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DarkWolf
10-11-2004, 04:30 PM
Hi Folks,

Very new to all of this and have been browsing for quite some time. I have a few questions that I'm hoping you all can shed some light on.

First, let me explain the reason why I've found myself here and why I'm asking for advice. At current I do ALOT of work with a local Basset Hound rescue here in Kentucky. -- I can hear you asking what that has to do with anything CNC. Well, if any of you have ever gone out to buy dog tags, you'll see they cost at least $5 each or so. Now, I can get the blank tags way, way cheaper. But I'd need a good, clean, easy way to engrave both sides of the tag with various info.. Since we're a rescue, money is very very tight. In fact, anything I do on this will be out of my pocket, which is almost as tight..

So.. Here it goes. What I'm thinking of doing is a very small two axis bed with a powered engraving tip that lowers via actuator to a set depth. The area that would need engraved would be at the most 2"x2" and the material would be standard thin die cut aluminum dog tags.

Is it possible?

I have several floppy drives from computers laying around that are either dead (access wise) or I just don't need. Since the unit would be so small I don't feel there would be a problem at all powering the two axis bed with the stepper motors inside. From what I recall, they're 6 wire steppers BTW, but I have to check before I even think of moving forward.

Software wise, I do not think I'd need anything in the CAD/CAM market area. I'm very tempted just to code my own and toss together a dead of Linux box to power and run it. But if there may be something out there that's either dirt cheap or open source, that'd be great and save me time when I do manage to get this up and running, if it's even feasible.

Come to think of it, I don't know much about CNC work or building my own machine, so I'll no doubt be full of questions.. I do understand sending commands to a controller via computer though.. My current "fun" project is building a set of animatronic eyes that I'll have interfaced with my main work comp.. Having spare servos on hand and a few Mini SSC's is useful.. Gotta do something with them.. :)

So what say you.. Is it doable.. Will it be dirt cheap and be able to scribe legible letters on a tag... Think it'll be cheap? Am I wasting my time???

Thanks for any input.. :)

Scott--

cncadmin
10-11-2004, 04:50 PM
I would like to donate a power supply to you're venture, I have one that would be perfect for a stepper driver set-up.

(A dog lover) :)

DarkWolf
10-11-2004, 05:12 PM
Thanks very much for the offer.. :D For right now though ideas and feedback would be great, just to make sure that I'm going to be able to move forward with this.. :)

If I can get a full game plan on the table and figure out how everything will work and indeed get started I'd be honored to accept.. For right now, lets just plan.. ;)

JFettig
10-11-2004, 05:34 PM
have you ever seen those manual engraver things? in jr high I used one, basicly it has letters and a little thing to follow the letters, you manually move it, and when you follow the letters on the template(wich you pick out individual letters) it engraves them into a peice.

I woudl suggest you looking into something like that, mainly because youll have to program each tag and it would probably easier to just set it up like that?


Jon

Chagrin
10-11-2004, 05:40 PM
I'd look somewhere other than at the steppers in a floppy drive - assumedly quite weak and my experience with them leads me to believe they have a fairly huge degree turn per step. Most surplus sites on the internet should have more practical NEMA 17 steppers that would be much easier to work with for very low moolah.

DarkWolf
10-11-2004, 05:47 PM
I'd thought of that, but I think it would be easier to do it this way. Each tag wouldn't differ too much, so working on a "template" basis in program would be easy. Plus this way a rough logo for the rescue could be placed onto one side. Plus it'd look better than a punch set... :)

DarkWolf
10-11-2004, 05:49 PM
~~~Most surplus sites on the internet should have more practical NEMA 17 steppers that would be much easier to work with for very low moolah.

NEMA 17 then? Sounds like something to look into.. Thank you for the tip.. :)

JFettig
10-11-2004, 06:07 PM
take a look at allelectronics.com they have a variety of small steppers.

Jon

DarkWolf
10-11-2004, 07:01 PM
take a look at allelectronics.com

Wow... Those are cheap prices there. Looks to be about $12 for 2 fairly good motors, though not much details.. What about controllers though?

Hey, cool... Peltier devices.. Always wanted to play with them..

Graham S
10-11-2004, 07:09 PM
The quickest and cheapest way to build it will probably be to get a few little THK rails off ebay. Short ones that are often too small for bigger applications are always on very cheaply. Then use threaded rod for the leadscrews and delrin for the lead nuts. Use normal bearings as thrust bearings. Use flexible PVC hose to link motor to leadscrew. Buy a super cheap rotary tool for the spindle. Motors off ebay too. The driver may cost a little more. You can use a PC power supply (available free for almost anywhere) as you don't need huge speed over small areas. Gor for 1mm pitch threaded rod and you have super high resolution.

Here is an example of some tiny slides, you don't have to use these as there are many ways to do it but on such a small scale they would work really well and are VERY good bearings:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=42899&item=3845460919&rd=1

Graham

DarkWolf
10-11-2004, 07:37 PM
The quickest and cheapest way to build it will probably be to get a few little THK rails off ebay.


I saw those today while looking around ebay for parts.. Not sure if the price is right though.. May be better off with a small shaft and some nylon to make bushings out of. At $25 per set, that'd put me at $50 for just the rails, where the nylon and rod may be $5 or so?

Precision isn't a big issue on this one, but I might keep those in mind for later on. No doubt after I get a taste of this I'm going to want to do more..

Graham S
10-11-2004, 07:48 PM
It was just an example. As the rails ARE the machine essentially then $50 would not seem so bad (only need 10 tags for it to pay for itself) and these things are rated for 10's of 1000's of Km of use so they will last longer than the machine I would bet.

I was thinking ease rather than precision you could knock up the machine in an afternoon at it would work like a charm.

If you are good at machining then use your nylon (or Delrin) and get building.

Graham

DarkWolf
10-11-2004, 08:00 PM
Graham,

Many thanks for the input as always. I'm not counting them out as an option and you do make a good point about it.. :)

Think I have the basic idea on motors and rails, plus there is tons of info in the forums on the rest of the rig and how to do it..

I'm still at a loss on the controller though.. At this point I am leaning to a 3 axis instead of 2 axis and an actuator.. But where to find a good inexpensive controller is leaving me a bit lost..

I'd be willing to work off of plans as well on the controller, as long as the parts are cheap and easy enough to come by (IE: order them from one or two places)..

Graham S
10-12-2004, 06:23 PM
Doing a google search would be a good start for drive schematics.

I built mine from these plans:

http://hans-w.com/cnc.htm

They are very similar to the Camtronics 3 axis bipolar chopper drive.

Also see:

http://www.cs.uiowa.edu/~jones/step/

DarkWolf
10-12-2004, 09:12 PM
Do all controllers work with all the software, are they standardized as to the controls?

I think I've seen some that say they're limited to their own software.. Guessing I should stay away from that..

Wouldn't mind having a 3-axis with pause, 3 homes, and 6 inputs to keep the axis's from going too far..

c_nut
10-13-2004, 12:13 AM
There is a piece of 'freeware' that I found that converts text input to gcode. If I remember right it has some ,need to, connected to it. I have it downloaded somewhere,home work or in between. Will search it out and get the url.
I would suggest Turbocnc. Runs in DOS--say old computer--no$ here. A $10 registration if I remember right. Three axis and more, feeds step direction or step controls directly thru parallel port. Do a google on turbocnc and see. I have two 12 volt steppers running on my desk and the motors are driven by four tip102 transistors fed step coil signals from the parallel port. A simple constant current source produces a good torque without expense.
I use a piece of software called Dualstep to test the motors and the power supply. I will try to get the info togther and post it for you. Will take a few days as I am loaded with that stuff that makes my wife happy. Over time.

Gotta go!
From the swamps off mile post 223 Interstate 10.

Graham S
10-13-2004, 05:39 AM
The registration of TurboCNC is now $60 however the downloadable version is fully working without registering. I am sure that given the circumstances the author would not mind it if you didn't register, especially if you ask.

I use TurboCNC myself, it works very well and is fully configurable to work with any parallel port based controller. You can have home and limit switches.

DarkWolf
10-13-2004, 07:49 AM
Thanks c_nut and Graham for the input as always. Sounds like a very good program indeed.


I use TurboCNC myself, it works very well and is fully configurable to work with any parallel port based controller. You can have home and limit switches.

So it works with most controllers? Very good.. I was looking at the one you posted ( http://hans-w.com/cnc.htm ) and it looks like a great setup. Especially with the ability to be expanded into a 4th axis.

Question though about it. I see only one limit input.. Can it be wired so that XYZ all have high-low limit switches (6 total) onto that one input?

Where do you think the best place would be to order the parts? I'm not sure where to get the chips.. Checked on partsexpress.com but I didn't find any.. It's been a LONG time since I was into electronics.. The most I recall is the 555 timer.. :rolleyes:

Graham S
10-13-2004, 01:31 PM
Yes just about any parallel port based controller.

Hans cnc:

There is a home switch for each input, these can be configured to act as limit switches too I think. Then for the other limit of each axis you put the switches in parallel and wire to the single limit input or indeed you could wire all switches in parallel into that single input. I suspect however that given the repetative nature of the task home switches would be handy.

Components:

Whatever you decide to build (and the one I listed is probably not the most simple/cheap option) digikey is probably the place to get the components, they have a huge range.

Graham

jeffs555
10-13-2004, 02:00 PM
Another good place for electronic components is www.mouser.com Their selection is nearly as good as Digikey, and in some cases they have things Digikey doesn't. I buy from both, but for orders under $25 Digikey adds a $5 handling fee and Mouser doesn't.

turmite
10-13-2004, 02:32 PM
Hey Scott,

Just another suggestion but look at mach2 as your controller. Cost $150 US with free upgrades, controls 6 axis, inputs for limits, home etc. It can be used to control your spindle on/off as well as speed if the spindle is controllable. If you are not building and selling machines you can use your one liscense (sp) to run multiple machines. How about the same control for both a mill, router, plasma cutter, and lathe? Just a thought. I have it and love it. Current version is very stable.

Mike

Graham S
10-13-2004, 08:05 PM
Total overkill, all he needs is to interpret some g-code and lift a dremel up and down. $150 is a bargain but just not required, read the first post.

Graham

c_nut
10-13-2004, 10:52 PM
OK I found it was not as hard as I expected.
http://www.deskam.com/download.html I think someone else mentioned Deskam before as a software to checkout. They have some other stuff for the well off experimenter.

The DeskEngrave is the free one you need. Actually I was mistaken this is 'free from hooks' freeware. Just type in the code adjust size and get a file out. Load this into Turbocnc and run it.

Turbocnc does more than 3 axis. One parallel port will do four, and it has inputs that can be set for normally open or normally closed switches and a few spare outputs to turn things on or off. Up to $60 ......hummmm, but it is a full version to try without cost to be sure it will do the job before you commit $$.

Look at http://www.dakeng.com/lathe.html to see how simple a controller can get. This is for step information directly being sent out the parallel port. Change the voltage for your motors and away you go. Can only do two motor per port this way but that is all you need and the on-off control lines can handle the stylus up/down.

I like the idea and was looking for a first project so I may build just such a Dograver as a test bed/learning machine. Now where did I put that 5 and a quarter drive I stumbled over last year.
c_nut

In the swamps 1 mile north at milepost 223 Interstate 10

c_nut
10-13-2004, 10:55 PM
Sorry I forgot been doing that a lot lately. I think.
Look at the schematics link at http://www.dakeng.com/lathe.html.

turmite
10-13-2004, 11:15 PM
Graham I don't mean to be disrespectful but I read all the post. It was this statement that made me think he might be looking further down the road.

"Precision isn't a big issue on this one, but I might keep those in mind for later on. No doubt after I get a taste of this I'm going to want to do more.."

Just trying to offer choices.
Mike

DarkWolf
10-14-2004, 08:19 AM
The DeskEngrave is the free one you need.
<snip>

I like the idea and was looking for a first project so I may build just such a Dograver as a test bed/learning machine. Now where did I put that 5 and a quarter drive I stumbled over last year.

Thanks a bunch c_nut.. That looks like just what I'd need.. :) Oh, and if you do give it a shot, let me know how it goes.. hehe..

Really tempted to rip apart some drives - Think they've got L297 & 8's in them??? :rolleyes:


BTW, turmite, I do appreciate the input and if I do build another down the road just for me, it will be big.. So I'd well need more.. For right now I'm just working to see how cheap and easy I can get off with building a tag engraver only.. But I'll be keeping all I learn at the back of my mind none the less.. :D

DarkWolf
10-14-2004, 08:32 AM
Hey.. Cool...

I just ran that and did a little playing.. With the help of this spiffy little program I should be able to map all the basic letters (All I need is A-Z 0-9) and write my own prog to be able to make things easier.. and multi line.. :)

WEE!



Ok, back to planing..

c_nut
10-15-2004, 12:55 AM
You are welcome. I found this during my study of Gcodes. I have another one that will do a scan to gcode conversion. It makes a very large file and not for a minimal machine, but if you were willing to wait for a long long run to finish...later on that.

Yes I will let you know what I come up with. Resolution with a 20 threads per inch screw and a 7.5 degree stepper is on the order of a little over 0.001" per step if I figured it right. (A 7.5 degree step = 48 steps per revolution x 20 threads = 48 x 20 = 960 steps for 1" of movement so 1 / 960 =0.001041666" / step) Loose a bit due to slop, no I mean slack and if it is 10% error you get 0.0104 resolution. I think this will be usable for a Dograver. Could most probably build this with a drill press only. Some high density plastic, a little aluminum, the rods I got out of that copy machine, a touch of genius, no no I meant elbow grease and …..

The Z axis is the first thing to settle. Is it stepper or solenoid driver? I was thinking of putting a small DC motor with lead screw to move it up/down. A output from the computer would turn it on and drive it down. When it reached the proper position it would close a switch and dynamic braking would instantly stop the motor. The lead screw would hold position, as it would not allow movement, which is what lead screws do. To raise it the reverse would happen. Two outputs from the computer, some limit switches and the dynamic break. Need to put a test bed together to see what repeatability I can get. I guess I have to figure what repeatability will be needed also.

Later.

C_nut

From the swamps north of mile post 223 interstate 10.

DarkWolf
10-15-2004, 08:06 AM
Hmmm... That's a good Q.. I'm leaning to having it stepper powered at this moment, solely for the sake of knowing that I can find plans to build a 3 axis driver almost anywhere.. Though I'm sure that the other way would indeed work well also and would save in the cost of the stepper and IC's in the driver..

I did find a good price on the L297 though.. $3.80 - $3.90 or so.. One site, they were pulls from existing boards.. Not sure about the other.. So that drops the price down greatly.. $4.95 or so for the L298.. Which reminds me.. Is the L298 the same thing as the L298N.. I've seen several types of L298's around.. All are basically the same, but it seems the N is the one that should be called for in all cases.

DarkWolf
10-15-2004, 08:15 AM
http://www.alltronics.com

This site also has a bipolar 4 wire stepper on hand for $6.95..

---
5 Volt, 0.4 Amp, 12.5 Ohms. 0.9°/step, 400 steps/rev, 12.5 Ohm coils. NEMA17 size (1.65" sq. x 1.0" H. with 0.2" dia. x 0.4" long shaft). Four leads (*Y, R, *BK, OR) with four-pin socket connector. Holding Torque (oz/in): Phase A - 7.2; Phase B - 7.2; AB -10.5 Inductance (mH): Phase A - 9.88; Phase B - 9.72 Resistance (Ohms): Phase A - 12.4; Phase B - 12.6 Leakage 500V: Phase A - OK; Phase B - OK; AB - OK Detent Torque (oz/in): 0.37 Minebea Astrosyn 17PY-Q202-03 NEMA17 size (1.65" sq. x 1.0" H. with 0.2" dia. x 0.4" long shaft) Wt - 0.44
---

No clue how good it is, who makes it, any other stats.. But the price is good.. ;)

Graham S
10-16-2004, 08:45 PM
Sorry Mike, also not trying to be disrespectful. I am further down the road and still using Tcnc, I must be a bit backwards ;)

Sounds like you are getting somewhere Scott keep it up!

Graham

TimW
10-21-2004, 08:59 AM
Hi Scott,
Sounds like a worthwhile project, hope it works out.

Another approach may be to adapt a plotter to engrave the tags. Small plotters like the Roland DXY-1100 (a flat-bed x-y plotter A3 size) can be found at almost giveaway prices. They are servo based and move a solenoid driven pen holder via belts. A high speed DC motor fitted with a small chuck (for a rotary engraving bit) could then be mounted on the pen holder. A suitable motor would be something like a Speed 400 or 600 (common among electric powered models - do a search) which is quite cheap ($10 - $50).

The advantages of a setup like this are :

- can be driven via most CAD packages like Autocad, TurboCad and countless other freeware packages. Also will work with programs like Corel Draw, etc. No g-code programming. Draw what you want engraved and then simply print it to the plotter.

- It is already built, and is quite accurate.

- Can be very cheap.

A disadvantage is the limited force that the plotter can apply to the tag being cut. This can be overcome by cutting the tag with multiple passes, since a plotter will be quite repeatable.

Vibration could be a problem but can be overcome by the use of a small motor for the engraving head. A dremel type tool is too large and not needed for this application.

Another type of plotter (such as a Facit) moves the paper under the pen which only moves in the x-direction. These types of plotter are sturdier since the pen holder runs on steel rails. All you would need to do is attach the tag to a piece of stiff cardboard with double-sided tape, then load the cardboard and off you go. The engraving head would be similar to the one used for the Roland type plotter.

Have a look at the Roland Vinyl cutting machine for an idea of what I am talking about. Of course it does not engrave, but cuts with a blade. Very expensive (hundreds of dollars).

Hope this helps, Tim.

Graham S
10-21-2004, 12:50 PM
I assume as well that the speed it not controllable on a plotter. The increased mass on the head may cause problems and the mass of even an S400 motor may be too much for the average pen lifting solenoid??? I'd say give it a try if you find it at a really give away price.

As an aside I found an IBM plotter with linear stepper motors, these can be driven with normal drives, that might be sweet.

Graham

c_nut
10-21-2004, 02:10 PM
DarkWolf
That stepper is a little too weak for this application. I do a power computation on a motor and if the amps x amps x volts do not equal 2 or better I pass on it. Two is minimum for what I have tested. At 2 it is worth testing but may be weak just the same. The old power in = power out - losses still holds. Bearing losses, and losses in the motor itself all subtract from power at the shaft. Some are better built than others.

At 4” of travel a slow speed is tolerable. To get speed you trade off power. To get power and speed costs in driver and motor capability. The 2 watt motor should give enough power to go fast enough so you do not fall asleep while it transverses to the other end.

The "Z" axis being stepper driven is a good idea and I am toying with it. I think it will add some weight that the "Y" axis stepper will have to move and thus require a stronger "Y" stepper. If the weights are close (stepper vs. dc motor and relays) I will put the stepper in. This will open up a lot of other possibilities without adding much in the way of complexity.

A 4" x4" plotter is in the works and parts are being collected as I type/speak. A decision to go with round rails and bronze sleeve bushings has been made but a backup plan is in the works. Sleeves have less drag than balls at low speed, I think. But just in case a ball mechanism is being considered as well.

Pictures at 10:00. (Notice I did not give a date.)

PS I have some schematics for steppers that do not use expensive chips. Interested?

I am new here so I would like to make the following statement for the record.

Disclaimer! Yes, I work in the valley not on the hilltop. I build only as good as I feel is needed and if another application arises I evaluate that and either build to suit or pass. I learned this building electronics stuff, which can get expensive very fast. I believe there is no universal machine. They all have limitations and to try to build for all situations is expensive and complicated. KISS is the keyword and when done right is a satisfying experience. I try to use finesse rather than brute force.

This is my philosophy and does not infer that you are wrong. I expect people to build differently and this does not make your decision wrong nor my decision wrong. It just makes them different. We all react to our experiences. Our experiences cannot be the same so our responses are not the same.

c_nut

From the swamps north of mile post 223 interstate 10.

Graham S
10-21-2004, 03:11 PM
If the steppers were run at 12v (PC psu) with a current limit he would have 4.8W of power into the motor.

I think ball slides give less drag period, not that I am saying that matters.

c_nut
10-22-2004, 10:05 AM
Graham S

I was talking about the motor itself, not how it can be used in a circuit. Why buy a motor that has to be pushed to work when motors that are capable of doing the job are available for about the same price and possibly less.

As to the ball verses sleeve question, I read that in a engineering book and my memory has holes in it so it may not be exact. There was something about speed involved and a cost factor may be involved. That was the ”I think” on the end. Should have stated it better. As in 'sleeve bearings fit this slow speed, low weight, low cost application better than ball bearings from a cost and complexity standpoint. Any shortcomings they have can be easily overcome '.

Parts are arriving and some scrap ½” MDF for prototyping the chassis has been discovered and acquired (from a machine shop no less). Some new motors need to be tested and I have to find my son old electric car, for it has the stylus motor in it.

C_nut

From the swamps 1 mile north of mile post 223 interstate 10.

Graham S
10-22-2004, 10:24 AM
Sorry but as he was going to use the motor in a circuit I thought it was relavent, it is normal to use more than the rated voltage with steppers and they will be faster and that extra speed will be for no extra effort.

I added my "I think" to the beginning of the sentence.

Graham