Expansion, Seattle Mini Maker Faire

First, a big announcement.

A month ago OpenBeam successfully acquired a lease on a commercial space.  We had to move quickly to secure the space, but it works well for our needs.

In the Seattle metropolitan area, warehouse space generally rents for about $0.95 per square foot, plus maintenance fees on the shared space of the property (in our case, the electricity for lighting the parking lot, for example, and various real estate taxes, the cost of hiring a gardener to mow the sidewalk grass, etc).  Unfortunately, in the Redmond / Woodinville / Kirkland area, spaces under 2000 sq ft is pretty hard to come by; and most commercial leases requires a 3 year lease.  OpenBeam as a company does ok, but we would still like to keep expenses as low as possible, and moving up from $400.00 per month for two storage lockers to $2000 per month is a bit of a steep jump.


We were able to find a warehouse space at 1260 sq ft (20 x 61 ft bay).  Not only that, they only required a one year lease.  The space is about 10 minutes from my current job, 5 minutes from Mike Z (the Z in ZT Automations) house, and with easy access to both I5 and 405.  It was also completely empty - they just put a bathroom in for us.  We don't need fancy offices; we just need a place to store pallets of extrusions and parts for both OpenBeam and ZT Automations.

As an entrepreneur, I've peed into a fast food beverage cup and discretely dumped out the contents a few times in my storage locker.  I considered it part of paying the dues; but I can't exactly ask hired staff to do the same.  The fact that we get a real bathroom now means I can actually hire staff / contractors and give them a decent place to work!

As an entrepreneur, I've peed into a fast food beverage cup and discretely dumped out the contents a few times in my storage locker.  I considered it part of paying the dues; but I can't exactly ask hired staff to do the same.  The fact that we get a real bathroom now means I can actually hire staff / contractors and give them a decent place to work!

We've been running OpenBeam and ZT Automations out of garages, storage lockers and borrowing living space from family members.  It is AMAZING how much time this sucks up - on average, we spent hours per week ferrying materials and supplies from one place to another as they are worked on.  Our dining room tables have at various times been the shipping station, the receiving station, the engineering meeting table and occasionally, a place for the family to eat.  And as we found out the hard way time and time again with the Kossel Pro project, for the lack of a single part, single envelope, or label, the entire operation can shut down.  Both OpenBeam and ZT-Automations have also grown beyond what we can shuttle to the UPS store; an average order for OpenBeam and for Amazon replenishment now requires 2 SUV loads to the UPS depot; the last printer order to our distributor left Mike's garage on a wooden pallet.  

Here's our shipping station - the shipping and counting scales are already there along with one of the two label printers.  The shelves holds various USPS Flat Rate boxes, plus all the different pouches for various courier services, Customs declaration forms, etc.  It's really exciting not to have to repack everything up and spend 15 minutes unpacking every time I need to ship a package.  

Here's our shipping station - the shipping and counting scales are already there along with one of the two label printers.  The shelves holds various USPS Flat Rate boxes, plus all the different pouches for various courier services, Customs declaration forms, etc.  It's really exciting not to have to repack everything up and spend 15 minutes unpacking every time I need to ship a package.  

Of course, with the new shop, one of the first things we are going to set up, once the bathroom is completed, is a photo / video studio.  A proper photo and video studio takes up a lot of room, and we have a nice white painted wall (perfect for those high-key pure white background pictures that we shoot for our technical documentation).  

Photo / Video studio will go on the other side of the bathroom wall.

Photo / Video studio will go on the other side of the bathroom wall.

Seattle Mini Maker Faire

With the birth of my son, Zachary, and the Kossel project stretching our resources thin, we have not been very active in our Maker Faire participation.  That being said, we've sponsored the Seattle Mini Maker Faire since our inception and since the SMMF's beginnings 3 years ago, and it wouldn't feel right for us to sit out.  We're happy to announce that we're sponsoring our local Maker Faire again, for the 4th  year in a row.  Not only that, we'll be having special discounts on OpenBeam merchandise at MakerFaire to help our local makers build cool things, and we'll be doing new product announcements at the faire!  See you there.

-=- Terence

Kossel Pro - now at SeattleAutomationz.com

We've been pretty slammed, and we've been neglecting the OpenBeam core product line for the last two years due to the work that's been poured into Kossel.  After a few months of planning, Mike and I took the next step and spun off the OpenBeam Kossel Pro project into a new company.

We will still be actively developing the Kossel Pro,  under the Seattle Automationz banner.  The decision was made specifically to spin off the 3D Printer so that we may bring on additional resources to help with the project easier.

A status update on the Kossel Pro project can be found on our new blog, here.  

As for OpenBeam, we've got a few new products on the horizion.  Stay tuned.

-=- Terence

Documentation, documentation, documentation.

Hello all!

Terence here, with another update on the Kossel Pro project.


In our mad rush to get units shipped out, we managed to corrupt the shared Google Spreadsheet that we've been using to track units going out and delivery.  Things have finally gotten to the point where I am no longer fighting fires left and right to allow me to take a half day of searching through all the email records, matching up tracking numbers, etc, to fix that hot mess.  After the audit, we found that we still owe about 18 printer kits.  We will be reaching out shortly to these 18 people to update them. 

After these last sets of printers, we still owe pre-assembled machines and we still owe plastic parts only pledges from Kickstarter.  Fortunately, we have plenty of extra parts.  I expect that I'll be getting to the plastic-only pledges in the next week or two (survey still needs to be sent).  With regards to the pre-assembled machine, our tech is in the process of moving after accepting a new job.  We are obviously waiting for these machines' assembly process to be completed, and we are also waiting for the new all-metal hot end.  We'll update in a week or two with the delivery status of both of these items.  

Manufacturing Update:

To make the project viable in the long term, it was imperative that we move as much of the kitting and handling to our overseas contract manufacturer.  (We simply do not have the space and human resources available to kit parts in the US, and at this stage of the business, entering into a long term commercial lease for a shop space seems a bit risky).  We were also able to get much better service from packaging vendors overseas:  We paid for cutting dies for all new packaging boxes, custom cut foam inserts, and the MOQ (up to a thousand piece for the foam inserts) and all that together, along with the NREs for the cutting dies, were still cheaper than buying and compromising with boxes from Uline.  

An example of our new kitting document, bilingual in Chinese and English.  My father's been helping with the translations, and in the few instances when I have to do the translation myself, I use Google Translate and Notepad to translate, copy and paste together my sentences.  My handwriting is still too poor for most handwriting recognition software to recognize (and learning Cangjie seems like an impossibly high bar to reach).  I do double check all the translations before they go out to our vendors.

An example of our new kitting document, bilingual in Chinese and English.  My father's been helping with the translations, and in the few instances when I have to do the translation myself, I use Google Translate and Notepad to translate, copy and paste together my sentences.  My handwriting is still too poor for most handwriting recognition software to recognize (and learning Cangjie seems like an impossibly high bar to reach).  I do double check all the translations before they go out to our vendors.

For the past few weeks, Mike and I have been rushing to update the kitting instructions to support our overseas vendor.  My Dad is also in Hong Kong right now, which really helps with the transfer; he's been handling the first article inspection of all the goods received, and also helping with communicating with our vendors.   We now have reached the point where our CM can start assembling the printer kits for us, which was a lot of hard work - but we expect work to go fairly quickly at this point on, and - more importantly - we can expect a relatively uninterrupted supply of kits, as long as we do our forecasting right.  This is a far cry from having to count screws, seal bags, and package and label parts, and will soon free us up to do engineering again, or at least maintain the flow of goods when Mike and I are bogged down by day job projects.

Customer Facing Documentation:

Studio OpenBeam... one day.  Photo gear does take up a LOT of room, especially if you are shooting large objects.

Studio OpenBeam... one day.  Photo gear does take up a LOT of room, especially if you are shooting large objects.

My wife have been threatening to evict me from my photo studio for the last month (I temporarily took over our guest bed room, after we got rid of the guest bed, before she could paint it and turn it into our nursery).  Now that ZT-KID-00101 is well on his way (in about 2 months), in between working on the kitting documentation (above) we've been banging away at the documentation pretty hard.  Tonight I'm happy to say that Rev 1 of the assembly documentation, covering mechanical assembly of the printer, is complete.  We'll be updating the links from KosselPro.com shortly.  We will update this with instructions covering systems power up test, firmware update, and best practices on the printer in the next month.

For those asking for more pictures, esp of the new hot end, please see below:

For those curious, these were shot with a Strobist setup.  On my last trip to Hong Kong, I picked up a bunch of YongNuo 560 IIs.  For less than the cost of a single 430 EX II from Canon, I bought 5 YongNuo speed lights, which are optically slaved, and had enough money left over for the collapsible background and the photo box.

Other Technical Updates:

Some days, it feels like our mad engineering rushes occur  between major Chinese holidays.  While our overseas partners are celebrating Qing Ming (or tomb sweeping) festival, we'll be writing and releasing the final build instructions for our printer kits.  Here are a few things that we've worked on in this period.

All Metal Hot End

We had one report of one of our early all-metal hot end jamming on ABS printing.  (Because of my pregnant wife, we are only using PLA for our testing until a better fume extraction system is setup, to minimize VOC exposure).  At first we though it was a thermal issue; turns out it was a roll of bad filament.  

And this is what happens when you read your print wrong, and do the calculations wrong for where to turn the dial to.

And this is what happens when you read your print wrong, and do the calculations wrong for where to turn the dial to.

The lathe we use does not have any sort of digital readout, so all our prototypes are machined by counting wheel rotation on the dial - much like how someone in Victorian era England would have made these parts. (Incidentally, when I started my machine shop training in college in 2002, I was the last class to be taught on fully manual machines.  Digital readouts and later on CNC were introduced by the time I graduated).   I started the project as an "OK" machinist and after a few frustrating setbacks, have gotten pretty proficient at making our prototype heat sinks.  I can now cut one in about 45 minutes.  

A not quite final all metal end effector prototype.  The one that's built to spec is currently being tested at MatterHackers - they've successfully printed Nylon and ABS on it, as well as quite a bit of PLA.

A not quite final all metal end effector prototype.  The one that's built to spec is currently being tested at MatterHackers - they've successfully printed Nylon and ABS on it, as well as quite a bit of PLA.

We now have the geometry of the heat sink finalized.  We were going to award the work to the shop I found in the LA area, but they quoted me 2 week lead time for my heat breaks when we awarded them the work 3.5 weeks ago - and not only have they been now pretty late, they've also been pretty uncommunicative.  Having been the small business owner trying to make it, I can certainly sympathize with what they may be going through, but we also have customers to take care of, and I'll be searching for an alternate supplier in parallel.

The good news is we've found a good supplier for heater blocks and nozzles, and we've also found a supplier for the fiberglass tubing used for insulating the thermistor.  We were really hoping to have a picture of our heat break to show, but unfortunately, we don't have an ETA on this part at the current time. 

New Heater Cartridges, power supplies and other small details:

For the next batch of Kossel Pros, we have commissioned custom heater cartridges with 22AWG wires pre-crimped, instead of the normal stuff with the high temperature insulation wires.  This will allow the crimp at the heater cartridge power terminal to meet pull test specs, as the current insulation is to wide to be properly crimped to the Molex SL crimp pins.  (Long term, we are going to switch to using ring terminals that anyone can crimp at home, but that requires retooling the plastic and the PCB and if we are going to do that, we might as well release the multi-material end effector that's been rattling inside my head for the last  year plus...).

Of course, leave it to the vendor to screw up on the cables from our first batch.  So my Dad is currently using it for a dummy load to test our power supplies.  Speaking of power supplies, we've found that the old vendor have been over driving the fan inside the PSU:  It was a 12V fan and they were running it on 24VDC. We commissioned a new batch of PSUs with 24V fans and they should run a lot quieter and last a lot longer.  

Finally, we've been making small improvements to the kit.   We've found a vendor that does good pre-printed labels (for cable labelling).  We also found laser cutting vendors and a new cable vendor overseas.  So far, pretty happy with the quality.

That's about it for this update.  We are pretty anxious to get the new kits in.  We'll be back in about two weeks with another update on the work we're doing to evaluate the auto-levelling routine.

Kossel Pro 1.1


Both Tom, our machinist, and I have been sick for the past couple of weeks.  Both of us are on the mend, but it does throw a wrench into the schedule.  Anyway, for those who have received a tracking # for their Kossel, it should be on its way to you on Tuesday.  For those who still haven't, please send an email to: kickstarter at openbeamusa dot com.

There are a few things that have been going on, with regards to the Kossel Pro.

All metal hot end:

The weakest link on the original Kossel Pro was the OpenBeam J-Head clone.  While it resolved some of the things that I didn't like about the original J-Head, it was a dated design, and horribly expensive to produce (and would be more so, in the next year, as global PEEK production dwindles).  The thermistor wires were potted in and not user serviceable.  Even bigger issue was that the J-Head costs a whopping $100.00 to produce, and the market wouldn't really bear more than $60.00 for a completed J-Head (or really any print head for that matter).  We've shipped over $1000 (in replacement cost, to us) of J-Heads as warranty replacements to our backers and believe me, it hurts.   

With all these drawbacks, we've been fast tracking the engineering to create a replacement print head.  The following micro frogs were printed on one of the early all-metal prototype print heads:

The new print head, which I'm going to un-creatively name the K-Head, traces its design lineage to the E3D V6.  We took referenced the E3D's nozzle and heater block designand made a change to the heat break to remove any ambiguity on the assembly process by adding a flange to the heat break to positively register it against the heater block.  We also changed the configuration on the cooling fins to make the heat sink compatible with the Kossel Pro's end effector.  The results speak for themselves; the micro frogs you see above are straight off the printer, printed with a 0.4mm tip, sitting on a US penny (international readers:  19.5mm diameter).  We have tips down to 0.2mm that are coming in for prototyping and testing.  We've kept the thread size of the nozzle at M6, so nozzles will be compatible with E3D's nozzles.  

The new print head will be built from a combination of Chinese and American made parts.  We've had a heck of a time finding machine shops that would talk to us or make small enough quantity parts, or give us a proper lead time estimate, but we now believe we'd be able to get the first round of prototype heads in hand in about 2 weeks, and hopefully scale up to full production in 4-5 weeks.

As a thank you to our pre-built machine backers, we will be offering the all metal print head as a complementary upgrade (and we'll be using your machines to dial in the new print head print profiles, since this would be one of the few times where we'd be able go get a sizable fleet of Kossel Pros lined up).  All of the machines that MatterHackers will be selling, will also come with this new, all metal K-Head hot end.  (EDITED TO ADD:  We will also be offering the new all-metal hot-end at "cover our costs" pricing for our existing shopstarter and kickstarter supporters)

Pre gluing the Carbon Fiber Swing Arms.

One of the biggest challenges of building a delta printer is fabricating the ball joint swing arms.  We've engineered a no-compromise fully ball bearing swing arm set, and we've included the fixture parts in all our kits to allow people to glue it themselves, but gluing the arms accurately is still a pretty hard endeavor.  

Starting with the machines available from the MatterHacker's preorder page, we will be delivering the machine with arms pre-glued, on a calibrated gluing fixture.  This will eliminate a HUGE variable that stands in the way of getting awesome prints.

Prebuilt machines:

Nick, our new engineering tech, had been doing a wonderful job building these machines:

After the machines are built, we'll start the fine tuning process (and also a good time to validate print profiles across multiple machines).  We'll also  use this time to roll in some of the community-originated updates.  Finally, we'll need to engineering packaging that can hold the machine and survive UPS shipping (another set of drop tests, to test the new packaging for the box.  Plenty of stuff left to do, but we are pretty confident in our ability to deliver.

New Packaging:

From a logistics standpoint, packaging and kitting the Kossels (to get all the kickstarter and shopstarter machines shipped damn near killed me and Mike.  We did what we had to do to get things out the door, but it was not a sustainable process.  What is sustainable is moving the kitting and packaging process overseas to a competent contract manufacturer and paying someone overseas for kitting operations.

Here's a sneak preview of the new packaging:

One issue that we've keep coming back to, is that it's awfully hard to do small scale manufacturing here in the US.  I was at MD&M West a few weeks ago.  When I hid my day job's trade show credentials and went to talk to a few cardboard box makers, they didn't even want to give me their business cards when I mentioned that our top seller (the OpenBeam precut kit) is in the 500 to 1000 units per year range.  Across the ocean, however, Chinese box vendors would love to take our business and make us 500 custom size boxes, or print us 500 labels on a roll, or sell us 200 custom made heater cartridges.  The cost of a custom box cutting die cost less than what Mike and I spend for lunch every day.  When  you add in the fact that import tax laws tends to favor big companies (allowing finished goods to come in tax free, but throwing up huge paperwork barriers for small businesses bringing in individual components and trying to kit in the US) going with an off-shore contract manufacturer just makes things a lot easier.

Most of my time the past two weeks have been spent on overseas manufacturing documentation and kitting instructions.  Part of this is because of the longer lead times required to spin something overseas up as well.  Overseas manufacturing transfer will be the subject of another blog post down the line - we had to learn a few lessons the hard way, but I think we've got the process going pretty smoothly now, and hopefully we'd be able to smooth out the bumps with the next batch of printers coming in soon.

End User Documentation:

We've been slowly adding to the end user documentation, you can see the latest pictures taken for them here.

That's it for this long, overdue update.  

-=- Terence & Mike

State of the Kossel Pro

Hello all,

It is time for us to give an official update on the status of the Kossel Pro project and Kickstarter campaign.  The first half of this update will be administrative in nature, followed by an in-depth technical outlook.

Project Administrative:

Between our Shopstarter and Kickstarter campaigns, we took on a liability of approximately 150 printers, of which 10 are to be pre-assembled.  To date, we have delivered approximately 100 of the 140 kits, and we expect to deliver the remaining 40 kits and assemble the 10 pre-assembled machines in the first 2 weeks of Feb.  We found that we ran short on a few critical components such as linear rails and motors – so we built all the printer kits we can build prior to Christmas break, shipped them to everyone who we got through to confirm address (with a priority given to Kickstarter backers, as they have been waiting the longest) and used the lull to work on documentation.

This past weekend, we received our last air shipment of linear rails and glass, stepper motors and carbon fiber tubing.  We’ve learned a valuable lesson in Chinese export laws and we’ve since moved our freight consolidation to Hong Kong.  Hong Kong is a free port – no import or export taxes, which drastically reduces the logistics challenge of getting packages out the door.  Once we figured out the proper paperwork to file, it took about 3 days and a mere $850 to get our latest shipment of linear rails and stepper motors shipped, via commercial air cargo (meaning, the cargo flew on a commercial airline flight, in the cargo hold, with people’s luggage.  In our case, it was on an Eva Airline flight out of HKG through Taoyuan airport in Taipei; other times it gets booked onto Korean Airline through Incheon.  Expeditors International handles the booking of the flights (on a space available basis) and clears it through US customs for us.  To save some money, I drove down to the air cargo terminal at Seatac Airport to pick our stuff up from a warehouse right next to the runway).  As a comparison, it took close to $5000.00 to get our last air cargo shipment out of China, via DHL as small parcel, to circumvent Chinese export taxation on the goods.   (It wasn’t that we didn’t want to pay export taxes.  We would have gladly paid them to get our stuff out of China.  The problem is we had no way of paying them.  Because our consolidator didn’t buy the material, he wasn’t able to pay export tax on it and have the books match up to support paying export tax – there would have been no POs from OpenBeam or a money trail to support making the export declaration and paying the export tax)

We have already started the process of kitting and preparing for final push to close out Kickstarter / Shopstarter liabilities.  Specifically, we have hired on additional help and will be using said help for crimping thermistors, heater cartridges, etc, and we’ve already got MOST of the subassemblies kitted.  Very likely, we’ll delegate Mike and Nick, our new tech to handle the 100% QC and packaging of the remaining kits, while I focus on completing the instructions.

Another batch of hot ends in the works.

We’ve lost a lot of “kitting time” due to our air cargo being held up in Hong Kong (since it was going on a commercial airliner, we had to file a declaration of conformance to IATA non hazmat standards, and since OpenBeam technically do not have a business presence in Hong Kong, there was extra paperwork to set up the export as a “known consignor”.  This resulted in our air cargo leaving HKG a lot later than we expected.  On top of that, end of January is when Washington State Business & Occupation taxes are due, and as part of doing our taxes (both state and federal) we needed to shut down and conduct an inventory.  For most businesses, such administrative tasks aren’t very visible externally, but when the entire company’s staff is also the kitting department, the inventory taker, the delivery truck driver and engineer, well, unfortunately these things takes time.

A batch of hot ends took a bit too long of a bath in the simple green... :-(

A batch of hot ends took a bit too long of a bath in the simple green... :-(

Finally, there are backers who had backed us to get injection-molded parts, stamped parts, etc.  We’ll fill these rewards towards the end of Feb.  As for those who have not confirmed their addresses (especially from Kickstarter), we’ll hold onto their printers in our storage locker and ping them every so often.

Life as a post-Kickstarter company

Neither Mike nor I are in a position to quit our day jobs; my wife and I are also expecting our firstborn son in June. There is no way we can continue to develop new products and take care of existing customers, given other pieces of work-life balance.  To make the company sustainable, we’ve planned from the beginning to resell Kossel Pro kits through distributors only and as part of the distributors’ responsibility, have them provide user training and after sales support.  We have since moved future pre-orders to MatterHackers, and we have already started, over a month ago, the procurement process for printers for post kickstarter / shopstarter fulfillment.  We are taking steps to move as much of the kitting process to our overseas contract manufacturer, and we are getting blanket terms from our contract manufacturer as well.  This will hopefully help ease supply chain constraints in the future – we are working towards a future where you can order a Kossel Pro and have it shipped to you immediately, but we are NOT there yet.  

Packing box in "Master Box" configuration to prepare for Amazon FBA shipment

On the home front, we are moving towards Amazon fulfillment of spare parts and individual kits as upgrades for the Reprap community and expect to be online in the next few weeks.  (Remember, we went through a similarly painful transition to move OpenBeam onto Amazon and to smooth out supply chain issues.  Except, back then it took MONTHS and it was our only source of income).  Our current projection for being able to resume Kossel Pro shipment is in April.  (The big schedule time bomb called Chinese New Year in the middle of all this does NOT help things).   

Kossel Pro Documentation

Like most (stereotypical lazy) engineers, we’ve pushed documentation to last.  (There’s 2 reasons for this; one is we really needed to build the printer a few times before coming up with the optimum recommendations for how to build the printer.  To do so requires production parts, which weren’t available early on in the project).  Unfortunately with the shipment out to our backers and subsequent time spent on support, we have not been able to spend time on documentation.

We are diverting as much of our resources as we can towards documentation, and we are using this time period where our subcontractors are working on kitting and prep work to get as much work on the documentation done.  We have now dropped the password protection on KosselPro.com and we will host all documentation there, marking clearly what is still work in progress.

Technical Details:

My boss at my day job always told us:  “If you really want to learn about your product – get a bunch of dudes to build you a hundred of ‘em.  Then line them up in a room, and bang on it”.

Obviously, both with my day job (designing and building scientific instruments, not exactly high volume manufacturing) and with the Kossel Pro, we really can’t afford to do that.  Our December shipment of 100 printers was the largest Kossel Pro deployment into the wild, and we’ve since learned a few things about the printer.  As much as we try to test for and mitigate real life scenarios, these tests are still devised and conducted by engineers who had spent the last two years obsessing over the project.  The real world, as we found out, is highly unpredictable.  We’ve been doing preliminary analysis and debugging on our machines in the field and these are some of the common issues we’d like to address:

  • Heater cartridge inconsistency and tuning
  • Control board failure due to cleaning of hot ends while energized
  • Probe deployment issues
  • USB port strain relief
  • Auto Levelling accuracy

Heater cartridge inconsistency

We purchased the heater cartridges from another manufacturer as “surplus stock” – the supplier had screwed the pooch and shipped them 24V heater cartridges and they use a 12V drive system.   Our specifications calls for a 24V, 40W heater, and working backwards, we needed to deliver approximately 1.667A at 24V (24V x 1.667A = 40W).  To draw 1.667A at 24V, the resistance of the heater cartridge needs to be approximately 14 ohms (Ohm’s law of V=IR; V=24V, I = 1.667, solving for R gives us about 14 ohms).

However, we are seeing, especially in failed units, as low of a resistance at 8 ohms.  At 8 ohms, the heater circuit will dump a whopping 3A of current into the hot end, for a power dissipation of 72W - nearly double the design limit.

Unfortunately, when we did the firmware tuning, we did not think that there was such a wide range of heater core resistance, and even knowing this problem replicating it is still difficult.  We are going to build a fixture to do 100% inspection on our heater cartridges’ resistance and we are going to have to start batching heater cartridges.

We are in the process of talking to Chinese heater cartridges manufacturers for a custom crimped and assembled heater cartridge assembly for the Kossel (we crimped the current ones ourselves).  Some of the things we will be controlling are the tolerances on the outer diameter (they were ALL over the place with our current batch of heater cartridges – we did 100% test fits with our J-Heads before shipping, and on a few of the units, we had to ream out the J-Heads prior to shipping).  We’ll also be specifying a UL compliant, but thinner insulation on the heater cartridge wires.  This will prevent the breaking of the crimped connector issue that we’ve seen with some of the heater cartridges, as we’d be able to properly crimp the connection wires (which involves one set of crimps compressing around the insulation for proper strain relief.

Control board failure due to cleaning of hot end while energized

We've had a few failures of the Brainwave Pro boards in the field.  Most of these boards failed the following way:

  • Print had peeled off the bed, or some sort of catastrophic failure on a print resulted in PLA smeared all over the board.
  • User heats the hot end up and while the board is energized, attempted cleaning with a metal wire brush.
  • Board dies.

In one case, the board’s failure also caused the MOSFET controlling the heater cartridge to fail short.  This is an especially dangerous situation as it results in the hot end overheating and will destroy the hot end.  It is also a HUGE fire risk.

We believe that cleaning the hot end with a metal brush caused a shorting of the 24V power for the heater cartridge to the thermistor contacts.  We followed the standard Reprap electronics design and this line is not protected on the Brainwave Pro (or any other Reprap electronics out there, for that matter).  However, most printer builders run at 12V.  Applying 12V to a microprocessor might make it unhappy, but it appears to be a fairly survivable scenario for the microprocessor.  Exposure to 24Vs though seems to be universally fatal to the microprocessor.

We are still investigating and we will be putting additional protection onto the next run of the Brainwave Pros (in the form of clamping zener diodes to protect the microprocessor lines).  In the meantime, the recommended procedure for cleaning out a clogged end effector is as follows:

  1. Invert the printer, if necessary for ease of access to the hot end.  To be absolutely sure, you can unclip the glass and leave the HBP in place.  Nothing should fall.
  2. Bring the hot end up to 180 deg C
  3. Using a NYLON (ie, NON conductive) brush, carefully brush away stuck plastic, staying clear of the thermistor wires!

If there's any doubt / questions, just imagine you are cleaning the insides of your computer.  You wouldn't go at it while the computer is energized with a metal brush, right?

We consider the permanent nature of the thermistor wires a feature, not a bug.  We want the thermistor to be impossible to dislodge from the hot end – as mentioned before, disconnecting the thermistor from the hot end during operation is a fatal error that results in equipment destruction and a huge risk of fire.  The unfortunate part about this arrangement is that if the thermistor wires do break the tip will have to be replaced.  It comes back down to not having the space to do a removable / servicable solution on the J-Head’s heater block.  Our next hot end (whose R&D is being accelerated, to deal with some of the issues that had come up) will feature user servicable temperature sensors.

Probe Deployment Issues:

There are a few issues and comments about the probe’s design and its deployment:

  1. The probe standoff loosens, and eventually flexes enough that it doesn’t push down on the switch.
  2. Concerns about the general slop and positional repeatability on the probe when deployed.
  3. Related to 1 – the probe impacts the plastic housing (and switch) too hard, drastically shortening the life of the switch.

Here’s what we are doing to improve things:

  1. We are revising the assembly instructions on the probe to call out the addition of Loctite onto the threads of the probe to stop it from loosening.  We are going to try to source the M2 FSC with Loctite preapplied for the next manufacturing run
  2. We are going to be talking to our vendor about changing the probe arm from round to a square profile.  This should resolve a lot of the positional repeatability issues on the probe.
  3. Unfortunately, this is not something that we can address.  The spring force is required to overcome the 75 gram force actuation limit on the switch (the lowest we could spec, by the way).  The nature of hooks law and how compression springs work results in the slam.

For those who are really concerned, the only work around we can offer is that you can deploy the probe by hand.  The switch in question is freely available from Mouser for less than $2.00, and the next generation auto levelling system does away with the auto probe all together.  In the grand scheme of things, this is way too far down the priority list for us to address.

USB strain relief

When we designed the Kossel Pro, we chose a full size USB B port for robustness.  During my time working with the original Brainwave, I’ve sheared my share of MicroUSB ports off that board.

However, what we didn’t factor in is the weight of the USB connector (on the cable end).  We are learning that a vertical USB port really requires additional plastic around the connector to provide strain relief.  One of the warning signs is that we see the sheet metal peeling from the shield of the connector.  This forms a sharp barb that catches the edge of the USB B connector, making it impossible to remove the cable (this happened on one of our engineering test printers as well as one of our user’s printers).

We've also found, on the engineering test printer, that due to the cable not being able to be removed, the additional stress on the board will cause intermittent connection on the USB port, to the point where the board is no longer usable.

To fix this, and to head off a major recall, we are planning, in the next week or so, release a 3D printable part that can be added to frame to provide additional strain relief to the connector.  We are certainly happy to catch this train wreck before more issues appear.

Auto Probe Accuracy

The G29 Auto Levelling routine that the Kossel Pro uses is directly from the Reprap Marlin firmware.  It was written and improved upon by Johann Rocholl, and it’s used by delta printer builders all over the world.

We now have reasons to believe that G29 doesn’t actually work very well. One of the biggest issues that’s been pointed out, by the software team at MatterHackers, is that the least-square-sum method that is used to compute the bed tilt really requires double floating point precision to work, and Arduino can only handle single floating point precision.  As a result, a lot of the precision is discarded and what we are seeing is actually rounding error.

It should be pointed out that this is NOT an OpenBeam Kossel Pro issue, this is a general delta printer issue.  Dudes a lot smarter than me, such as the software team at MatterHackers, are looking into different solutions and options.  Ultimately, the changes will be committed back into Marlin, and everyone in the delta printer community will benefit.

In Closing

We would like to thank all our backers and preorder folks for their patience – this project wouldn’t have been financially possible without our backers – and frankly, also without the support of all the people that have been buying and using OpenBeam for the last two years.  (OpenBeam essentially bankrolled a lot of the development of the Kossel Pro, to bring the project across the finish line).  We are aware of the shortcoming on the documentation and we are fixing them.  We are aware of some of the minor design tweaks required to polish the printer and we are fixing it for the upcoming production run (and making the parts available to our existing backers – we’ll figure something out).

At the just concluded 3D Printer World Expo in Burbank, more than one person had come up to us and complimented us on the engineering on the Kossel Pro – that it is one of the more polished open source hardware printers out there, and that the craftsmanship put into it by all our vendors – our machinist, our injection molder, our OpenBeam extrusion supplier, is very apparent.  We are certainly proud of the engineering that we have done, but over the course of the project, we’ve also identified shortcomings with the Reprap project, and we look forward to fixing and addressing some of these issues we have identified.  We look forward to continuing to carry the torch and innovate, and designing and building better tools to enable makers out there.

Thank you for your support of Open Source Hardware,

-=- Terence and Mike