# Specific 3D Printers, Scanners, & Hardware > Peachy Printer Forum >  Update #31: Delay Details #2

## Eddie

*Project Update #31: Delay Details #2*Posted by Rinnovated Design ♥ Like

*Hey Backers,*After reading the comments on the last update it was apparent that many of you would like more information regarding the recently announced 4 month delay. We’re more than happy to give you an in depth look at where we stand and where we’re coming from...
We’ve found that delays come in a few different forms, so we’re going to break them down into 3 categories.
*1. Expected Work*These are things we knew had to be done, or chose to take on in order to make a better product. In this case we simply underestimated the time it would take to accomplish these tasks, and that results in a delay. Below is a list containing a few of the more prominent ones:
*Developing the best mirror arrangement*
We explored many completely different mirror arrangements, and even got a bunch of them to print successfully. Who knew there was so many ways to make a 100 dollar printer! Finding the best way meant exploring a lot of roads that eventually lead to dead ends.
*Creating and Testing Build Instructions*
We greatly underestimated the amount of work involved in creating comprehensive build instructions for The Peachy Printer. Due to changes in the printer design, we also had to do this process multiple times.
*The Development of Snapfit*
We came up with Snapfit shortly after creating the first set of build instructions. We decided to hold off on shipping the first beta kits so that we could take the time to fully implement Snapfit. Due to all of the new features we added to the printer since PP18, the assembly time had grown dramatically. With the addition of Snapfit, we were able to reduce the build time by approximately 6 hours! Although implementing Snapfit resulted in a 3 week delay in beta shipping, at the very least it will save about 3 years (6 hours*5000 backers /24 hours per day /365 days per year = 3.42 years) of backer time that would have been spent holding and glueing parts. That doesn’t factor in all the time and resources wasted if a part was glued incorrectly.
*Developing a Damping System*
We knew from very early on that vibrations during a print would cause large defects or even failures. This meant that a good dampening system was essential for the Peachy Printer to produce quality prints on a consistent basis. We’ve since explored and tested many different approaches to this issue. While we’ve come up with a system that dampens vibrations well, it still causes memory. We are still working to develop a better damping system with less memory.
*Developing User Friendly Software*
In order for the Peachy Printer to be as easy to use as it is affordable, great software is necessary. Packaging for multiple OS’s, making and improving a GUI, adding tools and functionality, and simplifying the printing process are some of the things that we didn’t accurately estimate time for.
*Enhancing the Drip System Design*
While the drip system was one of the doors to a lower priced printer, there were many improvements to be made in order to make our drip system a reliable one. Things like clogging valves, inconstant drip rates and sizes, air bubbles, salinity levels and many other factors had to be dealt with.
*Creating a Flexible and Effective Calibration Process*
No two Peachy kits will be built exactly alike. It’s also a very hack-friendly printer. Coming up with a calibration process that’s as flexible as the Peachy Printer was no small challenge. Whether you’ve got a huge or tiny build volume, or decide to use different lasers, apertures, or mirrors, the calibration process remains the same!
*2. Unexpected Work*These are issues we did not foresee. They were necessary to deal with and resulted in a more functional printer, however they also lead to a setback in our timeline. Below is a quick list containing a few of the most notable ones:
- Finding that most types of thread cause memory, making it hard to predictably position the laser.
- Finding that oil damping also causes memory.
- Finding that we had to redesign the entire printer with orthogonal mirrors in order to avoid a lot of warping.
- Finding that many sound cards are AC coupled requiring us to design a circuit that demodulates an AM signal and write modulation software.
- Finding that many sound cards have different frequency responses that affect their ability to do amplitude modulation.
- Finding that using power from USB ports often affects the sound signal coming from the sound card.
- Finding that we need to calibrate for how drip size changes with drip speed.
 - Finding that normal valves are extremely sensitive to clogging when set to very slow drip speeds.
- Finding very odd behaviours caused by the power regulator that comes with each laser and deciding we must engineer our own specialty laser current limiting circuitry.
- Finding that acrylic plastic was no longer suitable for use after implementing snap fit due to it’s hard and brittle characteristics.
- Finding out that the optimum wire size for coils is simply far too small to handle and breaks often. 
- Finding that making coils with very fine wire required us to make our own coil winding machine. 
- Finding that a diode on the circuit had a lot more impedance than we originally thought, causing the circuit to not work well.
- Finding a way to simplify the process of tuning the circuit from one that involves 7 tuning knobs to one that only uses 2.
- Finding an inexpensive way for the user to know their circuit is tuned.
- Finding a way to turn the laser on and off with just an AM signal.
 - Finding that there is often a difference in ground voltage between the sound card and USB power.
- Finding that turning the laser on and off causes a positional offset in each mirror, and implementing various things to reducing that offset.
- Exploring FM and discovering that it has ill effects and expenses.
*3. External Issues*Below is a list of issues caused by external factors that resulted in a delay at Peachy:
- Due to communication issues we were unable to source a coil manufacturer in time for our beta shipment. As a result we decided to produce enough coils for the beta kits on our own winding machine.
- Our shipment of beta circuits took 40 days longer than expected to arrive.
- Our laser cutter took 50 days longer than expected to arrive.
All of the issues listed above have attributed to the current 4 month delay. Thanks to the amazing amount of support we received during the campaign, we have the resources to solve all of these issues. Unfortunately in doing so we’ve taken more time than originally estimated, however as a result you will see a much better product than we would’ve been able to provide had we only reached our original fundraising goal of $50,000. Now let’s take a look at what still needs to be done...
*Moving forwards*Below is a list of areas that need further testing and issues that we are still working to solve in order to reach first viable product:
- Memory caused by the dampening system (we’re working on a new magnetic damping system that may have very little memory)
- Resin Shrinkage
- Software usability
- Large prints
- Adding calibration processes for things like laser spot size at wide deletions, refraction, reflection, various non linearities, and offsets.
We hope that we’ve been able to provide you with a better understanding of where we currently stand, and why we are taking more time to further develop the Peachy Printer. If you'd like to read more about these issues, many of them have been discussed at3Dprintboard.  Thank you for your support.
Until next time,
*The Peachy Printer Team.*

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## Feign

Well, this is definitely a comprehensive list.  Not just good for summing up the process of developing the Peachy, but as an example for anyone who considers developing (or even just making a major improvement for) a product.  Nothing is just "a simple matter of implementation".  Even with something as seemingly simple as recieving a signal and outputting a laser image.

So it looks like there will be another round of heavily modified hardware beta units before the final production batch can even go through...

I'm not surprised that the Peachy will need more Beta testing iterations.  I'm more surprised at myself for thinking it would just be _that easy_.

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## BrockMcKean

I know the process of research and development can take a lot of time on its own. Add to that documentation,  public relations, and dealing with outside entities and you've got yourself a monstrous headache and a lot of unhappy people -- no matter how efficiently or quickly you work. I appreciate all of the hard work that Rylan and the rest are putting into the Peachy and to open source it. Also, I'm a little surprised with the few core team members that they have, how much they have accomplished in such a short time, and still find time to update everyone on major developments. More testing and setbacks just means more contributors! Keep it up guys.

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## User_Defined

I agree, nothing is ever as simple as it first seems. 

The grinding wheels of R&D usually produce something honest and real, and after all is said and done, something that you can rely on more and have a better understanding of.  It is far better to have something keep failing and get through every hurdle than to be lucky and have it work the first try by some fluke of a setup which leads you down a wrong path. (I know from experience). 

I really appreciate the updates, as someone said it may not seem like much in telling everyone what mistakes and failures were made/overcome, but part of the thrill in backing something is seeing it all pan out.. good or bad. It's like cheering for your favorite sports team! 

Also just as importantly these updates might inspire people to suggest solutions that the peachy printer team might have overlooked.

good luck to you all, and I am very eager to see some more prints (good or bad).



-UD

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## Feign

Also, at some point, it might be best to have a "reccomended sound card" list rather than try to make the printer work with every sound card under the sun.  Heck, I remember one thread that I can't find now that someone found a DC coupled USB sound card for impressively little cost.  Consider finding that or something similar and reselling it through the Peachy store.

I'm a little curious to hear about their new damper that they're coming up with, since everything else seems like electronics/programming fixes...  (Heck, I could think of lots of uses for a no-memory motion damper.)

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## BrockMcKean

> Also, at some point, it might be best to have a "reccomended sound card" list rather than try to make the printer work with every sound card under the sun.  Heck, I remember one thread that I can't find now that someone found a DC coupled USB sound card for impressively little cost.  Consider finding that or something similar and reselling it through the Peachy store.


I agree with this. You might be able to literally make it universally compliant with existing sound cards, but the next day someone in china will make a sound card with a higher SNR than you expect and the day after that someone in the US or EU will make one that has a completely different sampling rate. Just pick a best fit and let the community come up with further hacks and suggestions like this USB card or minor tweaks to the circuitry if it doesn't interface perfectly with their particular sound card.

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## Aztecphoenix

> I agree with this. You might be able to literally make it universally compliant with existing sound cards, but the next day someone in china will make a sound card with a higher SNR than you expect and the day after that someone in the US or EU will make one that has a completely different sampling rate. Just pick a best fit and let the community come up with further hacks and suggestions like this USB card or minor tweaks to the circuitry if it doesn't interface perfectly with their particular sound card.


just wondering but, can't you figure some way of sending the sound signal through USB to the Peachy? after all, isn't it all just pulse waves?

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## nka

They are not pulse, but signal. But yes, there's many way to make it work on USB... just need another kind of board... this is a hack a suspect we will see.

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## Feign

Wouldn't that just be called "using a compatible USB sound card?"
I mean, there comes a point where you just buy a pre-made solution and save the time and effort.


...Wait, who do I think I'm talking to here?

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## SamSam

I think that having a narrow list of "recommended sound cards" would be a poor idea.

When we backed this project, for $100 or more, there was no indication that there would be a list of recommended sound cards. If that happened, therefore, many of us would be out of luck -- either needing to shell out another $50-$100 for a new sound card, or simply screwed because our laptops don't allow sound card swapping.

Further, the list would get stale quickly, and in 5 years that "recommended list" might just be a small percentage of the market. If the new cards necessitate a hardware fix, then existing owners will just be out of luck.

A calibration solution is the only solution that should remain future-proof for a significant period of time.

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## BrockMcKean

> I think that having a narrow list of "recommended sound cards" would be a poor idea.


I think more likely what we're talking about is a short list of sound cards that do not fit the vast and overwhelming majority of sound cards that are in use today. Matching some widely used standard, like USB is quite easy, now. When USB was brand new different products worked differently with different implmentations of the same "usb standard" at the time. Even now there's no way to guarantee that the device you are interfacing with is going to provide some specific minimum amount of current. It depends on what other devices may or may not be connected and how much current the host can source in the first place. 

I don't think there's anything wrong with matching compatibility to 99% of sound cards and providing a simple USB solution for ones that require additional and/or different circuitry. Doing so would require a hardware-software interface where the software would have to detect the sound card, identify that it is a problem card, and send a special signal via audio out (or usb?) that toggles the circuit. What's worse, is if you want 100% compatibility with every sound card in existence, that probably would require _more than just two circuits_ to match it perfectly. 

Throw in age, oxidation and a bunch of other factors that _no one in the entire industry_ is going to account for and you have plenty of cases where a sound card will just simply not do the job it's intended to do in this system. Heck, if you plug a laptop into a charger most of them will have white gaussian noise as well, distorting the original sound wave. Filtering that and coupling the noise out is not so simple to do for EVERY sound card and every machine in existence.

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## Pete

Sorry for my absence guys (car problems and a downed hard drive  :Mad:  scuppered my recent efforts)

I think the original kickstarter campaign aimed to give everyone a DC coupled sound card, and the moment they moved into an AM world the problems began (FM would have been better as the amplitude wouldn't matter, but more expensive). Yes SNR is a factor but by far the most irritating factor is bandwidth roll off which causes the position of an on laser signal to be different to an off or on laser signal. The other is as peachy requires a constant audio signal if there is any drop in the audio buffer then that causes annoying artifacts (the more I work with python the more it seems like a joke language for getting stuff written quickly without caring about processing speed). Even classifying one soundcard would not give you a similar result on an 'identical one' necessarily. There are current fixes for this in the software however the hysteresis issues (known as memory here) need fixes implementing before the success of this can be truly evaluated. Another issue touched upon here is the USB current causing issues with the sound signal, most people are fixing this with  floating supply (a phone charger) it is essentially a ground loop error where return current meant for the USB is returned down the path of lest resistance so will then share the ground return up the audio ground, offsetting the signal and adding AC components in the case of the negative rail switcher and the laser controller.


Having said all this, I've been working on my own "USB petechy" and the boards should arrive in the next week or so. With one USB I can get all the power and comms (including drips) and will hopefully solve all of the above issues. I'll post pictures when they arrive, but there's not much to it, it should be ~£5 to build even in low volumes....then I just need to get it interfaced with the software, any volunteers?!

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## User_Defined

That sounds awesome Pete!

As for the hysteresis/memory issues, maybe it can be tuned for in software? Hysteresis usually is predictable, so I'm thinking it would just need to calculate an overshoot based on the anticipated deflection angle of the laser. 

Kindof like backlash compensation on CNC systems.

The peachy team would need to get a test setup to collect data on memory vs deflection angle, and then generate a lookup table based on 

1) the angle of the axis, 

2) the direction that axis is presently moving.

3) the present speed of the axis.

4) the future direction of the axis (acceleration or deceleration) 

This is all rather challenging, and I personally would have great difficulty implementing it. Officially it would be called feed forward hysteresis compensation. 

I wonder if there is any way to provide inexpensive closed loop feedback from the moving mirrors, because in that case you could get accurate positioning with a basic PID controller. 

I do remember that there are magnets on the mirrors... maybe a hall sensor could detect some positioning info? Or maybe if the magnet is moving quickly, a sense coil could get the EMF, send that EMF voltage wave back to the controller, then integrated the wave to provide the positional data (plus a constant) of the system based on Faraday's Law.

Important to note, that this EMF value can be considered as the "I" in the PID.... it may be possible to get a "P" or proportional feedback in some other way.

These are just ideas, so please correct me if Im wrong in any part.

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## Pete

I'd thought of some kind of feed forward controller, this could work, don't know if a software FIR filter would completely solve the problems, it would be really bad for prints to have any overshoot, especially on square corners. In my intial firmware tests I was getting about 50KSamples/s on both channels so should be enough to do stuff like this. I suppose if you were being crazy mental you could interleave every valid point with the laser on with an off point at one of the extents.....hmmm! 

The hysteresis fades to almost nothing with the damping system removed, unfortunately then any external vibrations cause significant wobblies and with the current drive system (when the audio buffer underruns) it is unuseable without the damping....a step reponse in drive leads to significant oscillation. I will try adding a LPF to my driver and remove the damping to see what I get.

Adding DC position feedback would be relatively trivial electronics but the mechanicals are probably going to be too precise to get decent results, also adding weight to the rotor....at that stage there's probably an argument for rigid bearings and more drive....then we've made some proper galvos......we should make these....http://elm-chan.org/works/vlp/report_e.html

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## Feign

> Having said all this, I've been working on my own "USB petechy" and the boards should arrive in the next week or so. With one USB I can get all the power and comms (including drips) and will hopefully solve all of the above issues. I'll post pictures when they arrive, but there's not much to it, it should be ~£5 to build even in low volumes....then I just need to get it interfaced with the software, any volunteers?!


I for one am incautiously excited.  Optimistic even.  Now if only we could get a word on this new damping system they're working on.  (How bad is the histeresis on the oiled-tab system anyway?  I really liked the simplicity of it when I first saw it.)

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## User_Defined

Megneto resistive sensor:

http://www.digikey.ca/product-highli...r-Series/52414


Taken from Wikipedia:

The AMR effect is used in a wide array of sensors for measurement of Earth's magnetic field (electronic compass),  for electric current measuring (by measuring the magnetic field created  around the conductor), for traffic detection and for linear position  and angle sensing. The biggest AMR sensor manufacturers are Honeywell, NXP Semiconductors, and Sensitec GmbH.


So Im sure you can sense the angle of the galvos with it. With something like this you might even be able to electrically dampen the system with a closed loop angle feedback from the magnetic sensor. 

For those familiar with control loop theory:

 Youd have your input signal with a voltage proportional to what angle the mirror would be.
Next it would go to your amplifier circuit to drive the mirror.
From the mirror you would then have a positional measurement by the magnetoresistive sensor.
The error is defined by where the mirror actually is, and where you wanted it, and this signal is fed back to combine with the original signal to close the loop and subtract away the error. A system like this should auto dampen.

The physical setup would need to be decided... I would imagine a circuit board re-work to get the sensors close to the mirrors' magnets... Or maybe they sell chasis mountable sensors. 

Personally I would have just made two PCBs for each mirror axis, combining their motors, sensors, drivers and tuning. Then they would mate with the snap fits. You could have the exact same PCB design for each mirror PCB.

A jumper connector can connect both boards together. When assembling the PCB's youd just populate the computer connections for one board, and leave the second blank (having the jumper wire connector between these two PCB mirror assemblies).

I hope I am being clear, the goal would be to modularize the design, and use a PCB for electronics, AND the mirror support structure. It might hopefully elliminate 

1) some wiring to the coils, as they would be now on board
2) the main PCB, making the overall device smaller
3) make it much easier for standardization and mass production.
4) use less plastic.
5) reduce assembly time, and possible wiring mistakes.

Im sure there are more advantages, the one I am most interested in, being an electrical engineer, is the standardizing for mass production.

BUT, All this depends on the accuracy and usability of these types of sensors.

-UD

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## Aztecphoenix

maybe to move into the future, we need to look into the past.

The old ZX Spectrum computers were designed to use any tape deck that you had available rather than a model specific deck and took in the audio signal and converted it into binary code, it also had the ability to compensate for the differences in tape deck output which means using the same technology for the Peachy wouldn't require he AC coupling and all the other stuff they are having to deal with. Schematics for the circutry are appairently online and as it is more than twenty years old any patents have worn off.


maybe looking into this might help with some of the problems the peachy is having and could solve the sound card problems.


to get a better idea of what I am talking about check out The Ben Heck Show episode he released on friday.

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## BrockMcKean

> Youd have your input signal with a voltage proportional to what angle the mirror would be.
> Next it would go to your amplifier circuit to drive the mirror.
> From the mirror you would then have a positional measurement by the magnetoresistive sensor.
> The error is defined by where the mirror actually is, and where you wanted it, and this signal is fed back to combine with the original signal to close the loop and subtract away the error. A system like this should auto dampen.


Yes, it would take care of any distortion in actual mirror position due to noise, or vibrations. However, what about the printing material itself? Just because you dampen the mirrors doesn't mean the resin isn't bouncing around. The resin has to be physically dampened somehow. Also, there are plenty of hall effect sensors that can be used in parallel as you are describing and in series with the coils as well. Not entirely sure what's different or special about that particular sensor from Honeywell other than the low power requirements.




> The old ZX Spectrum computers were designed to use any tape deck that you had available rather than a model specific deck and took in the audio signal and converted it into binary code


This is possible, but doesn't really make any sense to do. If you have a sound port on a device that is capable of running the peachy's software, it should have a USB port as well. To go from analog to digital and back to analog you're going to need some sort of "processor". Which means that you honestly might as well just use USB. The problems that arise from different sound cards range from different noise levels to different output levels. Analog is precise, meaning the signal must be exact. Digital allows for a lot of wiggle room. There's no way to build a circuit that will always be compatible with every sound card. Plugging a laptop in will usually produce some noise on the line, resulting in a distortion in AM. Some sound cards that are on-board desktop cards have a significant amount of noise on them as well. If you own a phone that wasn't taken care of as well as it probably should have been it will likely not produce sound without some minor distortion that may be inaudible, but will affect AM.

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## User_Defined

> Yes, it would take care of any distortion in actual mirror position due to noise, or vibrations. However, what about the printing material itself? Just because you dampen the mirrors doesn't mean the resin isn't bouncing around. The resin has to be physically dampened somehow. Also, there are plenty of hall effect sensors that can be used in parallel as you are describing and in series with the coils as well. Not entirely sure what's different or special about that particular sensor from Honeywell other than the low power requirements.


Adding a closed loop would make the system more reliable and reproducible, along with providing a memoryless dampening of the mirrors (something they claimed to have problems with). The resin bath can be dampened if people want, but it is of less concern than the mirrors. These are two different problems that must be addressed separately.

I linked that sensor as an example of something which can be used with the strength of magnets they chose for their design. Also, it is small, inexpensive, and comes in a standard surface mount package. Basically, I linked something that I felt might work, as opposed to a larger less sensitive model. 

- UD

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## User_Defined

Sorry for the double post!

I had a second look at the sensor I linked, and it was not the right type of sensor! The one above is a simple on/off sensor design to replace reed switches in low power applications.

What I meant to link was something like this:
http://www51.honeywell.com/aero/comm...C1501-1512.pdf

This device has angle resolution less than 0.05deg over 90 degrees operating range. However it does have a hysteresis error of 0.017deg (but over the entire range that is less than .02%).
Something like this could be easily used to implement an analog PID positional controller to ensure accuracy in the galvos and dampen the drive.



-UD

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