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MetLHead
07-10-2003, 10:14 PM
Hi all,

I've been hanging out at this site for awhile now and finally decided to show you all what I've been working on. This site is the best one I've seen so far for people like me who love CNC. I've put together a website where I'm going to be keeping all my photos and drawings and stuff. So please check it out and tell me what you think of it so far. It's at:

http://home.comcast.net/~smartinz

balsaman
07-10-2003, 10:26 PM
Nice! I like the router. Get it done!

Eric

hardmill
07-10-2003, 10:32 PM
I like it metl.
Golf clap for the furniture.
PEACE:D

CNCAddict
07-13-2003, 11:56 PM
Hey,
I've looked over your site and have a few questions. Does the CNC control software you are writing have the ability to run servo drives directly from the computer? I have a very good understanding of stepper systems but I would love the speed, efficiency, and controlability of servos without the $$$ spent on a hardware/software controller. I have seen many different servo amps available for under $100, and have been very tempted to buy one to play with. But I can't find a simple explanation of what input servo drivers require? Steppers are cheap and easy, but it shouldn't cost a fortune for a servo setup. I even think my HP printer sitting next to me has a servo drive in it to improve its quietness and speed.

Thanks,
David Bloomfield

Rekd
07-14-2003, 12:52 AM
Golf clap for the furniture

+1

Nice job! I've been looking at a lot of the machines you guys have been building, and I must say I'm starting to get a small itch.. :D

'Rekd

mlinder
07-14-2003, 01:33 AM
Rekd,

I feel like you.

I already bought servo motors and gecko drives through Jeff Davis at HomecCNC.


He's also building a power supply for me, as I am "electrically/electronically challenged".

Then I have to come up with a table design. I want to build a small router that I can use primarily for first article samples, so as to not tie up my 4 production machines. Probably a table with a 24 inch by 24 inch working area.


Mc Master-Carr and I shall become good friends I think.

Mark Linder

cncadmin
07-14-2003, 01:38 AM
Try this place too they have LOTS of steppers and many othe electronics all surplus- http://www.aaaim.com/cgi-local/shop991/shop.pl/SID=48117901350/page=STMS.htm#SSM2000

hardmill
07-14-2003, 02:35 AM
Originally posted by Rekd
, and I must say I'm starting to get a small itch.. :D

'Rekd

I blame it on the boss.
I got the same itch:p
PEACE:D

MetLHead
07-17-2003, 10:03 PM
David,

The control will not drive servos directly. There are a couple of reasons for this. The PC does not have the hardware required to run a servo amp, and for safety. A servo controller requires a digital to analog convertor, as most servo amps require an analog input. It also requires some means of counting the feedback pulses from the encoder.
So, to drive servo amps some external hardware will be required. I'm just not sure yet if I'll desing my own, or try to find something off the shelf.
As for safety, an external controller is much safer because it does not run in a multitasking environment, and is not prone to computer crashes or hangups.
Keep checking my website, I'm pretty close to having something you can download and check out for yourself.

balsaman
07-17-2003, 10:45 PM
Gecko 320's and 340's will run servo motors from step/dir pulses directly from your computer parallel port via cnc stepper control software such as turbocnc, cncpro or mach1 . They are $115.00 USD.

www.geckodrive.com

Eric

CNCAddict
07-17-2003, 11:31 PM
Ok, I don't doubt your abilities and it would be a HUGE breakthrough if you where able to design a simple hardware/software interface between the computer and the amp. I think the problem with not having a real time OS could be solved by using the real time linux hack, or maybe even DOS, but from what I've seen on your webpage I doubt you want to dumb down to DOS. Please keep us updated, this is very exciting.

Balsaman, I have been eyeing the gecko drives for some time and really hope you have success with them on your new CNC machine. I however have a question about how the drives will work in unison. If gecko drives buffer the incoming step and direction signals, what assures that the drives to get ahead or behind one another? Say on the x-axis you set the feed rate too high. The buffer for the x-axis starts to fill and the servo motor gets behind in its motion. The computer obviously doesn't care and keeps spitting out those step and dir pulses. Now if the other drives are working with a very small buffer usage, then won't the x-axis be all screwed up with circles looking like ellipses or worse? I guess one way to combat this would be running the drives at the least common denomenator when it comes to the slowest axis, but how do you find this setting? Am I missing something, or does there need to be somekind of control loop between the gecko drives so that they run in sync with one another?

David B.

balsaman
07-18-2003, 11:32 AM
I don't think the gecko's buffer the steps. As they come in the motors move one step (encoder pulse). There is a small following error that if the motors can't keep up to the stream of pulses, the drive faults.

I think Marriss of geckodrive said he is selling 2000 units a month now. If it didn't work, I doubt he would be getting so much praise on the email lists. Have you seen this thread? http://www.cnczone.com/showthread.php?s=&threadid=171&perpage=20&pagenumber=4 The link shows a gecko driven machine cutting a wooden plaque.

Many of us run the CNC software in DOS for the very reasons you state. I use TurboCNC which is a dos software. Another benefit is we don't need to have a 500 Mhz 'puter in the shop. I run my cnc on an old p166.

Mach1/Master5 is the only windows software that works well for our purposes (that I can afford). The rest are dos based.

Eric

anoel
07-18-2003, 01:50 PM
The Geckos and Software such as TurboCNC are simple to obtain and are inexpensive (Relatively).

The trick to getting people to move from Stepper to Servo would be to find a suitable DC Brush Motor. That is readily available and around $100 +/-. If I could land the needed Motors and encoders and drives for $700 or under I'd seriously consider building my "end all / be all" machine, and steer away from building a less expensive machine. Aluminum bar stock and ground and polished rods are not expensive. (linear Bearings can be inexpesive if you come up with an alternative to factory Pillow blocks as well.)

I could build a kick ass machine, for under $1500 using all new parts "If" motors were a reality.

(Of course If I has scrunging resources lie Eric then I'd be hooked up) Eric did you ever price out what new THK linear bearings and rails would have cost you if you had bought new? Holy s#!t!!! It's insane!!!!

balsaman
07-18-2003, 02:00 PM
Yes, it's insane. Literally in the thousands. A buddy of mine is building a machine. He was cleaning up his garage to make room and had some scrap metal to bring to the salvage yard. As he drove in the yard he noticed a piece of equipment sitting there to be cutup for scrap. It have 2 8' peices of 20 mm rail and 10 bearing blocks on it. Trying to to seem excited he asked the dealer is he could trade his scrap steel for a few parts off the equipment. The dealer had no idea what he had so he said "take what you need". My buddy grabbed at all as fast as he dared even tho it was pouring rain. he also got 2 lengths of 30 mm rail and 4 bearings for it. Talk about being at the right place at the right time! I saw his rail and it's like new! Better than the stuff I got. Most of my bearing blocks need new seals (which I plan on buying).

Eric

turmite
07-19-2003, 01:03 AM
I had been planning to build my own cnc machine before I found this site and am now more encouraged to do it. My question is steppers or servos and why. I know about the torque falling off on the steppers as the speed increases and for the most part there is no encouder feedback for a closed loop system. It was explained to the earlier this week by Mariss at Gecko that for my needs either would work about the same. With that being said is there a real reason I need servos because I have found some that produce around 900oz peak torque for only $130 if I take 5 of them.

I plan on building a moving table fixed granty machine with the x axis moving the most weight some where in the 200 -250 lbs range. I have a 1 1/8" double nut ball screw 48" long that will be moving this axis. The z axis will be ball screw driven as well but I don't know the size yet. The spindle motor weighs 62 lbs and is where most of the weight is coming from. Table on the y axis will carry a 24"by 58" by 1" piece of aluminum that a 4th axis will be mounted to. The most of the 4th axis will be made from aluminum as well.

I know this is not necessarly a homeshop machine but I am at least going to try to build it because I need it in my business.
Any help would be appreciated.

turmite

www.turnercustoms.com

MetLHead
07-20-2003, 12:55 AM
Well, I'm not trying to start up the debate between servo and steppers. Basically, I started the whole thing with servo's in mind because I already had the motors and amps. Also, my thinking is to be able to apply this control to larger machine tools where stepper motors are pretty much non-existent (In my ten years of retrofitting I have never seen a machine with stepper motors on the three primary axes). But using an external controller opens up the possibility of running either servo or steppers. Not to mention all the other goodies that are typically found on a machine tool, like manual pulse generators (handwheels) and PLC's and pushbutton controls (vs keyboard). Check out http://members.aol.com/eagle1cnc and you'll see the kind of stuff I'm used to working on.
Of course, I'm in the same boat as the rest of you, I don't have the cash money to spend on expensive hardware. So I'm slowly working on putting together something home built. Right now, I have a board that I put together that converts step & direction signals from the PC to servo control signals with encoder feedback. I have tested it with DeskNCrt and it works pretty good. But my goal is to put a USB interface on it and run it from my control. So I'll keep you posted on my progress. And let me know if you're interested in trying the software, I'll be needing beta testers.

CNCAddict
07-21-2003, 02:00 AM
You can put me first on the list of beta testers!! This is exactly what I have been waiting for....hardware/software interface between the Computer and amplifier. Please keep us informed...and the more pictures the better. I can't believe you are gonna try to use USB....that is generations beyond anything else in the DIY CNC universe.

David B.

MetLHead
07-23-2003, 12:54 AM
Just an update... I've added some documentation to my site so you can see a bit more detail on the control's operation. These doc's are works in progress, so I will be updating them periodically.

http://home.comcast.net/~smartinz/cnccontrol/controlmain.htm