Success! Mini Machining Center under Mach3 control - Video link

[Dan13]

Spunk,

As you say, you power the LED and the transistor gives you the output signal, which goes into Mach3 like Hood said. for any given sensor the manufacturer would supply a typical wiring diagram. You'll need to use resistors in line with the transistor and the LED to limit the current to the nominal. The resistor values (or the equivalent current) would usually be specified be the manufacturer.

The output signal from the transistor would usually be too low requiring some kind of an amplifier before it's fed into Mach. A simple solution would be using a schmitt trigger for that purpose.

Daniel

[Hood]

I use an Optek OPB917B it has everything you need except for a limiting resistor for the LED, 220 Ohm is what I use when powering from  5V.

Hood

[simpson36]

Photointeruptors come in a lot of different flavors, some costing under US$ 1.00
Some have lenses over the LED and some do not. Some have wires attached and some have only bare pins. Some have polycarb housings and some use much cheaper plastic. Some are rated for vibration and some not . .  etc. etc.

In order, I have had lots of false signals from stray light and dust with the un-lensed parts, pins break off very easily on the parts with bare pins sticking out (in fairness, these are meant to be mounted on a PCB, not have wires hanging off them), plastic housings that dissolve seemingly in anything except distilled water, and finally, some just litterally fall apart. The 4th axis was the 'acid test' that killed a number of these parts, some of which were actually working fine as homing switches.

After the above experience with various recommended products, I have settled on the following rather expensive unit US$ 7.25 approx. It has wire leads, lenses covering the optics (to keep out dust and swarf), an indestructible polycarbonate housing that can bend a .060 aluminum tab that gets out of line and hits it, and can tolerate vibration.

It is a Honeywell model HOA 1887-012

I now have these on all of my machine axis and also on the 4th axis and they will be used on the commercial verison of the 4th axis as well. You simply need a 100 to 150 ohm resistor on the 5V that feeds the LED (red wire) You can use 5V or up to 30V for the trigger side. For example if  you use 5V from a BOB, you can daisy chain 3 of these and still have 3.5V return to the BOB. I have a little "Remote LED driver board" to boost signals, but it has not been necessary to use with these Honeywell interrupters and the Homann designs BOB.

[Peralta]

You have done a great job, and I hope if you have time you show all your works. I think it's been a long time when you finish this study. I am very interested in what you have done.

[simpson36]

Thanks!

The X2 featured here is now sold and gone. My new mill is scratch built completely from aluminum and is slightly larger than an X3. There are still some details to finish up and the high speed pulleys are not done yet, but I have just started cutting metal with it. I will be posting photos and videos soon. Unfortunately I do not have time to do a build thread on CNCzone or anything like that.

Here is the latest video which simply demonstrates the newly finished pneumatic spindle lock on the 4th axis. I now have a larger disk and an new belt guard (not shown in the vid)  extends to cover the new disk.

http://www.youtube.com/watch?v=glYDe94hxb0

[Flying Scot]

Hi Simpson

I am also building an indexer based on your design.
I think I may be using too small a servo (150watt) so was intending to use a brake or locking system.
I don't intend using heavy cuts but most of the parts will be 5" aluminium.
How does you brake work is it just by putting pressure on the outside of the belt?

Regards

Arthur

[simpson36]

It is a disk brake. The disk is .062" 2024 aluminum and is intended only for holding and not for stopping. The servo motor provides deceleration. The mechanical disk caliper is from a 'pocket bike'.

The lock was 'added on' and not part of the original design, so it could be better integrated, but other than having the disk extend past the frame (which requires an elaborate belt guard), everything worked out satisfactorily.

The servo drive is a 'Dugong' model from CNCdrive and they are modifying the firmware for me so that the drive's max amps can be set back a fixed amount under software control. This will coordinated with the lock event. The purpose of this is to prevent the motor from overheating if it disagrees with the location of the lock event. Keeping the amps below the motor's continuous rating will prevent possible overheating and damage to the motor.

[simpson36]

Here are a couple pics of the new mill showing the spindle lock. In this case, I may want to use the brake for stopping the spindle, so it is a thicker steel part.





Next photo shows nearly fial assembly. Belt guards nor installed yet, etc.

[Flying Scot]

Thanks for the pictures.

I can see the brake clearly now.

You mention the problem of the servo dithering while at rest. If was only going to use the 4th axis as an indexer would I be better using a stepper motor instead?

Regards

Arthur

[Hood]

Quality job there Simpson 

Thanks for the pictures.

I can see the brake clearly now.

You mention the problem of the servo dithering while at rest. If was only going to use the 4th axis as an indexer would I be better using a stepper motor instead?

Regards

Arthur

You could use a stepper but also with a servo you could have a macro so that when you apply the brake you disable the drive a split second later, that would solve any tripping problems.
Hood