Long time lurker here,

I've been looking into building a 2'x4' to replace my really crappy cnc shark. (That thing is a piece of garbage.) I was originally going to use 40 series profile from 8020. It's so expensive though since everything has to be that much bulkier to handle the loads I would like to apply. So I just decided to build a tiny machine with the intentions of machining aluminum. I had a few designs already for the larger machine, but there was no point in reinventing the wheel for something this size. I absolutely dislike belts. I feel like they would be just as bad as the HDPE flex that the Shark is putting me through. Lead or ball screws were the objective. So when I saw this, I got excited. It's a smaller version of my larger designs, and is far less expensive.

With that said, I have all of the mechanical components on order. They are sourced from Openbuilds, Chris (plates), and fleabay (flange bearings). I plan on using 269oz steppers, DQ542MA drivers, and the Pheonix. The Shark pretty much broke today (well it didn't but when the flex kills larger endmills with 0.6mm passes at less than 250mm/min, I consider it worthless), so now I'm in full swing with the electronics too. The Pheonix is currently unavailable. The plan is to cut aluminum, which I have done plenty of on even the crappy Shark, which has even smaller steppers.

Kevon

 

That vertical mount is a pretty nifty idea. It would be better if the cross bar had threaded holes every 50mm or so. That would allow you to clamp uneven pieces if you needed to.

 

Currently building a bigger version of this maschine with taller y-axis side plates. Just created a thread on the forum for all to see, and also posted the upscaled side plates (dxf file) for anyone who wants that

 

Just curious if anyone has done a build using the 3mm Stainless Steel plates available on ebay?

 

For $15 more, you can get 1/4" aluminum from Chris.

 

Yeah, that's what i'm thinking. I was just trying to weigh the advantages/disadvantages of Stainless Steel vs Aluminum. Chris is waiting on a part for his machine which he advised should be up and running within a day or so.

 

Is that really true? Let's say stainless steel has strength of 517N/mm2 and Aluminium of 240N/mm2. Doesn't that suggest that

3mm * 517N/mm2 (steel) <=> 6.35mm * 240N/mm2 (alu)
1551 N/mm3 (steel) > 1524 N/mm3 (alu)

even the 3mm steel plate would be stronger that the 1/4" aluminium?

What's the math behind your 4.45mm?

 

Strength based on thickness isn't linear like how you have it.

 

Do you have a pointer on how the math should look like then?

 

Sorry for the short response. I was at work.

It's been forever since I've touched material properties, but this is essentially what we're looking at. I'm not saying that this is the full story, but this is definitely much closer that simply multiplying a value by a thickness.

We should be able to just substitute yield strength in for Eb. With all else equal, our new equation would be T(aluminum)^3 * Eb(aluminum) = T(SS)^3 * Eb(SS). Now we just plug and chug.

Without doing much searching, I used 302 SS although 304 is a more common standard. For the aluminum, I used 6061 T6. With the numbers in the chart below, a 302 SS 3mm plate is equal to a 3.877mm plate of 6061 T6 aluminum. I figured it was safer to use values from the same graph than to search around from different sources.

Now don't take that as an absolute. I could be wrong on the specifics. I'm only just trying to show that material properties are rarely linear.

 

I'm glad to see that we are both using the same equation. The part that had me unsure was wether to use elasticity or yield.

Elasticity for anyone following along.
198GPa for 304 Stainless Steel
68.9GPa for 6061 T6 Aluminum
Ratio = 2.87:1

If you redo the math I did, you would come to the same conclusion as Rick.

 

Guys, very long time lurker here, as i have bugger all knowledge about CNC, came across this build and loved it, great concept, great documentation, Kyo, take my hat off to you sir! thanks.
Today I went to a Machine Shop, to see if they could make me the plates. The place was bit like they were stuck in the 1980s, they had CNC machines, the size of cars, and were doing some serious engineering. But when I showed them, the Stetchup files, they said where are the dimensions? Then I showed them the DXF files using, the A360 free viewer, again no dimensions, also whats shown on the screen doesn't seem to have any depth. They said they work with STEP files, does anyone have the files in this format, or can they be saved in this format? My understanding is / was that the files shared by Kyo, are 3D meaning that all the info is in the file, for example, size, width/depths of holes, etc and a CNC machine, would be loaded with one of the files and bob's your uncle, out pops a plate, or am I miss guided?
Thanks for the advice.
Nick

 

Kyo thanks for this. I have sent files to the machine shop let's see what they say.

Gary thanks, the issue would be the postage, I'm in Spain

 

I got my frame parts in today. I forgot to get regular ball bearings for the z and I'm still waiting on the plates to be made, so I'm just at a stand still.

I have to say that I am very impressed. I was scared that the v wheel setup wouldn't be as tight and rigid as I was wanting, but it's definitely miles ahead of the crappy Shark. The CBeam feels great too. I'm curious to know how it would hold up at the full 1000mm for the gantry though.

And don't worry. I won't be spamming this thread with my build.

 

Kyo what was your opinion of your RPi 3 to Phoenix USB CNC controller w/DQ542MA drivers setup? Is there a huge advantage in the G540 w/your new GRBL shield? Thanks!

Max

 

Hi Everyone. I'm new here. Hopefully this question finds someone to answer it and it doesn't take up too much time. I go to the Files and Drawings, and open up the Plates.zip file and double click the, say x-axis Rear Plate Rev 2 and it opens on my system with a program called DWG TrueView 2013. I can see the drawing in two forms, one called Model and one called Layout 1. I don't see where there are any dimensions called out. Is there a way to 'turn dimensions ON' ?
Are the drawings meant to be templates or are they meant to be used for accurate machining ?
Any help on this small question would be great.
Thanks,
Glen

 

I am a bit confused about the spacer story at the side plates. According to the instructions it's a 6mm spacer plus a 1mm shim and then either the mini wheels or the big wheels - but from the specs it looks like the wheels don't have the same thickness. The big wheel is bigger than the mini wheel. What am I missing?

 

I got a bit further myself already by checking the Sketchup Model. As for the thread - would it be in this 9 pages? or where to search?

So in the sketchup I saw the shim for just the small wheels - but then the question is whether the height of the big wheel is the height of the mini wheel + 2mm. Found it a little hard to find the correct information. Now IIUC the thickness of the wheels is 8.80mm and 10.23mm - but that doesn't really matter because the bearings make up the real thickness. So for the small one should that be

2(bearings) * 4mm(height of the bearing) + 1mm (wall inside the wheel) = 9mm

and the big one

2(bearings) * 5mm(height of the bearing) + 1mm (wall inside the wheel) = 11mm

11mm - 9mm = 2mm

Correct like that?

 

I am hoping to begin this project soon. One thing I would like to experiment with in addition to normal cmc work is milling PCB. Is there any mods I should consider for increasing resolution?? The documentation is great which convinced me this is the way to go. Thanks for such a great design.

 

Plenty of big for PCB milling

I guess one could use belts on all the motors to increase the resolution in expense of travel speed.