Newbie- Fist CNC, Need guidance

[rcpilot82]

Well, I got some time, and some small stuff done. I have determined the location of the routers new home and painted the area and made a very sturdy table for it by acnhoring 2X6's to my block walls. all that is left to build as far as the table goes is the safety plate between the router and the control area and a set of bi-fold plexiglass doors with a nice looking frame to close it all off. I had planned on putting a post in the middle of the span but it is so strong that I don't see a need to do so yet. I am hoping to get the electronics next. attached are some pics of the router in its new home.

[rcpilot82]

ok, so I took my drawings of my router to a local cnc machine re-builder and he said that I should use servo motors /encoders/amplifiers, not steppers, and that my frame is really weak and it will not be accurate even running a dremel tool as a spindle!! now I am no engineer but, having personally tried to flex this thing (unsucsessfully) I don't think it's that weak. he also said he wouldn't have used aluminum to build it, again, I question why not given the application. so anyway, what are your opinions as far as strength of the frame? am I missing something big, or am I getting some bs off this guy? Now I am starting to second guess myself.

[fatal-exception]

I would say he's full of ****.

I think you have a good start, but don't get discouraged if you find it to be too weak, just add more material. That's the beauty of the whole thing, it's not done until you say it's done.

Paul

[Gir]

My guess is that he's trying to score himself some business. Servos are better, yes, but not necessary by any means. Steppers will do everything you them to do. Your frame is probably more than sturdy enough for what you're doing, and if it racks at all you can use the newly (ish) found method of securing it with a moving knot.

You're looking good! Keep up the good work!

[rcpilot82]

Thanks for the replys, This guy shocked me when he said it was ONLY 2'x5', I'm standing there thinking this thing is pretty big as far as a hobby router goes in my opinion. then I saw some machines he was working on.....freaking huge cnc's, He kinda killed my rush when he didn't have anything nice to say about it. anyway, what is a moving knot?? We will find out if it really works.... hopefully by the end of fall.

[.xXACEXx.]

i just went back and reread your post,as i had not been following it from the beginning.as i am a machinest i can tell ya,your machine will not cut 1/4 inch deep with a 3 inch face mill in cast iron,which is prolly what the machine re-builder was meaning when he said what he said about using aluminum and servos,...but....thats not what you were building was it? so id say just what others have said , build it as you need it...you said in the first post you were going to cut wood and foam....the re-builder guy prolly didnt know this and was offering some good advice on building a machine which is "build it better than you THINK you will need"....if he did...then GIR was right,hes prolly just trying to get some business, you dont need a cast iron machine to cut foam ,but cast iron IS a must if you are going to be hogging big cutters and deep cuts,your machineshould do what you want...if not....just do some bracing here and there .hey at least you have got a REALLY good start on your machine...im starting to think ill never even get started on one...lol

[rcpilot82]

xXACEXx thanks for the input, yeah I told him I was only cutting wood and foam and using a dremel as a spindle, so maybe he didn't understand me correctly, whatever I will continue on and see what happens. I got my computer all hooked up last night, and have a network in my house that I tied into so I can draw on my good computer and cut with the router computer. the mach program is all installed and ready to go, I figure I may as well do what I can while I wait for the cash for the rest of the parts.

[Gir]

Originally Posted by rcpilot82 anyway, what is a moving knot??

Here is the thread talking about the moving knot. It's described very well several times in different ways, so keep reading and it should start making sense. As mentioned in the thread, it was originally used in draws to keep them square, but has an excellent use in our kind of machines that aren't always as accurately built as they should be.

Tyler

[harryn]

To me, your setup looks like a good hobby machine. If you stay within your end use goals, it will be fine.

One way to look at his comments, is to ask yourself the same question that we all ask ourselves - If I had a project that needed more power, more precision, less vibration, more speed - what might I change / improve ?

Usually, you can find 4 - 5 things that we all wish we had / could have
- Maybe a little thicker metal parts (1/4 vs 1/8)
- A little better spindle (perhaps kress vs dremel)
- Stronger motors with flatter torque curves (either a good quality stepper or servo setup - personal choice IMHO)
- Better linear motion parts (many options, but we all have to deal with budget reality - no point putting 10 K in motion parts on a home balsa cutter)
- Vibration dampening - could a few pieces of rubber here and there help - you will know when you hear it sing.

My brother and I have similar conversation on "how rugged" to make things. He has real journeyman manual machinist training and knows the "right way" to do metal work. His experience is mostly steel and some aluminum. My needs / experience are wood with dabbling into foam and aluminm.

He stocks steel and Al but there is not a 2x4 in his house. I have only a few Al parts (for the router), no steel, but various kinds of wood stock for projects. (if only we lived in the same state).

Anyway, keep moving forward. Just don't buy wimpy motors.

[rcpilot82]

OK, I am back! I have aquired enough cash to get the hobby cnc pro 3axis board with the 305oz steppers. I have one question before I order though. does anyone know if this setup will be able to move ALL 3 AXIS at the SAME time? i plan on doing some 3d shapes to make molds and I need to have the X,Y,Z move together. sorry if thats a stupid question but I just want to be sure before I order.
Thanks

[ger21]

Any drives can do that. It's the control that you need to be concerned about (Mach3?), but all the hobby software controllers can do full 3D.

[rcpilot82]

sweet, I guess I'll place my order then. thanks for the help!!