[Kickstarter Update] - First shots off the injection molds!

Hello everyone! 

We've reached another very significant milestone in the Kossel program.  First shots off the injection molds!  Below are pictures of the parts.  

The parts above represents the bulk of the custom, made to order parts that were designed for the OpenBeam Kossel Pro family of 3D Printers.  (In addition to this, there is also 1 extruded profile making up the top and bottom vertex, as well as a stamped metal plate for belt tensioning).  Close to half of the funds raised went into the production of our custom tooling and dies for all these parts, with the lion's share going into the injection molds.  So it is a HUGE relief to finally see parts coming out of the machine.

One of the tricks in injection molding is calling out dimensions and changes that need to be "tool safe".  This sounds counter-intuitive, but in injection molding, it is easier to add plastic than to remove plastic.  (In fact, the phase for "remove plastic (減膠)" is known to elicit colorful language from tooling engineers).  When you add plastic material to a part, you are removing material from the mold, which is a lot easier to do than when you have to remove plastic from the part and add material back into the mold.  (One method to remove plastic is to disassemble the mold, xray weld additional steel into the are, then machine it back down to where it needs to be.  Other creative methods include wire EDMing out a chunk of material and inserting a plug that's machined with the new geometry, but that will result in a witness line where the patch occured).  

Excerpt from the engineering drawing for the ball bearing rod end joint.

On our ball joints, it is crucial that the ball bearings press in snugly, without falling out when the part is flipped over.  We have shipped ball bearings to Western Tool for test fit purposes, and unfortunately, the fit is just a bit sloppy.  This is relatively easy to correct as it is a tool safe change to do so.  

Obviously, with a sloppy ball joint, we can't give the "go ahead" for production yet for the early bird kits.  There is a set of parts in transit to me for approval, and we have submitted the production purchase order, but until I can get my hands on them and sign off the parts, we are in a holding pattern.  We should receive the parts next week and I am really hoping that aside from the ball bearing being a bit sloppy, everything is ready to go.  (Looking at the pictures, it appears that the probe pin is a bit warped, but this can be fixed by increasing the cycle time on the machine).  

Molding will take approximately 2 weeks to complete all the parts, pending machine availability.  A good shop aims for about 80% machine utilization rate, so it may also be a week or so before we can get open time on a machine to run our parts.  

After a few month's of delay, it is finally a relief to start seeing light at the end of the tunnel.  We have not been doing a very good job on updates, but with the new milestone reached (and being able to breath a bit easier), I am hereby committing to one Kossel related update on our blog, every week, until units ship to our customers.

-=- Terence