New Machine Build- 13X40 Clausing-Colchester 8000 Lathe CNC Conversion

[mecheng10]

I'm in the early stages of converting my 13X40 Clausing-Colchester 8000 lathe to CNC. Has anyone out there done a CNC conversion of this model or a similar one?

-Brian

[Jay Beeson]

Hi Brain--

I just got a 13X40 clausing and am going to convert it to CNC -
Lets keep each other informed on our progress--Jay--

[mecheng10]

It looks like there at least a couple of us working on this at the same time. Thats great! So far I have installed a VFD for the spindle motor and done most of the basic mechanical work to automate the cross axis. The VFD was a necessity for me even before doing the CNC conversion because I needed to be able to run the 5hp 3-phase motor from a single phase supply, and a VFD was the most cost effective, reliable and feature rich way to accomplish this.

I ended up using a Polyspede Speedstar PC1-50 for the spindle VFD. It works pretty well except for the auto deceleration setting and a couple of quirks in the way some of the inputs are designed. I'm not sure why the auto deceleration on this drive doesn't work very well with my lathe. I'm wondering if it is just the enormous inertia of the 8" chuck running in high gear (2500 rpm). I've used this feature on other VFDs for lower inertia loads and they seem to work fine. This one doesn't seem to be able to tell that it is trying to slow the motor down too fast and trips for over-voltage on the DC bus. It seems odd that this happens, because I thought the whole point of using this feature was to let the drive monitor its bus voltage and slow the motor down as fast as it could without doing this very thing.

I've also purchased my servo motors and drives for the motion control; 750W brushless servos from Majestic Machinery. I love them so far. Kirk from Majestic has been a great help in answering my questions, and the drives and motors have proven to be very well made and easy to use from what I have done with them so far.

I decided to try to re-use the lead-screw drive for the cross-axis and directly couple it to the servo rather than convert to ball screws at this point. This is mainly due to cost and space constraints. I don't think there is enough room under the cross slide of my lathe to put in an appropriately sized ball nut and I didn't like the idea of mounting a ball screw on either side of the slide because it would get in the way and would have to be guarded extremely well for safety reasons and to prevent it from getting chips wrapped up in it. The 750W servo seems to have no problem accelerating and running the cross slide at blazing speeds (for my purposes anyway) of 600 ipm even with the extra friction of a lead screw and without the benefit of any type of drive reduction. This greatly simplified my design and was definitely worth the tradeoffs of using what is probably an oversided motor for this application.

I'm still working on the design of my carriage axis motion system. I will use the same 750W servo for this axis and I will use a ball screw for this action mainly because of the larger mass that needs to be moved and because I didn't think there was any other good way to drive the carriage that would results in reasonable backlash. I have the ball screw already but I need to design and make the mounting brackets yet. I will most likely remove the taper attachment that is currently on the lathe (no need for that if it is CNC controlled) and use its mounting points to attach the ball nut to the carriage. Then I will just have to mount the screw bearings and motor to the bed casting and figure out how to cover the screw.

What a great project!

-Brian

[asuratman]

Hello,
What BOB will you use with the 750 watt servo? You will use BOB from Majestic Machinery? Tahnks.

[mecheng10]

I'm using the C11 breakout board from CNC4PC.

-Brian

[BrassBuilder]

Sign me up too! LOL

Here is a posting I just did concerning close to this same topic. I am still in the deciding stages on this:

http://www.cnczone.com/forums/showthread.php?t=90408

Are you going to use steppers or servos for the X and Z? I was thinking a Nema 42 stepper on the Z axis and probably a Nema 34 on the X.
edit: Brian, I reread your posting...I see you are using servos.

Will a Gecko 540 work on this setup?

Thanks for any input.
Mike

[Jay Beeson]

Hi All--

I purchase a Hitachi Phase Inverter to enable the lathe to
run on single phase 220 V--

The Inverter works Very good and I am glad that
I purchased it-- X200 series --

To use this Inverter I had to bypass All of the stock wiring and switches--

I was making some chips to get used to the machine--

I happened to put my hand on the back of the head stock case
right behind the Chuck--
The case was HOT as a fire cracker and I knew something was not right--

So I started taking things apart and found that there is a Electric Brake
that is mounted under a case behind the chuck--

By Bypassing the stock wiring it made the brake be in the ON position--
After figuring out what was going on I removed the electric brake
coils and brake plate -- and put the cover back on--

While I had the transmission case apart I noticed that the only
time the oil was being pumped threw the pipes to the upper bearings
was when I had the lathe spinning over 2000 rpm --

So I blew compressed air threw the transmission oil filler passage--
to see if I could clear out any blockage there might be--

Doing this seemed to help a little but make sure to have the head stock
cover case back in place or you will get to see a gusher of oil
come flying out from the transmission - Not a fun mess to clean up --

Any way the pump still was not pumping oil to where is should have
so I pulled the off the Oil pump pulley and replaced it wit one
about 1/3 the size of the stock pulley ( about 1-1/2 inch dia.)

I had to drill out the center hole on the pulley to 5/8 inch--
Doing this helped A Lot -- the pump is a impeller type and the only
filter screen is on the Oil Return into the oil storage tank--
So I have no idea why the oil flow is not better???

I also called Clausing factory to see if I could get a manual
for the lathe -- The people there were VERY helpful and emailed
me a pdf of the manual for Free -- Sweet--

After looking threw the manual I found out that there is a
small screw on the cross slide that will take ALL of the slop
out of the cross slide--
1/8 of a turn and there is Zero backlash on the cross slide --

This lathe came from a tech school and looks like
it was almost never used ---

The lathe has a Rohm 8 inch 3 jaw chuck on it -
the chuck has about .001 run out on it and I have been doing some
some research on the chuck and I have found 3 different
articles on how to adjust the chuck-- all 3 say different stuff--
The chuck is a D1-4 mount --
I pulled the chuck off last night and cleaned and reinstalled
to see if it made any difference -- Not much--

I also read that using ONLY the the chuck key slot that has the
ZERO with the Arrow pointing to the key slot will be best
for getting the most accurate centering of the 3 jaws--

I messed around with it some and it dose seem to center better
using Only this slot to tighten the chuck up
but I need to test it some more--

This is the second Clausing lathe that I have owned -
and I have to say it is a Great piece of equipment --

A 40 year old Clausing is Much Better than a
New Chinese lathe / junk -- Jay--

[mecheng10]

Jay,

Unless your VFD has a braking resistor, you may want to consider re-installing your brake and using a relay output from the drive in combination with the rectifier from the existing wiring on the lathe to leave the brake engaged while the motor is not powered and disengage it when the motor is on. My VFD does not have a braking resistor and I've found it takes too long for the spindle to wind down in high gears with the 8" chuck. The brake slows it down a lot quicker.

-Brian

[Jay Beeson]

Hi Brian--

My Inverter dose have DC braking built in and
it dose slow the the chuck down perty fast--

The inverter manual says that it uses some type of
DC braking that will slow things down some what
and if I want it to stop even faster
I can hook up resistors to the inverter to stop things More quickly --

After looking threw the lathe manual I see that there is also a second mechanical brake built into the the lathe --
It looks like a pulley disc with a wedge shape brake shoe
that presses into the groove in the pulley --

I did not see this brake while I had the head stock cover off
but I really was not looking for it ether--

There is a mechanical linkage hooked to the
braking arm and I think it may be to adjust the mechanical brake --
Not sure tho--
I have only been able to use the lathe a few hours so I am not
sure that everything what I wrote above is absolutely correct--

It is going to be awhile before I start converting to CNC mode
so I will be adjusting the mechanical brake and adjusting
the braking on the inverter--Jay--