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TechAhoy Inc.
801 Woodward Ave.
Ridgewood, NY 11385

P: 917-994-2441
E: info@techahoy.org

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801 Woodward Ave
Ridgewood, NY 11385
United States

(917) 994-2441

A Friendly, Neighborhood Makerspace

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What’s happening at TechAhoy? Check back often to find out! 

Jobs and Troubleshooting the MMU2S

Ian Smith

First and foremost, we are hiring!

We are looking for a creative and energetic individual who loves sharing knowledge to join our team as a Makerspace Instructor. If you or someone you know is interested, check out our jobs page to learn more and apply.

hiringannoucement.jpg

We added a new tool to our virtual belt - the Prusa Multi Material 2S upgrade kit (MMU2S). We’ve had our eyes on the MMU2S since February, but put off ordering due to the lengthy lead times. Lead times dropped recently and we finally placed an order!

As excited as we were and confident with the Prusa brand our initial impressions were underwhelming. We have assembled three i3 MK3 kits and two i3 MK3S kits without issue and all five printers performed amazingly out of the box. The MMU2S is a different experience all together. The instructions, while clear, forked several times depending on whether you were upgrading from a MK3S/MK2.5S or MK3/MK2.5 which lead to a slower overall build as we flipped back and forth in the manual ensuring we were on the right step. And there was this curious, little feature - a razor blade to cut the strings produced by the extracted filament. The seat for the razor is barely present, nothing more than a groove, which lead to a major issue right away.

The razor would slip out of the blade-holder and create a cut on the front-PTFE-holder (pictured above right). This happened more than once and finally cut so deep it created a jagged edge which required the front-PTFE-holder be reprinted to prevent future jams. We weren’t the only ones who encountered this problem - note the 24 comments at Step 21 in the Pulley Body Assembly chapter. We took a suggestion from a few commenters and added a drop of super glue to the razor before securing it with the blade-holder and reassembling with our reprinted front-PTFE-holder.

Although we were able to resole that issue we encountered another one which again seemed out of character for the Prusa brand. The main draw of the MMU2S is its ability to print five different filaments at once. To facilitate this capability, Prusa includes five spool holders and what it calls a buffer assembly. The spool holders work well enough - they provide a smooth glide for the spools as they unroll. But, the buffer assembly is awkward to say the least. The idea is each filament has it’s own layer through which it can glide from spool to PTFE tube to MMU2S and by default the buffer assembly is affixed to the back of the MK3S which creates a logistical challenge. To change filaments, one would have to reach behind the printer and pull or push the filament through the PTFE tubes attached to either side of the buffer. Naturally, the filament wants to curl which means it doesn’t slide straight from one side of the buffer to the other. Under normal circumstances this would become a very frustrating process when swapping filament colors.

So, we ditched the buffer completely and designed our own guides to use in conjunction with our IKEA SKÅDIS pegboard! (You can download the 3D model from our Thingiverse collection.)

Our guides work pretty well, but the MMU2S is still prone to jams and requires a lot of babysitting. Fortunately, Prusa has incorporated some really great error detection into the MMU2S - the printer will kindly notify you that MMU needs user attention if there’s an issue retracting or inserting filament during transitions. The MK3S will even power down the hotend and then reheat automatically once you’ve intervened. So, despite the frequent jams we’ve yet to experience a true print failure.

It probably goes without saying, but print times are considerably longer due to the time it takes to constantly swap filaments. And the filament wipe towers produce substantial waste; in the case of the pink sheep the wipe tower was larger than the final print!

All that being said, when the MMU2S is working it is a sight to behold - it really complements the MK3S; print quality hasn’t suffered in the least! Even if the learning curve has a longer tail, the MMU2S will really add value to our print farm. We are putting it through the paces now printing a cheeky smile and some 80’s style sunglasses for legü. The latest version of PrusaSlicer is a cinch to operate; you can easily place complicated multi-part STLs and select their respective filament colors without issue.

We are excited to have the MMU2S in-house despite the issues we outlined and we look forward to mastering its setup and printing jam free!


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project of the week: robbienano

Ian Smith

This week we focused on learning a completely new (to us) thing, PCB manufacturing! A PCB is a Printed Circuit Board, it’s the thing covered in small digital components you see inside electronics, and it’s typically green. Smart phones, tablets, laptops, desktop computers, entertainment systems (console and handheld), TVs, stereos, microwaves, and smart refrigerators…they all have PCBs!

We are going to offer “learn to solder” demo sessions in our upcoming open house and felt it would be great if participants could take something with them when they are done with the demo. The soldering demo sessions will involve attaching two small blinking lights (called LEDs) and a battery clip to our custom designed PCB we have nicknamed robbienano. This lil’ robot is roughly 2” x 2” and is designed to be worn as a lapel pin, but we think it’ll look great just whether it’s hitching a ride with you or relaxing on your bookshelf.

To begin the project, we had our code cadet sketch out a quick robot using nothing more than good old fashion construction paper and pencil. Once we had the drawing in hand, we took a picture with our smart phone and copied the image onto the computer. We used Adobe Photoshop to trace the drawing and added a little color.

From this point, we had to do a serious deep dive into Autodesk’s Eagle, which is used to create the PCB layout and schematic. Following Eagle’s Schematic Basics Part 1 guide, we learned how to create a schematic by finding parts and connecting their positive and negative terminals together. Fortunately, robbienano’s schematic is very straightforward - just two LEDs (labeled LED1 and LED2) and a battery clip (labeled G1)!

robbienano-schematic.png

After our schematic was complete, we pulled up the Autodesk PCB Layout Basics Part 1 guide and began designing our board. At this step we took a big deviation from the guide and reviewed a few other resources regarding PCB art. This was hands-down the hardest part of this week’s project. We had to design art with four colors, reference multiple tertiary guides regarding basic functionality within Eagle, translate techniques between InkScape (a seemingly integral component used to manipulate art in Eagle) and Photoshop because InkScape isn’t natively supported in the latest version of OSX, and navigate through process holes that exist because the online resources assumed a familiarity with EDA (electronic design automation) software (aka Eagle) and until this week we weren’t even aware of the EDA acronym! Serious. Challenge.

But, when we had fully digested everything as best we could the PCB layout process came down to these steps:

  1. Create an outline of robbienano and import it into layer 20 (Dimension) in Eagle which represents the overall shape of our PCB.

  2. Add art to the following layers:

    1. 21 (tPlace) which represents the white outline on top of robbienano

    2. 22 (bPlace) which represents where the white logo will go on the bottom of robbienano

    3. 29 (tStop) which represents where no color, or soldermask, will go and thus reveal the copper of robbienano’s eyes, teeth, and chest

    4. 41 (tRestrict) which represents where no copper will go which will create a darker purple color for robbienano’s shirt/pants and arm sleeves

  3. Place the components from our schematic onto robbienano and flip them so they will be soldered on the bottom

  4. Trace a giant polygon on the top, around the shape of robbienano, which will be a ground (GND) “signal” for the ground plate, effectively filling the entire shape of robbienano with copper

  5. Route the electrical connections between LED1, LED2, and the battery clip, which is almost like digital soldering

With all the art work in place and the electrical connections routed we just needed to upload the PCB board and have it fabricated. We settled on OSH Park, a fabrication house here in the States that offers cheap prices, fast turn around, and fast shipping. We placed the order today and our first, custom designed PCB for “learn to solder” classes should arrive next week! Hurray!


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project of the week: r/c fig #3

Ian Smith

We spent last week working on legü, our lifesize, robotic LEGO. On Monday we finalized a print which allows him to finally move! legü, can now swivel his head to and fro and is proudly perched in our storefront window.


This project has moved from concept to reality one print at a time, and it has been a lot of fun to see it come to life. We are tackling a lot of of new-to-us concepts such as: gear types, gear ratios, servos, the integration of bearings and smooth rods, “components” vs. “bodies” within Autodesk Fusion 360, and deciphering how to print parts that are too large for our print bed. A lot of this means we are constantly reprinting parts! To print the extra large pieces, we have to cut them into parts and then put them back together, somehow, after the printing is done. So far we have used a combination of magnets and super glue. legü’s head is made from three sections: the top nub, the middle face, and the bottom neck.

Learning how to use “components” within Fusion 360 allows for a more comprehensive design and means we can also make “exploded views” like the image below!

techahoy_legobot_explosion.gif

This animated GIF shows the head, neck, and neck base. The neck consists of the green object, grey servo (rectangle looking thing), smooth rod with two bearings, and two yellow spur gears. The neck base is the grey object on the bottom which will reside within legü’s chest.

So far most of the time spent creating legü has been waiting on parts to finish printing. For example, the green object which acts as the base of the neck took 3 hours to print and we printed four iterations! It can be a challenge to wait that long for a print, take the time to assemble the parts, and then be confronted with this bewildering behavior like this!

We were expecting legü to slowly pan left-to-right, but instead he seemed to be shaking his head “no” with each turn. We spent quite a bit of time debugging this and determined legü’s head is simply too heavy for quick movement using this particular standard servo. Servos have very little finesse; there is no throttle control. When you tell the servo to move to a certain position it will move to that position as quickly as possible and stop. But in our case, legü’s head, while mostly hollow, appears to be too heavy. The weight of the head generates inertia that the servo is not strong enough to handle - the servo moves to the desired position as quickly as possible and when it stops the inertia generated by legü’s head causes the servo to turn just a bit more before actually stopping. And since the servo has turned a bit more than it should it “bounces” back to the planned stop position. It’s a bit like spinning someone on a small merry-go-round and then trying to stop them immediately. The force you exert attempting to stop the spin will cause the merry-go-round to stop, but sometimes right after it stops you will cause it to turn a bit in the opposite direction. We tried a few different coding work-arounds to address this “bounce” and finally found that if we swivel just a tiny bit the “bounce” affect is minimized. So, now we turn a tiny bit, stop, wait a few microseconds, turn a tiny bit more, stop, wait a few microseconds, and repeat until we’ve turned the head as far as we want. Fun!


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projects for days!

Ian Smith

Since our last update we’ve been working on a variety of projects. We made further progress on legü, our life-size remote control LEGO minifigure. We unboxed and setup all sorts of goodies including: two Prusa i3 MK3S kits, a Ubiquiti UniFi edge switch and access point (to better serve free wifi), a big box of tools from Adafruit, and some organizational supplies. And we printed a bunch of random supplies because we #printallthethings!

Our big order from Adafruit included a batch of Raspberry Pi 3s, including the new Raspberry Pi keyboard, along with several soldering irons, helping hands, and general small electronic tools. The MK3S kits brings the total number of 3D printers in our farm up to five (three MK3 printers and two MK3S printers)! We have multiple nozzle sizes to choose from and the Prusa MMU (multi-material upgrade) is on order and expected to arrive later this summer.

Both the MK3 and the MK3S have a print volume of 250mm x 210mm x 200mm which means we need to employ some creative techniques when printing our lifesize LEGO minifigure, legü. For example, legü’s head is over 210mm tall which means we need to split it up into sections, print each piece, and then somehow reattach the sections. We decided to use magnets as it offers some future flexibility should we want to swap out parts, to give legü different looks and style. Earlier this week, we printed out the top of his head and the middle section which contains the eyes and mouth sockets. That section alone took 20 hours to print!

We also spent a few moments to design our own bathroom signs. Our printers are configured with a single extruder, but we were able to obtain the multi-color look by changing the filament at various layer changes throughout the print job. The figure/letters are taller than the blue background, so we changed from blue to grey filament when the printer was done filling in the background. And the eyes are taller than the figure, so we changed from grey to purple/green when the printer was done filling in the figures/letters. They attached to the bathroom doors with double-sided tape. Easy!

And we may have spent a little too much time perfecting this small Allen wrench holder for our pegboards. We found a great set of models for our IKEA SKADIS pegboard on Thingiverse and used of the universal hooks to create our own Allen key tray for the keys that came with each MK3/S kit.


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project of the week: bulbasaur planter

Ian Smith

This week we worked on a 3D printed planter using a Bulbasuar model located on Thingiverse. The model looks great and printed really well in Colorfabb’s Bronzefill filament.

IMG_1522.jpg

We ran into one large issue during the first few hours of printing; our Prusa i3 MK3’s filament detector wasn’t enabled so the print kept on going when our spool of fillament ran out! Unfortunately, we didn’t notice right away and the printer had no issues chugging along layer by layer sans fillament. Fortunately, we noticed the issue after only a few layers (approximately six) and were able to salvage the print. This was to be one of our longest prints to date, at almost 7 hours and we were already 1.5 hours in, so we debated whether we should cancel the job and start over. Once we added more filament the gap appeared only to be cosmetic and thus we pressed on!

There’s a bit of a gap there, Russ…

There’s a bit of a gap there, Russ…

Once we removed the planter from the print bed, we did notice a bit of a wobble at the base. Although there was substantial infill before and after the gap, the missing perimeter wall left the model feeling slightly unstable. So, we decided to MacGyver it up and add a “bandaid”!

We measured the gap which was roughly 2mm in height, printed some narrow strips to use as bandaids, grabbed an old soldering iron tip, and then welded/melted the bandaids along the gap. Presto! The perimeter walls were reinforced and the whole model felt very substantial.

All we had to do from there was spend some time applying a bit of elbow grease to sand down the bandaid and remove some of the larger layer lines throughout the model. As you can see from the timelapse video below it turned out pretty well.


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