Wednesday, January 23, 2008

Getting started

On Monday I arrived in Medellin ready to get this project rolling. The first thing I did was work on recruiting more resources. I visited the space at the university and it is great. I will post some picture tomorrow. I also narrowed down my list of materials to use on the basic frame. I settled on 135x135x5mm tubing. 165x60x3.4mm tubing and 300x100x7mm tubing I purchased 4,4,1 6 feet length of each. The total was around 1550$, it was easy to find since this typical structural tubing for construction. Again the idea is to use easily available materials. If anybody is curious the company name is Ferrasa. I also when around some other place looking higher quality steel for some ideas I have in mind but had limited luck. It seams McMasterr Carr is cheap compare to the prices here for specially steel.
I ended up Monday night creating a project plan, it looked tight and the first item on the list was to get the base design and constriction underway by feb1. The there is the axis of motion and last the spindle around the 2 week of feb.

Tuesday was the day I when tot he university, looked at alterative shop space with a company call Hybritech. A good friend from Boston is starting his own company and gladly offered warehouse space. The university although it has some limitations on schedule is much better equipped, not fully equipped so we will have to work some creative magic. I also spend a good part of the afternoon visiting the steel suppliers. I found out for example that no one takes my AMEX card so I will also have to get creative in that area. Alter in the night I mold over my design options. I finally got something simple and that will do the job.

Wednesday morning I was a little stressed. I had requested the full approval of the budget so that I didn’t have to authorize each individual purchase. So everybody was on hold and waiting. Finally before noon I got the go ahead. I was off with a different credit card to make the first purchases. Initially my card won’t go through, I tried calling the credit card company and after 10 failed attempts finally got thought. I know I am off to rough start but slowly the momentum is going.

Wednesday afternoon I was sailing smoothly detailing the base frame. SolidWork 2008 acted up a few time but after dinner I hasn’t given me any trouble. I also spend some time worried about simple decision like choosing which screws to standardizes. I chose m4, m6 and m8. So I am preordering this as well as taps, clearance and tap drill, and not to forget the washers. One I say the base semi complete I started looking for a t-Slot table. I am primarily worried about the height and the lead time. Initial web surfing gave me some hit but nothing like what I need. It occurred to me that with thick enough material I could simple machine the table flat with the machine it self. I plan to put killer bearing on this things so it should be a breeze. With the proper backing one can make a very nice table this way, I am even thinking of grooving it for drainage. The table base will probably be made from the 300x100mm tube with a threaded hole pattern for attaching vices and work pieces.

During the morning as I was discussing the budget with my boss I also made an important decision. Instead of relaying on find a spindle I was going to make it. Yes I am crazy. Not really the problem is the cost and the lead time. The cheapest I have found it 5350 plus shipping, import taxes, and other extras like a pull up bar and cylinder and an oil cooler and not to mention that I won’t get it on time (5 week lead time) have driven me way. I will keep looking in case anybody knows someone but I will make my own. I was thinking about it being low rev and making it with regular bearings or build it with hybrid ceramic bearings but I will first try a hydrodynamic spindle I even came up with two ways of make in the two basic designs with tools at hand.

As it turns out spindles and ball screws are two things people here have been trying to make with out any luck. I got a solution for the ballscrew but right now its not worth the time and effort. I am getting the call screws from THK. I know THK is expensive so if anybody has any ideas that have short lead times let me know.

I also fond some nice glass slides to make this machine very accurate, it will be tricky to make them work with other encoders but will try. Now I have work on matching the motors/controller to take the linear feedback. I found then in Travers. By the way I hope to have the time to set up a site wit the BOM for the machine so that all information is in one place.

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