[CRG]

I am embarking on the journey of constructing my own CNC router. I've spent the last couple of weeks researching the basics and deciding on a design.

I am after, if I may, an honest, expert, opinion of the "DIY CNC Router" on Instructables. The build looks straight forward and it seems to do everything I would need and more.

I very much appreciate your time and advice. Thank you.

[ger21]

Without even looking, I can tell you that I've never seen a cnc on Instructables that was close to being any good.

However, a major factor in determining if a CNC is any good are your expectations. And to make it more confusing, most people don't really know what their expectations are.

I think that most people getting into CNC assume that all CNC's will give similar results, and that cheaper ones are just slower, and take shallower cuts. Many find out that these inexpensive machines have so much flex in them, that they can't do what they wanted.

The bottom line is that a good CNC router, needs to be built extremely rigid, with good quality components. This tends to exclude most if not all low cost machines.

Do you have a link to the machine you're looking at?

[CRG]

Thank you very much for your reply. The link is DIY CNC Router

The construction and manufacturing is not an issue for me at all. I just need advice on the design and engineering. I'm am desperately looking for a design and plan to build that is reliable and thought out. I have a fair idea of structural principles and have worked from that but translating it into CNC builds is very difficult. There are many that look great but my expertise is not in engineering.

Again, thank you. Any advice or suggestions are very much welcomed and appreciated.



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[ger21]

The link is DIY CNC Router

Very poor design, imo. A lot of things could be done better.

What do you plan on doing with this machine?

[CRG]

I will be using it mostly for timber work. Maybe light aluminium as well. Predominantly mdf. Stencils, signs, engravings, wood working machine parts etc. It is mainly a hobby machine for crafty bits and pieces. I am a carpenter/cabinet maker and I have a workshop and the tools to construct any design I'm just after, as I say, the best DIY design. I wouldn't want a working table over 800mm x 600mm, 400mm x 600mm would be around as small as I'd like though.

[SatanKlawz]

Does not look good, if you have the ability to manufacture easily just keep looking around and take features from designs that you like and compile it into your own type of hybrid design. I am near 5k into mine total so far and its not even close to a top of the line machine.

[CRG]

Thanks. I'm not wanting a machine that's anywhere near 'top of the line'. I just want a design and plans for a well thought out machine that I can run from. Use as a datum or baseline. The engineering and design is so important I want a really good 'DIY' staring point.

After your advice Im steering clear if the Instructables design. Joe's 4x4 hybrid but maybe adapted to be a tiny bit smaller is an option. I've looked at a couple but I'm still unsure. Again any suggestions would be very much appreciated. I'd really like a hybrid of steel, aluminium and mdf if possible.

Thanks again.


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[SatanKlawz]

Skip the mdf

[sajurcaju]

First, a big caveat. I've built a lot of stuff in wood and metal, hand work to machine tools, but I've never built a cnc machine. Not quite true, I did attempt a plasma cutter cnc 20 years ago, but I didn't have a clue about a lot of cnc things and it never got to a useful point. So I'm mostly competent (at least I think so), but just learning cnc over the past 4-5 months.

There are a huge number of designs out there to crib from, you can spend acres of time looking at them.
This site cleared up a lot of details for me:
Homemade CNC Router The Builder's Guide (FREE!)

This is a site that I leveraged for a lot of ideas:
----? mikelow ?----
My setup looks something like his, but not nearly as nice. I've gotten as far as the gantry structure, but still have to put the Y and Z axes on. I'm doing this on spare weekends over the past 4 months.

Aluminum extrusions are expensive, even if you find a deal. Plain aluminum shapes (like plate, rectangular tubing...) are substantially cheaper. A lot less money is steel. If you don't have machine tools or the ability/equipment to do a good job welding, you may find the extrusions your best choice despite cost. You also have to consider time; extrusions and all their little connectors and special nuts should be able to just screw together, a lot faster than doing a lot of cutting, drilling, tapping like I'm doing. I spent a couple of months working on the design and then started building, with only a few major revisions along the way. I think you've *got* to draw out the whole machine in a cad program like Sketchup (free). I don't see how someone inexperienced in cnc could just throw a machine together. Anything you can build from less finished materials will save you money and cost you time. This is a hobby for me, and I enjoy the build process. YMMV.

You need to think a lot about what you want to do with the machine, what sorts of stuff, and then apply that to what software you will use. There is a lot of good stuff (also beyond software) here:
Guerrilla guide to CNC machining, mold making, and resin casting
but I include it because it really helped me in figuring out what I want for software.

Personally I'm probably looking at Deskproto. I will do some signs, but I don't think I need specific software for it. I'm interested in doing stuff like bas relief images and (eventually) adding the ability to turn the work while cutting (cnc lathe, decorated cylinders). I'm going to start with f-engrave (free) and see how far that will take me.

I like the plastic bearings riding on al. extrusion. They do have a fair bit of friction, but given that I can make them instead of buy them (I bought the plastic from 80/20 and made the aluminum parts), they are relatively inexpensive. No experience yet, remember! I made my lead screw nuts following this process: Making Acetal leadscrew nuts the easy way
People will probably add comments to this thread about how plastic bearings wear, but I don't hear that same complaint coming up on plastic leadscrew nuts. Maybe I just missed those posts. I don't expect to do that kind of volume on my machine.
McMaster-Carr has nice looking lead screws, including multi-start at reasonable prices.
Gecko had a sale so I suddenly bought a g540 instead of some of the other electronics I was looking at.
A good source for plain aluminum pieces (maybe not the prettiest, but the best prices I found): Industrial Metal Sales Buy Metals Online
There is a lot of variation in stepper motor performance, comparing similar torque motors. Mainly what I'm referring to is torque vs speed curves. In the size range I wanted (250-300 oz-in holding), two Leadshine motors had the fastest (worst) fall-off of torque. By far, the best motors (given the g540 3.5A limit) were the low inductance 320 oz-in version from cncrouterparts.
I'm hoping to learn a lot using f-engrave software, which is free. Then I'll consider going to Deskproto.

My machine will cut something like a 34" x 30" area. It looks like the cost of the hardware/motors/electronics will be about $1800.

I think that's the high points so far. Read lots of the posts on this forum!

Steve

[CRG]

The Rockliff design looks good and cost effective. I'm considering buying the plans for that. Is that in, your opinions, a well designed machine? I know it's mdf mostly and I really want to avoid that but I really need plans to work from.


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[wizard]

The Rockliff design looks good and cost effective. I'm considering buying the plans for that. Is that in, your opinions, a well designed machine? I know it's mdf mostly and I really want to avoid that but I really need plans to work from.


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I'm not familiar with that design but I do have a massive negative opinion when it comes to MDF. I just never like the material and the dust that goes along with working with it. Admittedly it does have some nice characteristics for machines if you can keep it dry.

As for materials, if you have a well equipped wood shop then yes do consider wood for construction but you really need to explore concepts like torsion boxes and other construction methods leading to stiff structures. Do consider alternatives for things like the gantry beam though. A steel box beam for the gantry can save you considerable effort and simplify some things.

In a basic sense wood construction is very time consuming as you need to assemble a bunch of torsion boxes, frames and such in a very robust way. The use of aluminum t-slot extrusions is almost the opposite as you basically bolt everything together if it is supplied in kit form. Note though that if you have a wood working shop you really don't need to buy kits as you can cut bulk extrusions fine with wood working equipment. The only gotcha is that you need to make sure your machines are tuned for accuracy.

I guess what I'm trying to point out here is that there is nothing wrong with a hybrid design made out of different materials. Especially if you have some materials laying about.

As for designs there are so many examples on the web I don't even know where to start. As for plans that is another issue all together. All I can say is that many of the plans out there leave a lot to be desired mainly because they aren't as robust as I'd like to see. In that regard do consider a DIY approach.

[sajurcaju]

I'm not sure what's going on, but my post has vanished.

Wizard, I don't know why anyone has a use for mdf.

CRG, I looked at kits for some time. They seemed like a good tradeoff between diy and six months of weekends. I like the looks of finelineautomation kits, they also sell plans, but I did not look at their stuff in detail.

Steve

[CRG]

Thanks guys. I really appreciate your help and advice.


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