Looking for CNC Mill Part I

[balsaman]

Turbocnc is giving me the finger.

I have designed and built a servo controller for my pcb machine to be. When I hooked it all up to my old P120 with turbocnc, it does not work. After some frustration and shouting, I decided to go back to basic and check the output of the P port with leds and a scope.

I have found that the STEP signal of my turbocnc (the latest version, dl'ed a month ago) is messed up, even with the standard ini that comes with turbocnc. I have tried every pin available, and combinations thereof, but it seems software. The dir signal is clean, crisp, and does what it it supposed to do, but the step signal remains high forever. The ports work, I have checked that with the port monitor and my own programs.

I am testing this all with jogs, and currently on pin 5 and 6, but like i said, I tried it with other. The step signal refuses to go low. It is one continuous signal, I checked it with a Fluke Digital Scope. I have no clue what the hell is wrong.

Now, what could be the problem, the computer works, the software is the same everyone is using, and the leds are quite quite normal too. ;)

What the heck is wrong?

You had better set the step rate real low to see the step signal go low. It could be pulsing and your voltmeter can't react. Set the step rate for 1 hz. You should be able to see one step per second.

Eric

[mrbaseballny]

If I use the following design and build it 36 inches long, 24 inches wide and will a 1-2 inch cutting depth will it work OK. I'm only planning on using it to cut depron, balsa, and light ply. Nothing over 1/2". I know some drivers boards are not recommended that you go over a certain dimension. Why is that?? and how can I get around it??

Thanks

[crankorgan]

mrbaseballny,
The only thing good about that design is it uses my Centering Block design. Building this machine bigger will reveal it's design flaws. I had a similar design called Routezilla which got lifted by several people flaws and all. If you make the Y rails longer the rails will flex under heavy cuts and you will see the bearings lift off the rails. The weight of the Y-Z axis and cutting forces will distort the rails. The main design of the machine you show comes off a French RC website. I reworked my orignal design that became Routezilla II.

Cranky

[mrbaseballny]

Cranky,

The only problem with you routezilla 2 plans are they are recommended for experienced builders, I"m not an exper t builder but I've never built a cnc router. I can't afford to "tinker" around to find the best solution. I need something that I can use relatiely easy to cut out my balsa, depron and maybe some light ply. the reason I want to make it larger it to be able to plac larger sheets in the cutter and cut wtihout having to "reload" the machine every couple of minutes. What do you suggest?? I have asked around before and noone has ever replied with a suitable suggestion.

[crankorgan]

mrbaseballny,
I know this guy would never recommend my stuff but if you are serious and have products to make, I would go with one of these machine. (see link) Just remember having a machine is only a piece of the puzzle. Run from anyone who says CNC is simple, he is usually out to take your money!

http://www.k2cnc.com/

[TimKoene]

Thanks for the replies people.

@Balsaman:

The problem with the step signal not going low is not that it seems to have a duty cycle of 100%, but rather stays high forever after I pull my finger of the jog key. I have tried setting the pulse width to 0, I tried setting it to 99, and it did not make a scrap of difference. The port is good, it reacts to everything I can throw at it with the built in port monitor on active mode.

Besides, the digital scope should be able to pick up signals that exceed 20MHZ without any distortion. It didn't cost 2000 bucks for nothing ;)

All my tests have revealed that the port is okay, but some software setting is not. I have no clue which, because even after a clean install without me tampering with any settings of the program whatsoever, I still have this same problem.

I am at a loss about what to do. I really hope I can get this working, because I have the X, Y and a part of the Z axis already completed of my wooden router, and have a small servo crosstable waiting to be used with my servo controller.

Thanks again for all the replies!

[crankorgan]

Tim,
During power up hit your DEL key. In the setup of the BIOS of the motherboard you will see settings for the Parallel port. ECP-EEP or something like that. Change it! Also try a new copy of TurboCNC. The default settings should produce results on your scope. Is this a LapTop? Is your cable pin for pin? Make sure you have a parallel port cable not a Null-Modem you found laying around.

John

[balsaman]

Does the step pin need a pulldown resistor? say 1K to ground?

Eric

[xairflyer]

Can't believe this thread is still going strong !

Never got a chance over the summer to finish my machine and it has lay untouched since about july.

Don't want to be one of cranky's statistics of people who never finish the project !!

[crankorgan]

Eric,
With logic circuits they usually have more current pulling to ground. That is why you add a pullup resistor. This helps the logic circuit produce a correct HIGH or 1. He should scope a new copy of TurboCNC at the end of the cable without a board connected. Every so often you get a weird problem like this.

Cranky

[xairflyer]

I have decided to order HobbyCNC's board very well priced, (I think it worked out about 80 euro delivered hard to beat that) and keep my single driver boards for manual testing etc.

I am trying to set up my rails and it takes a bit of time, I think I will need to add some supports to prevent flexing especially on the Y axis. Dont know whether to go with a fixed piece of wood or some sort of adjustable screw.

There are so many different programs I am slightly confussed as to which to load first, just to get things moving and to run a simple cutting program like a square or circle etc, for first cuts.

What would you guys recomend to start with.

[DICKEYBIRD]

You load your controller software 1st and run it's configuration utility to get your steppers going in the right direction and the timing right. After jogging around to make sure things are responding well, go to the controller software's manual command line and type G01X0Y0F1. Be ready to hit the panic button if it doesn't head towards home! You do have a panic button don't you? ;)

Good luck and let us see the results of your 1st productive chip making. :)

[xairflyer]

Thanks for that, when you say your controller software you mean something like turboCNC ?

[DICKEYBIRD]

Yessir, that's the software that interprets the G-code and sends the appropriate signals to the stepper motor controller board to make the stepper motors turn.

You can type in manual G-code commands based on the coordinates of the part or much more practically, draw it in a CAD program (TurboCAD/AutoCAD, etc.) save the drawing as a .dxf file, then input it into a conversion program (ACEconverter, etc) to convert it into a usable G-code file.

These are the methods I use. There are of course, other programs that do all this in one application but are more expensive.

[xairflyer]

OK got the picture.

There are so many programs talked about on these groups, until you actually run them it is hard to know which does which !

I registered turbocnc 3.1 I see now that ver 4 is out can I upgrade or do I need to re register again ?

[balsaman]

Upgrade is free for registered users.

[EnglishGent]

Gentlemen, you too Cranky
I have read all the pages of this thread and thoroughly enjoyed them, lots of good info.
Here are a few photos of my machine in progress. My Z carriage is a little different from most as the guide rails are at a 45 degree angle to the Y rails this saved me 2 inches in machine width and kept the router close between the rails as was my goal. Also notice I used Bondo (auto body filler) to make the seat for the router, it fits nice and snug without distorting the router case. I will post some more photos as I progress, man this is fun!
Derek
[/IMG]

[uscra112]

EnglishGent, that's a bloody brilliant Z-carriage design! Kudos!

[crankorgan]

Another clone of Routezilla. There are several on the net.

[uscra112]

Did you do that angled-box Z-slide design, Cranky?

[crankorgan]

No, I designed my machine for greater access to the router. The angle is all sizzle and no steak. I also use gravity and balance on my design. This eliminates the need for 45 degree bearings that will lift off the rail during heavy cuts.

[uscra112]

Right, the fact the box is mounted 45 degress twisted means nothing.

But the idea of putting the rails in the corners of the box I like a lot. If you cut all the box parts square, the Z-axis comes out square in both Z-X and Z-Y planes without hardly trying. Then the screw goes neatly into the third corner.

For a 2-D router the squareness doesn't mean much, I know, but if you're thinking 3-D cutting it means a lot.

I've studied a Gosh-awful number of machine tools, dating from 1900 to 1980 or so, and I don't remember ever seeing anything quite like it.

[crankorgan]

Everything there is from my Z axis of Routezilla II Forget about the shape the secret is my centering blocks. That hides bad designs-poorly made parts and alignment problems. Lets see it work without out the blocks. That design took me hundreds of hours.

[EnglishGent]

Cranky
I appreciate the contributions you have made to this thread. What does it take to make a machine, you know 6 tubes lined up with bearings, a router and some stepper motors to cut wood without you calling it a clone of one of yours? How much access do you need to the router, does it need replacing often on your machines? Four nuts accessed through the holes in the back of the Z carriage and my router falls out the front, not too hard. The main reason I chose 45 degrees was to squeeze every inch out of the overall size of the machine, while trying to keep the router from hanging too far out from the rails. My Y carriage will run under the cutting surface not over it as on your Routezilla . I wanted a cutting area of 12”x 24”x 3” in a small overall machine footprint, will Routezilla work that large?
Derek

[crankorgan]

Derek,
First off your greeting was "Gentleman and you too Cranky" which was a bad start. Your designs are not designs they are cloning. There are reasons why I design the way I do. You will understand that when you stop copying and start designing. Moving the exhaust of a car from the side to the back does not change the car. Removing MDF and making an axis open does not change the mechanics of the machine. Routezilla II has been around over a year. Now you come along redesigning it and showing up where I hang out. Excuse me for pointing out the obvious. You are a HACK and a Want-To-Be.

John

[EnglishGent]

John,
Sorry if I offended you with my opening, it was meant as a little bit of humor. Also sorry to offend you by posting where you hang out I’ll try to curtail my posts here.
Derek

[crankorgan]

Happy New Year

John

[uscra112]

Not to stir you up any more, John, but please let me remind the assembled multitude that basic principles of the Universe cause the same basic designs to evolve independently over and over. Even your roller-skate-wheels-on-a-round-bar design is as old as the hills. I saw a barn door using that system in my youth, and that door had been erected when my old Dad was a wee sprat - probably about 1920. Your contribution, (and it's a big one), is to apply it using components that are readily available and cheap.

Long ago when I was married, my wife worked at a high-tech software developer in Cambridge, MA. At a company party I once asked the president of this company whether he patented or copywrited his products. He said "neither - it takes too long. We just work like demons to stay one jump ahead of our competition".

[crankorgan]

Happy New Year

John

[uscra112]

Yes, I've been on the thread a long, long time, too. Check Post #7.

We all wish you well, but we also wish you'd take all the FLATTERY kindly and bask in the glow.

Phil

[crankorgan]

Happy New Year

John

[uscra112]

You're totally unforgettable man! How CAN you think such a thing! Be careful with them bears - I just read the second story in two weeks about guys getting EATEN by bears ! http://www.outdoorsunlimited.net/cgi-bin/news/viewnews.cgi?id=1103558685 The other one has photos - it's way to gruesome for E-Zone.

Cheers!

[crankorgan]

Happy New Year

[uscra112]

See ! People do appreciate you !

Merry Christmas !

Phil

[EnglishGent]

John,
My apologies again for the “you too Cranky” but after reading all the posts in this thread I felt I new “you” a little bit, hence the rib. If the material used in constructing a machine is the design then yes John I cloned your design as I also used MDF and pipes. The reason I posted my photos was to show how I approached the design (oops) arrangement of the Z guides (oops) pipes in hope it might spark some conversation (although not this kind) . All of these CNC routers I have looked at on the internet are very similar to the machines I have worked on at Hewlett-Packard as an Equipment Technician the last 10 years, we have several in our PCB lab. I admit I used YOUR idea of using pipes and MDF ( it was a very good one and full credit is yours) but the DESIGN is mine not a clone of yours any more than yours is a clone of an industrial machine. Although a Ford and Toyota are both cars (to use your analogy) they are not the same design. Now, I truly appreciate the contribution you have made to this thread and in no way meant to offend you so can we call a truce and quit quibbling over the definition of the word design. Your website (plus a few others) inspired me to build a machine, I thank you for that also. Feel free to use my design of angled pipes in any of your future designs.
Truly yours
And Merry Christmas
Derek

[crankorgan]

Happy New Year

[EnglishGent]

OK John,
I hope this doesn’t piss you off but the idea for my centering blocks came from my old telescope. It seems they use a very similar method of using screws to line up the spotting scope to the main telescope. So whoever came up with this means of lining up a tube I copied there idea. You still get credit for the pipes and MDF.
Derek

[crankorgan]

Happy New Year

John

[EnglishGent]

Last one John,
I only use two centering blocks per axis, but I could of only used one you are right. I used two as an easy way to anchor the loose ends. I have tried to be cordial in our discussion, no need to resort to name calling, you are older than 13 aren’t you? By the way what is it I “Want-To-Be” and how many of us are there?
The Hack
Derek

[crankorgan]

Happy New Year

[B Vial]

pppppppppffffffffffttttttttttt.........

useless posts!

Lets get on with some real discussions as we all know crankorgan invented the internet and the wheel.

[Dongledell]

Too bloody right useless posts. I've been really enjoying this thread up till now. Haven't posted a great deal because I'm still taking it all in, but this turn sucks. As someone said a few posts earlier - it is the nature of design in this world that similar methods will appear to a problem independantly of each other. I could point out that my father, who has been making his own workshop tools for 60 years, has been using gas pipe and bearings as runners for years, but obviously he couldn't of because that would mean he must have stolen CrankyOrgan's design, which he clearly didn't as the first time we could convince him to sit at a computer was only very recent.

Crankorgan, I highly respect the work and effort that you put in here, I myself have had several inventions stolen piecemeal - and I dont just mean a small part or concept, I mean stolen in every damn respect, and it hurts like hell, especially when you see a company become EXTREMELY rich off the results, but not all people do hack, and it is perfectly possible for someone to come up with a similar solution to a problem without necessarily copying it from you.

Can we please now go back to the interesting stuff, where everyone shows and discusses how to make better CNC machines.

[Joules]

Errrrr, Guys!!!
If you post design details on a "PUBLIC" forum, you kind of loose the exclusivity to your work, unless it's protected by fat lawers... Get back to the points... Everyone works off everyone elses back... This whole forum wouldn't exist without computers. And if you look in any victorian engineering supplies book, you will find we haven't moved on m,uch.

Joules

[crankorgan]

Have a Happy New Year

John

[xairflyer]

Got my hobbycnc board in the post today - 4 days from the US to Ireland brilliant that especially given the time of year.

Just have to get things cutting now over Xmas.

I have a new computor power supply I have been using with my single stepper boards and resistors, will this be ok to use of should I look at 24v instead of the 12v

[HobbyCNC]

Got my hobbycnc board in the post today - 4 days from the US to Ireland brilliant that especially given the time of year.

Just have to get things cutting now over Xmas.

I have a new computor power supply I have been using with my single stepper boards and resistors, will this be ok to use of should I look at 24v instead of the 12v

Use the most voltage you can for best performance. 24VDC or more.

Dave Rigotti

[Tree_Magnet]

Holly wa wa wa don't stop this is actually entertaining :D

[Photon]

Use the most voltage you can for best performance. 24VDC or more.

Dave Rigotti

Dave,

Is it possible to simply connect 24V to the controller, or do I need to change things on the board (ballast resistors, etc.)?

I have your 12V package, not the chopper board.

[HobbyCNC]

Dave,

Is it possible to simply connect 24V to the controller, or do I need to change things on the board (ballast resistors, etc.)?

I have your 12V package, not the chopper board.

Of course you have to change the resistors! This is called out in the instructions.

Dave Rigotti

[EnglishGent]

Hello Everyone.
Everything is lined up and screws tight – now to try and wire it up.
I need to figure out where I can put it in my crowded garage, I’ll probably lose some more counter space. Anyway, I would like to thank all the contributors to this thread for the valuable information posted here. I would like to especially thank John Kleinbauer for his pioneering work in building a low cost CNC router. He showed us the way. Here are the photos of the finished mechanical parts of my machine.
Derek

[mrbaseballny]

Derek,

Did you follow plans or is this a homebrew?? if you used plans what ones??

Just curious to see what everyone is using as a "base" idea.

[EnglishGent]

Mr. Baseball,
It is homebrewed. I looked at a lot of internet sites that talk about or offer plans and since I have a mechanical background I just flew by the seat of my pants. I did do one thing very different than any others I have seen and that was to angle the Z carriage guides at a 45 degree angle to the Y guides. I didn’t care for all the ones with the router hanging off to one side and tried to keep mine centered as close between the guides as possible, it also saved me a couple of inches in overall machine depth. The overall size of the main base is 27” X 37” and has a working area of 12” X 24” X 3.25” which was my intended goal. It was not hard to build but you do need a good table saw, drill press and a little wood working knowledge. Everything came out very tight but glides easily before the feed screws are hooked up. It was a lot of fun building it and encourage you to try one, either homebrew or from some of the good plans available on-line. This thread is full of good ideas and there are experts here willing to answer beginner’s questions.
Have fun
Derek

[furyflyer2]

Lets see how you do without me! I am sure you have so much to offer having never posted. You don't care where the info come from as long as it is FREE. For those who want the truth read this thread from the beginning. Unlike those Want-To-Bes. Those who can do! Those who can't copy!


John


I read you "news" section, I have never heard so much wining, you claim that cnc home building has hit a plateau. I think you have hit a plateau, you treatment of others is deplorable. My site is packed with people building their own machine even posting their own designs for free. After reading your cheap shot on your website, I had to chime in. It's a shame that you have made a bad name for yourself and the cnc community. Are you mad at people who "copy" nature too?? Just because people are so called "copying" your designs does not make them any less of a design.
You can post all you want about me and my site, you are the one missing out NOT me. Sorry your not selling any more plans, like you use to I guess my site my have somthing to do about that. Well have a nice day.

[crankorgan]

Have a Happy New Year!

John

[furyflyer2]

You're too funny, this is only ONE thread, http://cnczone.com has 6980 more threads of more content and less crank. Their is no comparison, plus their is over 100 posts a day from the most polite and knowledgeable people on the planet all to HELP beginners get into CNC.

This thread was started in sep of 2003, my site was started in march 2002 and now has over 7,500 members and over 56,000 posts. CNCzone was started to help promote CNC home machining all I have seen from you is making enemies.
So your plans of world domination is coming to a close...........

BTW, my decision to start the site has NOTHING to do with any sites, it was because of the lack of good information that could be found in one place. I didn't even know that this thread existed back in the day.

[crankorgan]

Have a Happy New Year

John

[furyflyer2]

Paul,
My plan was to show people that cheap easy to build CNC machines could be made. I did just what I set out to do and nothing more. Like I said, I did not pull any sneaky tricks like you did, I use my real name. I never HAWK my products or Website. I answered questions. You should try it!

John

John,
MMM that's what I did to, here are free plans- http://cnczone.com/forums/showthread.php?t=6054&highlight=free+plans , I answer questions that I know, after all that's why I started the site, because their are much smarter people out their than me, I guess you could say I'm a humble person, you should try it out some time, it's all the rage. Wow it's a crime to promote a site that actually promotes ways of building cheap cnc machines..... if that's a hawk and being sneak, well i guess I am guilty...


Paul

[Bez]

I get so tried of this Furry Flyer guy, trying to tear John down. You can go back thru this thread and see where time and time again where he be-littles John ideas, plans, website, invovations that have made this hobby affordable for people like me on a limited budget. Several times I have even seen you use differernt names to do so. I never could have never got into this hobby without John's help. I have seem time after time people copy his work and claim it for their own! It's no wonder he get cranky at times, about it, so would I, exspecially with someone repeatibly atacking him, and his livelyhood. Why are you so threatened by him? Your site is obviouly geared to a more high end client. Not someone just starting out.
I can't believe how much free advice and time I have seen him give on this site.
His plans are top notch, easliy adaptible, easliy affordable, easy to build with common easly found materials. His customer service is great, he answered all my dumb newbe questions. He shipped everything I have ordered from him very quickly. I think John is a all around good guy! I also think it is very bad for you try to hurt John by giving away a free set of plans. So I wonder who is really starting to get a bad name in CNC... In my book it is Fluryflyer not John!

[crankorgan]

Bez,
I am try to stop the feud between Paul and me this thread is here since 2002 not 2003 Click on FIRST Happy New Year!

John

[furyflyer2]

Yep, it's time to move on, me and John have agreed to bury the hatchet.

BTW Bez, cnczone is for DIY, meaning beginners, not just "high end" users.

[Bez]

Yes I think it is a good idea to move on.

I usually don't post very often, and I have read this site from start to finish, and I guess I just "had enough" so to speak.

I started to say some other stuff, but I don't want to fan any flames.

I'm glad you two are "burrying the hatchet" I'll do the same.

Lets start over with the New Year!

[hcjets]

I can second Bez's comments about John. I purchased his plans after looking at a few others. I can say that his plans are very well written, easy to follow, and his support has been over and beyond what I would have expected.

And I know once I complete his machine I will have something that works and will do what I want it to do. John's designs are proven and work period!

JR Gautreaux

[BennyLaird]

Well I finally started to put her together. This is th Z axis so far.

I have 7 inches of travel with virtually no slop. The Dremel will be clamped on with a butterfly nuts holding the other half of the MDF holder (not Shown)

The Stepper motor will mount on top and a thrust bearing on the bottom with a delrin drive nut attached to the Z axis.

More as I get it done. I'm designing as I go to suit the components I have but will use the already proven ideas from CNCZone et al.

[Joe41]

Hi Benny, what type of controller are you going to use? I too would love to build a router table and also foam cutter but have information overload :(

I suppose I really need someone to sell me complete package (controller board, motors, screws and plans) sort of like an semi ARF kit :) Crank organ seems to have good feedback on his plans and stuff but he doesn't post over here :(

Do you know if any one sells a router table kit?

Joe

[BennyLaird]

No Joe, wish I did LOL.

I did get all my electronics from Low Cost Retrofits up in Queensland. Came with software, drivers and steppers but was $900 Aust.

I'm hoping mine will work but time will tell.

[Joe41]

Thanks Benny,, your project's looking BTW
Joe

[OzDragonFlyer]

looking good benny, let me know if you need any difficult parts cnc cut to speed the process.

my table (http://www.rcgroups.com/forums/showpost.php?p=2730457&postcount=2168)

[BennyLaird]

Will do Oz, yours is magic! Hopefully my second machine will be along those lines. Have to get your sources etc if I can.

Made up the Dremel clamp today and it is rock solid, thought I might have tp shim it a bit but I can't get it to move so should be fine.

[mrbaseballny]

BennyLaird,

What are the dimensions of your machine?? it looks like it will be large by lookingat the photos you posted.

[BennyLaird]

Well I won't know exactly till I finish her but the Z axis has 7 inches movement and I should be able to get about 12 or more on the Y axis. Also hoping to get 36 inches from the X but I will be able to reduce this if I have problems.

It is basically to cut balsa kits so I needed enough for a sheet but I'd also like to do ply and depron.

[aolshove]

Just thought I'd share my 7th Sojourn router project with y'all. ;)

http://www.olshove.com/CNC/

[mrbaseballny]

aolshove,

Why is the router so loud? is that the normal noise that the steppers will make?? it alsmost sounds as loud as my little dremel tool:)

Nice looking machine, I am still looking for the best route to take to build my own router.

mrbaseballny

[uscra112]

aolshove,

Why is the router so loud? is that the normal noise that the steppers will make?? it alsmost sounds as loud as my little dremel tool:)



Steppers move in series of little jerks - not a smooth motion like a regular DC servo motor. Reducing the supply voltage would help the noise, but weaken the response. The waveform that the stepper controller sends to the motors probably also has something to do with it. The MDF panels we make our machines structures from have little mass, and are not stiff like cast iron, so they tend to amplify the noise.

Generally we have to live with it, or spend the big bucks to use closed-loop DC servos, which are a whole different kettle of fish.

[OzDragonFlyer]

no probs benny, be happy to help out.

Balsa,depron and ply are great materials to start out with.. I've been routing a homemade 3D foamie from depron here (http://www.rcgroups.com/forums/showthread.php?p=3106911#post3106911) . From 1 hour with a knife to a few minutes on the table.. 'aint technology grand. :)

[hpghost]

I have started to look how cnc hobby can be interesting and how I can apply it to my needs.
I have seen different people/companies selling some drawings to make cnc routers.
Many of them are saying: "longer travels not recommended", why?
where is the restriction? driving board?
In fact how the software know the maximum travel? (in fact does it?)

Why it is a problem if for exemple i change a 300x300x30mm travel into 800x300x100mm travel????

[DICKEYBIRD]

Welcome hp....there is no limit to the travel as far as software is concerned. The practical limits are defined by the rigidity and friction of the machine and available stepper motor power. Big machines require BIG parts, BIG drive mechanisms (slides, chains, belts leadscrews, etc.) and BIG motors with BIG electonics which equals BIG $$$.:)

[hpghost]

so, If you can increase size without increasing too much the weight of the parts in motion, i suppose the steppers doesn't need to be increased (or just a little).
Anyway, this is more or less the answer I was predicting,

Thanks!

[OzDragonFlyer]

One of the biggest costs associated with larger machines is the drive mechanisms. At first thoughts, simply throwing in a replacement longer leadscrew/ballscrew may be the easiest solution, when in fact it isn't. Longer screws will whip around more at higher rpms, creating binding on the leadnuts and power robbing oscillations on the axis it drives.

The screws have to go up considerably in diameter to lessen this effect, which not only makes them more expensive, but heavier, and needing larger motors to overcome their inertia. Bigger motors need bigger drivers.. and so it goes on. If high traverse rates are not needed however, gearing down is an alternative to upgrading the motors.

A lot of large commercial routers use rack/pinion style drives, which is now becoming more economical. Properly geared these will give almost as much torque as conventional screw type drives. Just be careful to keep debris out of the rack, even a small chip can cause the machine to fault to a stop (and cause ruined parts)

For an 800x300x100mm router a screw drive would be fine.. screws would need to be at least 1/2" on the longest axis depending on how fast you are planning to spin them. Support it at both ends with bearings for best results. I've used 3/8" leadscrew up to 600mm before they start becoming problematic at high rpm. Some manufacturers have datasheets for recommended lengths and support types for their various screws which is really a great help to hobby builders.

good luck!

[Rossz]

I'm wondering where is Kranky, he seems a nice guy, even a lots of people attacking him. Ive been following cnc stuff for last couple of years,
lots of so called innovators appeared, fighting for a small peace of idea.
This is a kinde of competition. It helped the mankinde since antiquity, whay
ancent Greace had the 10 smartest people in that period in the world?
Because of the freedom of ideas. Here is the same happening. The tehnology
prices are dropping, more people building stuff from internet. I would like to see open source PIC servo driver. That would really help to this hobby.
Now from the legal standpoint, who invented the weel, it is a long and costly
debate. Even the Geckodrive owner wudn't stand a chance on the court against some crucked lawyer, or even a paralegal who has all the time on the world appearing on court. Also if the copywright notice is not posted on your work, you may loose it after a period of time. Then it becomes in Public
Domain. It is free to copy but you have to mention the source. To copyright
work in public domain, you need EXTENSIVE changes made to claim as your own. So obviously most of you didnt make a big buck out of this hobby, so you dont have money to buy justice. My lawyer charges 450$ per hour, one
hour minimum. Just a simple matter takes months to resolve. See the costs?
Also nowdays one mans innovation doesnt count, cant compete against teem of engineers. But if a man is working hard 24 hours a day, like Kranky,
he will be better off. But good education also count, every third Japanees
engineer is able to do revers engineering on the machine from first sight.
Also som German hobbysts build earlier aluminum cnc machines with linear bearings. The market is huge and I hope that everyone would finde its place
regardeless of selling, building or just studing. I have to credit Mr. Kranky for
many things, his plans, ideas, and mostly persistance and his love thoward
this hobby. I reccomend his plans to everyone, they are affordable, informativ, and you will learn a lot by doing. After you will be smarter and prouder person.
So, I woud like to see Kranky here more often, talking about software,
and stuff which these machines can actually make. This is what is missing,
even from some comercial sights.
Best regardes Rossz

[balsaman]

Another thing is speed. A large table requires faster drives, because it's one thing to go 15" at 15" per minute, quite another to go 60" at 15" per minute. Most hobbiest say they have lots of time, so speed doesn't matter. In reality it's like watching paint dry. Faster drives is $$$. You got $500-$1000 for drives and motors alone? Another argument is "I will start the machine and then go do something else (like have a nap)". This is a recipe for disaster, especially for "one off" parts, because try as you might, the program doesn't always do what you think it should do. Almost always due to operator error. Ever see what happens then you plunge your router into wood up to the collet and let is run (rub) there under load/pressure for a haf an hour? No you have not because if it happened the garage burned down.

Eric


I have started to look how cnc hobby can be interesting and how I can apply it to my needs.
I have seen different people/companies selling some drawings to make cnc routers.
Many of them are saying: "longer travels not recommended", why?
where is the restriction? driving board?
In fact how the software know the maximum travel? (in fact does it?)

Why it is a problem if for exemple i change a 300x300x30mm travel into 800x300x100mm travel????

[hpghost]

for the speed, no problem, if I have to stay close to the machine 3 hrs, I will stay...
I can work on my 2nd computer in the same time...lol

anyway, I will not have so many large pieces to make.

[uscra112]

OzDragonFlyer hit the nail on the head. I've got experience with the gigantic routers that the full-scale industry uses, and I confirm that the screw length/diameter issue is the controlling factor. Which is why larger machines use rack-and-pinion drives. Backlash in rack-and-pinion systems is an issue, which is dealt with using special gearboxes or dual servo systems.

But another way to do it for our scale of machines is to rotate the NUT, not the screw. This has it's own problems, but it IS a way out. Some of the high-speed machining centers we see now in the auto industry use this design.

A way to lessen the "whip" of a long screw, which also handily increases it's longitudinal stiffness, is to TENSION the screw. This requires stiff, heavy structural elements to keep the machine frame from bending under the tension load, but it will do a lot for you in this regard.

[mrbaseballny]

OzDragonFlyer hit the nail on the head. I've got experience with the gigantic routers that the full-scale industry uses, and I confirm that the screw length/diameter issue is the controlling factor. Which is why larger machines use rack-and-pinion drives. Backlash in rack-and-pinion systems is an issue, which is dealt with using special gearboxes or dual servo systems.

.

Does anyone have a photo that will show the rack and pinion setup? I'd like to see what your speaking of:)

Thanks

[uscra112]

Mmmm, no photos that I can lay hands of quickly. In any case it's a bit trickier than we hobbyists will want to get into. You have to have two pinions engaged with the rack, and then you have to twist one against the other to take out the backlash, and at the same time drive them both to make the axis move. The old way was to build a fairly complex gearbox with extra gears, some of them helical, and use endwise pressure on one of the helical gear sets to make the output shaft twist. It takes a lot of structure to resist the loads. Each of these gearboxes cost a hunnert grand at least. Although admittedly they were driving 100,000 lbs with a 25HP servo. That exact solution is really not something we could afford to do for a hobby machine. The later way (probably still used) was to have two DC servo motors, one for each pinion, and drive one against the other to maintain anti-backlash. This takes servo algorithms that aren't to my knowledge available to us hobbyists, and requires DC servos. It won't work with steppers. But I'll think about how to do a twin-pinion gear train using cheap components, and post if I come up with anything useable.

[OzDragonFlyer]

an example of a trapezoidal rack and peanut (oops pinion) gear

[cnc2play]

here is a movie of a plexiglass rack & pinion in action

http://maeweb.ucsd.edu/~mae3/spring2002/mae3_13/web/robot.mpg

[cnc2play]

so far i have built the X-axis of Cranky's 7th Sojourn as in the
pic below. i have stalled on building because i have yet to acquire
some aluminum channel for the other axes. i have noticed quite
a few builders here from my area (Oakville, Ontario).
Does anyone in my area have any left over aluminum channel
they would like to part with for cash of course ? i'm willing to
pick it up personally.

[OzDragonFlyer]

nice! great workmanship there.

You may later want to add some rollerbearings underneath to stop the table lifting upwards and off the rails if you plan to do any heavy cutting.

[crankorgan]

nice! great workmanship there.

You may later want to add some rollerbearings underneath to stop the table lifting upwards and off the rails if you plan to do any heavy cutting.

Not needed! The weight of the Trolley on the rails exceeds that of the cutting force of the Dremel many times.

Designer of the 7th

[xairflyer]

I thought about rack and pinion back at the beginning, is there much of a problem with backlash or is it non existant with a setup like this.

[techno_guy]

Hello group! i have built one cnc machine and willl be posting pics soom. it is accurate to 3 mils and has run fine for over two years. Made of aluminum extrusion, it has served me well. it has an 8"x8" travel and I use it for everything from milling pcbs to engraving to milling out small wood parts for my planes.
I have enough parts for about three more machines. Let me know what you guys think...pics coming soon...

[uscra112]

Backlash is a problem in every rack-and-pinion. IF the backlash is the same throught the whole travel, and IF the position feedback comes off the motor, (as it essentally does for a stepper system, for the sake of the discussion), and IF the axis controller board has the capability, then you can tell the controller board to add or subtract increments to compensate as the axis reverses direction. This might be adequate for our purposes. But if the backlash is NOT constant through the whole travel, you'd have too much compensation in one area, and not enough in another. You make the backlash constant by using accurate pinions, accurate racks, (i.e. precision steel, i.e. more expensive) and by making the axis slide (pinion mount) travel very very parallel to the rack, so the mesh depth remains constant. If your cutting will be +/- .005, a rack system with backlash comp could be adequate. If you want better than that, then you'll have to use mechanical means to control the backlash, such as I described earlier.

Even without comp, backlash might lead to vibration problems under circumstances I can imagine.

Sorry, but I've been too darn busy to diagram that anti-backlash gearbox, as I promised. Maybe - if things quiet down around here - next week.

[Gary Blaylock]

Hi everyone,

I throught I would post some pics of my projects. This is a sign I made for a friend today. The background is machined .25 deep. The material is man made decking board. ( Cuts really nice with the router)

The clock is being machined from plans I got from Brian Law. I'm using .375 aircraft grade plywood for the gears. The plans are .dxf and only need to be cleaned up for converting to g-code.

Gary

[Gary Blaylock]

Pic

[Gary Blaylock]

Pic

[Gary Blaylock]

Pic

[Mick Molloy]

Man that clock is nice... do you have a link to the plans?

[Jojje]

Brian Law: http://www.woodenclocks.co.uk/

[Tom Verstappen]

Very nice!!!

[balsaman]

Nice clock. I doubled up on the thickness of the pawl part. As drawn it was too thin to hold up.

Eric