Z Axis thoughts

[Ivydene25]

Hi,

I am new to this forum and have been following the Peachy Printer for a long time. I love the concept and the approach, but given who I am I couldn't help thinking about the Z axis - dripper mechanism. In it's simplicity and function it is perfect for this sub $100 printer, but I have been thinking if there is a cheap more traditional alternative.
My thoughts are around building a Z axis based on a small stepper motor with an M3 screw driving a simple light weight platform mounted on to two 3mm steel rods via dual linear bearings. Attached to this would be a build platform that would enter the build vessel.

The key is the use of Micro/PIC to control the stepper and set the appropriate response to the mic / dripper cable.

Given a thread pitch of the M3 screw (0.5mm) and stepping angle of (7.5 degrees) we get 48 steps per revolution which equals 0.0104mm height difference per step. 7.5 Step angle is conservative so in theory the resolution could be better. The size of the container would not matter and would require no changes.

A bit of interfacing to the printers code through the mic cable would enable an appropriate signal to be sent once the platform has been moved down. (Emulating the dripper signal)

My view would be to still use resin floating on Saline and to lower the platform into the saline as the print is built. This enables the same support to the print as if you were using the usual dripper mechanism.

As far as cost I think it could be done for about £25 and a bit of time.

OK there are questions that I would ask about this?

How do you configure the start position in relation to where the printer is focused?
Calibration should be strainght forward once the focal point is understood. Is the focal point changed as the print is printed to account for the different distance to the resin? This may have to be changed as the distance to the resin would be constant.
How much time is required between steps to allow the printer to describe each layer? Could this be fed back to the Micro from the printer?

Please excuss my ramblings but I thought that it might be worth a discussion.

So hopefully now I can sleep again! Ivydene25

[Bryce]

I think I understand what you are proposing, and it seems feasible. It seems like the same concept at the Form:1 from Formlabs, only flipped 180 degrees so that instead of the build platform rising from the resin with the laser underneath pointing upward the platform lowers down into the resin and saline mixture. I do believe that this would be adding unnecessary complication by adding a third axis of mechanical movement. Also with that method you are limiting your resolution compared to using drops which you can vary the size and number of drops and the dimensions of the container can be adjusted to make it even higher resolution if the surface area is larger. A few things that you might want to take into consideration if you attempt this are the displacement of water caused by the lowering build platform and lowering mechanism, the materials used for the platform and mechanism so as to prevent corrosion from immersion in salt water, and the vibrations and disturbance to the surface of the resin caused by each lowering. If you were to gear down the stepper motor you should be able to increase your resolution in the z-axis with your design. A possible benefit of your design is keeping the level of the resin at about the same height, thus keeping it as close to the focal point of the laser as possible. I do find your concept interesting and would encourage you to try it and let us know how it works out and how you accomplish it.

[Ivydene25]

Bryce,

It is possible to get stepper motors with much better resolution than 7.5 degrees and with micro stepping a better resolution would be possible.
I have thought of using a very light weight build platform with minimal vertical support, perhaps carbon tiubes to a simple lattice build platform. The only increase in volume would be the carbon tubes which should have a minimal effect for a reasonable volume build container.
At the moment the things I don't know are:

The focal length of the laser
The timing of each layers scan time and how this is coordinated with the drips
Where the laser is focused in the resin (at the air to resin or resin to saline layer)
How does the current Peachy Printer configure the build height / focal length

My view I suppose was that if the focul length of the laser was kept the same and not changing then the accuracy would be improved. Also the repeatability of the system would be more consistent.

Within the PIC it would be possible to configure the steps per layer and the initial start position. If the Peachy software is counting drips this can be replicated or a single pulse could be used on the mic cable.

There would not be a need to change the resolution based on the build volume.

The technical details help to understand the best approach to controlling this and feeding back to the software.

[rylangrayston]

I Think this hack would be a very good improvement to the performance of the peachy printer. Atho drips are amazing at coming in regular tiny amounts, they are not as accurate or precise as the system you propose.

Because we at Peachy are very excited about these kinds of modifications we have intentionally added features that will make doing things like this really easy.
The feature your looking for already exists. basically you hook up an arduino( or and micor that can conect as a serial device) to the printers computer and the peachy software will ask for more drips any time it has finished printing a layer. You can simply use this more drips request start advancing your stepper motor. You can use a digital io pin to pulse the microphone once for each steps the steper takes. There is no documentation for this yet but all the code is very readable and on git, I think the feature is called "serial drip control" in the current gui.

in short :
1)in setup printer - setup options, turn on the serial driper feature
2)Attach an arduino that listens on the serial port
3)when the arduino recives a 1, turn the motor on and emulate drips on the mic line
4)when the arduino recives a 0 stop the motor and the emulated drips.
5) post pics of your superior prints here in this thread ( seriously I haven't tried this hack with stepper motor linier guide system yet and im dieing to see the results)

... jeezz its 5:44 am, Im going to hit the sack now, see if I can fall asleep before my alarm goes off at 7.

[Ivydene25]

Thanks Rylan, for the additional information I will have a look at the code and see how to set this up. It looks like you have already thought of this as an approach.
I was going to use a smaller simpler PIC to help keep the cost down, something like a PICAXE which even has a BASIC language. An easydriver stepper controller requires two pins Direction and step and another to look for the serial signal.

I will look at the basic hardware and software and await a Printer.

Cheers

[Chayat]

6) post build instructions so we can all copy you!