No, the design is from somebody else and who posted it some time ago in resources. There you can also find a picture of how it is suppose to work.

 

Let me rephrase that: Is it as stable as bolting the two slots together with screws?

 

They go in pretty tight and will line the two profiles up. I guess if you use enough of them it will be surely as strong as the bolts. Aesthetics are also better, no visible holes in the profiles. You can also use them to attach v-slots together in different ways. Make a corner profile for example out of 1 20x60 and 1 20x40. Very strong and rigid.

I make them from ABS, which is pretty strong. PLA would be less strong, I think.

 

Did you see one of the newest build is proposing pouring into the gap aluminite (or whatever) to 'fuse' the two lengths together. The 2 lengths would have to be clamped solid during the process and hardening. If there is virtually no shrinkage, it would certainly make a permanent full length custom fit 'bound'. The build shows a concept crosscut/profile view also filling the other open spaces. The latter might add rigidity, but will definitely add a bit of weight...

 

Yeah, I did see it. It might work out, but indeed you need to be sure that the profiles are perfectly aligned in all directions before you start pouring. The prep of the aluminum must be very good to, or it won't hold. Personally I don't like to make it that permanent. If you go wrong in any stage of the build and it shows up after you did the bonding….you're ….let's say ……very unhappy.

 

Some pics of the v-slot connectors inside the profile, to give an idea about how it works. They can be ordered, price $ 1.15 a piece, shipping not included. The file from resources was not perfect tight and so I had to redesign the model.

 

Can you upload the modified model or have @Sage add them to the ressource?

 

I cut a lot of MDF and have found I get the cleanest cut cutting at 100 IPM @12000 RPM as shown on my digital router. I use this setting with both 1/4" 2 flute and 1/4" V bits.

 

It's a one shot deal so better be good at it.

Here's a video of what some do with the stuff, so it seems pretty solid :


Would the 6,000 psi tensile strength rating (click for one type of alumilite specs and cost) be plenty ?

 

Looks good ... colour disappears out of sight, so safe to have the red near the OX

 

Interesting... This works out to a .004" chip load per flute. I usually use a .001" chip load with Al or plastics... so, you need a bigger chip load when cutting wood or MDF?

 

Hi everyone,

I'm the new guy proposing to fill the voids with urethane resin. I'm hoping to try out my idea this weekend.
Since I have to disassemble some parts anyway to install the nema23 Z motor and X & Y axis cable chains, I figured this is as good of a time as any to try filling the voids.

If I can find my force gauge, I'm going to try and get measurements on before and after deflection of the beam.
Hopefully all works as planned...but if not, thankfully 20x60 isn't too costly and I can buy more for just a few dollars.

-Brian

 

If you check with the tables of Onsrud they give for the same bit a chip load of:
Alu .004 to .006
MDF .006 to .008
Hard Wood .005 to .007
Which seems to confirm your thoughts about bigger chip loads for wood than alu.

 

Thanks, that is something I can work with! I found some info on the web about max speed for a given nema stepper.

In my case, with 12V power supply the nema 23 of Openbuilds can have a max. speed of 32.16 RPM. This comes down to a maximum travel speed (not much torque needed) of 1,916mm/min. For shallow cutting I can use a 50% torque translating in about a feed rate of 950mm/min. For deeper cutting I would choose a max feed rate of 400mm/min.

With 24V power supply the RPM's double and at 30V it would be 80.4 RPM.Max. power is than 84 Watt. That sounds to me more adequate for proper feed rates. Of to the shop and find me a 30V or even higher power supply.

 

"Would the 6,000 psi tensile strength rating (click for one type of alumilite specs and cost) be plenty ?"

I have no idea. I think it is possibly just epoxy resin with aluminum powder ready mixed in it? (No it is not! It's a blend of polyols with 1.5% black carbon in it). That the color turns light defeats that idea, though. Anyway, I think it might be to thin (viscosity?) and possibly pours out every little opening it can find, becoming messy.

ABS has a tensile strength of 40 Mpa (5801.508 psi) an elongation of 30% and tensile modulus of 2.3 Gpa (333,586.80 psi) where epoxy has a tensile modulus of 3.5 Gpa. So the Alumilite would be a bit stronger than the ABS connectors, but at what price? $ 30.25 for an 28 oz. kit (I think that should be enough to fill the profiles?). For an X axis of about 1000mm you would need about 50 of these ABS connectors to connect two v-slot grooves between the 2 profiles. At $ 1.15 a piece that would be $57.50. Almost twice the price of the Alumilite but no mess and you can reuse them over and over again. If the gantry needs to be taken apart for any reason, no problem with the connectors, with the Alumilite you can forget that.

I think it's a matter of what each person considers to be paramount in this case.

 

Looking forward to the before and after deflection measurements.

Will you do it in two steps : first fill only the joining faces, measure effects on deflection, and then fill the remaining voids in extrusion for the added stiffness (and where most of the extra weight will be coming from) ?

 

Yep, you're right! For the bonding and the application of ABS. Bonding to anodized aluminum is quite some operation and preparation. Wonder if this stuff is suitable for the bonding of aluminum?

But one can ask himself; How rigid does the X beam needs to be in real life operation with the OX? It depends on the span one is using, I guess. And what if the X axis is getting too rigid? Wouldn't the forces on the beam be transferred to other parts that might break and cause even more damage? Or cause flex in the other v-slot profiles, resulting in inaccuracy from the other axis?

Just for fun: what if your X beam is so rigid that your router mount breaks during operation? I can see the monster already flying around at 12K or more. Run! Forest! Run! LOL

 

What if the person was to apply a release agent on the extrusion before assembling and pooring the Alumilite ? The stuff would still fill all cavities (mostly smooth surface of extrusion grove) BUT should now form a removable custom fit rail. To minimize the 'mess' factor one might clamp the extrusion pieces together (longer sides), place some putty in the outside joint and then clamp those faces before a pour is done. There should thus be no leaks possible, except for the open ends (putty could come to the rescue there as well).

Key disadvantage I see : lots of work and clamps are involved with the Alumilite approach. But likely a better 'joint'. BUT, no need for 3D printer. Although we don't all have one, models like the somewhat recent KickStart "Micro" at 300$ (then) makes it accessible. All those clamps might cost 300$ to buy if the person does not have them ...

Pushing that centre 'plug' down towards the centre of 1500 mm worth of extrusion might not be so evident, especially to keep a tight grip of both length of extrusion ...

I would guess it's a toss up. Then again, I have not tried either approaches, nor the bolting approach, which could have it's challanges.

Staying tuned to see the results ...

 

I don't like the MSDS of the Alumilite. http://www.alumilite.com/MSDS/Alumilite Black.pdf

 

Serge, I'm quite happy with what I can do with a 3d printer (although the printing volume is only 150x150x140). If the choice was spending $ 300 on clamps or 3d printer, I think I would give the printer the benefit of the doubt. I already saved myself a lot of money on all kinds of things that I could print instead of buying. Not even mentioning one can make things that are not even for sale and super custom made!

 

What if instead of bonding or otherwise joining two or even three lengths of 20x60, with all of the headaches discussed to date, one is to use a single length of, say, just for fun, 40x60 (or even bigger) ?

The 40x60, which does not yet exist in V-slot flavor, would be as rigid or more rigid than the two 'fused' 20x60 lengths... Are we saying that would be a problem : too strong of an X beam thus affecting what now becomes the weaker parts of the rest of the OX ?

Would the cost of the 40x60 be that much more than two 20x60, before or after adding any of the 'fusing' alternatives ?? The cheapest being bolting the two lengths together. The other two might come close in raw material cost, applying them being where the difference in cost would show up most (I think).

 

Hi RogueGeek, it is not urethane based but made of polyols (or is that a kind of urethane?). According to Wikipedia, it seems to be more some kind of polyester? and if so, the bonding quality with anodized aluminum is going to be poor or not at all. If it were an epoxy resin with carbon in it, I would have more trust in it.

 

Personally, weighing the bolting, filling with resins and the ABS connectors I come to the conclusion that the resin solution has too many uncertainties in it. So it leaves me with bolting or connectors. The connectors will give a better holding than the bolts, since the contact surface area is larger than with bolts. They will also force the profiles to be exactly parallel to each other. If you put enough of them in there, it will definitely stiffen the X. But…that's just my opinion. For me it will do.

 

Serge. Great idea about doing two separate measurements. I really hadn't considered making two measurements of the deflection like you described.

Prauk. I was using the term urethane since that is the general term that Alumilite uses on their website. http://en.wikipedia.org/wiki/Polyurethane
http://www.alumilite.com/MSDS/Alumilite Clear.pdf

I'll hopefully have time to try the resin this weekend and see what the results are. Whats the worst that can happen besides rendering $30 worth of rail unusable.

 

Also designed this little slide in tool holder for the router bits. It goes on the front of the Buffalo, where the tool change area is. Can add as many or little I need/want.

 

The MSDS in your link of the Alumilite Clear says it is of the Polyether Polyol chemical family. So if they broadcast it is an urethane, they are contradicting their own MSDS. Not giving me more trust in the product.
But indeed, the part B is an Aliphatic Diisocyanate Prepolymer (poly urethane belongs to that).

 

Maybe a separate topic? Like "Pimp my OX"? LOL

 

That's why I'm waiting for my "Micro" 3D printer to come in ... sometime early 2015, unfortunately.