Newbie- About to build. Needs some last minute thoughts.

[mikeofaustin]

Hello all. New peron here with dreams in his head.

Probably fairly simple questions:
I don't need the size, and an X and Y of around 12" or less will suite me fine (and ~3" or 4" of z travel). I really like the simplicity and compactness of the Sable 2015, but it needs to be redesigned for better performance (the sable has a travel of 7.9" x 5.9"). And for the redesign, I'm thinking the overall construction plans, would be followed 95% (not counting dimensions of course).

Here are some thoughts. The all plate aluminum design technique used to build the sable makes for an easy assembly. It just requires another much larger mill to create the parts. I'm hoping to design it so it's just a matter of truing the ends of the raw plates (as opposed to milling the entire square pattern), then placing holes where they would need to go (stepper, screws holes, etc).

I'm 'guessing' 1/2" plate all around will be good enough for NEMA 23's (thoughts?).

The linear/round rails would stay, but I'd upgrade to ball screws.

Overall, I "think" this can be put together fairly simply with just plate aluminum. Thoughts?

After I get my bill of materials together, I'll submit an RFQ (to the RFQ area) as I simply do not have the large mill. In the RFQ, I'm hoping that a more experienced person will be able to source the aluminum plate from their current supplier (as it really doesn't make since for me to buy then ship to them) and create the parts (from my specs), and ship to me. I figure I can source all the other materials needed myself (motors, rails).

One last thought. I wouldn't even know where to start to come up with an estimate that someone would charge to create the pieces for me on their 'much bigger mill'. If the whole turn-key expense if a lot, perhaps it would make more since just to buy a better machine (but I'm hoping it's more a 'labor of love' and the price wouldn't be so much). I'm hopping that by building my own, I can stay under the $1K price (minus PC and software). (?)

In case it matters. My primary function will be milling PCBs for around the shop here (that's how I actually stumbled upon the sable).

[stevespo]

I can't give you any advice as to what it would cost to source and machine those parts, but I do think it's going to be more expensive than you think. My local machine shop charges $60/hour and it adds up fast.

You'll need precision plate (expensive) or start with extruded parts and have them flycut/faced to accurate dimensions (time and labor). I also think you'll need the screws, end blocks, and rails on-hand in order to do accurate drawings and improve your chances of success. I do think that 1/2" plate is reasonable for that size machine and NEMA 23 motors. No problem there.

Motors, wire, enclosure, connectors, breakout board, drivers, power supply can easily run $300-400 and that's for a pretty basic setup. Limit switches, Estop, relay controls - all extra money. Small expenses, but they add up very quickly. It all depends on how much you can scrounge and what the parameters are.

You might want to consider doing the construction yourself. If you have a chopsaw/tablesaw and a drill press, you can fabricate most/all of the parts yourself. If you have any machine shop experience, you can do the work accurately enough and perhaps save money instead of sourcing it out. 8020 extrusions are another option, with the compatible rails, screws from www.cncrouterparts.com

Yet another option is to pickup one of Widgetmaster's beautiful little CNC machines, which are ready for motors and electronics.

I'd encourage you to design/build your own, if you're looking forward to a project. If you're resourceful enough you may be able do it for under $1000. If you're intent on ballscrews and precision linear rails, that target may be very hard to hit.

Steve

[mikeofaustin]

Thanks for the reply. Yes, I'm very hand in the shop. I 'could' do it all myself, but again, I simply don't have that big, massive, monster of a machine to do the initial truing of the ends. My thoughts were, if I can build this thing without 'facing all sides', I'll be o.k. I mean, not 'all' sides have to be faced.

Also, the 8020 stuff, I just don't like the look of it. To me, it just seems like it wouldn't be accurate enough. (is that stuff machined or molded?)

I keep hearing about this 'widgetmaster'... but I can't find him anywhere. Have any links?

edit:

I found it. (don't know why I couldnt before).

Anyway, I emailed him for prices on the wide and the midi.

[jsheerin]

80/20 is extruded aluminum. There are tolerances for it in their catalog. Whether or not it's acceptable depends on what you want to do. I and lots of others have built wood routers from it that work great. The nice part is that you can get premade parts to bolt to it for motor mounts, lead screw bearings, etc. from cncrouterparts.com and then cut it with a miter saw and bolt it all together. Other people have built metal working machines that hold tighter tolerances using 80/20, but they have taken a pass across the top of the 80/20 to make sure it's flatter than it might be as delivered. For example, see: http://www.5bears.com/cnc.htm
So if you have some examples of what you plan on making or what tolerances you want to hold, we could give you better advice.

John

[mikeofaustin]

As far as what I want to build... isn't' that the holy grail? When your wife wants to know why you've taken up all the garage space, and sees these charges on the credit card and then asks you, "what can you do with that thing".... isn't you answer, "Everything!".

Seriously though. My main purpose would be to cut some PCBs. I know this doesn't take a lot, but I'd also like the lower TPI and stronger motor for faster cuts. Also have the precision that backlash won't leave me cursing... And, if down the line, if I need to cut an aluminum face plate for an oil cover to a dirt bike, because the side stand went through it, I'd like to be able to cut it, and have it not take a day. Or, if I need a precision cut for a tool, I'd like the precision too. The parts I have in mind aren't big, but I fancy the idea of 'big' quality' in a small unit. (I wont' be cutting any wood). ...and something from my brain tells me, that something that's hollow, like 8020, as opposed to a solid chunk of 1" x 1" stock, simply doesn't compare. I don't know, this is just what my noodle telling me these things. I just keep going back to, "a solid chunk of aluminum" idea.

I wish the gadgetman had more photo's of his gear. They look very promising. The midi or wide would be right up my alley.

edit:

Sorry... "widgetmaster". (I've closed shop for the night and am now on my 4th cold one).

[stevespo]

Mike, as you look around the forum you'll discover that there are lots of ways to achieve your goals. It might be with a machined solid aluminum frame, steel, 8020, or even some of the MDF/baltic birch machines will easily do what you require.

My own machine is 8020 and 1/2" aluminum plate. It's very solid, very rigid, with good mass. I can machine aluminum and hit tolerances of .001". Mainly I cut wood, and do high precision pearl inlay, but it's a good "all around" machine. Brass, plastic, etc.

As far as the 8020 tolerances go, there is a stated spec - something on the order of .012"/foot. In reality, I've found it much, much better. I couldn't fit a .0015" feeler anywhere over a 2' span (using a Starrett straightedge). I mounted my rails directly and didn't have to shim or scrape anywhere. My entire table is square to within +/-.003" over a 40" span. So, yes it is very possible to build a precise machine from 8020. Many people have done it, including some very solid milling machines used to mill steel.

The nice thing about the 8020 is the speed at which you can put things together. The strength/weight ratio is excellent. There's a deflection calculator to help you size parts. The t-slots give you the ability to position parts and then lock them in tight. There are motor mounts, end blocks, linear rails, etc - available at good prices. It's not going to be right for everyone, but it has a lot of upside.

I'm NOT trying to sell you on 8020, just present some other ideas that may help you meet your goals. Definitely go ahead with your original plan, if that's what you're most comfortable with. The main challenge (in my mind) is keeping the cost under $1k. Spec it all out, source out your materials, see where you end up. Some people are just naturally good at finding bargains, and find a way to come in under budget.

Just keep the credit card statements away from your wife...

Steve