yet another beginner

[audball22386]

This will be my first machine and I intend to build something similiar in configuration to the free plans posted here. Its only going to be 24" x 24" or 36" x 36" for small engravign and cutting. I intend to have mounts for both a dremel tool and a rotozip.

The design and construction arent my problems, but the motor and drivers and controller boards have me VERY confused. I'd like to make this as cheap as possible as its more of an intro to the field before i move onto a bigger table. So my thoughts were to use the same skate bearing setup and black pipe guide rails. excpet i intend to use all thread instead of a more expensive ballscrew. It seems all thread is a popular choice on smaller hobby machines.

Anyways, I was looking at the stepper controller packages on hobby cnc. Do i really need 200oz or 127oz steppers? to drive such a small machine?

This is also another type of stepper i've seen where the Stepper Motor and Stepper Drive are all one piece and manufactured that way. http://www.amci.com/stepper-motor-co...fectly-matched

Has anyone had any experience with these? They have a local distributor 15 mins from me and i plan to consult them on pricing.

Once i have my steppers what is the preferred connection method to a ballscrew or all thread etc? If i go direct drive, how do i link the motor shaft and the shaft on the ballscrew or allthread?

Sorry for tossing so many ideas out at once, but before i forget about them i wanted some feedback from people who have been there before.

Thanks,
Mike

[H500]

Mike: I'm using 110 in-oz motors, direct drive on 1/4-20 screws on a dovetail type cross slide that has much more friction than the skate bearing system.

If cost is an issue, 127in-oz should be OK. If cost is not a major issue the bigger motor would be more future proof.

Matching motors to drive is not difficult, so the one piece system is unlikely to provide any noticeable advantage. Just keep in mind that the low cost drivers can only put out 3 amps max, so make sure your motors don't need more.

[audball22386]

The steppers i posted the link to have me a little confused, because they have seperate drivers built right into the motor. How would one go about hooking those up? Would they need a specail control board or soemthing of the like?

Also, how did you hook your motors directly to your screws (all thread?)

Thanks Again,
Mike

[H500]

I had a quick look at the data sheets and the drive appear to use the standard step-dir interface, except that it is opto-isolated. You might need a simple circuit to interface it to the parallel port. I really doubt that the motor is low cost compared to the hobbycnc offerings.

I have a mini lathe, so it was no problem to add a bearing and a flex coupling. I had surplus motors and this one seem to have a slightly crooked shaft. That's why I designed such a unusual flex coupling. The simplest coupling can just be a rubber hose.

[buscht]

mike, a 36"x36" machine is actually pretty big for a first time home build. The larger the machine the more critical and difficult everything gets for alignment.

Bigger motors will allow you to cut and rapid travel at higher speeds. They will also help overcome some slight binding in your carriages. You don't want any binding, but sometimes it happens.

Another thing to keep in mind that with 1/4" allthread, you won't be able to go too fast anyway as the thin shaft will whip like crazy when it spins fast.

Concerning the motors with the attached drives. I also expect that it will cost more than the hobbyCNC setup and ultimately be more complex. I think that you will need a breakout board that will allow you to hook up from the PC and then branch out to the individual drives.

Here is an example
http://cnc4pc.com/Parallel_Port_Interface_Card.htm

I turn down the end of my drive screws and use a lovejoy couple to attach the motor to the screw. A cheaper and simpler way is to just use rubber tubing and hose clamps.

Good luck

[Hobbiest]

mike, a 36"x36" machine is actually pretty big for a first time home build. The larger the machine the more critical and difficult everything gets for alignment.

You beat me to it! If this is your first build, and you want to get your feet wet, go small. Get the motors and hardware that your budget can allow, and build the machine as inexpensively and small as possible. Get your software, and hardware figured out, then build your larger machine. You will probably find that your "needs" will get a lot smaller.

[audball22386]

I've managed to eliminate almost all my cost by using what i already have here at home, but i still lack steppers and controllers. Are hobbycnc and xylotex the most reasonable choices as far as packages that work right outta the box for the most part? Also are they the most cost effective packages you guys have seen?

[H500]

I believe you have to solder the hobbycnc boards together yourself. As far as I know, xylotex is ready made. It is the most cost effective ready made "good" board I'm aware of, but admittingly, I never seriously researched them since I did my own.

[audball22386]

Well since this is my first project, im thinking i'll go with the Xylotex 3 axis board, and then get 3 bipolar steppers from automation direct http://web1.automationdirect.com/adc...ors_-z-_Cables

I was thinking of goign with the 276oz/in steppers since then when i build a bigger table i can turn it around and utilize the same steppers on it etc. But thats just my thought, as far as a 24" x 24" table goes, is a 266oz/in stepper overkill or is it more like playing it safe?

Correction on that as i just realized the automation direct steppers are rated at 2.8amps not 2.5

[H500]

I don't think they're an overkill. The more the merrier! There should be no problem using the xylotex and these motors. You just need to set the current limit under 2.5 amps and accept a slight reduction in low speed torque.

If you don't mind soldering together your own, you can get the hobbycnc kit. They can handle the full current and more voltage

[audball22386]

Ive soldered, but never soldered together a circuit board. extent of my soldering skills are mostly connecting wires. Is it feasible? cause thats definetly the cheaper of the ways to go.

Also, isnt the hobbycnc board designed to run unipolar motors where as the ones on automation direct are bipolar? I'm new to all this and maybe i'm just missing anything, i appreciate the information.

[Lewis Riley]

Hi All, I have just finished soldering up one of the HobbyCNC boards, and it was great. I have had previous experence working with boards ( apx 17 years ago ) . If you take your time and follow the instruction , It will go good. You can join thier support group and ask all the questions you want, and you get answers right back. It was a pleasure to do the board. I don't have it all up and running yet, but soon. Lew