Drawing requests: Y motor area, rear mirror, belt attachmen

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Drawing requests: Y motor area, rear mirror, belt attachmen

Postby BenJackson » Sun May 29, 2011 12:45 am

Things I've noticed that could use illustrations. The common theme is that these are all near the top of the assembly tree and the only current view is in the overall illustration:

  • The Y motor area. It's well described in the doc but a picture would be nice.
  • The rear mirror bridge. Mainly I can't figure out what screws were intended here: M3x8 panhead + #4 lockwasher does not go through the acrylic plate. Even with the lockwasher precompressed (or removed) it would not engage many threads. I'll probably use my own M3x10 here.
  • Belt attachment detail. Only really necessary once, somewhere, to show the stackup. I've had to go entirely by pictures here and used #4 + washer + belt + plate + nylock nut. The lip of the washer against a belt tooth seems to do all the work.

Couple other misc comments:

  • The Z motor plate could use a slot to help index it on the rail. Otherwise you have to measure depth to match the normal brackets which are installed flush with the rail. Also the datum for the bearing placement (inside edge) doesn't exist on the motor plate so you have to apply the offset to get the outside edge (and assume the bearing is in the same place relative to that corner).
  • I accidentally used fat nylon spacers on the X motor which worked fine except the skinny ones don't work on the mirror bridge. You could simplify the kit by going with all fat nylon spacers.
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Re: Drawing requests: Y motor area, rear mirror, belt attac

Postby bdring » Sun May 29, 2011 2:26 am

I'll add a detail view of the Y motor area to the main assembly drawing.

I checked the rear mirror bracket. There does appear to be very minimal thread engagement. It probably grabs on some and not others. I'll look at changing that to M3x10mm.

I'll try to show the belt attachment detail. The best view is on the gantry drawing right now.

That is a good idea about the Z plate. I have plans for a major overhaul of the "optional" Z axis. It was designed to be a later add on, but since it appears that everyone orders it up front, I can do a better job of it.

Please post a picture of your nylon spacers. I had problems in the past with "cold flow" in nylon where the screws loosen over time.
Bart
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Re: Drawing requests: Y motor area, rear mirror, belt attac

Postby BenJackson » Sun May 29, 2011 3:19 am

bdring wrote:Please post a picture of your nylon spacers. I had problems in the past with "cold flow" in nylon where the screws loosen over time.


I'm not sure what I'm trying to illustrate here. This shows the X axis with proper spacers along with the fatter ones (that will pass an M5) sitting on the motor. I originally had the fat ones mounting the motor and didn't realize until I needed them for the mirror:
IMG_0589[1].JPG


As a bonus I show the underside of one of the mirror mounts. You can see how the threaded holes have a fairly deep chamfer, requiring a longer thread.
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Re: Drawing requests: Y motor area, rear mirror, belt attac

Postby bdring » Sun May 29, 2011 12:46 pm

Spacers - I total misread what you were talking about...never mind what I said.

I assumed there was something like the chamfer. If the screws will start, they work. I will change them to M3x10mm. Thanks for the picture.
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Drawing Revision

Postby bdring » Sun May 29, 2011 2:14 pm

I added a sheet 3 to the main assembly drawing to show a better view of the Y motor, rear mirror and Z upgrade. I also cleaned up some hardware issues. I'll adjust the BOM before sending out more hardware kits.

I added an alignment notch to the Z upgrade plate. That will give a good starting point for aligning that plate. This assumes everything else is perfect, so expect some slight tweaking to get a smooth running Z.

Ben, thanks for helping me improve the documentation.

http://www.buildlog.net/sm_laser/drawin ... _rev_5.pdf
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Re: Drawing requests: Y motor area, rear mirror, belt attac

Postby BenJackson » Mon May 30, 2011 1:33 am

Thanks for the new illustration.

It looks like M3x10 + #4 split lock washer works better for the Y and Z motors as well. The new illustration shows some kind of washer on Z which does not work with the M3x8 panheads in the hardware kit. Without washer the M3x8 will catch just under 2 threads.

The new illustration also shows a regular 1/4 20 nut to jam the coupler where the Y drive shaft attaches. The hardware kit I got doesn't have (or even list) a normal 1/4 20. I tried to use one of the 1/4 20 thin nylocks but it's a pain and I don't recommend it. The conical end of the Y shaft makes it nearly impossible to start the nut nylon-first (which you can usually do if you thread it on once the other way to loosen up the nylon). Also, unless you leave a couple of other nuts jammed on the drive shaft it's tricky to tighten the nylock down. I thought nylock might be "better" here but I should have just used a regular 1/4 20 nut.

And finally the new illustration shows a stack of 1/4 20 + washer + 1/4 20 on the 10" Z lead screw (above the motor mount). What is that for? It does explain the lone 1/4 regular washer in my hardware kit. 1/4" 20 nuts are missing as I mentioned.
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Re: Drawing requests: Y motor area, rear mirror, belt attac

Postby bdring » Mon May 30, 2011 12:09 pm

If the M3x10 works better everywhere, that helps me.

The 1/4-20 on the Y threaded shaft was added. That should have been there, but I missed it. You can run a nylock nut on backwards, but I think the resistance created by those works against the fine adjustment you want. You want to be able to move that nut without rotating the shaft. As much as I hate added a new bag of hardware, I think it is worth it here. There is usually no need for a locking nut when you tighten two nuts against each other.

That is for manually adjusting the Z. Before the motor was designed, I used a nut driver on that. You can ignore if you have a Z motor.
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