Gluing Vrail onto extrusion?

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Gluing Vrail onto extrusion?

Postby gavztheouch » Sun Jan 02, 2011 2:48 pm

Has anyone following Barts plans tried gluing the vrail straight onto the extrusion?

I am thinking about gluing the vrail straight onto the extrusion with epoxy, then maybe adding two or three screws to secure once the glue is dry.
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Re: Gluing Vrail onto extrusion?

Postby bdring » Mon Jan 03, 2011 1:00 am

The JB Weld method worked well on the buildlog bot, but it was not too easy to apply. I am going to try Loctite Super Bonder Gel 409 on the 2x laser tonight. I will report the results when done.

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409.JPG
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Re: Gluing Vrail onto extrusion?

Postby bdring » Mon Jan 03, 2011 4:19 am

The gluing went well. First I cleaned all parts with mineral spirits to remove any oils. I then put a small bead in the inside corner of the v rail. The small tip on the glue nozzle made that rather easy. The glue is quite clear and hard to see, so make sure you have a lot of light. I then pressed the v rail onto the extrusion. The glue is supposed to have a 75 second hardening time. I found that it grabbed almost instantly, but the excess that squeezed out took about an hour to fully cure. I got some on my fingers which cured instantly. This got a few finger prints on the parts.

I let it set for over an hour, but I did not need to clamp it. After curing I was able to clean off any excess glue fingerprints by scraping my fingernail access it. The bond is quite strong I pulled very hard on all parts and it did not come apart.

I only did one of the three pieces so I could try something different on each. I think the next one, I will put the bead on the wider part of the v rail rather than the inside corner. As I install it, I will slide it into place to spread the glue over a larger area and be less likely to squeeze any out and get it on my fingers. It might make it cover more area too. The bead size might be easier to see and control.

The new 2x laser only puts v rail where needed. This reduces the amount needed. I cut the r vail with a abrasive cutoff wheel. It cuts it in about 5 seconds, but leaves a little burr that you need to be sure to remove so it does not affect the fit. It also leaves a bit of a heat mark, but barely noticeable. This is one of the Y rails.

DSCN0640.JPG
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Re: Gluing Vrail onto extrusion?

Postby twehr » Mon Jan 03, 2011 12:59 pm

bdring wrote:I found that it grabbed almost instantly, but the excess that squeezed out took about an hour to fully cure. I got some on my fingers which cured instantly.


If is is grabbing that quickly, how are you ensuring placement so the two rails are parallel?
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Re: Gluing Vrail onto extrusion?

Postby bdring » Mon Jan 03, 2011 2:07 pm

It grabbed lightly in 3-4 seconds. I was able to set the parts in the proper position. I probably could have repositioned for at least 30 seconds and completely removed the part without much effort for several minutes. I deliberately picked a shorter Y rail to practice just in case. I did my best effort to get it right. I might try a slow, sloppy job to see if it still works out. It seems pretty foolproof though. The v rail has a slight undercut to the corner and the extrusion has a small radius, so the glue has a place to flow. It is easy to feel the metal to metal contact when you install it.

So far I think I got good results with both JB Weld and the Loctite 409. I think the Loctite 409 was easier and more foolproof. I might try a thinner version of the instant adhesive, they they tend to grab even faster.

It appears to be as good or better than the screw method because there is no variation between screws. The width is probably same with both methods but there could be some variation in height on the screw method. Drilling puts some stress on the rails too. I always slightly countersink the holes on the mating side of the v rail to make sure there is no burr or extrusion of the material.

I have some granite inspection tables and flatness gauges at work. I might measure the finished parts.
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Re: Gluing Vrail onto extrusion?

Postby twehr » Mon Jan 03, 2011 3:03 pm

What I was wondering about was more the method of ensuring that, looking down from the top (seeing both rails at once like railroad tracks), you have them parallel. Do you use a spacer between the rails or is there some kind of natural fit between the extrusion and the rail that it can only go one place?
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Re: Gluing Vrail onto extrusion?

Postby bdring » Mon Jan 03, 2011 3:45 pm

The v rail is design to register itself on the corner of the extrusion. This is actually what led me to Misumi in the first place. They have the smallest corner radius of all the major extrusion suppliers. The screw method relies on this too. The holes are over sized and tightened after the rail is registered on the corner.

The rail has a little relief in the corner that prevents little dings and burrs from affecting the fit. The radius on the extrusion helps too.

Misumi sells precision machined surface extrusions if you want to go crazy with the quality, but that is only one surface. I think it would help with block and rail more than v rail.


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Re: Gluing Vrail onto extrusion?

Postby twehr » Mon Jan 03, 2011 4:11 pm

bdring wrote:The v rail is design to register itself on the corner of the extrusion. This is actually what led me to Misumi in the first place. They have the smallest corner radius of all the major extrusion suppliers. The screw method relies on this too. The holes are over sized and tightened after the rail is registered on the corner.


That explains it well. Thanks!

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Re: Gluing Vrail onto extrusion?

Postby bdring » Sun Jan 09, 2011 2:35 pm

I finished the other two assemblies. I tried a new method this time. The last method had great results, but a little oozed out and got on my fingers. This time I put a wavy bead of the gel Superglue on the wide part of the v rail instead of in the corner. As I installed it, I slide it into place with a wiping action that spread the glue across the surface and towards the corner. It takes about 1-3 seconds to do and I think you probably have three times that amount of time. You probably have at least thirty seconds to put the bead on. The thick bead take a long time to dry.

I think this will be my official recommended method.
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Re: Gluing Vrail onto extrusion?

Postby gavztheouch » Sun Apr 03, 2011 5:55 pm

To everyone that has purchased v-rail, how straight are your sections?

I have just checked out the sections I have bought from a supplier in the UK and they are bent in more than one direction. This is going to make gluing them to the extrusion difficult. I need some way of holding them in place and a glue strong enough to take the tension of the rail always wanting to spring back into its resting position. Should I complain and ask for straighter sections, or is this the norm with v-rail. I paid a lot more for this stuff here in the UK, than the source Bart has in the US. I though it was expensive for what it was, but worth it for the accuracy it offers. Now it has turned up bent I can't see where the value it in this stuff.
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