Ok, I was away for a while but it was for a reason. I spent most of last week finding and ordering components. I flew back to the U.S. on Thursday, spent more time ordering, on Monday searching locally and driving around, and yesterday I spent most of the day packing. Today I traveled back to Colombia and brought a ton of gear – literately.
But most importantly, I got somewhere with the design. For starters it got trimmed down in weight by 50%. We’ve designed a clever concrete filling system. (See the pictures below.) The mix is regular concrete with medium sand and a bit of plasticizer to reduce the water content and reduce shrinkage while also improving concrete flow.
We will be cutting open one of the beams tomorrow. I’ll post pictures of that. And we decided on adding shear damping to the exterior of the frame members
I also feel quite happy with the screw/motor setup. Thanks to SureServo’s free tool we quickly modeled the system and matched the motor torque to system inertias and loads. If all goes well, it should work.
Today all the pieces arrived in Colombia without a problem. I got a quick overview of what happened in my absence of which the noticeable things are the beam filling and the modules for the machining bed. After some straightness issues that got resolved I am pretty happy with the result. Keep in mind that this is a very cost effective design, for about $300 US. I also found out about two places that locally do castings. I hope to visit them tomorrow and find out more.
We also found a suitable 7.5hp spindle motors (a Baldor M3770T) for about $650 USD, which is below MRSP states side (about $960 USD). I could of gotten something cheaper form AutomationDirect for around $500 USD but it would of cost $300 USD to bring it over, plus the import hassle.
A spindle from SKF has also been ordered. I should get it in about a week. It was the single most expensive piece at around $5,000 UDS. It’s a 4000 Series triple ceramic bearing on the nose, 9,900 rpm and over 700 lbs of thrust load. It will be a nice spindle to test with. I am sure we could get the cost of this spindle down under 2k once we source it without the time pressure.