[dan dimock]

Andy
Would you please re-post your manual, when I try to download it I get a block saying the file is damage an cannot be repaired.

Thanks so much for all the help you have given me on this project.
Dan

[Lionclaw]

Just uploaded it again. http://www.comptonsoft.com/cnc/lc50man.pdf

[tangocc35]

HI Andy:

I have found a part--marked "YC-D", which I cannot identify--either location or purpose.

Can you clarify?? Nice bit of Ply

Thanks

John

[tangocc35]

Hello Again:

Cancel the previous--it was staring me right in the face!

Sorry to bother you.

John

[ballendo]

Hello,

This hinged wire support is a bad thing...

Wires will QUICKLY fail if they are subject to a "tick-tock" bending as you've created here. We all intuitively know this because when we WANT a wire to break we bend it back-and-forth uintil it does; which is often sooner than we think!

A Belden Cable engineer that I spoke with many years ago during the design of one of my early cnc's (Belden's "infinity" cable was JUST about to come out) told me that in tests, Belden discovered that a typical cable will begin failing after only about 30,000 flexes of the "tick-tock" type.

Compare this to the rolling motion given by typical cable cariers, which the Belden testing showed to be good for more than 6 MILLION cycles with the SAME cable type!

Intuitively, this makes sense as well. We are now spreading the flex/wear across as much of the wire area as possible.

There ARE inexpensive ways to accomodate/create the HIGHLY desirable rolling motion of commerical cable carriers. I have a pic in my B's stuff folder at the yahoo group CNC-Pics of a huge Cincy mill's cable carrier. It is nothing more than a sheet steel backing (we'd use plastic for machines of the size we see here) with regularly spaced aluminum blocks to carry and direct the rolling motion of the wires and hoses.

IMO wire management is the great lurking problem with MANY of the DIY-CNC builds. The wires WILL break. Many will not realise it at first; been there, done that. Because it will masquerade itself as failing drives, motors, poor mechanical alignment, bad motor driver(s), Encoders, etc.

And more importantly, it will probably end up blowing up drivers and possibly power supplies. Cable management should NOT be an afterthought!

For MANY using poor wire management the clock is ticking. tick-tock,tick-tock, tick....

Hope this helps,

Ballendo

Before I crash for the night, I wanted to post my latest modification. I've been having problems keeping wires organized and out of the way. A plastic cable carrier seemed to be the best option, but seeing as I like to DIY as much as possible and save money where ever I can, I came up with this.

[Lionclaw]

Ballendo. You are correct in thinking that bending the cable will cause breakage, but if you were to look closer at the way it is attached you would have noticed that the points where it is attached are a good 4-5 inches from the pivot point, thus allowing the bend to form a semi-circle rather than a sharp angle.

Sorry for those who have been waiting on responses or requesting to order kits lately. I'm trying to muddle my way through my last semester of college right now and I'm under a lot of stress. Wedding, commissioning, graduation... all within a few weeks of each other. The next couple months are gonna be CRAZY!

[ballendo]

Andy,

Yes, I saw that. But it is still a tick-tock motion and not a rolling motion. Just a heads up as it WILL work for awhile; maybe even a "long" while. But it WILL fail sooner than a proper wire carrier technique.

And please don't take this as anything but admiration and constructive criticism. If I didn't think your design was a winner; I wouldn't bother commenting...

Ballendo

Ballendo. You are correct in thinking that bending the cable will cause breakage, but if you were to look closer at the way it is attached you would have noticed that the points where it is attached are a good 4-5 inches from the pivot point, thus allowing the bend to form a semi-circle rather than a sharp angle.

Sorry for those who have been waiting on responses or requesting to order kits lately. I'm trying to muddle my way through my last semester of college right now and I'm under a lot of stress. Wedding, commissioning, graduation... all within a few weeks of each other. The next couple months are gonna be CRAZY!

[Lionclaw]

I thought about it after posting and I realize what you're saying. Something like an IGUS cable carrier would definitely be the way to go. This was just a simple low cost solution.

I apologize for being a bit snappy. Like I said, lots of stress. Last night I was trying make some signs for someone at my detachment. The plywood they provided was the warpy 1/4" construction grade stuff. Trying to mount and cut it was so extremely aggravating I wanted to scream.

[the__extreme]

Hi Andy,

I know all about the school stress! I'm in my 4th year of a 5 year Mech Eng & Management program at McMaster Univ. in Hamilton Ontario. What college are you at / which program? PS - really like your machine! I noticed you had the same 84 oz-in steppers on your machine that I have. Maybe they're still there, I don't know if you've upgraded. How did you find they performed? And if you want some G-code done for Mach3, let me know. I have access to Mastercam & Edgecam. I think I can import most CAD types - Inventor, Solid Edge, AutoCAD, etc.

- Shawn

[Lionclaw]

Hi Shawn. I'm at Cal State Long Beach doing the Computer Engineering program. I've enjoyed the curriculum, but I think I might have been more at home in the ME program. I'm still using one of the 84oz steppers for my Z axis. I upgraded to the 200oz for the X and Y. I did some 3D engraving a few days back and the real slowdown was the Z. For 2D stuff it works just fine. I think i'm going to go with 300+ oz motors on my next machine. I was looking at the kelling 425 oz bipolar motors. I'm mainly just waiting to see how the allegro 3986 drivers work out so I can go that route. I believe they offer better torque at lower speeds, which I'm hoping will work well with the 4tpi threads I'll be using.

[ballendo]

LionClaw,

No worries. I was just trying to point out that "simple and low cost" up-front may become complex and high-cost (due to flakey operation and repair of the machine) sooner than a person might think.

As for the holding of thin stuff, look into vacuum clamping. Once you begin using it, you'll never look back!

Ballendo

I thought about it after posting and I realize what you're saying. Something like an IGUS cable carrier would definitely be the way to go. This was just a simple low cost solution.

I apologize for being a bit snappy. Like I said, lots of stress. Last night I was trying make some signs for someone at my detachment. The plywood they provided was the warpy 1/4" construction grade stuff. Trying to mount and cut it was so extremely aggravating I wanted to scream.

[ballendo]

Hello,

Be sure to look at the WHOLE torque curve, and not just the holding torque spec!

It's waaaay too easy to get a "Tim the tool man" attitude about this CNC stuff. ("Mine's bigger'n yours" or "I got the 425's, baby. What wimpy-@$$ motors did you say you were using?!")

An an engineer yo know you don't get something for nothing. And FWIW, folks have been using size 23 motors with 5TPI ballscrews for decades.

Design the WHOLE machine; not just one part.

There is a tradeoff with every choice. Find the proper BALANCE and you will have a great machine. Start going after specsmanship and you might regret it. Bigger is NOT always better. Especially where steppers are concerned. Look at reflected loads to the rotor and inertia matching, for instance.

Power supplies are another place where bigger/more volts is better tends to show up in this DIY-CNc world. Tread carefully there as well, IMO.

Hope this helps,

Ballendo

Hi Shawn. I'm still using one of the 84oz steppers for my Z axis. I upgraded to the 200oz for the X and Y. I did some 3D engraving a few days back and the real slowdown was the Z. For 2D stuff it works just fine. I think i'm going to go with 300+ oz motors on my next machine. I was looking at the kelling 425 oz bipolar motors. I believe they offer better torque at lower speeds, which I'm hoping will work well with the 4tpi threads I'll be using.

[mike hide]

Hello,

Be sure to look at the WHOLE torque curve, and not just the holding torque spec!

It's waaaay too easy to get a "Tim the tool man" attitude about this CNC stuff. ("Mine's bigger'n yours" or "I got the 425's, baby. What wimpy-@$$ motors did you say you were using?!")

An an engineer yo know you don't get something for nothing. And FWIW, folks have been using size 23 motors with 5TPI ballscrews for decades.

Design the WHOLE machine; not just one part.

There is a tradeoff with every choice. Find the proper BALANCE and you will have a great machine. Start going after specsmanship and you might regret it. Bigger is NOT always better. Especially where steppers are concerned. Look at reflected loads to the rotor and inertia matching, for instance.

Power supplies are another place where bigger/more volts is better tends to show up in this DIY-CNc world. Tread carefully there as well, IMO.

Hope this helps,

Ballendo

Asa mechanial what exactly are "425s baby"., and reflected loads are you talking geared tool loads, inertia matching /sounds cool but what exactly are you talking about? mjh

[dan dimock]

I guess I"m a dum ass but I am building this machine by the plans, I think if it worked for Andy, then it will work for me.

[the__extreme]

Asa mechanial what exactly are "425s baby"., and reflected loads are you talking geared tool loads, inertia matching /sounds cool but what exactly are you talking about? mjh

Hi Mike,

I could be way off here, but Ballendo is referring to the specifications & chracteristics of the stepper motors.

"425" is really 425 oz-in, the static holding torque of the motor. If rated current was flowing through the motor coils, it would take 425 oz-in of torque to turn it. He also made a comment about the torque-speed curve earlier. The faster the steppers spin, the less torque they will produce.

Reflecting the loads is not so much through a gear box, but the rotor has a mass associated with it, hence a kinetic energy & inertia (momentum) when spinning. The part of the machine that the drive screw or belt is driving can also be reflected to the rotor, giving an equivalent inertia parameter.

Once you characterize those and other parameters, choose your desired operating speeds, accelerations, etc., you can then pick a motor that will deliver the desired performance. Its one huge optimization process, and as Ballendo stated, you may not necessarily get the increased performance you want simply by buying some bigger motors, because they may not match your machine characteristics very well.
For example, if you want to cut faster and buy new steppers with high holding torque (say 425) but with very low high speed torque, there probably wouldn't be a whole lot of gain in switching.

On the downside, it can often be difficult to calculate some of those parameters, in which case, you'll be making assumptions & simplifications, so that the motor (or other component you're selecting) may not match anyway.

As for Andy (Lionclaw), I'm confident he knows enough about spec-ing his components to match his machine, and won't expect an optimized system if he doesn't spend the time on some detailed calculations. I know I get sick of all the numbers & analysis after a while.

Hope that helps, and is accurate! I'm sure someone will correct my mistakes if I've made them.

- Shawn

[mike hide]

Ah, ah, a glimmer of light even though just a flicker. Building the gantry section over the last couple of weeks with out the benefit of a cnc machine most of the construction is out of solid 3/4" and 1/2" mdf. It is not until these components are finished does one realize what the weights [masses ]are . In my case at least the Z axis is the lightest, with the carriage next and the gantry itself being by far the heaviest. The thought did occur to me that It might be worth considering different motors for different axes .I am assuming the "static holding torque to be similar to the motor stall torque. Using similar motors in all axes and the fact that all axes work in conjunction with each other the high inertia loads in the x axis will in effect limit the response time of the machine as a whole . What seems to be cosidered a limitation of stepper motors with their torque speed characteristics would appear at least to me the ideal driver for this application ,I suppose with the exception of servo motors where brute force is required and a dead beat response [i.e. no oscillations]. In other words the maximum torque occurs at low speeds where inertia [acceleration ]loads are greatest.

Now I am on my soap box perhaps the dumbest quetion of all........What does a 4th axis [5th and up] do . does it operate a rotational axis in one of the linear ones ,x,y or z for instance ,how exactly is it defined . Hobbycnc offer both three and four axis boards, I was wondering if it would be worth getting the for axis system and operating in the three axis mode until one builds the 4 th axis ,if that is possible that is ? mjh

[the__extreme]

Hi Mike,

I'll keep this short since we're getting off topic from Andy's thread. Yes, you're understanding the motor-matching concept. And yes, 4th & 5th are rotary axes, "A" rotates in the X axis, "B" rotates in the Y Axis and "C" in the Z. With standard 3-axis XYZ, you can do topography, 2.5D (not quite 3D), since you can't tunnel sideways into the part. If you think you might want to add a 4th axis, for the small additional $$, I'd say go with a 4 axis controller from the start. You would need to be careful that the machine you build has enough space beneath the spindle to add such an axis. For example, the gantry on Andy's machine in this thread may need a slightly higher gantry to accomodate an A axis.

Don't take this the wrong way, but there may be a better place (different forum) to ask these questions. As I understand, the moderators watch the threads in order to maintain the original topic, in this case, Andy's 2nd build. We should really respect that the thread content be related to his machine, and carry on discussions like this elsewhere. PM me if you like.

- Shawn

[Lionclaw]

Building a DIY 4th axis is actually something I'm quite interested in, so feel free to discuss it all you want. I've got the basic model in my head right now. I might have some free time to model it up this weekend.

Basicaly, the DIY 4th axis will consist of a small torsion box that bolts to the table end. The first prototype will be built with MDF and HDPE. I might use aluminum for some parts if the HDPE doesn't hold up.

The main components will include a 5" or 6" dia 3-jaw lathe chuck (probably from littlemachineshop.com), 2 tapered roller bearings with 2" ID (probably from VXB), and a 6" dia .5" thick delrin disc hobbed into a worm gear.

So, basically it would go:

Lathe Chuck > 3/4" HDPE backplate > Roller Bearing #1 > 1/2" HDPE Bearing Mount > 2" MDF Torsion Box > 1/2" HDPE Bearing Mount > Roller Bearing #2 > Delrin Worm Gear.

I intend to tie the whole thing together with 6 socket cap screws mounted close to the ID of the roller bearings. This way the through hole diameter of the whole thing will hopefully be a good 1.25" or more. I'll drive the worm gear with a piece of 1/2-10 acme rod. I haven't thought a whole lot about where/how to mount the bearings and motor for the worm gear screw, but I don't think that will be too big of a deal.

I'm thinking the cost of all components would be somewhere around $150-$200 (the chuck alone costs close to $100).

I found a few very encouraging sites and threads about making DIY worm gears.

http://bedair.org/Worm/Worm.html
http://webpages.charter.net/mbonfire/wormgear.htm
http://cnczone.com/forums/showthread...t=rotary+table

[joecnc2006]

Andy, Here is a sample of one John did if that helps, he used the worm gear setup. and a couple other references. I plan on adding one also to the end of the machine as an addon and using a bolted plate for alignment. having the whole unit removable.

http://www.crankorgan.com/4thaxis.htm

http://www.cnczone.com/forums/attach...7&d=1166748937

Joe

[BMG]

Andy, Here is a sample of one John did if that helps, he used the worm gear setup. and a couple other references. I plan on adding one also to the end of the machine as an addon and using a bolted plate for alignment. having the whole unit removable.

http://www.crankorgan.com/4thaxis.htm

http://www.cnczone.com/forums/attach...7&d=1166748937

Joe

Could some of the geared assemblies off copiers be used for this? I pulled 1 worm gear stepper off a copier with an attached gear assembly. I have yet to figure the turn down ratio, but I am sure its large in comparison to the motor rotation. The one I found had only a 40 oz-in stepper on it but with the gearing, I am sure it would probably work for a starter.

Brian G.