[Friction_Burn]

Hi guys,
I'm starting my build of the momus 2.0 design cnc. Just ordered all the aluminum parts from onlinemetals.com, I have a couple of questions.
-any tips or tricks that you have all learned while building
-which are the pros and cons of the different boards hobbycnc / xylotex / gecko
-recommendations of cam software?
I'm hoping to be able to use it for a range of materials from wood, plastic and aluminum, and possibly brass.
Thanks

[OCNC]

What's you're budget?

Are you planning on cutting true 3D surfaces or mostly profiles with holes and pockets(2.5D)?

Chris

[Friction_Burn]

The budget I"m hoping to stay between is 1500-2000 all together, (maybe more if my wife lets me). I have a older pc that I'm planning on using so that won't factor into cost. I'm guessing I'll mostly be working with 2.5D at first, but would like to option to go into full 3d surfaces later on. Ultimately I want to be able to make replacement knife scales out of different materials, G10, aluminum, carbon fiber, micarta, etc.

[OCNC]

The budget I"m hoping to stay between is 1500-2000 all together, (maybe more if my wife lets me). I have a older pc that I'm planning on using so that won't factor into cost. I'm guessing I'll mostly be working with 2.5D at first, but would like to option to go into full 3d surfaces later on. Ultimately I want to be able to make replacement knife scales out of different materials, G10, aluminum, carbon fiber, micarta, etc.

I would recommend the Gecko G540 for your drive electronics and Mach_3 for the control software. When you say you have an older PC (I don't really know how old 'old' is) I would make sure that it meets the Mach_3 minimum requirements. Mach_3 is rock solid running on XP. EMC2 is also considered to be pretty good control software. It runs on a Linux based machine and is open source so that can help with a budget. Since it sounds like you want to do some fine detail work it would be good to think about using a high quality router with an after-market low run-out collet set.
For CAM software I use MadCam for Rhino and also VCarve Pro 6.5. The cost of the three of these together would kill your budget so I'm not very helpful on this topic except to perhaps say that I didn't buy them all at once. DIY CNC is very much an evolutionary endeavor. Additionally it's very helpful if you learn something about how to program G-code directly in a text editor. I recommend 'CNC Programming Handbook' 3rd. ed. by Peter Smid. Grasping the concepts in this book, and it's not particularly difficult, will allow you to look at a G-code file and understand what your CAM program is doing. You'll also gain the ability to program directly for most 2.5D work should you wish to. Not having CAM or CAD software is not necessarily an impediment to making parts.

Chris

[GTFreeFlyer]

The best tip I have is to spend a few minutes before machining a part and study what is it used for and with which other pieces it mates with. Whenever possible I clamped multiple pieces together, in the positions they would be relative to one another at final assembly, and match drilled holes thru both of them at once under the drill press. This made it foolproof at final assembly and everything went together perfectly without having any mismatched holes. This comes in very handy especially for the rails.

For the wood, cut the large panels slightly oversize and then flush-cut the overhangs after nailing them to the structure using an oscillating tool or something similar. You can spend less time making perfect measurements this way.

[Friction_Burn]

I would recommend the Gecko G540 for your drive electronics and Mach_3 for the control software. When you say you have an older PC (I don't really know how old 'old' is) I would make sure that it meets the Mach_3 minimum requirements. Mach_3 is rock solid running on XP. EMC2 is also considered to be pretty good control software. It runs on a Linux based machine and is open source so that can help with a budget. Since it sounds like you want to do some fine detail work it would be good to think about using a high quality router with an after-market low run-out collet set.
For CAM software I use MadCam for Rhino and also VCarve Pro 6.5. The cost of the three of these together would kill your budget so I'm not very helpful on this topic except to perhaps say that I didn't buy them all at once. DIY CNC is very much an evolutionary endeavor. Additionally it's very helpful if you learn something about how to program G-code directly in a text editor. I recommend 'CNC Programming Handbook' 3rd. ed. by Peter Smid. Grasping the concepts in this book, and it's not particularly difficult, will allow you to look at a G-code file and understand what your CAM program is doing. You'll also gain the ability to program directly for most 2.5D work should you wish to. Not having CAM or CAD software is not necessarily an impediment to making parts.

Chris

Thanks Chris, I have been leaning towards the g540, but didn't know if the extra $$$ was worth it. It seems like whenever I would try and find a review of any of the boards I would only get they opinion and not a pros/cons list of each. I think I'll spend the extra $$$ and not have any regrets.
Thanks for the info on the book. I came across it in a forum while searching information, and forgot the name of it. I'll look into ordering it to occupy my time during down times of the build (saving up for the g540).

[Friction_Burn]

The best tip I have is to spend a few minutes before machining a part and study what is it used for and with which other pieces it mates with. Whenever possible I clamped multiple pieces together, in the positions they would be relative to one another at final assembly, and match drilled holes thru both of them at once under the drill press. This made it foolproof at final assembly and everything went together perfectly without having any mismatched holes. This comes in very handy especially for the rails.

For the wood, cut the large panels slightly oversize and then flush-cut the overhangs after nailing them to the structure using an oscillating tool or something similar. You can spend less time making perfect measurements this way.

Wow, I hadn't thought of clamping the two pieces together and drilling them for an exact match. I'll be sure to use that tidbit of info when it comes time to mark and drill. As for making the initial marks where is a good place to get a precision fractional ruler?

[GTFreeFlyer]

You don't need too much precision/accuaracy if you match drill. For example, when attaching the steel rails to the steel angles, there are several holes in a line. Don't worry too much about the spacing between each of the holes. As long as you match drill you can put the holes wherever you want. I tried to get close to equal spacing so that it didn't look funny when taking a quick glance at it.

As far as where to buy stuff, you'll be amazed how many things I got from Amazon. They have everything, reviews included! Rulers, tools, drill bits, electrical stuff, etc. etc.

[OCNC]

I used a precision rule like the on shown below. I also used a dial caliper for marking off uniform spacings. It's very easy to walk off equal increments using the jaws to scribe lines.

Chris

[mlmcquiggjr]

I put the economy 3 axis Hobby CNC board in my Momus and it runs great. I used the mid grade steppers for X and Y but stuck on the big one on the Z. The transformer, cap, diodes all fit the electronics bay. In drilling the many parts I utilized the Veritas optical center punch
http://www.leevalley.com/US/wood/pag...,42311&p=45502
I use Mach 3 and Vcarve PRO with excellent results.

[GTFreeFlyer]

Another thing popped up at me today when I was planning my electronics layout and that is that internal real estate is crucial. The more space you can get inside the bays, the better. Of course, you'll probably be alright if you aren't building a computer into the machine like I am, but it's always nicer to have more room than not. If I could rebuild this part of the base, here's what I'd do:

Look at version 2.0 plans page 97. See the top picture how there are three verticals mounted on a horizontal? I'd eliminate that horizontal piece and mount the verticals directly onto the base's top panel. Of course, extend the length of the verticals to account for this. The inner skin can join to the three verticals by nailing it, and a glue joint at the base would probably suffice.

My two cents...

[GTFreeFlyer]

Here's the flush cutting I was talking about.

What you see here is the back part of the cover (the fixed part). I'm getting ready to trim off the overhang of the top panel. Doing it this was makes it easy to transfer the tapered angle of the sides into the top plate (I'm building version 1.2). As you can see, there is significant overhang because I wasn't concerned about making perfect cuts with the circular saw. I lined up 1 of the 4 sides, glued and nailed in place, and then flush cut the remaining 3 sides with the oscillating tool. Total time for flush cutting 3 sides was around 5 minutes. The oscillator does it fast!

[momus_cnc]

Look at version 2.0 plans page 97. See the top picture how there are three verticals mounted on a horizontal? I'd eliminate that horizontal piece and mount the verticals directly onto the base's top panel. Of course, extend the length of the verticals to account for this. The inner skin can join to the three verticals by nailing it, and a glue joint at the base would probably suffice.

Actually, I wouldn't recommend eliminating that lower plate. The two "walls" are also torsion boxes of sorts, and leaving that part out is essentially leaving one side of the torsion box open. It will be much less strong. The glue joint you suggest won't be enough to transfer stress between the remaining pieces. An example would be a cardboard box with the edges between all 6 sides taped. Very stiff. Remove one face of the box and it becomes a floppy mess.

You could potentially leave the lower plate out if instead of using just a glue joint you used a length of metal angle to make that connection. The top skin (part F) would effectively become the missing 6th side of the box. Use a little short piece of angle to anchor the bottom of the middle vertical rib to the top skin as well.

If you really need that additional 3/4" of space, I'd recommend making the entire machine 3/4" taller. Increase the height of the wall ribs and skins, the front and rear plates, and the front and rear of the cover. It will give you more Z axis clearance, and you will never complain about having too much of that. If you are doing work that is very thin, you can simply add spoilboard thickness to bring you back up closer to the gantry.

Of course, don't forget that the left side of the machine also has the same size cavity as the right. All you need is a hole and a door for access. With a little planning, you could run wiring through the base from one side to the other. Or install a conduit for future wiring needs.

-bob

[Friction_Burn]

Thanks for all the great suggestions so far everyone, I think im going to go with the G540 3 axis kit they have on cncrouterparts. As soon as the aluminum shows up I'll be starting the build.
Bob, did you run into any problems fitting the G540, power supply and everything else inside the cavity? From the pics you have in the build manual it looks like there is plenty of space?

[momus_cnc]

It is no problem at all to fit the G540 and power supply in the electronics bay. I went with a G540 kit from Keling and couldn't be happier. The G540 is an awesome piece of equipment.

-bob

[GTFreeFlyer]

It is no problem at all to fit the G540 and power supply in the electronics bay. I went with a G540 kit from Keling and couldn't be happier. The G540 is an awesome piece of equipment.

-bob

I second that. There is plenty of room for the G540 and the power supply. I am only cramped on space because I'm putting an Atom D525 motherboard, hard drive, and additional 12V supply inside as well. Yeah, I guess I'm a little bit of a pack rat

I didn't think about the torsion box thing that Bob mentioned above. Listen to him, he's right. I'm an engineer and concur that he is right. That was the program manager part of me speaking nothing but hot air when I mentioned to remove the lower horizontal

[Friction_Burn]

I have another question guys. On the bill of materials page 28, it lists 2 different timing belts mcmaster part # 6484k445 and 6484k451 to get OR 10 feet of another belt. Also it has three different sets of precision rods, anti-backlash nuts and shaft couplers to choose from. What is the difference between the sets of components, is one set preferred above the rest?

[momus_cnc]

it lists 2 different timing belts mcmaster part # 6484k445 and 6484k451 to get OR 10 feet of another belt.

If you are ordering through McMaster, order the two part numbers. If you are in a location where they don't ship, or you can't source the same sized belts from another supplier, you can make the belts you need from the 10 feet of open-ended belting.

Also it has three different sets of precision rods, anti-backlash nuts and shaft couplers to choose from. What is the difference between the sets of components, is one set preferred above the rest?

What is best might depend on what types of things you'll be making with the machine. The higher the pitch of the lead screw, the faster the Z axis can travel. The trade off is that it will have lower resolution. A good general screw/nut/coupler would be the middle option (two-start.) If you will be doing work with lots of highly contoured 3d surfaces that require a lot of Z motion, go with the highest pitch (4-start.) If the work has lots of Z motion, a lower pitch screw may slow down the whole job, as X and Y speed will need to be slowed by the control software, to not outrun the slower Z. If you are doing work with very fine Z axis requirement, something like lithophanes, then go with the lowest pitch (single start.)

I'm currently running the 4-start and love it. Perfect for my needs.

-Bob

[GTFreeFlyer]

Bob, I think you have thread pitch vs. speed backwards? Higher pitch should equal lower speed. Higher pitch means more threads per inch, therefore requiring more turns to travel the same distance as a lower pitch screw.

It's confusing because a higher start (i.e. 2-start, 4-start) is actually lower pitch to make the nut travel faster.

[momus_cnc]

Hmm, I might be confused in my understanding of the terminology? Since pitch is the distance from one thread to the next, I always assumed (perhaps quite wrongly) that "high" pitch, or large pitch, equals a greater distance between threads. As opposed to threads per inch, where "high" would mean a smaller dimension from one thread to the next. I could be totally wrong on this one.

But I suppose I should have used the term "lead" as opposed to "pitch" since we are talking about multi-start screws. They can have the same pitch but different lead.

-bob