Hardware store design CNC router #1

[hllrsr]

Guys,
I haven't had much time lately to do more then just check messages every couple of days, but as far as electronics go may I suggest you have a look at:

http://www.hobbycnc.com/driverboards/4aupc/4aupc.htm

Yes they are unipolar, but they are chopper drives, not ballasted.
The packages are a decent price, and if you check here:

http://www.hobbycnc.com/downloadslin...loadslinks.htm

Under the downloads section, there is an article on bashing a Computer p.s. into a 12vdc supply to run your machine.

Also, while time has been tight, I have managed to get some time to try an idea for a supported rail system using 1 1/4 EMT fastened to (on top of) 2 pcs of Aluminum angle put back to back to make a reasonable facsimile of Tee rail similar to this:

http://www.pacific-bearing.com/produ...C-7B27301462DA

Easy to do, not expensive, and all you need is a couple of clamps and a drill to make the pcs.
Will post pics when I get the chance.

Iain

[ger21]

Mike, what kind of plywood are you using for $29?

Buy your bearings on Ebay, they're much cheaper there. Here's one example http://cgi.ebay.com/16-ABEC-7-Roller...QQcmdZViewItem

Dave, the Xylotex is a chopper driver, and doesn't need resistors to run at higher voltages. I think if you tried one you'd find a huge difference between that and your FET.

Imo, there are 2 entry level driver/motor options.
1) As already mentioned, Xylotex, with the motors they sell for $50 each. A 3axis drive + 3 motors is $295. The motors are rated for 269 oz-in at 2.8a. Since the Xylotex can only supply 2.5a, you'll only get about 240oz-in
(269 * 2.5/2.8)

2) HobbyCNC with the motors they sell for $55 each. http://www.hobbycnc.com/driverboards/4aupc/4aupc.htm The kit with 3 motors is $214. These motors are 200 oz-in. This drive comes as a kit, you'll have to solder it yourself. I've heard it can be done in less than 2 hours.

24V power supplies can be found with some regularity on Ebay for $10. http://cgi.ebay.com/Nidec-Potrans-24...QQcmdZViewItem

Although the HobbyCNC motors are a little smaller, the drive can be run at 36+ volts vs the Xylotex 24-28V. This can give the HobbyCNC a little higher top speeds, although the power supply may be more expensive.

Bottom line, I think Mike's $200 target is a little low. Probably obtainable, but low. All the little things add up fast. A better guess imo would be ~$300, + $300-$350 for motors and drives. Somewhere in the $650 range plus a PC.

[mattbyrne]

So are there any other pro's/cons for HobbyCNC vs. Xylotex

The price diff is not that big and I have no problem soldering the board. Can someone tell me anything that would make me buy one over the other?

[Jimmy Southern]

Hey Carl,

I really like your idea with the angle iron. I was also noticing that the midrange thread has been somewhat stale as of late. Since your design really does not fall within the parameters of the hardware thread, why don't you start up a design based on your angle iron idea. Put it in the mid range thread.

I think if we go any further with it in this thread, we will loose the ability to work toward the strength of the system. The budget is just to limited in the hardware design to take advantage of the great possibilities that are available with this design.

Now, just a few ideas for the design. Go for an all steel or aluminum design, similar to the renderings you posted. This thing would be very strong and quite easy to build.

This is just my opinion but I would like to see it built with the correct budget. I think to get the most out of it you would probably be in the $1500-$2500 budget range.

Keep the good ideas coming and great renderings by the way.

Jimmy

[izzlestar]

Yeah Jimmy, I was working on re-designing it to use wood/MDF as sort of a torsion box idea, but like you said, the design just begs to be made out of all metal. That was the exact thought I was having. I am definitly going to building a machine based on this idea, So I'll push it over to the midrange thread. I love the hardware store specific designs though, there is something guerilla about it. -Carl

[Jimmy Southern]

Hey Carl,

Thanks, I just got through posting on the mid range thread, putting out the call for helpers. I will be keeping an eye out for a very coooool home brew mid range machine.

Holler if you need us,
Jimmy

[Wolfspaw]

I am intriqued by Carl's idea as well. I was wondering about using 90 degree aluminum angle and applying thin (.060) strips of adhesive-backed UHMW where the bearings ride. Anyone have experience with skate bearings on UHMW?

[Bibber_DK]

I Love this idea ... it rocks.
i think i'm gonna try this on my machine ,
with some dustwipers (don't actually know what this is called in english).
i'm currently planning , and will try to build in this idea.
There really is a ton of good ideas on this site.
Thanks.

[mikeschn]

I've got the tool holder done. Good thing that we are nearing the end of the pipe design... it sounds like there is a lot of interest in the angle iron design now!

Here's the tool holder...

And I think all that's left is the thrust bearing...

Mike...

[mikeschn]

Steve,

I am going to work on the thrust bearing next. Looking at your design, I wondered, is it necessary to keep the acme thd rod in tension? I'd like to put your dual bearing arrangement on the side of the machine opposite the stepper, and not put the acme rod in tension. Your thoughts?

Mike...

[spalm]

From what I learned from reading and being told by many others is that the screw must always be fixed at the motor end.

The non-driven end needs a bearing, but not always a nut (so no, the rod does not have to be in tension, but will probably help if it is).

Steve

[ger21]

Originally Posted by spalm From what I learned from reading and being told by many others is that the screw must always be fixed at the motor end. The non-driven end needs a bearing, but not always a nut (so no, the rod does not have to be in tension, but will probably help if it is). Steve

As long as everything is in alignment, it shouldn't matter which end is supporting the screw. This might depend on the type of coupler used, though. Putting it in tension will let you spin it faster without whipping, if you can get enough tension on it.

I think you can get away without a lower bearing on the Z axis, but the X and Y should have them at both ends.