After such a long time of trying, I finally got this thing finished. Now what to cut?
So far I have only run my spindle a few times. I mostly plot with my machine. It is quieter. I do have some bits on order for it. What I really need is a quieter spindle though. A wood router blasting away for an interminable length of time is a bit much for me here. Although with ear plugs it is marginally tolerable.
What a feeling!
I know what you mean, Paul. Mine is out back in the garden house, so it doesn’t bother the neighbors or anyone else, but it is loud. It is also bolted to the table that it is sitting on, so it also resonates even more. The one thing I don’t like is the leadscrew on the x-axis. It’s only a 12mm thickness and too long, I believe. If I try to get any speed out of it, it vibrates. I might change it to a thicker one.
@Robert_Tamer
Do you have tension springs on your lead screws? Fixed both ends with springs is about all you can do. In that configuration theoretically I think you can run 6 foot leads at about 2,500 RPM? Which with a 10 TPI pitch would net you 250 IPM The real trick is to run balls screws, or a multi start lead. Then you get fast rapids without having to run high RPM. A 5 start thread with a 2 TPI pitch gives a 5 fold speed increase over a single start thread. Then at half the rotation you’re still going over twice as fast.
People get all wrapped up in motors, but it is the leads, and the linear guides where the real performance lies.
My main leadscrew is 1100mm x 12mm with a 3mm pitch. There is no lateral play in it, but when I try to jog it with any real speed, the vibration is bad that I have to stop. Last night I made my first cut with the machine (first paid job), and it worked just fine cutting aluminum at low speed. I’m thinking about upgrading it to a 20mm thick leadscrew. Your thoughts?
@Robert_Tamer
what is your rapid travel speed now? How many RPM are you currently running your lead screws at? How have you fixed the ends of your lead screws? Do you have bearings on both ends? Are your leads locked to the bearings? Are you leads as short as they can be? Or are you running overhang to reach supports? With all of those questions unanswered I cannot have any meaningful thoughts.
With everything being as it should be you should be able to achieve respectable performance with what you have now. 200+IPM is not out of the question. That would be 5,000mm/m for all of you metric loving weenies out there. But I ain’t gonna calculate the RPM you’d have to spin at to go that speed. I just know it is possible based on rough conversions in my head. I’m not going to actually do the conversions though right now. Too much work.
Gawd I hate the metric system. Such a pain in the ass to deal with. Why can’t you people use a civilized scale? One with some style, and class. You know, the only reason they came up with the metric system was to thumb their noses at the ruling class? Those peasants!
Ok Paul, I’ve been doing all the checks to give you what I have. By the way, even as an American, I love the metric system… much easier.
The leadscrews are all locked down with collets on both ends, from the outside pulling, not the inside pushing. I actually used expensive bearings to cut down on noise. No overhang, but like I said before, it’s just a 12mm leadscrew. I should have use a 20mm minimum. The motors were set at microstepping 10 (2000 pulses per rev). I changed that because I found today that the motor would sieze at high rpms. I dropped it down to 2 (400 pulses) for troubleshooting purposes. Per mm travel that gives me 133.33 pulses and the rpm is set to 1500mm/m. If I go any higher, the leadscrew starts to vibrate on the x axis.
I ran a lot of tests on it today for accuracy and found that I am running about 0.003 to 0.005. What do you think?
@Robert_Tamer
Well, I did some calculations over here and it seems to me that your setup should be capable of traveling a lot faster than what you are managing now. At least twice as fast, and possibly even three times faster? Theoretically even slightly faster than that, but that is really pushing it. Leads your diameter can run up to 2,500 RPM absolute max. 3X would put you at 2,323 RPM I think? Which while not sane, or practical, is remotely possible. My personal comfort level is about 1,200 RPM. You’re only going 500 RPM now. To me that means you could double that. So you’re just going to have to disconnect things, and by feel determine if there is any kind of mis-alignment that is causing your issue. Something has to be out of whack.
Guess I’ll get back to checking everything. I’ll see if I can make a small video so you can see what’s happening with this.
@Robert_Tamer
likely you’re going to have to discover it for yourself. It is something you’re going to find through sensitive feel. Some touch of roughness, binding, or maybe even play? It doesn’t take much to throw things out of whack. Although I am not even so sure now if the trouble does not lie maybe with your drive?
I had some roughness on my Y axis and it turned out to be a loose wire that was causing it. Initially I thought that maybe that stepper motor might have been damaged though? So assumptions can be wrong.
Plus it is your machine so you deserve the satisfaction of discovery. How sweet that can be! When you finally excise the gremlin that has been buggering up the works.
There are troubleshooting methods. Ways of tracking problems down methodically. Like if you can change identical parts in your machine to see if a problem moves on you. That is definitely a valid strategy.
Just looking at it may, or may not uncover the problem. But doing stuff can often lead to a solution. Even if it is just accidental. Rolling up your sleeves and digging in is your best way to get to the bottom of things.
Remember, you’re never beat, until you say you are. Tenacity is rewarded.
@Paul Frederick - Well, I did finally find the problem. It seems that if the hole for the bearing at the front of the x axis is not as tight as it can be, it will vibrate to a point where the spindle also vibrates. At the moment it is secure. I put a bronze bushing around it. By the measurement is was only 0.4mm larger than the bearing, but enough to cause problems. I had to shave the bushing down, but for now it is holding and the speeds are up to 2400mm/min. I think next I’m gonna cut the front and rear panels from 10mm aluminum. That should do the trick. When I get more money, I’m gonna do the sides with the same. Thanks for the help too!
@Robert_Tamer
Hey, congratulations on finding the fault.
I figured there was some little thing. That’s all it takes. The devil is often in a detail overlooked. With a lot of balls in the air it is hard to keep track of all of them all of the time. So building a machine we can be focused on one item, and another slips by.
But going through things with a fine toothed comb, we can usually find the bug that escaped us previously. Because then whatever had our attention earlier is out of mind.