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Archive for September, 2014

CNC Surprises

Thursday, September 18th, 2014

No Cigar

I feel like updating the saga of my CNC progress. I have learned a great deal about CNC, but in relation to the amount that I need to know in order to be competent, I know just about nothing.

First thing: do not build a CNC lathe. Do not even waste your time. A mill will do nearly everything a lathe will do, plus a million things a lathe can’t begin to do. You can thread with a mill. You can turn parts with a mill. You don’t want a lathe. Believe me. And if you have a lathe, no one will want to help you, because only about 10% of CNC hobbyists use lathes. Even software makers ignore us.

Second thing: precision is expensive. You can fix a machine so the computer compensates for backlash. But it doesn’t actually work. Say you’re milling a round hole instead of boring. You have to make the cutter travel in a big circle, as well as rotating. Every time an axis changes direction, you’re going to get error due to backlash. The only way to get rid of it is to use ballscrews, and cheap ballscrews don’t really work, although they may make you feel good. On the web, people with cheap screws talk about backlash figures between 0.005″ and 0.010″, which is huge.

When I got ready to build my lathe, I figured the machinery itself would be simple to create. The plans I bought didn’t mention ballscrews. Then I got it running and found out I had 0.018″ of backlash on the z screw. The software compensates on simple parts, and that’s very good. It’s worth a lot. I can do a lot of stuff I could not do with a manual mill, and I can do it with good accuracy. But sooner or later I’ll want to cut a part that requires a sudden change in direction on z, and I won’t be able to do it well.

Another annoying lathe issue: you have to tell the computer about the cutters you use. When you use a tool, only a tiny part of it will touch the work. The computer has to know where that contact occurs. Tools have rounded corners, so there won’t be a sharp, defined point where the tool makes contact. It will vary as the shape of the work and the direction of tool movement change. Lathe inserts vary a lot, so you may have to have a whole bunch of tools defined. I’m not sure HSS is useful at all, because you can’t grind it precisely. If you try to tell the computer the radius on a tool made from HSS, you’ll definitely have error.

I have not used a CNC mill, but it stands to reason that it should be less complicated. Say you’re using a half-inch end mill. You know exactly where the lower surface is, at all times. You know where the sides are. Not complicated. Maybe I’m wrong, but I can’t really see myself spending days telling the computer about the small number of tools I’ll use.

I’m going to keep the lathe, because even with limited precision, it can be useful, but I would not waste my time building another one. I’m hoping to use it for threading and tapers, as well as curved parts like dial handles. Things like that will justify its existence until I get a mill going.

People are telling me I should have bought a used machine. There are a lot of old CNC machines out there that have obsolete electronics. I may be wrong about this, but I will relate what I understand to be true. Years ago, CNC required big dedicated computers and expensive controllers. In 2014, a secondhand PC can handle most of that stuff. There are old machines out there with screws and motors that still work, but they have heavy, useless built-in electronics. Commercial users want to get rid of them, so hobbyists buy them and bypass the ancient circuitry, running them with Mach3 or LinuxCNC.

I would love to have an old vertical machining center, which is just a very fancy milling machine with an enclosure that keeps chips and coolant contained. But they’re gigantic. There’s one for sale down here, and it weighs over 8000 pounds. I’m crazy, but not that crazy. Also, what if you buy one, and the screws are no good? You’re out maybe six grand, and then you have to put another two or three thousand in. Arrgh.

I am thinking I should get a new Chinese mill, like an R45 clone or a Grizzly G0704, which is a little smaller and less rigid. I would have to put decent screws on it, which would give me gastric distress, but it would do just about anything I want to do. I still have the ability to add 6 more axes to my controller, so I should be able to keep the lathe and add a mill with no problems.

I bought Dolphin CAD and CAM, which is a pretty good commercial program. They gave me a big discount. I haven’t gotten to where I can actually use it, but I’m working steadily. I have managed to get Mach3 working (most of the time), so I use it to fine-tune the machine. Yesterday I cut a #2 Morse taper in aluminum, just to see if it would work. Tapers have to be very precise, but the geometry is simple, and the tool doesn’t change directions while it’s on the work, so I figured there was some hope that my lathe would pull it off.

Below is a photo of the taper. It fits fine in the center bore of my rotary table. I put Sharpie ink on it and tried to rub it off on the inside of the bore, to check for high and low spots, but I couldn’t see any problems in the result. It would definitely be sticky enough to hold a drill chuck in the lathe’s tailstock.

09 17 14 Morse 2 taper cut on mini-lathe

If I can make tapers that actually work, it will be a nice ability to have. I should cut an R8 and see what happens. My experience with lathes is that even with error in the chuck, you can get a very nice, round part as long as you don’t move it around while cutting it. If you take it out and put it back in, it won’t be in the same position. I don’t think it’s unrealistic to try to make an R8 taper, but the dial indicator or test indicator will tell me for sure.

I am enjoying the lathe. I plan to keep working on it until it can thread. But compared to a mill, it’s…handicapped. That’s just how it is.

Not so Fast

Monday, September 8th, 2014

I am a Deacon

Many times in my life, I have had things placed in my hands and then taken away, as if someone who hated me found out and ran to me to “correct” things. It happened again yesterday.

On August 16, my church had a meeting, and they named new deacons, ushers, and one minister, plus a house prophet. My pastor stunned me by announcing that I was going to be a minister, which is a purely spiritual function. Deacons have to do things like cleaning, driving, and so on. Ministers go to the front of the church when the spirit moves, and they pray for people and lay hands on them and so on.

As a recent entry on this blog says, I was pretty happy about this. I have never asked for any type of promotion at any church, and I don’t promote myself. I have turned jobs down. They asked me to manage the kitchen at my old church, and I said no. I won’t drive the van for my current church, because of the liability. Driving is for people who have no net worth, unfortunately. If you have anything, you can be sued. Anyway, I was shocked and pleased to be a minister, because it was exactly what I wanted to do, I had not asked for it, and I wasn’t going to have to spend two more years proving myself.

The week after the meeting, someone said I was supposed to do something or other as a “deacon,” and I corrected them so there would be no confusion. And I’ve been talking to my friends about how wonderful it was to be recognized and put to use. I’ve been going to the front of the church to do minister work, trying to get it right.

Yesterday, someone on Facebook congratulated me on my anointing as a deacon, and I corrected it, and then my pastor’s wife corrected ME! She wrote “DEACON” in capital letters. That was news to me. The word used at the meeting was definitely “minister.”

So regardless of what was said at the meeting, I have actually been appointed to the deacon team. This means I’m doing exactly what I’ve been doing as an armorbearer. I still have that job. There has been no change at all. I just have an additional title. We don’t have any specific duties or authority. We don’t get training as deacons. I don’t know what the job is, yet.

The whole thing is very embarrassing, but what can you do? It wasn’t deliberate. Sometimes people mean to say one word, and another one comes out.

Yesterday I was fairly disturbed by it, and I went to God and tried to figure out why it bothered me. Before I was appointed, I was happy, so why wasn’t I happy after being moved up and then back down? And then he showed me a few things.

He reminded me that spirits and people have been trying to kill and suppress me all of my life. Things that should have worked out have been taken away from me, even when I did things right. People with lesser ability and character got honors that were supposed to go to me. I had opportunities to make money and succeed, and they were destroyed suddenly, in spite of my efforts.

I probably shouldn’t say this, but when I was 16, I got to go to Europe for six weeks with a bunch of other kids, and a pretty girl who had decided to lose her virginity asked me to take her out. We went on a double date with another girl and a friend of mine, and the friend started acting like the pretty girl was his date. I got shoved completely out of the picture. Years later, I found out he had sex with her that night. Obviously, it would have been bad if it had been me, but it’s exactly the kind of thing I’ve had to deal with.

At my old church, they made me a security guard. I was a scientist, a published author, and a successful lawyer. I was a great cook, and they needed help in the kitchen. The leadership was working-class and lower middle class. They were not highly educated, nor were they sharp or capable. I could have been useful. They made me a security guard and shut me out of the inner circle. This was how they operated. They had a phenomenal guitarist there–an established performer who has played concerts all over the US–and they put him in charge of frying disgusting SYSCO chicken. They took the worship leader–a man who went to college on a voice scholarship–and replaced him with the pastor’s son, who sang off-key. They put the worship leader in the kiddie area, where he entertained small children.

When I saw the minister position slipping away, memories of other things I had lost came back to me. This is why I was disturbed. If I had been made a deacon from the start, I wouldn’t have thought about any of these things. I would have been glad to get that far. But when you’re told you have something really good, and then you find out you’re getting something pretty good, it feels like a step down, not a promotion.

David was rejected constantly, until he became king. Even Samuel rejected him, until God forced him to anoint him. Rejection is a pattern anointed people go through. If you have an anointing, and you get promoted, and God is in it, it won’t be because you listened to some idiot preacher who tells people how to network. It will be because God forced people out of the way.

Rejection is something anointed people can count on. The thing I’m wondering is how deep it runs. I know the prosperity preachers are wrong. I know we’re not supposed to have orange mansions and mink-lined doghouses and all the other tacky stuff rich preachers love. But I also know that we’re supposed to have good things in this life, eventually.

I had another problem like this at my church. They asked a bunch of us to come in and be in a video. We posed for the camera, and they sent us home. They didn’t tell me what my image would be used for. Then they showed the video to the church. It showed various people posing while a voice told about the iniquities they dealt with. When my face came up, and voice said, “PORNOGRAPHY.”

I was not too happy about that. I will not sit here and say that I use the Internet and have never looked at naked women, but I never told anyone this was a major issue in my life, and I certainly never agreed to pose falsely as a porn addict in a video. I told them they could go ahead and use it if they wanted, but some of the media people got angry when I went on Facebook and pointed out that it was a dramatization, not a confession. They said it made them look unprofessional. Well, it made me look pretty funny, too! People were telling me how sorry they were for me, because of my “problem.”

I never said I wouldn’t talk about it, but evidently they thought I had agreed to be silent when I told them to go ahead and use it. I’m a lawyer. We think in fine print. I would never have agreed not to talk about it. Not in a million years. Anyway, it caused a brief stink, and I saw it as an effort by the enemy to drive a wedge into the church. These things happen. You can’t let them stop you.

When I found out I was a deacon, the memory of the pornography thing came back to me. It was as if someone was saying, “You are NEVER going to be accepted.”

Little things like this can eat at you. At my old church, the kid who ran the media booth dropped part of a heavy plywood set on me and nearly killed me. I had bruises and scrapes, and a lot of skin was scraped off the back of my left ankle. I had pain and trouble walking for weeks. I had to drive myself home and pay the medical bills. That wasn’t right, after I drove up there in my free time and tried to help them dismantle the set. The thing that hit me barely missed the back of my head. If it had hit me, I would be dead or brain-damaged. They could have reached out just a little bit, but they never did. You can forgive, but you can’t forget. For the rest of my life, whenever I have a hiccup in my relationship with any church, no matter how blameless everyone is, I’ll remember that.

I see the minister misunderstanding as an attack, to make me feel rejected. Somehow the enemy got my pastor to say the wrong word by mistake, to see if he could stir up these old feelings. Well, it won’t work. I’ve been counseling people for a long time, and as I told someone yesterday, now it’s time to take my own medicine. Because I helped other people, I know how to help myself. I’ll have whatever God wants me to have. God has never rejected me. I have not fallen off the fast track. The plan is still succeeding, whatever it is.

This summer has been a real bear for a bunch of people I know. This is just one more challenge in a series. I am really looking forward to the end. We’re not going to have problems this intense, continuously, for the rest of our lives.