. It will help all of us to control the mini-factory and the different tools.

We also have detected some new possible applications:

• UV resin 3D printing – we already talked about that. It is the well known Stereolithography (SLA) method. It consists in 3D printing objects with an UV laser in photo-sensible resin. We already drafted some blue-prints using the optical pickup and probably will be our next project.
• Bio-polymer 3D printing – consists in 3D printing in  bio-polymers for tissue engineering. It seems easy: just add a UV photo-initiator to any hydro gel and 3D print on it with the UV laser beam. The benefit to use the pickup could be the precision because the laser beam is perfectly focused and close to the hydro gel surface. There are labs and universities around the world working on that.
• Microscopic applications – we don’t have too much time to research more areas, but we dream with this kind of projects. It consists in using the pickup as a laser microscope or molecular tweezers.  In theory the laser beam is 0.5um wide so maybe is possible to do something at this scale.

Finally we promised to publish Dr. Futai’s document. Here it is:

http://www.digchip.com/datasheets/parts/datasheet/287/MLX75012.php

It is the datasheet of the photodiode array which we believe the pickup uses. This document confirms us the functionality of some of the pins we discovered last year and others we didn’t have any idea about it. It also allowed us to have a better control of the pickup’s laser diodes.

There is a lot of undiscovered pickup functionality yet. I hope our project had inspired some people to research more pins and end our job. For us it is enough as we covered our goals and we will continue with our real project: the PCB mini-factory.

Sounds good, isn't it?

The PCB samples we ordered have arrived today. They have a professional look. We will build one and test it as soon as possible.

We ordered some PCBs to a professional manufacturer because we wanted to test if the circuit still works while reducing traces, clearances, vias and sizing. Usually the quality of this kind of services is far away from the quality we can obtain at home, even with the robot. But as the circuit is so sensible to electric noise we wanted to know if it works better in a proffesional way.

This PCB is based on the latest driver circuit version....

We were almost to throw in the towel trying to focus with the red diode when we did a quick test with the infrared one. We have a few pickups with the red diode burned but the infrared diodes seem still alive. When we discovered the way to turn on/off the blue and red pickup’s diodes we were also able to manage the infrared one (The infrared light is invisible to the human eye but you can see it through any video camera). But for some reason we didn’t see any wave in FE signal when trying to focus with it.

Reviewing old CD/DVD player’s manuals we saw that the photodiode is usually divided into two patterns: one for DVD and another for CD. That made us think that some pickup pin had to have the function of change from one photodiode pattern to the other. And so it was. There is a pin which allows switch from Blu-ray/DVD to CD mode. If not used, infrared diode turns on but no wave is obtained while focusing. We slightly modified the driver circuit and now we are able to focus with the infrared diode. The good news is that limiting the current with a resistor it seems it doesn't destroy itself. We still need to test a little more but it looks promising.

On the other hand, last week we designed and built the solder paste dispenser toolhead. The idea is that the robot also automates this task.

We used a small stepper motor, a linear axis, a small leadscrew and a syringe containing the solder paste. A few weeks ago we developed also the Eagle Cadsoft’s ULP program which generates the g-code file to move the robot and deposit the paste in the component's pads....

We are still fighting with the electric noise. As we said in previous blog entries this problem affects the focus signal.

We are using the PHR-803T electronics and the astigmatic method to focus de laser on the PCB. To obtain the S-Curve we calc and amplify the A,B,C,D signals obtained from the pickup’s photodiode array and generate an analog signal (FE or Focus Error) which we read from an Arduino port. In a similar way DVD or Blu-Ray players focus the laser beam on the disc surface but using more complex circuitry because they have to do it in real time as the music or movie is playing. We only focus the laser beam once when begin to print the PCB so our circuit is more simple.

We developed all this method and electronics last year and were working fine in MKI, but in MKII we did the mistake to mix the digital and analog circuitry on the same PCB, so the digital circuitry induce noise on the sensible analog signals and eclipsed the S-Curve.

We think the solution will be to isolated digital and analog circuits on different PCB areas and use different GND and VCC lines connected in a star configuration to a common point. Also to reduce PWM traces length ad minimum, isolate connector pins and decouple everything with some tantalum capacitors which are more suitable to the range of frequencies we are treating. We also included a choke to see if it filter well the power suply noisy frecuencies.

So we redesigned the circuit and the board and here it is: (courtesy of ZofzPCB 3D Gerber viewer)

The smaller area is the digital circuit: the noisy neighbourhood.