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Have you talked to JT at Shoptask about it? Though you should not have to, can you have it re-ground? Could you post a couple of pics a little further away to get a better perspective of the problem.
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Alright, I thought I finally got my table issues solved when I had my gibs surfaced by a local tool grinder, but after I started running some cnc programs that actually tested all axes simultaneously, I'm still having serious issues. Before I had the gibs surfaced, I was getting constant vibrations that shook the crap out of the machine. Now it's it's only occasionally, like at a certain point when cutting a circle. To keep it even close to usable, I have to tighten the x gib right up to the point that the motor skips and looses step. If I'm lucky, I get one good part for every 3 screwed up parts.
So I finally got sick of this and decided to take the table apart and see if I can find any problems, and here are some pictures of what I found:
Now I'm no expert, but this looks like crap to me. Aside from the bad part on the casting, it looks like somebody just hit the ways on the table with a grinder to clean them up. I don't see how this could pass any kind of quality inspection, and this is a new patriot machine I just picked up three months ago. I'm open to any suggestions or insight.
Have you talked to JT at Shoptask about it? Though you should not have to, can you have it re-ground? Could you post a couple of pics a little further away to get a better perspective of the problem.
That's interesting. This issue seems to follow these machines no matter where they're manufactured...if in fact that has changed as it supposedly did.
I bought a Tri-Power from what was supposed to be one of the last runs at the old factory before they stopped production in favor of an ISO certified factory. While I have not taken the machine apart yet, it seems that I have a similar issue as well as the table "rocking" when changing direction on the X axis. Does yours do this as well? From what I've read on here and other forums, this issue comes back to bad castings and/or poorly machined surfaces. I'm interested to see what I find when I do get mine apart. This is even more interesting because the main casting (among other things) on my machine is not the same as the original Tri-Power, as pointed out by another member here, it's the same as the Patriot. Why would my machine have the same configuration as the "higher quality" Patriot when it was supposedly manufactured in a different plant? The plot thickens. It may seem like I'm bashing, but I'm really not. I did reserch before I placed the order and more or less expected these problems. However, I paid half of what you did, so you have every right to be upset. As stated earlier, give JT a call and see what he has to say. He's always been good with me.
Here's the thread pointing out the casting differences.
http://www.cnczone.com/forums/shopma...er_set-up.html
I talked to JT before I took the table apart, and he said 99% of the time the gib is what causes the problem, I haven't talked to him since. I just took the table and saddle to a local machine repair place today and asked them about cleaning up the dovetails on the castings and checking for squareness. They said they'll call me tomorrow and let me know what they find.Originally Posted by LX Kid
Yes I have the table rock issue, which did get a little better after I had the gib surfaced. Even though I don't think I have a problem with the y axis, I brought the table in along with the saddle for them to check just to make sure.
I didn't call JT because if I can have somebody local fix the problem, I won't have to deal with shipping the saddle and table back and waiting God knows how long for another one that may or may not be a good casting. And I'm pretty sure that having a real machinist rework the dovetails on the castings will yield a much better part than a replacement I would receive from China.
I'll post back as soon as I hear from the machine repair place.
We had one machine with a hard spot in the casting, so when it was machined, it left a high spot. We talked to JT about it and he suggested the same solution- take it to a local machine shop for re-grinding and send him the bill. Its faster and cheaper than waiting and swapping parts. Fortunately for us, we had other machines in house and took care of it ourselves.
Instructor37, I sent you a PM.
I've got a question related to the dovetails or ways in general all the patriots & some other Chinese originating machinery are surfaced in the same way. It simply looks like someone with a surface grinder knocked off the high spots & went on to the next one. What's confusing is that if I took my fingernail or a piece of brass across these surfaces I rarely could feel any tooling marks. In otherwords I could see grinding marks but without looking you'd swear it's smooth as glass. Can anyone explain why?
Wormwood
From what the guy at the machine repair place told me, the surface is flaked. That basically means they take a tool and scrape the surface in different areas to create low spots that are about .0001 deep for oil retention. The only surface mine has this on is where the table slides, you can see it in my pic with the bad spot on the casting. Whenever you have two surfaces that slide together, one of the sides should have this done.
After the gibbs were ground did you MIC it for consistency throughout it's length? Your gonna have to check all the mating/sliding surfaces for imperfections where QC inspections may have failed. Use some machinist dye and look for spots that need scraping. Just some suggestions. Here's a YouBoob demo of scraping if you haven't done it before. There are other scraping demo's to be seen there too.
[nomedia="http://www.youtube.com/watch?v=LUEQhgGazAo&feature=related"]YouTube - Scraping in a tapered gib[/nomedia]
I completely forgot about updating this thread, but better late than never.
So I got the table casting back from the machine shop, and the x axis dovetail was .005 high in the centers. So they cleaned them up with a dovetail cutter, and charged me $195, $45 of which was having a cutter ground to the correct angle.
So I get the machine put back together and adjust and re-calibrate everything, and start to test it out. The good news is that vibration problem is much better. It's not totally gone, but its good enough where handles and stuff don't rattle off the machine anymore. The bad news is, the table rock issue is still there. Not as bad, but still noticeable. I started cutting some 1" test circles to really dial in the calibration, and so far the circles are always just a tad ob longed. There's always a few areas that I measure to be about 6 to 8 thousandths away from being perfectly round. It took me a long time adjusting the backlash settings in mach3 just to get it that good. I was hoping to get it within 3 or 4 thousandths. I'm thinking the reason I can't get them any better is because of the little bit of table rock I still have.
And now for more bad news. I have some cad drawings of parts I've been working on for my tube bender project that I finally thought I'd be able to cut. The entire program's estimated run time in mach3 was about 2 1/2 hours. Everything starts out ok until I hear a loud buzzing noise coming from the Y axis motor for a second before it continues. That was the sound of the motor losing step, which means the part is ruined. The table was close to the middle of it's travel, nowhere near it's limits.
So not wanting to waste another piece of 10" by 17" 5/8 stock, I decided to raise the mill head and do a dry run with no weight on the table. Sure enough, every once in a while, the Y axis motor buzzes for a second and loses step. This is the first time I've ran the machine in cnc mode for anything longer than a few minutes for small test shapes and what not. So I look underneath the table when I move the Y axis to observe the ball screw, and I notice it has a wobble to it. It's not an extreme wobble, but noticeable when you stare at it. I don't know if this is causing the problem or not, but I don't know what else it could be. I was extremely careful when I took the table apart, and cleaned everything really good before I put it back together(not like it was really dirty anyways, I've hardly been able to use the thing).
So I'm tired, frustrated, and out of ideas. This machine just has one problem after another, and I don't like having to spend money to have something fixed that's brand new. I've seen some people make some good parts in other threads on here, so I think it's safe to say I got a lemon. I'm going to call JT later today and see what he has to say.
One more thing, when you bring the cutter down to the work piece to set the tool height, do you notice the bracket on the end of the spindle that the ball screw attaches to seems to have a lot of flex in it when you apply light downward pressure against the work piece? I checked to make sure everything is tight, but it still doesn't seem to sturdy.
I just happened to come across a video someone put on youtube of their Y axis doing the EXACT same thing as mine. Older machine, but the EXACT same problem. It happens at about 18 seconds in:
[nomedia="http://www.youtube.com/watch?v=uhw7AmBzWLM"]YouTube - ShopTask CNC Machine[/nomedia]
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