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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Sun Feb 19, 2017 3:14 pm 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Ok, pictures!

First, the reason for doing this modification: The lines here are about 0.200" long. They are at roughly 45° from horizontal. Both were done at the same speed and power. The top is wavey, the bottom isn't :D

Image

The two brackets:
Image

Right side bracket and part of the carriage:
Image

Yes, I still need to come up with a more elegant solution for the homing switch. :lol:

An album with more pictures:
http://imgur.com/a/fxmf3


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Fri Feb 24, 2017 12:04 am 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Well, that's annoying :?

50ish hours of run time after install, I ran a couple jobs that had long engraves following the X-axis. I'm getting noticeable wiggles in the lines, depending on where it is along the x-axis. The same wiggles are repeatable, and get worse the faster the carriage moves, so it appears to be caused by slight wiggles in the rail.

When I first got the rail I noticed there were some tighter spots where the carriage would slow down just slightly. If the machined rail is out of true at all, it will be magnified and show up on the work surface. Of course this fine for most applications, just not this one :lol:

I'm wondering if something like this would be a better solution, since it has no moving parts. I sent PBC a question through their site, so I'll see if they get back to me or not.

Grainger has the mini-rail for ~$150 for both carriage and rail (though I'm not sure if they're a matched pair like they should be).

http://www.pbclinear.com/UGA-Low-Profil ... near-Slide
http://www.pbclinear.com/Mini-Rail-Mini ... near-Guide <---- this one says the carriage and rail are matched at order time, so carriages ordered later may not fit well.


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Wed Mar 01, 2017 11:23 am 
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Joined: Thu Oct 30, 2014 11:43 am
Posts: 755
Location: Finleyville, PA
Country: USA
Laser Type: 5th Gen 45W hobby
I would check if those are rated for side loading like the other rail is. Do you have your preload set correctly, and double checked the carriage? ive run a lot of engraving on this machine since the mod, and no wiggles or binding. Just the occasional wipe down with a very light oil (Weapon shield CLP is my choice) to clean it up.

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Azzy's Design Works - teamadw.com
Equipment: 5th gen FSL hobby, 45w, w rotary and frustration, KNK MaxxAir 24" plotting cutter, Roland LEF-20 Eco-UV Printer, Thunder Laser Nova 35 100w


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Wed Mar 01, 2017 5:51 pm 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
I set the preload loosening the top adjuster a few degrees, then tightening the lower one to raise it up. Kept doing that until there was zero play in the carriage. The load arrows are pointing down, and I'm adjusting the center wheel to push upwards, so the outer two wheels are riding the bottom rail.

For this test I put 6 lines 0.050" apart, and ran them on the Raster tab at 100% speed. At lower speeds the wiggles are less pronounced. I still see the wiggles if I engrave the same pattern on wood or paper. This is acrylic stuff "Duet by Gemini".

The bottom set of lines was what came through a single sheet of paper, so that's why it's washed out. The top set had three passes per line. The third group had one engraving pass per line.

I also got my order from FSL today, so I replaced the X belt and the idler (even though the new still has a tiny bit of play in it :roll: )


Attachments:
2017-03-01 002.jpg
2017-03-01 002.jpg [ 2.1 MiB | Viewed 295 times ]
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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Wed Mar 01, 2017 6:59 pm 
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Joined: Thu Jun 13, 2013 6:11 pm
Posts: 1066
Country: USA
Laser Type: 4th and 5th
Any chance your Y is a bit loose? That may give you some slight wiggling.

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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Wed Mar 01, 2017 7:32 pm 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Before this latest test I did check the Y axis. On the right side, I found two wheels that didn't roll smoothly (either the bearing wasn't pressed in all the way, or the stud was too short. When the screw was tightened the bearings would bind a little, making the movement not smooth). I replaced them with extras from the x-gantry, and now they spin nicely.

The left side was loose, no bad wheels, so I adjusted it to zero play.

Tightened both belts, then adjusted them to travel together.

Doesn't mean they aren't loose again though :lol:

The pictured wobbles are in the middle of an 11" long line, hopefully reducing any wobble to the X axis, and not the Y axis.


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Thu Mar 02, 2017 1:52 am 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Scatterplot wrote:
Any chance your Y is a bit loose? That may give you some slight wiggling.


hoozie wrote:
Doesn't mean they aren't loose again though :lol:


Yep, they were loose, again. I could spin one wheel on each side freely. Snug them up a bit, and it's fighting the edge of stalling the stepper and reducing wobble.

With them tighter, the engraved line definitely had less wobble to it.

"I knew it was a hobby machine. I didn't know the machine would be the hobby"


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Thu Mar 16, 2017 12:50 am 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Well, I just realized that my x-rail has some twist in it. Only ~1/16" over the length, but, by the time it gets to the work area, it's bigger than that. I found it after investigating why I was cutting a rhombus rather than a square, and that to make it actually do a square, I had to move one y axis block to be 1/8" farther from the case than the other.

Funny story: A client and I worked with a local rep for some motors and gearboxes. I sent PBC linear a request for information about some other linear rails. Who else calls me about that request? The rep I've worked with in the past. Even funnier is that we haven't talked in a year, and the morning before he called, my client said we need to talk to him again about a different project. :lol:

Anyways, I'll send him an email asking about my twisted rail.


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Thu Mar 23, 2017 1:38 am 
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Joined: Thu Feb 02, 2017 3:06 am
Posts: 120
Location: Oregon
Country: USA
Laser Type: 5th gen Hobby
Mcmaster was kind enough to send me a replacement rail. That still has the tiniest amount of twist in it. :?

I have it installed and squared up by having one of the y-blocks just under 1/16" different than the other one. But, it's cutting squares that are actually square, so I'm going to leave it for now.

Although, I'm wondering if I extend the aluminum angle bracket all the way across, if that will help straighten up the rail.


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 Post subject: Re: Linear bearing mod for x axis
PostPosted: Thu Mar 23, 2017 10:04 pm 
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Joined: Thu Oct 30, 2014 11:43 am
Posts: 755
Location: Finleyville, PA
Country: USA
Laser Type: 5th Gen 45W hobby
It might help, but you will be loading the Y axis more. Check your brackets agst a machinist square. Mine are within .002 of square. I used really thin plastic, you could use aluminum foil, to act as shims on one side or the other.


As for the hme switch.. mines been oogly like that ever since. If it works, just leave it :D

_________________
Azzy's Design Works - teamadw.com
Equipment: 5th gen FSL hobby, 45w, w rotary and frustration, KNK MaxxAir 24" plotting cutter, Roland LEF-20 Eco-UV Printer, Thunder Laser Nova 35 100w


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