Simple cnc project question

[Txchevy]

I looked over the plethora of fourms here and honestly have no clue where to actually post this but, it seemed most appropriate here as it will be used in conjunction with my plasma table.

I was wondering what would be required to build essentially a cnc controlled cutting fence? It needs to only work in one axis. I already have the mechanics of it figured out I just need to come up with a way to control it.

I would like a simple up and down button or a key pad to enter a number in inches and it zips off to that point and stays put ( I can build a clamping system if need be. It seems simple in my head but, I'm not sure how to approach it. Ive gathered that I will need a stepper motor, stepper driver( geko?), 8 digit lcd screen and a control panel for inputs as well as a way to tell the driver to send the stepper to the required point. I remember something similar to this being an option on my fathers old table saw but we never upgraded to the option. This will greatly improve productivity and accuracy ( as I wont have to always be looking for my tape measure)

Is it possible to build this stand alone (no pc) for @ 400?

Thanks In advance,
Cory

[WSS]

Originally Posted by Txchevy I looked over the plethora of fourms here and honestly have no clue where to actually post this but, it seemed most appropriate here as it will be used in conjunction with my plasma table. I was wondering what would be required to build essentially a cnc controlled cutting fence? It needs to only work in one axis. I already have the mechanics of it figured out I just need to come up with a way to control it. I would like a simple up and down button or a key pad to enter a number in inches and it zips off to that point and stays put ( I can build a clamping system if need be. It seems simple in my head but, I'm not sure how to approach it. Ive gathered that I will need a stepper motor, stepper driver( geko?), 8 digit lcd screen and a control panel for inputs as well as a way to tell the driver to send the stepper to the required point. I remember something similar to this being an option on my fathers old table saw but we never upgraded to the option. This will greatly improve productivity and accuracy ( as I wont have to always be looking for my tape measure) Is it possible to build this stand alone (no pc) for @ 400? Thanks In advance, Cory

Veeder root or dynapar may have something available. It would probably be three components, a din display, a stepper and a encoder. I use something similar for stopping a weld. the veeder root display sends a signal to stop the motor when it reaches zero. That said I enter the number I want before hand and it stops at zero, If I need 72", then I enter -72, when the count is zero (via .001"), it triggers a relay. I use a 100 count (PPR) encoder to be simple with a 1/2-10 acme thread for movement. I really don't need .001" but it works good. Easy math.

WSS

[Txchevy]

I think I understand. This is my first attempt at anything of this nature but enjoy the challenge.

So, the display counts down via the encoders input and a stops at the supplied point when it reaches zero. I would guess I would need to have power supply that would connect to the display. The display will count the amount of counts from the encoder and acts a basically a on/ off switch for the power supplies current.

I've looked around for a suitable and cheap display and have yet to come a crossed any thing that seems suitable. Most all read rpm or temp. Would I need a unit that reads rpm?

Maybe something like this?

Danaher Dynapar Corp MT100S00 Max Tach 1 115/230VAC - eBay (item 220684039658 end time Oct-23-10 19:39:30 PDT)

or this

Dynapar Counter & Tachometer #MTJR1S00, MCJR2500 Used - eBay (item 280577086047 end time Oct-25-10 06:36:39 PDT)

with an encoder such as this

SUMTAK ENCODER OPTICAL INCREMENTAL 100 COUNTS/REV. NEW - eBay (item 350340894806 end time Nov-10-10 10:36:18 PST)

If these will work any suggestion for a stepper as far as force? Will 620 oz/in steppers work. It will need to be able to move roughly 75lbs pieces of tubing supported on roller bearings so there will be very little friction to over come.

Thanks your help is greatly appreciated,
Cory

[WSS]

Originally Posted by Txchevy I think I understand. This is my first attempt at anything of this nature but enjoy the challenge. So, the display counts down via the encoders input and a stops at the supplied point when it reaches zero. I would guess I would need to have power supply that would connect to the display. The display will count the amount of counts from the encoder and acts a basically a on/ off switch for the power supplies current. I've looked around for a suitable and cheap display and have yet to come a crossed any thing that seems suitable. Most all read rpm or temp. Would I need a unit that reads rpm? Maybe something like this? Danaher Dynapar Corp MT100S00 Max Tach 1 115/230VAC - eBay (item 220684039658 end time Oct-23-10 19:39:30 PDT) or this Dynapar Counter & Tachometer #MTJR1S00, MCJR2500 Used - eBay (item 280577086047 end time Oct-25-10 06:36:39 PDT) with an encoder such as this SUMTAK ENCODER OPTICAL INCREMENTAL 100 COUNTS/REV. NEW - eBay (item 350340894806 end time Nov-10-10 10:36:18 PST) If these will work any suggestion for a stepper as far as force? Will 620 oz/in steppers work. It will need to be able to move roughly 75lbs pieces of tubing supported on roller bearings so there will be very little friction to over come. Thanks your help is greatly appreciated, Cory

The second item you listed shows a counter as one of the items, thats it. However, a tested item may be less risky (or new). On the encoder, get one with a cable attached. It makes wiring easier. If you have the time, your effort learning the danaher/dynapar part number scheme is helpful. Each number letter means something. Go to there site and build the exact one you need and look at the part number it generates. Then look at ebay. I did this recently and found one that was workable on ebay for about a third of new and I did nit have to wait 5 weeks for it to be built. I like the hollow shaft encoders. even if it is too big you can build a collar/adapter. My veeder root displays that I use are hooked to 110vac, so no power supply is needed. It puts out the right voltage to the encoder for feedback as well. I think it is a range of 5 to 24vdc? Good luck! When all said and done you will have something that may be a nice tool for others as well, maybe a side business.

WSS

[WSS]

Thinking further, You really do not need a stepper motor. A 110vac or a 90vdc motor would work. If you need to stop/brake rather than coast to a stop, a 90vdc motor would be better because you can put a resistor in between the + and - poles to brake to a stop. If your setup has a heavy COF, then it may just stop on it's own right where you want it when the power is cut. Then a simple 110vac or a synchronous motor will work with much less wiring.

WSS

[Txchevy]

Thats kinda what I had gathered from some of my research. I think I'm on the right track. I've always been intrigued with electronics but have absolutely no formal training or education to speak of other that working with 12vdc when working on automotive electrical. I an handle the mechanical side but the electrical side I'm lacking. Is there any books or websites you can recommend that might help me gain a bit of knowledge in this( even just the fundamentals would help immensely)?

Well heres the progress so far.

Great tip on breaking down the part number to find the perfect counter.
I picked this counter up off ebay last night for 5% of its retail value nib. I believe from what I've read it should work perfectly.

MAX Position 1, Position Indicator / Controller | Electronic Preset / Predetermining Counters

I believe from what I've read I need to find a incremental rotary encoder that will give me 100 counts per revolution which will give me a .001 resolution although its probably over kill for this application. Which is what you stated earlier.

No luck as of yet with out going retail.

I've had little luck in finding an acme lead screw long enough for my application as I need a roughly 10' piece

I did come across this 12' section on 3/4" -10, 4130 treated
McMaster-Carr

Connecting it to a motor and a encoder my take some work as there isn't any readily available solutions out there.

Any suggestions on how to spec the proper motor needed?

[WSS]

Before Al Gore invented the internet, I would read through any reference book available. I also had a automation store a couple of blocks away which had some really sharp people. Shoring was needed to hold up the floor were the books were stacked. Now my research is done online (Thanks Al!). The problem here is that it is minus the hands on help. But the Zone has lots of sharp people, read through the threads and tie the ends together. You have the desire to do it, so the rest will follow.

Here is a link to a acme screw supplier: Lead Screws, Acme Screws, Acme Lead Screw Assemblies

That is a really long run. You may be better with a 2tpi or something like that. One of the problems with log lead screws is whip. You probably could not spin faster than 200rpm. At 10tpi, it moves pretty slow, where 2tpi is zipping along. You will have to do some on location math to see what will work for you. A belt drive could work. Or a rail/spur gear.

Keep us posted on your progress.

WSS

[Txchevy]

Seems its time to so some searching. Maybe a trip to the local library this weekend.

Thanks for the link. Ya it is quite a long distance. I may actually go with the heat treated 3/4 10tpi for the added rigidity and resistance to sag. One benefit of the application is that it is not a requirement to move fast or change rapidly as it will one make one move per operation and will only be used 10% of the time it running. The main key is for it to be accurate and repeatable and to stay in position as the material rotates.

I've briefly looked over gear and pinion sets for motor engagement but haven't looked into it as mounting would be more complicated. I did see someone use chain for a drive system that looked promising but backlash could be a problem when changing direction. I ll post a CAD drawing after work of the project so things make a bit more sense.

Thanks for the advice,
Cory

[Txchevy]

Heres a quick drawing of what I have planned. The rotary chuck will sit on the mounting plate on top of the linear rails. The structure will be attached to the end of my plasma table. This will allow me to work with tubing up to 19ft in length by using the 10ft travel of the tables gantry as well as the extended movement of the independent movement of the sliding rails the rotary chuck will be mounted to. This design is completely experimental at this point and all in theory in my head for now. I hope to bring it to life with in the next month.

The table is controlled with a 5 axis bladerunner kit from CandCNC.com. From my under standing the most axis's you can run off this type of controller is 5 ( 4 independent and 1 slaved to x or y due to serial connection issues) hence the reason for wanting a standalone control for this independent add on.

Well tell me have I lost my mind or does this idea have some feasibility to it? It seems doable to me although it will be a bit complicated and expensive.

Ive come a crossed this screw from Roton Products. It seems like a mid point between acme screws and ball screws in terms of accuracy and cost. Any thoughts?

3/4 X .500 Right Hand Hi-Lead Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

With this screw(3/4 x .500) if my math is correct I can achieve .02 accuracy, not perfect but much better than I am currently getting by hand operations. 2 rev per in x 100 revs per count. at 200 rpms the system can travel 100ipm From what I've learned any further drop in tpi and the resolution and thus accuracy will begin to suffer greatly.





Well hope that sheds some light on my odd requirements.