My 8020 router build

[Senna]

Hey Rick...

Well... you've reached what most in the build process call a MILESTONE! It's alive...! AND all bright and shiny too...!

If you need screen snapshots of Mach3 settings pages to help navigate that morass... let me know.

Steve

[RicknBeachcrest]

Thanks Steve,
I'm sure I will be calling on your assistance with Mach3 in the future, but for now it's back to the nuts and bolts of the machine.

Rick

[RicknBeachcrest]

I had to find out. So this was a good excuse to get a Starret dial indicator.

The ends are within about .001" but the center is off by .005".

I'm tempted to reverse one of the rails and see if they bow in the same direction then.

Any one have an opinion?
Thanks.
Rick

[JerryBurks]

The ends are within about .001" but the center is off by .005". I'm tempted to reverse one of the rails and see if they bow in the same direction then....

I have a hard time to believe the rails are actually bowed (if they were not seriously mistreated). I suspect the mounting screw threads are not in line or otherwise push/flex the rails. You could just take out the middle screws and leave the ones at the end in to find out.

For my rails (supported round ones) I first glued them onto the substrate and then drilled/threaded in-place so that they don't warp, set or slip because of the machining and screw forces. That way I got them parallel to approx. 0.001" over 12" distance for the gantry and about 0.002" over 36" for the x-axis. But that was for a wood frame machine and may not be a good way for your nice and clean metal rig. In any case, 0.005 sound a bit too much and may even cause binding if the Y-plate is very stiff.

[louieatienza]

I had to find out. So this was a good excuse to get a Starret dial indicator.

The ends are within about .001" but the center is off by .005".

I'm tempted to reverse one of the rails and see if they bow in the same direction then.

Any one have an opinion?
Thanks.
Rick

It's very possible they bowed when the bolts were tightened.

THK's recommended procedure is to mill a lip for the "master" rail to datum off of. I'm sure you could use a known good straightedge to effect the same thing. Once you know it's perfect, you can use the "master" rail to aligh the "slave" rail.


You can make a "dummy" carriage, that you can use to align the slave rail to the master rail. Doing it that way will help get the rails as parallel as possible.

EDIT: Just remembered, the surface of the extrusion, near the slots, are actually canted 1-2 degrees in, which helps keep the screws and t-nuts from loosening, but might affect the linear rails when tightened...

[RicknBeachcrest]

Thanks for your ideas/suggestions. I think I will loosen the bolts in the middle and run the truck down the rail and see what the readings are. The rails are new so they have not been miss-treated.

The rails are mounted with a 1/8" piece of alum. bar between them and the extrusion.

[RicknBeachcrest]

I put a straight edge on the rails. One was dead straight and the other was about .005 bowed. I took the bowed one off and replaced it with one of the others (all four rails are the same size). I checked the replacement with the straight edge first. I snugged each bolt down with the dial indicator next to it. When the indicator started to move, I went to the next bolt. Then I went back and repeated the process until all bolts were tightened.

Now I can run the trucks down the rail and they are within .001" of being parallel.

Lessons learned: Tightening the rails down can pull them out of straightness.

[ger21]

Lessons learned: Tightening the rails down can pull them out of straightness.

The straightness of linear rails is 100% dependent on the installation. They are not rigid enough to maintain straightness when bolting them down. This is true even for very large sizes.

[eloid]

run the guage block on the master rail along the the top side of the 8020 extrustion. and make a video of it... I bet your master rail is out, and youn eed
a datum off ref, as post by others.

once your ref is bang on make small truck with the gauge block bolt down to it, loosen other rail and tighen the rail down as you go with the
gauge block (fixed) and adjust as you need, and the tension of the rail and blot as required. do this for the master rail and the the other rail.

[RicknBeachcrest]

I thought I would post a vid of the final (like anything is final with a home build) alignment.

[RicknBeachcrest]

run the guage block on the master rail along the the top side of the 8020 extrustion. and make a video of it... I bet your master rail is out, and youn eed
a datum off ref, as post by others.

I did check the alignment of the top rail to the extrusion using a couple of small blocks and my digital calipers. I check every 6 inches or so and the top rail was within a few thou of being aligned with the top of the extrusion. I think I can be satisfied with this.

Rick

[mark_detroy]

great job!!!, if your had a fixed link between linear blocks you would be bang on..

[RicknBeachcrest]

I think I need to re-visit my method of attaching the linear rails to the extrusions. I thought I found a good method using the 4 mm t-nuts. The problem I found is that once they bite into the extrusion, they really stay put. This creates a problem when you need to readjust the linear rail. Also they tend to deform the aluminum slightly, so that fine tuning the rail is difficult.

So what I would like to find is some steel bar that is pre-drilled and tapped for M4 bolts spaced 60mm on center. Does anyone have an idea where I could find something like this? I tried 8020 surplus and didn't see any.

Thanks.
Rick

[Drools]

Sorry if I missed it but what size of THK rails are you using? 20mm or 25mm.

[louieatienza]

I think I need to re-visit my method of attaching the linear rails to the extrusions. I thought I found a good method using the 4 mm t-nuts. The problem I found is that once they bite into the extrusion, they really stay put. This creates a problem when you need to readjust the linear rail. Also they tend to deform the aluminum slightly, so that fine tuning the rail is difficult.

So what I would like to find is some steel bar that is pre-drilled and tapped for M4 bolts spaced 60mm on center. Does anyone have an idea where I could find something like this? I tried 8020 surplus and didn't see any.

Thanks.
Rick

Misumi sells predrilled and tapped to spec. I realized after-the-fact, so when I have my mockup complete, and ready to break it down and locktite everything, I will purchase some...

You can also buy the t-muts with the spring, or jsut plain t-nuts without the teeth...

[RicknBeachcrest]

Misumi sells predrilled and tapped to spec. I realized after-the-fact, so when I have my mockup complete, and ready to break it down and locktite everything, I will purchase some...

You can also buy the t-muts with the spring, or jsut plain t-nuts without the teeth...

I've looked at misumi's website, but it seems very confusing and a bit overwhelming to me. I'll take another closer look this time.
Thanks.
Rick

[RicknBeachcrest]

Sorry if I missed it but what size of THK rails are you using? 20mm or 25mm.

I'm using Hiwin LG Linear Rail, 15mm rails

automation products from Automation Overstock: LGR15RxxxxH, LG Linear Rail, 15mm, *specify length, Hiwin LG 15 Rail

[Drools]

My installation went quite smoothly bolting the rails directly to the extrusion but I'm using 25mm rails which overlap each side of the slot by a healthy margin. Is it too late in the build to mount the rails to a .25 or .5"” thick plate first? I’m thinking about the deforming of the slot when weight and cutting forces are applied.

[louieatienza]

Long Nuts -For HFS8 Series Aluminum Extrusions- -L Dimension Configurable- | Mechanical Components for Assembly Automation - Misumi eCatalog

It's like a Rubik's Cube... doesn'e make much sense ate first, but once you get the hang of it it's cheesy cakes!

[louieatienza]

My installation went quite smoothly bolting the rails directly to the extrusion but I'm using 25mm rails which overlap each side of the slot by a healthy margin. Is it too late in the build to mount the rails to a .25 or .5"” thick plate first? I’m thinking about the deforming of the slot when weight and cutting forces are applied.

I think if you're motors are able to deforem the extrusions you got other problems!!!