ArcEye wrote: As an interim measure, if it is stepper powered, it is quite simple to define it as a rotary axis and just jog it manually.
tenaja wrote: I have not converted my Compact 5 CNC's to LCNC yet. However, if your tool changer is the same as the ones on mine (in photos I've seen they look the same), then the motor is NOT a nema 17 stepper. As described in your OP, they are typically just a DC gear motor; it is driven one way for a specific time (to pass the pawl), then driven the other way to stall on the pawl. Not likely to be a difficult routine to write, but not as easy as turning a stepper. I'm not trying to discourage you, and maybe your TC has been retrofitted, but I just want you to be aware.
No stepper is mounted on this ATC. My OP was probably confusing. I bought the ATC along with a separate Nema 17 stepper that the eBay Seller had intended to mount and control with Mach 3, but he never got around to it. The ATC was still new in its original Styrofoam enclosure.
Again, I jumped on this ATC because I thought it might be a long time before I got another shot at one in mint condition. But I don't have any business trying to sort how to make it work on my own right now. I have a lot of basics to master first. Just couldn't help but wonder if anyone else had one running with linuxcnc. I also asked in the Yahoo Emco group. No replies so far. I found several threads in which the Emco Compact 5 ATC was discussed, but I've yet to run across a photo of (or even a reference to) an unmodified EMCO C5 PC with a stock ATC mounted.
What I've gathered about how the Emco C5 ATC was designed to work is included below. I'll share it for the sake of anyone else here who might be interested.
The conclusion I took from
this thread in the machsupport.com forum
is that the C5 tool-changer lacks sensors and “is very open loop.”
The forward rotation is timed by a resistor capacitor circuit. The value of the two components determines the time of the forward motion. Then the circuit reverses against the stop at a reduced voltage which is constant. (Posted by Jeff K at
groups.yahoo.com/neo/groups/Emco_cnc_use...ations/messages/4539
)
One of the power supply outputs is 10 Volts. This is an unregulated voltage but it is smoothed by 3x10.000 uF capacitors. This output is used to drive the stepper motors.
In forward motion the turret motor is connected directly to this 10V output. There is no difference in the open voltage or with running motor because of the high power of this output. Five diodes (1N4007) in series are connected parallel to the motor with cathode to the plus and anode to the minus side. This has no effect in forward motion.
In reverse mode however three parallel resistors (100 Ohm, 4 Watt which gives 33 Ohm) are connected in series with the motor. Now the diodes conduct so over the motor will be 5x0.7=3.5 Volt. The internal resistance of the motor determines the current that will flow with this voltage. The motor can take this without getting hot over time.
BTW in my machine the 10 Volts output actually gives 13.5 Volts. This means that over the resistors remains 13.5-3.5=1o Volts. With 33 Ohm this gives 10/33=0.303 Ampere. So the motor reverse current is 303 mA. (Posted by Henk at
groups.yahoo.com/neo/groups/Emco_cnc_use...ations/messages/3161
)
The DNC board has 5 different connectors. X62 is the one for external connections.
When you send a low pulse to pin2, the turret starts rotating until it overruns the next position. Then the DNC board will reverse the turret motor with reduced current. It will keep doing this even after the hitting the lock. That way the turret will be held to the lock with some torque. The length of the pulse is not important. (Posted by Henk at
groups.yahoo.com/neo/groups/Emco_cnc_use...ations/messages/2048
)
C2 is the timing capacitor for the forward movement and it works together with R67 and R68. The other one, C1 is a power supply capacitor.
If the range of the potentiometer R68 is insufficient, you could either replace C2 for a new one or replace R67 by a resistor different value.
If you want to speed up the process, you could do some tuning to the DNC board. In most cases, the turret loses time because it overruns the lock position too much, then returns to the lock position and wait there a while before starting to turn again.
So, the optimum speed for the standard turret is to stop moving forward right after passing a lock position. Then turn backwards until it hits the lock position and stay there for only a short moment before starting in forward direction again. The turning speed of the turret will remain as slow as before, but the overall speed will be improved.
To set the timing for optimum performance you should know that only the forward pulse is variable (to be set with potentiometer R68). So you should make the reverse pulse variable also. You can do this by replacing resistor R69 with a resistor and a potentiometer. Now you can set reverse timing with this new potentiometer. When adjusting reverse time make sure that the turret hits the lock position every pass when turning backwards. Otherwise it could get out of sync after a few passes.
The value for the new resistor and potentiometer depends a little on the value that Emco used in your board and the condition of the old capacitors. The length of the reverse pulse can be calculated by (R69*C3)/1000.
If on your board R69 and C3 are 330K and 10 microF the reverse pulse will be 3.3 seconds, which is very safe but also slows down the process.
If you replace R69 with a 150K resistor and a 0 to 100K potentiometer you can set the reverse pulse from anything between 1.5 and 2.5 seconds.
The forward pulse is determined by R67, R68 and C2. The length of the pulse is ((R67+R68)*C2)/1000.
Emco used different values in different DNC boards. When on your DNC board R67 resistor is 22K and R68 potentiometer is 0 to 10K and C2 capacitor is 100 microF you can set the forward pulse from 2.2 to 3.2 seconds. If necessary you can replace R67 with a different value to shift these limits.
Remember that the turning speed of the turret is not always the same, depending on temperature and other circumstances. This will cause problems if you set timing too critical. (Posted by Henk at
www.machsupport.com/forum/index.php/topi...ations/messages/1633
)
I found a fairly high resolution scan of the wiring diagram for a C5 CNC. It was uploaded in three parts, which I stitched back together in Photoshop, making a 5.24 MB jpg, which converted to a 4.75 MB pdf file. I’d be pleased to put those up here, but given the size thought I should probably ask first.
tenaja wrote: I have seen some photos of broken pawls; replacing it with something thicker seems reasonable.
Me too, but my first thought was to wonder whether the original design reflected some purpose (e.g., to act as a fail-safe mechanism).
Below is a photo of the EC5 CNC DNC board.
image missing http://i1308.photobucket.com/albums/s620/ElBudro/EMCO/DNC-board_zpsbf5eef8c.jpg
