Dual Extrusion Cupcake - ABS Plastic & Silicone

Winter Project #1: Dual Extrusion Cupcake

So, I needed a simple, hackable platform to explore 3D printing of 2 or more materials. I was particularly interested in combinations that involved a thermoplastic such as ABS, PLA, etc... and other non-thermoplastic materials such as RTV silicone, wood filler, etc...  I happened to have a MBI Cupcake CNC lying around; I had replaced it with a far better printer years ago. The Cupcake CNC was my first 3D printer that I had built, so I was quite familiar with the strengths and weaknesses of the Cupcake CNC. So, I modified it. It is better for it to be used in the name of research than to be gathering dust.

The non-thermoplastic materials that I was focused on could be dispensed with a air extruder similar to MBI's Frostruder MK2 or a motorized plunger system such as FAB@HOME uses. I decided to go with the air extruder because of it's simplicity and minimization of hysteresis.

I really didn't like MBI's Frostruder MK2, it seemed overly complicated. I did not understand the reasoning for the air solenoids on the Z platform with the extruder held in a more complex package than needed to be......after all this is 3D printing, something can be printed that holds a syringe barrel quite easily. So, I moved the solenoids(I tried finding a 3/2 solenoid, so I wouldn't need 2 solenoids but I had a hard time finding one in 12V for a reasonable price) to the upper left side of the Cupcake. This freed up some room on the Z-platform and I designed and printed a nice syringe barrel holder that mounts in front of the MBI MK5 plastic extruder. This syringe barrel holder eventually evolved into a toolhead holder(more on this in later posts) and after a couple of iterations I had something that I was confident would work. Next, was the electrical work.

I  used RepG's M106 and M107  M-codes to cycle the Fan output of Gen3 mainboard. That fan output was the signal that would be used tell the air extruder to pressurize or vent. Now, I only had one output, the fan, on the Gen3 mainboard to control two air solenoids. Therefore, I made a custom air extruder controller out of an Arduino Uno that would controller the solenoids depending on the output state of the fan pin. In keeping with my motto of trying to keep extraneous portions of the design off of the Z platform, I mounted on the left side of the makerbot. Ah... now the software.

Fig 1: Modified dual extrusion Cupcake

Using RepG's G54, G55, etc... g-code offsets made coding the tool offset easy. I made some quick python scripts for a object 25mm X 25 X 8mm tall that would combine my to two g-code files, one for the thermoplastic and the other for the second material, together. So, now I had a single file I could run and print with. The python scripts that generated the g-code made it easy to characterize and optimize the dispensing of the the material from the air extruder.

Now the really test, dual extrusion of ABS plastic and silicone.

Fig 2: Silicone calibration and initial ABS + Silicone prints

Fig3: Calibrating Silicone and ABS extrusions




Fig 4: Success! On the left is a completed one without the silicone being fully enclosed and the one on the right  with the silicone being fully encased by ABS plastic.

So, by the end of it all I had printed ABS and silicone within a single print.  After all this time,the Cupcake was definitely showing it's limitations and it boils down to how much more time and money(mainly time) do I want to put into the Cupcake to get it printing to "modern" resolutions, if that is even possible. Also, the build size in the Y direction is reduced by 35mm due to the tool offset and  thus reducing the Y direction build envelope by 35%. I have had my Cupcake for over 3 years; several generations of new low cost printers have come and gone within that time span with better hardware and better software & workflows. Now, hope is not lost for the Cupcake... remember that I created a toolhead holder. So, other toolheads could be mounted and I have a couple of different ideas that could be used on that. However, I have a MakerGear M2 on its way so I can further explore dual extrusion(shhhhhh.... maybe even tri, quad, etc... extrusion too.)

Now, I need to package up all the files and post it to thingiverse.

Now, I am back...

Well, I have been pretty busy for the past year. However, I should have more free time to devote exploration and posting of ideas and research related to 3D printing and its applications. I finished getting my garage organized into a small workspace at the end of September of last year only to enjoy about a month of good weather until it got around 7 degrees C(45 degrees F) in my garage. I did get some decent research done, even through the winter, although I still need write up and post my findings.

Back in the saddle

Well, it has been awhile not that anyone really cares. But, I should have more free time now to finish off a few projects that I want to finish, the printable water filter and a few others. So, look for some posts here very soon.

Printable Clothes Line / General Object Hanger

Well, it is kinda of windy where I live and I have blankets that need to be air dried. I wanted a setup that would be easy to setup, take down, and wouldn't take much space. So, I designed a fully printable clothes line. The bodies/anchors are printed and the line is 3mm filament. You can also use it to hang other objects up to such as plants, etc... I will also be using it to hang outdoor Christmas lights this year over a large spans that the lights themselves could not span without sagging horribly. 

Yes, I could have used rope with some knots. However, it would have not have been so easy to remove.... and not nearly as fun to do.


Check it out on Thingiverse:
http://www.thingiverse.com/thing:25859

A quick thought...

So, while looking for bunk beds for my kids, I noticed how in many of the bunk beds the bolts and/or screws are countersunk yet the caps are exposed and detract from the look of the furniture. I am not the only one who has noticed this, as read on reviews of the said furniture. I instantly thought of.... Hey, I can print a removable cover. However, that was quickly dashed by the next ensuing thought..... Hey, if it is removable my youngest is sure to try to remove it and that could be a choking hazard if it was removed.  So, that kind of answered the question about exposed countersunk bolt and screw heads in kids furniture.

This lead me to another thought. Who is responsible for 3D printed design if it becomes hazardous for someone or something(a pet)? 

You can have number of parties involved or just a single person. I will look at the aspect where you have a maximum number of individuals interacting together.  A designer to create the design. A operator to print the design. A end-user that uses the printed part. However, the end-user may be more than one single person, it can be anyone that comes in contact with the physical design and may not use the design as intended. So, who is ultimately responsible if a printed part causes harm?  A very interesting conundrum that will surely be addressed in the courts in the coming decade.

Well, last Friday I started designing a water filter to be used possibly for emergnecy relief that is made using an inexpensive home 3D printer. This is only an alpha but here are some pictures more details to follow in the next couple of days. Enjoy.

Figure 1. Solid model of prototype water filter

Figure 2. Solid model cross-section of prototype water filter

Figure 3. 3D printed  water filter case prototype

Figure 4. Water filter case split

Figure 5.  Separate water filter case pieces

Distributed Rapid Manufacturing Using 3D Printers For Disaster Relief (Part3)

This will be just an overview of the main points of quality control for distributed rapid manufacturing using 3D printers that I have identified. I am sure that there are plenty more aspects to this subject, since this subject has never really been discussed.

The main points that aid in maintaining quality.

• Device Design
• Simplicity
• Ease of assembly 
• Intutitive to manufacture
• Use of standard materials
• Documentation of Manufacturing Process Parameters Used
• Printing process setup, general specs.
• Program printing parameters posted.
• Inspection(Duh!)
• Assure that the device or any of it's components is not out of spec
• Documented inspection procedures(SOPs)
• Operator
• Registered users akin to how HAM radio operators are licensed 
• Motivation

Design

1. Simplicity - Making  a device simplistic is a must for maintaining quality in distributed manufacturing It allows for more give in the system as whole. The system encompasses not only the actual device but manufacturing processes that must create the part and the operator that must assemble the device. This facet has a trickle down affect to other main points such as inspection, etc... Such as if the device is designed to be inspected with simple calipers,etc.. Also minimizing interfaces whether they are mechanical, electrical, fluid,etc.. or any combination of these. Interfaces are a point were failure can be introduced. For example, instead of using two pieces and joining them together, spend a little more time and make a design where a single piece can be used instead. Never settle on a design and constantly innovate to make that design more simple. 
2. Ease of assembly - By making the device easy or intuitive to assemble, errors can be minimized during the actual assembly process. 
3. Intuitive to manufacture -  If the device components impute the way they should be manufactured then errors can be reduced by an even experienced operator, since the system software(RepG, UP! V.1, etc...) often allow for 6 degrees of freedom(x, y, z, theta_x, theta_y, theta_z) set by the operator.
4. Use of standard materials - In order to create a more standardized version of device the materials must be readily available and fairly common. The most prominent material in the hobbyist, DIY 3D printing world is PLA, and ABS plastic. Preferably this material would be sourced from a single vendor if possible but other vendors could be used if needed. Also, if a design uses other materials the designer/operator must be conscientious of how operators in other parts of the world must obtain the materials.

Documentation of Manufacturing Process Parameters Used  

1. Printing process setup, general specs - This must be documented to help "standardize" setups between different machines and operators. This is needed because of the wide amount of differing hardware that exists today in the DIY, and hobby markets that may print "slightly" differently than another machine.  The biggest factor is that these machines are often assembled by the operators and can vary widely machine to machine. So, the more we know about a general setup the faster configurations from the setup can be shared to other operators
2. Program printing parameters posted -  This goes for any process, especially in the DIY and hobbyist since there is a wide variety of program tweaks that can be made in Slicer, SkienForge, etc... in order to repeat the process the settings(infills, feedrates, nozzle temp, etc..) must be documented and shared

Inspection(Duh!)

1. Assure that the device or any of it's components is not out of spec - Well, this is a given. However, it does tie in nicely with other main points such as simplicity and motivation.  If the device is made as simple as possible only the minimum amount a measuring equipment(hopefully the easiest, most available, and most intuitive to use) is needed. Motivation to do a good job is a must especially when dealing with inspection. The operator must want to put out a quality part, since after all they are doing this pro-bono, there is no wage involved.
2. Documented inspection procedures(SOPs) - Inspection SOPs are needed so that each operator is inspecting the device and device components in a consistent manner with proper inspection equipment.

Operator

1. Registered operators akin to how HAM radio operators are licensed - While I hate to register operators that make the devices, I think it is a necessary evil. To be registered, a operator would need to passing a test that encompasses the print, inspection, and assembly of a sample device. This would ensure that the operator is competent and the test would be given by an authorized registered operator.
2. Motivation - The operator must have the proper personal motivation to design, print, inspect, and assemble a device for emergency relief. After all, all of this work is being donated. This ensures that the operator does his or her best in each of those categories to make sure that a quality device is manufactured.  Because, the goal of this device is help  individuals or families in need, and may even save their lives.

Whoa, that was longer than expected. Again, like I said in the beginning of the post there are probably plenty of more. I am sure that in the very near future that this problem, maintaining quality in distributed rapid manufacturing 3D printing environments will rise to the general discussion in the DIY and hobbyist communities.