The test fits shall continue until everything is fixed

Hello everyone!

We've had an interesting weekend.  Our T1 plastics were supposed to be delivered last Friday so I could have the entire Memorial Day weekend to work on printers, but they were held by customs.  The reason?  I was a bit too descriptive on my part naming.  The ball joints were called "Deltabot Ball Bearing Joint A" and "Deltabot Ball Bearing Joint B".  Because the part name contained the word "Ball Bearing", US Customs decided that it was now a bearing housing instead of just a regular plastic part, and held it until they could get my Federal Tax ID on the shipment so that I can be taxed accordingly.  

The tax rate is 2.9% value of the shipment, which for 30 pieces of engineering samples, came out to less than a Big Mac and Fries at McDonalds.  The cost of losing a long weekend, however, is far more damaging.  This goes on to illustrate just how messed up our tax laws can be.  Of course, in final production (after Kickstarter campaign), the kitting of the ball bearings, plastic parts and packaging will be done in offshore and the completed assembly will be declared as hobby / construction toy part, which can be imported tax free.  The fact that I can import finished goods tax free, but get taxed per individual line item (4.9% on bearings, 3% on screws, etc) shows how backwards our tax laws can be and how it does not encourage small business owners to keep jobs in the US.  Interestingly also, if I had just named the part "Deltabot Joint", chances are it would have flown straight through customs clearance.  Either that or my house would be raided for weed by the DEA - you never know. :-P

Mrs. OpenBeam was conveniently out of town on a business trip, which makes such annexations of common living areas slightly more OK.

The good news is that MOST of the issues have been solved now at T1.  The bearing press fits, crucial to achieve low friction, backlash free motion in the ball joints, have been fixed.  We've added cavity identification markings into the tool - each part shows a different number depending on which cavity it came out of - to better allow us to track problems with injection molding should they arise in the future.  

Bearings now press fit into all the ball joints nicely with just the right amount of resistance.  This is a major win.

Other fixes included cleaning up some flash issues on the end effector, and better processing to bring the parts within tolerances and flatness specifications.  At Western Tools, their injection molding machines actually monitor each shot's parameters and continually compares it against the programmed machine settings, and should the processing parameters drift, the machine will alert the operator and stop operation.  This means that once we dial in our manufacturing processes, parts will be stable and consistent.  It doesn't stop us from performing incoming inspection on each batch, but we are less likely to have issues this way.

The snap fits worked perfectly the first try.  We got REALLY lucky.

Of the remaining problematic parts, only 3 parts remain:

*  There is still some fit issues on the ball carriage rail's top and bottom halves.

*  Some of the geometry for the self-terminating loop isn't quite right, and it's hard to install the timing belt as a result.

*  There is still a bit too much slop in the nut clamp.

These are relatively minor, and we expect that it'll take 2 weeks or so to fix.  While we can greenlight production on the rest of the parts, some of the parts share the same mold and may have to wait until mold changes are done before the part can be ran.

I was driving to work this morning thinking that this phase of the project is taking longer than expected, when I realized that as far as complexity goes, the Kossel actually has more plastic parts that had to interface with other mating parts perfectly than my previous two products I've designed for my day job.  The last product I designed, a microscope stage top incubator, only had 9 plastic parts and didn't have the tolerances required on this project.  My other project was designing the mechanical of a low end florescent microscope, and there, only one set of parts (the hinge) required high precision.  And both of these projects were funded from a very generous R&D budget that didn't blink twice about expedited delivery charges and overnight shipping.  

In the meantime, I'd like to share with you some more pictures.  We have pictures of the Mini Kossel and the Kossel's heated beds, thermal images of the hot end on the Kossel Reprap showing the benefit of our ducted fan cooling, as well as thermal images of how uniform the heated beds are.  Also, I'd like to show some pictures of test prints that we've done on the Kossel Reprap as part of our work tuning the slicer profiles.


-=- Terence