Thursday, August 20, 2009
Rocket parts and fruit
In spite of the whimsical picture and title this is a serious post.
I can make rocket parts, or I can buy rocket parts. I can grow my own fruit or I can go buy fruit.
I design embedded electronics as my primary profession. When I first started I built elaborate breadboards and test circuits, I even played with etching my own PCB's. Now I order pcb's from the prototype PCB vendor for everything. Even test circuits. What changed?
I'm much more experienced and my designs have a lot more experience behind them. I've learned what works and what does nott I can read a data sheet (including what is not in the data sheet, often the most important part.) I've also learned that spending the money getting a proper prototype PCBs and assembly is a more cost effective use of my time.
At home we have a peach tree, it grows wonderful peaches to the point that we are all tired of peach pie by the time it drops the last peach. There is a sense of satisfaction from growing your own. All the rest of our food we purchase.
When I started working on rockets it my attitude was more hobby and satisfaction from doing oriented. You can see from the old blog posts we built valves, gearoxes and even weird tanks.
As the project has matured and we've started actually doing work for customers I'm starting to realize the value in off the shelf stuff. My attitude is becoming more business like.
For a number of years now we have been sending drawings and material to thunderbird waterjet here in San Diego and having them cut out parts. We had the hemispheres for our tanks spun by AMS industries. Yet the vast majority of our parts have been fabricated by us for us. We don't generate elaborate 3D models and then fabricate the parts, we build a little, scratch our head and build some more. If we did not have in house machinging capabilities it would significantlyy impede our progress, having to wait for an outside vendor to fabricate every bracket and doodah would take forever. I think this lack of inhouse capabilities is one of the things that has slowed Masten down. Yet fabricating everything in house does not make sense either . Some things like the regen rocket motor I documented on this bblog were fabricated in house from detailed drawings. I think that was an error. I'm in the process of fabricating a new regen motor from stainless. I sent the drawings out for quote on MFG quote and was astonished at the price quote I got. The stainless part among the fruit is the first signifcant custom part we have not fabricated in house. Several more parts of that assembly are due soon. I can't imagine the nightmare of machining that part out of solid stainless, yet the vendor did a really good job for a very fair price. (I'll talk more about the vendor and ordering process when I get the full set of parts, so far I'm pleased.) One of the down sides is that our welder is going on vacation for 10 days and the ordered parts are going to just miss his departure, so we won't be testing much for about two more weeks.
Its not always easy to know what to build and what to contract out, I think its really important to have in house fabrication skills and equipment, but I also think we have erred in not sending more work out.
A final question for the peanut gallery, I'm 90% sure the vendor making these parts underbid the job. They had a couple of programming problems and probably scrapped more metal than their profit margin. As a business man I feel strongly in win win arrangements with vendors.
If the business is not win win then eventually the vendor won't be there next time you need him. Would you bring this up with the vendor and offer to cover some of their loss?
(Clearly by the terms of the quote I don't have to)
Posted by Paul Breed at 8:21 PM