Centroid Community CNC Support Forum

Hello!

I got hold of an EMCO PC TURN 55 that I wanted to upgrade with an Acorn. I had much success last time with a milling machine so time for a lathe!

I've gathered some information around here now to get started and I have some sort of plan and what needs to get done in no particular order.

1. New VFD

2. Use the original stepper driver board.
>Here I need to use a differential line driver after the DB25 step/dir output because of the original driver board inputs.

3. Use the original homing sensors. There is one PNP proximity sensor and one micro switch for each axis. The proximity switch is on the ballscrew timing pulley so I guess it's thought of like a servo index signal.
>Here I put the proximity sensor behind an opto relay to make it look like a NPN switch which in turn will be in series with the micro switch. Have
not tested it yet.

4. Get the turret going with the original turret drive board (just a relay and some resistors) and a macro. I tested it manually and it works just fine! This motor is 24V forward and 12V backwards/holding. I've seen some having 12V motors on their PC TURN 55. Might be replacement motors or different models. Anyways..
Edit: Works! See third post.

5. Install an encoder for the spindle. This will be 1:1 with timing belt.
Edit: Some ideas in third post.


So while waiting for some parts to arrive I started with the Turret. I went through ACORN_Counter_Based_Home_Sensor_Turret_Instructions_rev4, checked the parameters again after power cycling etc. Put M18 in MIDI and got back Wating for memory #51 (M101). Shouldn't the turret start looking for the index?

Pictured here is just the main board with a DB25 break out board with inputs from the turret sensors. Next is the relay board with the turret forward output.


I'm using the S14986-ACORN_rev4_EMCO_PC55_2_SENSOR_TURRET_LATHE_STANDARD_CONNECTIONS except I will take step/dir from the DB25 and use two inputs to home the axis.

Hello ARTMEK,

Looking at your report, i noticed you do not have any outputs or inputs assigned for "ToolTurretSyncBit" (For homeing), "ToolTurretCounter", and the Output "RotateToolTurret".

please read over the installation instructions for the Counter Based Lathe ATC carefully.

If you do all steps correctly, then when you command M18 to home the turret, it should then rotate until it sees the ToolTurretSyncBit input.

I noticed the report provided is quite a few days old. Can provide us a fresh report by pressing Utility (F7) > Create Report (F7) and save the .zip and upload the new one here with your updated settings.

Thank you Chris,
I was so sure I did it right first time so started looking elsewhere..

I did as you suggested and now it works fine!
I think I did something sketchy when trying to make a custom profile and load it in the wizard.

#850 - 0.5
#851 - 0.6
This gives me fast tool changes and seems to repeat good. I've done initializing and indexed the turret a few rounds and looks just fine.
I don't understand why it says T0102, T0203 or T0503 and not just T01, T02 etc.. Guess I have to watch some lathe tutorial
Edit: got it now. Tool number and tool offset.

With that done I started with a holder for the spindel encoder pictured below. 3D printed block and laser cut nylon. I need to make a hole in the lathe enclosure because the encoder builds a bit much with the cable gland. I will share files here when it works.

Back again with some updates:

1. Got the VFD working, no problem there but I need to get back to it when installing the encoder and aim for rigid tapping. I get the spindle up to 3k rpm and can stop in about 1sec.

2. Got the original steppers drivers up and running 3000mm/min with enough torque. I ditched the differential boards I ordered, could not get them to work and I really tried. Might be too low voltage or current for the differential line reciever on the emco board. Ended up going directly from the Acorn DB25 to the differential line reciever output pins on the emco board. Worked just fine.

3. Home limit situation is under development. Planning to use, FirstaxishomeOK and SecondaxishomeOK or HomeAll. The switches are more or less in the middle of the axis movement so I will add soft limits to that.

Is there a way to make the homing macro back off from the switch and go slower a second time to get better accuracy? That could already be the case..

Back again with some updates:

3. Got the homing working and added M18 in the end of the homing macro to have the turret initialize also. What does the L1 in the homing macro mean?

It's on page 251 in the mill operators manual. Stop homing after homing switch contact and skip looking for the index pulse. Used for step/direction drives without encoder index pulses.

Centroid closed loop homing will hit the home switch, back off to clear the home switch and then seek the marker pulse on the encoder and then set home at that position. this provides very accurate homing as the cnc control is not actually using the switch to locate and set the home position. it is using the switch to get in the ballpark (within one revolution of the axis motor) and then uses the marker pulse on the axis motor encoder to actually set the home position.. very accurate. With Acorn, most step and direction drives (with a few exceptions) don't have marker pulse output so the L1 command is telling CNC12 to ignore looking for the marker pulse and set home position as soon as the switch is cleared. in this case home position repeatability is as only as good as the home switch is. which is usually no big deal for most users as they reset WCS each day/job anyways. (For Acorn lathe users however it is nice to have very accurate homing so the center line of the chuck can be maintained day to day which eliminates having to reset the X axis WCS each time the machine is powered off but most just reset it day to day, job to job because of the expense and low availability of drives that output marker pulse)

Hello again!

Thanks for the explanation. I think Emco used the proximity switch on the ballscrew as an index pulse. Seems to give me good accuracy on both axis when homing slow like 100mm/min.

I got it up and running a pawn after some hiccups with G99 and tool offsets. Still haven't got the timing belts for the encoder delivered..

Found a MK2 behind the chuck which will come in handy later for a collet chuck of some kind.

Problem now is that I don't get the MPG (CWP-4) going. When I press the MPG button on the VCP the button does not turn on. I have the coordinates displayed and changing on the MPG but thats it.