Well, I've read and reread Mr. Richards' post several times and I've pondered the control systems for a while. I hate to admit it but I think this is over my head. As most of you are aware, I'm certainly no electronics whiz. I know I volunteered to try to figure this out but the crap I'm likely to come up with will most likely be worthless and only set us back. Sorry Gerald, Mike, and the rest of you guys. :(

box on gantry
 

Gerald, this is what I was thinking of doing on the gantry, as in post #70.
Does this look like it could work to you? Proximity sensors and relays are NO, so that when hot they are all in a closed state. All sheilding tied to box with star washers and terminal rings, also grounded one side only in control box.

I think two of the seven conductor will need to be dedicated to the voltage supply to the box (a +12v and a -12v). Which will leave 5 avaliable. I am only using two of the "three pushbutton type" stations so I think I will be okay with just the 7 conductor cable only.

This brings a 12vdc supply onboard the Mechmate gantry for anything else like laser pointers or lighting, ect. under the gantry.

Sorry my drawing res is kinda bad I can't figure out how to save as a photo from my CAD without pasting to clipboard first and it kills the res.

When you do a screen capture from CAD, go for GIF format rather than JPG.

Will look at details later . . .

Schematic for installation:
prox_layout.pdf

I received a message from Ed, but have also fielded a few queries from others on how the Proximity relays really work and how to wire them to the PMDX using only 1 input.

1 - refer to the pdf schematic link above. You can also see pictures of the installation in post 247 of my this thread.

Steps (and JR will keep me honest - I am nowhere near my machine right now to check things)

1 - wire according to schematic.
2 - set your mach 3 settings in the Ports and Pins box to input 15.(or your setting. For example. Map x - home to 15, map y - home to 15, map z - home to 15.
3 - I'll check my configs in the morning to see if I have it active hi or active low....I can't remember right now.


Mapping all the homes to the same pin number will allow mach 3 to cycle through the homing sequence and set the z, then y, then x.

In the Mach screen you push the long vertical bar (near the DRO readouts) to "refall" and it will run this sequence.

That is all. It works well and all the time.

thanks sean, I have mine working now.

There were some issues though. I am using pin 12. Doesn't matter you can use any of the unused pins on J5 as long as you enter that pin in the ports and pins. Remember also (i didn't at first) to assign A to home to the same pin #. After grinding gears for a second I remembered my slave motor.

I had to reverse the homing direction by changing to home neg for X,Y and A in the homing window of mach 3. Z doesn't have to change.

Active low boxes stay unchecked so they be active high.

Only issue I have left is the travel to home speed is slow all the time not just the last inch.

got the travel speed set now for 80% that is better

Ed

Good progress.

That travel will always be slow as when the machine is homing, it does not know where the the last inch is, it only knows to look for a limit switch somewhere in that direction. Its best to jog close to the limits and then "refall".

If I remember correctly, the big iron machines like Multicam will not allow you to jog until it is referenced, but Mach3 allows it.

Alan,
Your very correct. If you lost the home on my big multicam, you could not jog the machine except at "seek" speed. Which is the same slow speed it looks for the home switch. A real bummer if you lost home in the parked gantry 10 feet away from home. It took 10 minutes to rehome the machine!

Ed....great to hear you got it all worked out.

SEan

Here's a thought. Could a proximity switch be used to change the jog (feed) speed. If so, theoretically speaking, one could use two proximity switches set a few inches apart. When the first one is detected it will slow down the jog rate so you would not over run the second one when homing.

I'm only using Mach 3 on the test bench, not on my machine, so I'm not fully aware of the day to day sequence of events that you use when starting up your machines; however, on my machine, I manually jog the X and the Y axes to a point about 2 inches from the proximity sensors, and then run my homing routine. The manual jog, even from opposite ends of the machine, takes only a few seconds. I move the Z-axis to a point about 1/2-inch above the contact plate before running the Z-Zero routine.

Mike,
I do the same thing. It only takes a few seconds to get close, then run the routine. Works like a champ - every day.

Sean

I just checked, it takes 16 sec. to home 101" (full table length) on my machine.

Dead?
 

I really liked where everyone was going with a "professional" control box mounted on the y-Car. "Richards" - would it be possible to get a design based on the last few posts?

Yes, but you need to included expansion, please.

It looks like we're making this much too difficult. Look at the 7408 chip and the 7430 chip to see how many inputs can be combined to make one official input. Typically, all the limit switches can be connected to the same input. In the same manner, all of the proximity switches can be connected to one input. All that is normally needed is one "glue" chip like the 7408 or the 7430 to handle everything.

Two weeks ago, I had to deliver a very simple CNC type device to the Maker Faire in San Mateo, California. It used three N/O switches and one proximity switch in its circuit. The whole circuit cost less than $10, including a proto board, 4N25 opto-isolators and wiring.

Sometimes, it seems like we try to find the most difficult way to solve a simple problem. All of the suggestions on this thread would work, but most are overly complex.

Keep It Simple Stupid (KISS).

I have not seen any better than Mr. Richards.

Gerald's circut drawing works good , that is how I did mine. I have power now at the gantry I used a jack like in the photo below and wired as in my drawing earlier in this thread. I had it all correct first try just didn't know enough about Mach 3 to know to hit the ref all home tab:o


If you use the microswitches you could maybe build the circut for less than $10, if you don't include the cost of the enclosure box. I think the concern was on the microswiches was durability and longivity in the dusty enviornment? The advantage of capacitive proximity sensors that some are using from factorymation is that they are sealed from dust and moisture and although nothing is foolproof, probably will be more durable than the microswitches. At least that is what I gathered from reading this thread from the beginning and some of the personal pages.

I may have mislead when I gave the $10 figure. The $10 is for the glue chip and the proto board. It does not include the limit switches/proximity sensors. The proximity sensors that I use cost about $75 each (with cable). The 22mm push-button switches that I normally use cost about $15 each.

Hi Sean,
After reading a few post on this proximity limits, I’m still very curious to see how you type of installation fits on the Y car.
I’ve seen your pics from your thread #247 and David’s new ones, but David uses Diell BIG 18mm in a different holder approach.
If not to much asking, could you post a few detail pics out of your Y car proxy installation ?
Thanks, Robert ;)

Robert,

Couldn't find your personal thread ...

Here are a couple of pictures of my Y car Prox. What are you wondering about?

That darn high gloss paint. :)
Attachment 1438

Attachment 1439

Robert - the spec'ed proxy is 12mm for M1 18 022, so the 6mm isn't too much larger. I purchased the 18mm units due to cost - $10. If you maintain the same center line (1" from the back edge of the angle), using a different sensor shouldn't be an issue. I think the bigger issue is the total length of the sensor, it's distance needed to sense the rail and the height of the cable (right angle or straight).

I'd recommend waiting to build the stops until you have your gantry and y-car done and working. I'd then weld the end-stops onto the rail after you have mounted the stopper lips (M118022). Just in case....

Greg -

Can you tell me what that bracket bolted to the y-car next to the proxy sensor is for?

Thanks,
david

Pics of the proximity mounts that I promised last night.

Attachment 1565
y axis

Attachment 1566
x axis


Attachment 1567
z - axis

A question about the proxy sensor holes. On the drawings Gerald indicates 20mm. My biggest drill is 18mm and I don't own a reamer. Can I leave it at 18mm ?

18mm "should" work for most cable connector ends. I happen to use a modular *make to suit your needs* style of QD connector for proximities. It's body needs a 19mm hole to clear. If you have the standard off the shelf factory made connector, the hole may work for you. If you want an easy larger hole, you can pick up a Greenlee (TM) or similar variable stepped drill bit that will makes holes from 1/4" up to 7/8" - (7mm to 24 mm ) The bit is around the 40 dollar range, but Harbor Freight has them for around 20 dollars US.

...and yes, the y chain bracket is placed just off centerline on the y car. You can see it just above the sensor in the photo. The mamba parts were not release yet when I built my MM. Thus, I had to improvise my E chain bracket and support from scratch and guidance from Gerald across the pond on clearances and location suggestions.

Have a great day.
Sean

I think Kobus is talking about the 20mm proxy target holes in drawing 10 10 246

Kobus,

How big around are your proximity sensors? If they are smaller than 18mm you should be fine.

JR,
Thanks...typing before coffee dangerous! 18mm fine for target hole as long as your centermark and drilling is accurate. The 12mm sensors I used work fine on 13mm holes in other applications.

I have not bought the proxy sensors yet. So when it comes to that I must just make sure that they are smaller than the sensor target hole (18mm)

I wonder what actual size the holes have to be to break? It would seem that sensor type, distance from hole, metal used, etc all have a part to play. Does anyone in the automation world have some input on this?

I did find this:

http://web1.automationdirect.com/sta...k910series.pdf

Sorry if I am interrupting, but look at this one,seems to be a nice package for the limits and affordable too.http://cnc4pc.com/images/C16R1_A.jpg
http://cnc4pc.com/images/C16R1_D.jpg

http://www.cnc4pc.com/Store/osc/prod...roducts_id=183

what say? is it comparable enough to the proximity switches?

The opto devices will work, BUT, as always there may be a problem.

As you can see, the device is built in a "U" shape. On one side of the "U" is the infared LED, on the other side of the "U" is the detector. In the face of the "U", is usually found a hole (1/8", 3mm). That hole is small enough that dust and debris can easily clog it. Normally, whenever the light beam is interrupted, whether by clogging or by sensing the target, the machine would stop.

With the amount of heavy dust that a CNC router makes, it would be very difficult to use that kind of detector.

I'm sure you could make these work, though be aware of:

• These are optical based sensors and thus can be triggered by dust or chips
• Requires redesign of the X and Y stops. Also, due to their size, they would have to be very percise
• The current design with proxys allows for tripping if the X or Y come off the rails anywhere between to ends (they do this by looking for the rail and then tripping when they don't see it). To do this with these sensors, it would require a vertical rail along the entire length of X and Y.
• If the gantry or car jumped off the rails, it would likely break the sensors
• The cords (6' each) are too short and would have to be lengthened
• There will be a much higher possiblity of accidental tripping due to the low voltage of the sensors and lack of shielding cables
• The kit includes 6 sensors, the MechMate only requires 3 (or four if you want a sensor on both sides of X)
• It is possible to use industrial proxy sensors with relays for about the same price. I purchased mine from automation-overstock.com, the proxys were $10 each ($40 total) and the quick disconnect 15ft cables were $5.50 each ($22 total). Add to that about $10 in relays.

I should have take a picture of my machine today.
The "snow plow" effect was working well. I had inches of buildup on the end of the machine and proximities worked the whole time.

Optical scares me in this application.

Sean

I believe you are correct. In the end I used four relays I pulled from junk yard cars. Total cost: $2.

Found some interesting reading about the capacitive proximity switches. I kind of understand now why the dust doesn't affect them.



http://www.kirbyrisk.com/allen-bradl...ximit/2922.pdf

Thanks all for your inputs. anywayz this thread does point to wiring of the proximity switches to the mechmate control box dosnt it........wait let me look back.

how, thank's a lot for this reading, i understand a lot of thing's now i start with this.

a question to Gerald, how did you fix the proximity target in 20mm hole after adjustement.

thank's

hi mickey, I haven't seen any posts lately by gerald he must still be on vacation.
If you epoxy them it would be a permenant set, would it be better to use a spot of silicone? That stuff holds well but yet can be removed later if needed, and it shouldn't take much at all to hold those into place.

I am not sure if you would ever need to remove them if they are in the correct spot but for some reason it seems IMHO not to epoxy or JB weld them into place.

ok ED thank's, i go with epoxy it's very strong and if i make litle spot i can remove it if i whant to make change.