Crane's 8020 Light Duty *Concept

[louieatienza]

Originally Posted by crane550 I have been wondering about this. I'm actually planning on using 3/4" 6061 instead of the 1/2" that is shows currently. I will fix it right now. Done. Still, I have wondered about this. Was wondering if anyone has had any experience with this setup. I see it all over, and have often thought it looked weak.

It probably would be fine for a light-duty machine! Heck, I bet the steppers stall before you bend that 3/4" aluminum!

[louieatienza]

Originally Posted by datac For Louie... and ONLY Louie..... Did you still mount the rails via T-nuts (or variation) in the slots ? I milled some flat too once to get a better mount, but the extrusion pulled and warped worse than it was originally, making it all worse than it had been. Obviously, extrusion isn't stress relieved making this a challenge. As I recall, it was Bosch stuff, and it was not a thick enough wall to mount anywhere but via the slot. Tried it too with Paletti...... I think half the problem is with the typical 2 degrees.... the extrusion tends to move even when you pull up along spots on the slot. Perhaps you had much thicker extrusion ?

The GFS extrusion from Misumi is a bit thicker than Bosch. Also Bosch uses 6063, where Misumi uses 6061 so that might be a factor as well. Finally, while you can mill the surface to glass smooth in the front, the inside lip will still have the 2 degrees, so that may be a factor as well. My idea is to just mill a 25mm slot about 1mm deep for the profile rail.

Misumi sells some extursions with faces ground flat as an option, so I guess they're not too worried about it! My current build is here if you want to see what the profiles look like compared to Bosch... http://www.cnczone.com/forums/diy-cn...ml#post1068289

[crane550]

This project has officially moved out of the concept realm and into fabrication. I have been debating what materials to use for the prototype before I committed to have $400 of aluminum water-jetted. Originally I thought about using MDF, but could not stand the idea of all the dust, plus MDF is just cheap and crappy to work with.

While getting some fitting for my dust collector at Woodcraft I came across a high density ply wood. It was coated with a thin fiberglass film, and seems to be really really hard stuff. At $60 for a 2x4 sheet it's not the cheapest stuff out there (8x more expensive then MDF) but very affordable when you compare it to aluminum.

Anyways, I bought a sheet for my prototype. I have to say it some of the coolest stuff I have ever worked with. It machines like a dream, does not chip, and is easy to clean. All I will need to do is seal the edges and it will be moisture tight.

I re-aligned my current CNC and re surfaced the top since I wanted these to be as accurate as possible.

[crane550]

Here is the assembly so far.





Set it on the floor and did some deflection tests. I set up a dial indicator and pressed for all my worth on the side while my wife monitored the meter. It deflected about .030, and that was me pressing for all I had. I have a couple of ideas that could stiffen this up, but the truth is only half of the bolts are in so far and hardly any of the components are mounted. I am calling it good for now.

The 1/4-20 bolts sticking out are just temporary because I don't have the correct T nuts to go inside the 80/20 yet.

[pippin88]

Looks nice but I don't see the point in raising the frame (by those end caps) if using dual drive. Stiffer if you have the whole frame resting on whatever bench it'll be on IMO.

[louieatienza]

The green looks cool... I believe that's phenolic coated plywood? They use them for concrete forms, very strong...

A long time ago I did a job that spec'd some of that material, all the edges were just sanded and oiled, which gave a pretty cool effect, especially with all the finger-joints we did.

[crane550]

Originally Posted by louieatienza The green looks cool... I believe that's phenolic coated plywood? They use them for concrete forms, very strong... A long time ago I did a job that spec'd some of that material, all the edges were just sanded and oiled, which gave a pretty cool effect, especially with all the finger-joints we did.

Yea I was thinking of rubbing some Tru-Oil on the sides to seal it up. Should work good. I really like the look of this stuff better, and think it's lightyears better then MDF for this kind of stuff.

Alex

[TrickyCNC]

it does look real nice .

very 'pro' looking

[sarcastro]

crane what's the size of the 80/20? dimensional-wise 2x2? and the .03 deflection was across the deck or across the gantry?

[crane550]

Hey,

The force was applied against the risers across the table. I guess you could say I was applying force in the -Y direction.

I really need to re-check this. There are a lot of factors that could have lead to an inaccuracy, as well as the fact that the table is not yet fully assembled.

Been too busy with school to work on this lately, but I look forward to getting back to it.

I have actually been getting a lot of people recommending I just keep the wood and not even bother moving to an aluminum machine. We will see how well the design works first, then go from there. I hope to start on the carriage tomorrow.

Alex

[cnctube]

Alex,

I think when you're done building and testing your prototype you'd better bring it by and I'll test it extensively for you! Lol

Looking good.