Lab-Volt lathe

[ajm291]

Hello,

I'm converting a Lab-Volt 5500 (heavy) cnc lathe over to acorn.

I replaced the original processor with the acorn and relay board.

I replaced the original encoder with one from automation direct.

I reused everything else with the addition of a SI-5 isolation board to the KBIC spindle drive.

Everything is working from a basic functionality perspective. I have movement on Z, X and can control the spindle. My E-Stop switch is working too.

I need some help on the axis configuration.

I'm using CNC12 Lathe v4.20.1 software

Let's start by focusing on the Z axis:

The Stepper drive is set to "Half Step" which I assume means: 400 steps/rev

The Stepper motor has a 21 tooth timing pulley on its shaft coupled via a timing belt to a 25 tooth timing pulley on the ballscrew.

The ballscrew seems to have a 1.25" lead, (measured with a dial indicator while manually turning the ballscrew 1 revolution)

Based on this info, what is the formula (or value) I should enter in the "Overall turns ratio" field?

Also - how can I check this via MDI? I read TB036, but nothing happens when I issue a G1 command. It seems like the SW just hangs so I hit esc to cancel this command.

Here are some pics of this conversion.

[cnc_smith]

MDI defaults to G99 feed per revolution. If the spindle is not running there is no movement. This might be your problem if you did not have a G98 in your command line. For checking travel on the lathe incremental move for Z is W and for X is U. In your MDI command for Z use a G98 G1 W-1.00 F2. The machine will move 1 inch towards the chuck at 2 inches per minute. For X use a G98 G1 U-1.00 F2. X will move towards the center of the spindle. In diameter mode the DRO will change 1 inch. The indicator move distance for X will be .500.

[ajm291]

MDI defaults to G99 feed per revolution. If the spindle is not running there is no movement. This might be your problem if you did not have a G98 in your command line. For checking travel on the lathe incremental move for Z is W and for X is U. In your MDI command for Z use a G98 G1 W-1.00 F2. The machine will move 1 inch towards the chuck at 2 inches per minute. For X use a G98 G1 U-1.00 F2. X will move towards the center of the spindle. In diameter mode the DRO will change 1 inch. The indicator move distance for X will be .500.

Thanks! Those commands are working.

[martyscncgarage]

Dana is saying you won't have movement with out the spindle running. Otherwise you have to go into MDI and issue a G98 command first, then it should move without the spindle running.

Counts per rev should be 400, set both Z and X to that.
Make sure your axis travels are correct Z+ toward tailstock, Z- toward headstock. X- toward spindle center line, X+ away from spindle centerline

Do you have a long travel dial indicator? If so, gently chuck it up in the spindle and make sure the other end press against the carriage.
Jog the carriage in the Z- direction until it just starts to make the indicator move. Zero the indicator and set part zero there.
Then call G1 Z- move. Say for example you called G98 G1Z-1F10
Notate how far the Z axis actually moved. Say it moved 1.5"
Divide the move called 1.0 by the actual move, 1.5 which is .66666666, now multiply that value by the value currently in the overall turns ratio field. Let's say its currently 5. The new value would be 3.33333333 enter that, save the settings, exit CNC12 and start again.

Becareful when you do X, if you call a 1" move, remember, the carriage will only move .5" (Diameter mode typical) so adjust your calculations accordingly.

I have attached the method in the All in One DC installation manual for Coarse and Fine DRO adjustment as reference. (We are starting to work on an Acorn Installation Manual) I also did a video on this:

[ajm291]

Thanks Marty. the X axis warning was good to know. I commanded a move of 1.00", but only got 0.5" of movement on the dial indicator.

The overall turns ratio value seems to like 0.96" the best. I'm using a dial indicator on a magnetic stand to measure the carriage movement for both Z and X axis to get me close. Jogging positive and negative directions seems to be repeatable. I'll watch the video and read up on the material you posted.

Here's a pic of the machine. I mounted that piece of aluminium extrusion for the monitor arm. I have the intel nuc PC mounted to the monitor and monitor arm via a bracket. Seems to work really well. I made that E-stop set-up too so I could eliminate the original labvolt front panel controls.

Stoked so far with the conversion!!

[martyscncgarage]

Nice! Thanks for sharing your project...