Spindle Head

Feb 19th.

Part of my luggage still has not arrived. This was upsetting; the Y travel ball screw is missing as well as a number of pieces that we need to proceed, such as the inserts. After a call to AA in the US, because apparently they don’t give out information to the Colombian agents (upsetting to know) it turns out my luggage had been sitting in Boston for over 12 hours before being sent to MIA. But it did arrive today, the airline arranged for a driver to take me to the airport because we still need to go through customs. Everything arrived just fine but I did loose over 3 hours in the ordeal. Now we don’t have any excuses.

Today was a productive day. We took drastic action with he Z axis. Last night I started to redesign it. Today Camilo quickly took over the CAD modeling, I visited one of our suppliers and found and bought the material for the new spindle housing. I also had a meeting with Andres and Milton. Andres will be helping with programming of EMC that is a flavor of CNC Linux, and Milton will be helping with the electrical parts. Tomorrow we will sit down and start drawing the electrical diagram.

Today I got some very good feed back from people. Jesid, for example, made a good point about the machine needing to be more modular so it could fit through smaller doors. He talked about his uncle and how he would love to have one but it would have to fit trough his doors. Its size might turn some people off.

Esteban suggested nailing down the spindle enclosure before proceeding with the Z redesign. That was a good move.

Next some pictures at last:
A rendering of the machine design

Testing the Y axis fit
The team examining the setup.

Beam inserts

Feb 18th – Boston – Medellin dreaming up how to thread the beams.

It’s Monday and the day started very early. To catch the 5:30 am flight to Miami that then pulls into Medellin at about 2, I need to be up by 3:30 and leave home by 4. Today I made it to airport by 4:13, a hair before the large early morning international crowd. This weekend was relatively productive. I wanted to get more work stuff done but ended up doing more home stuff, spent time with Diana which was much needed, catch-up with the mail and friends that where visiting town. I am happy that I managed to get almost all the pieces of equipment that I came here to get - ballscrews, spindle and metering tools. I am still waiting for a communication cable to a new displacement gauge and vibration measurement system. I am hoping to get those during my next visit.

The next things on my mind that I will concentrating on this week;
Electrical diagram for the machine.
Sourcing of enclosure components.
Hook up electronics-controller-motors-screws and get stuff to move.
Build the y,x and x axis.
Talking about the axis, I have this idea to place threaded inserts into the concrete. For inserts, I picked extra long brass inserts (the type used in plastics). These inserts have a thread length-to-bolt diameter of over 2, which will guarantee plenty of grabbing length along for the screw also, since we place the insert from the inside. The insert is in compression against the inside wall of the steel beam. I am also considering testing a combination of an epoxy based cement with or with out regular concrete. The idea is to use the epoxy-based cement along the insets and let regular cement fill in the rest of the space. This will accomplish several things - for one it will reduce cost, since the epoxy base cement is a lot more expensive. It also has better strength and damping properties. Also, the combination of these two masses may have a beneficial affect on the structure, reducing the likelihood of resonance. There is also the possibility to further improve the structure by shifting the neutral axis of the concrete with that of the steel beam. This is accomplished by inserting a filling of different density in an asymmetrical location. In this particular case, I am thinking of using a 1 inch diameter piece off wood. It will also reduce the weight of the structure of a bit. Now I am sure you can get fancy with shape, material and location of this insert but we will keep it simple for now.There are other things to take into consideration. I plan to first pre-drill the beam as straight as possible, with a through hole for the screw, then place the insert inside the beam and thread it through with the screw and hold it in place. Once all the inserts are in place but not locked down, I can double-check their alignment with a straight edge. Actually I will not tight them down completely because this action will certainly move them, causing misalignment. Remember we want them as straight as possible so we can later have more place with the entire rail. Since the through hole on the rail is 7mm, the M6 screws give us half a millimeter place on each side. The more scattered the insert the less clearance there will be. Now, and other idea is to hold the screw in place with something like silicone or hot glue - this will certainly hold them in place but will not be permanent.

I would then process to turn the beam with the insert side down and fill in the first layer of epoxy cement, let that set and proceed with regular cement.

Thursday 14. Medellin – Miami - Boston

I am back. Yes I did it again, I dropped off. Hey, this isn’t easy building this machine for the first time so quickly - it can drive someone crazy. By the way, don’t leave your cell phone behind in a Colombian airport. It is almost impossible to get back because you can’t leave the terminal boarding area once you are in!! Ok I didn’t try hard enough. My brother managed to convince someone to bring it in for me.

Fabrication has moved along very nicely. This week it seems not much progress happened but it did. We completed the welding on the base, lots of hours went into that. I’d say about 30 hours. We cleaned off and rust proof/primed the base by Wednesday afternoon. Now we have a working surface off which to start referencing all the linear motion components.

We also made some time to dive into castings. Initially I did not want to consider it, but I think it makes sense for smaller parts. We called around and indeed we found plenty of local suppliers that range from 2 to 5 dollar a kg for gray cast iron class 30. Currently we are having the support for the motors cast so that one piece holds the motor and the drive end of the linear screws. We also have a design for a T-slot table, which we will execute if we have time. We have to make the molds, which is not all that difficult. I guess casting will work for people that have access to small casting operations. They can spend a few weekends making the part replica and then take it in for a pour.

Now looking back at this week I feel confident the project will pull through. There is still a ton of work to do but we have the horse power to pull it off. Here is why. I found a great local supplier of motors and electrical components. Their prices are quite good. I just bough a 6.6 hp GE general-purpose motor (made in Colombia) for approx $350 USD with a two year warranty. With the supplier close by I know I can get plenty of support. Then there are the people. The project has a great staff now. Let me start with Jesid, he is our tech. Sometimes he works part-time for the university but for now he is full time with us. He is a funny guy, he has is own quail eggs business. When I asked him how many quails he had he said it’s a small operation but I make a living. He has 6000 quails and pack about a 100 boxes a day. The whole operation takes him a few hours a day so the rest of the time he gets bored out of his mind. His dad used to own a hardware store so he grew up being quite a handy man. Jesid has great work ethic, and he works hard. We don’t have to supervise him and he is always asking for more.

There are the dLaC guys –Estaban, Juan and Pedro. They have taken the roll off leading fabrication. In contrast to their design office in the most trendy square in Medellin, these guys now spend their day in jump suits, working with Jesid and chasing everything that needs to be made. I sit most of the time in the garage with them, working on my laptop and we call on each other for question and ideas. It’s been productive to work this way.


There are Lina and Camilo. I decided to hire help on the CAD side out of concern with the amount of work that preparing the document will take precisely at the time when we are doing the most testing on the machine. Lina started first on Wednesday and she quickly got up to speed with SW2008 and got started on the castings. (This gave me the time to chase down that motor supplier.) Seeing that this was quite a good idea and the fact the Jesid and the dLaC guys where running out of work and the fact that I could not continue to relay on all nighters to design them parts. (Design after a few night of little sleep is not recommend to anyone…not good.) I asked Lina if she new anybody. She said - I know just the right person and he is sort of available. Should I call him? She did and two hours later, Camilo came in. Camilo and Lina have been friends for a while and they graduated this December. Camilo is freelancing partime with the city on science museum project and Lina is waiting to go to France in the Fall to start her masters. Anyways, Camilo took on the enclosures for the machine and in an afternoon he had modeled a significant portion of it. I am so happy to have them helping out!

Then there is Hans Ley, a retired German machine designer that fell in love with Colombia and is now working as a professor. Hans is quite busy with his own stuff but from time to time he throws me a bone. This week he pointed me to a PC base CNC control board that I have been looking for. This was great the holdback in the motion control design so it just leaped forward. Plus he has three students that we are trying to convince to jump on board. They are CS/EE guys. They where initially intimidated because they had to pick the hardware but now that that is done they can focus on getting CNC Linux to run the machine.

And finally there is the staff at the university: Gabriell - CNC machinist; Jorge – Master welder; Juan, who runs the CNC plasma cutter; Jairo, who runs the place; and “The Beast” – he’s like Jesid but I actually don’t know his real name. Everybody calls him “La Fiera.” He is super cool and always willing to lend a hand. They are all very excited about the project and they are doing their part. They all have quirks of their own. For starters, there is Plasma Juan. He is an EE major the prefers to work the CNC plasma machine than graduate. He works part time for the university while he finishes his degree. He is the kind of person that would fit at MIT - he wears his welding hood while he bikes. Most people in a rush to cut something would rather not go through him since he likes to explain in detail what we will need to do. But people like him can teach you a thing or two, plus he is totally into the project and has delivered beautifully cut pieces very quickly. Plus, he can’t wait till we are done and pitch the idea of an Open Source CNC plasma cutter.

Then there is Gabriel. He is the most excited and vociferous. He was the one that pushed for us to do castings and got us some initial quotes. He is also inviting all the local vendors of CNC related stuff to come in case we need something or they can be of some assistance. But what cracks me up about Gabriel is his obsession with the New York Yankees. He’s been begging me to bring him back a jersey from the States. The only problem is that I live in Boston, and I tell him I don’t think they sell Yankees stuff in Boston - it may be against the law or just plain stupid. So I tell him that I will have to order it online and that I will have to charge him for the shipping. He doesn’t like paying for the shipping for parts. I’ll get him the jersey anyway, but will not give it to him until the end. I’ll make him work for it.

Then there is Jorge, the welder. He’s the first Jorge I have ever worked with. Jorge is a perfectionist and initially he wasn’t too happy about our not-so-refined approach to welding. It took some time to convince him that a regular Joe in the countryside with a stick welder should be able to do this. Plus stick welding is ideal for thick gage structural welding and is more forgiving. Sure it doesn’t look as nice as what he can deliver but having Jesid do it is like 5 times cheaper, the university rate for Jorge is relatively high. He is happy now with fact he is only going to get the really important parts. The closer we get to the spindle, the more I am going to need his skills. I tell him, but not far away at the base, which is the first phase of the project. Jorge has his own quirk – he is obsessed with his helmet. Well, he has the only auto-darkening helmet around which the university purchased for ~$500 USD five years ago. He treasures this helmet. It is in remarkable condition – no, seriously. And he doesn’t like when others - especially students - use it. I asked him why and he showed me the scratches they have put on it. It’s a fire red Miller Elite helmet with flame detail. He constantly puts it away and even hides it but they find it anyway. Jorge asked me if I could find out what it costs to get one states side. It was only too simple to Google to find out the his helmet went for ~$350 USD, twice as much as other brands with the same specification. I haven’t told him but when I get back I’ll tell him that for 150 he can get something as good with flames and skulls.

As you can see, they are quite the crowd. I am starting to feel like Santa, who instead of returning to the North Pole returns to Boston. I don’t mind as long as it is not imposing, and although Colombia’s economy is in rapid growth (~7%), hardware is still expensive, especially if it is imported. It is one of the easiest ways for the government to ensure tax revenues. Colombia examines 50% of the containers that enter the county. Everything has a tax code or something like it, and when you compare the selection state side tagged with a 30% off sale at places like Travers - hands down the US is the most affordable place to buy tools and gear. This should say something about our ability to compete in manufacturing but does not seem to correlate. I am sure this topic needs a much larger discussion.

Now back in Miami waiting to connect. I am sending my last orders behind. I left my laptop behind for lina to continue the design and tomorrow she will be visiting a few foundries to show them what we need. Camilo has a new Dell Inspiron loaded with SW2007. It’s super fast and smooth. It makes my hp NW series look slow. Now I want to update my PC - bad news, because a fully loaded hp mobile work station will cost about $2,600 USD.

While I am in Boston, I will focus on the electrical diagrams for the machine to ensure that I have enough time to order everything. I also have to ship the spindle and ballscrews and some other gear. Juan and Esteban will be cutting the x and y axis and drilling the hundred or so holes that support the rails. Now, making these holes with modern machinery should by no problem. The problem is that we are not using any machine that is in working principle bigger or better than what we are building. If we manage to do this, then truly anybody can build this machine. So making the holes will take some time. I have to remind them to take some pictures.

There is one aspect that is starting to worry me, and that is implementation of a tool holder. I am not sure what I will be getting from SKF. Too much to worry about and I have not paid attention to this. Will call them tomorrow to find out.

Now to end this very long post. I have to say that this would’ve not been possible with out the incredible support that I have been getting from everybody my family, specially my brother and everybody in Medellin. I bring this up because I do not have this kind of support network in Boston. Most of my friends have come and gone and some have even moved back to Colombia. So although logistics and ordering would of been a lot easier state side, I feel very encouraged by everybody around me to put in the extra long hours that the project has demanded. Plus, you can beat the climate – it helps when you don’t have to worry about the snow.

Saturday 9th

Today was a special day. For the first time in 13 years, I spent my birthday with my parents and family. The day started out well at 8 am. I was in the shop with Jesid and Juan finishing up the weld on the base after all the pieces had been tacked. Once we got done, we thought about flipping the machine over (right side up). See, we welded it upside down over leveling jacks to ensure that the top two faces of the structure which is where the Y-axis rail were as planer as possible. There was a small debate about how to move it. Juan was kind of scared of flipping it over. He was worried that the weight would be to much to bring down with any kind of control. Let use a lever I said, plus it should not be over 400Kg, with the three of us and the machine’s broad stance it should not have been a problem. Well, caution prevailed and we brought over a hand jack/forklift thingy to aid with the job. We left around 1, Jesid was going to come in early on Monday to finish the welds he was not reaching easily before.

The afternoon included a spectacular late lunch prepared by my mom, a cake cutting with relatives in the early evening, and a trip to a night club with my brothers and some of their friends. I have to say I had fun, we talked a ton about fashion and sport baiting suits and danced a bit. I needed to take my mind off CNC machines for the evening.

Finding Componets

Tuesday 5th

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.

Wednesday 6th

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.

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.

Availible resources

One of the first things I did as soon I decided we could do this in 6 weeks was call up the crew in Medellin. And I asked to call or go to local steel suppliers and asked them what they had at hand that we may use in the project. The guys came back with this list



I then turn the list into to this diagrams, which when printed on a regular printer was to scale. This is a great way to get a feeling for how big things are, will they hold a thread or welds and most importantly what will fit into what. Remember the viscous shear effect, it relays on concentric structural members with narrow gaps in between.








Next step will be to turn this into a cad library, this way we can easy insert tube members into the design. Juan is working on doing just that over the weekend.

This is a nice segway into talking about design, which I have been thinking and sketching a lot in the last few days. This is the part with lot of drawings so it should be fun. I usually start with pen and paper, before going to cad I like to have mental image o what I want. As the mental image gets more complicated I recourse to pen and paper as a quick way to keep track of all the detail. Plus if you have a hard time drawing something then their may be physical constraints you may not be awarded. The paper or note book drawing are also very important to conveying ideas to the team in Medellin. As I draw out a concept I simply take a picture with cell phone and email it right ways. This way next time we talk they know what is in my head.
















In

The picture bellow are pretty self explanatory