Hercus PC160 Lathe Project

[Commotion]

Hi, after the sucessful retrofit of my Hercus DTM320 with the acorn and the continual problems with the original control system in the PC160 Lathe i decided to remove all the original control gear and start the retrofit of the acorn.

The original control system is identical to what the DTM320 had in it but it was all custom built for hercus and i cannot find any documentation on it what so ever.

This is all the original control gear i have pulled out. it looks like it had some singleboard computer type thing with a laptop memory module on it and a similar stack-able layout like the beaglebone black/green. i cant find any numbers or markings on it to identify it so i dont know what it is but it ran windows XP and had a proprietary control board attached to it. its a shame its problematic as there has been so much effort been put into designing and building all this componentry.

The spindle motor is a large version of the axis motors, a 60V DC servo motor. i will replace this with the 0.25kW AC motor i had running in the DTM320 before upgrading to a 0.55kW motor.

The axis servos are DC motors and i joined a hercus group on FB to learn more about them and find a suitable servo drive to run the existing motors to save on purchasing additional motors. i was told that the HEDS encoders on the servos were no good and to use the motors i would have to replace the encoders with AMT102 encoders and use a Gecko 320X drive. That added up to too much cost to me so i ordered a leadshine DCS810V2 drive and decided to take a gamble on running the drive motors as is with the original encoders. reading the specs on the encoders and drives i couldnt see why is wouldnt work. after messing about and finding the first encoder cable i tried was faulty i had a spare DC servo motor running of the DCS810 drive. i then pulled the caps off the end of the z axis servo and discovered that the servos in the PC160 had HEDL encoders which were differential line driver type. luckily the leadshine drive works with both single ended and differential where the gecko 320x only takes open ended encoders so i wired it up and it held position. i connected it up to the z axis on my DTM320 since it was setup for the same ppr already and BAM it worked.

I have ordered the spindle encoder, a second DCS810, 48v power supply and 24v/5v power supply, & VFD. im going to borrow a mates acorn which he hasnt got around to fitting yet so i can get it up and running sooner and will buy him another one when he gets around to needing it.

I am looking forward to getting familiar with the CNC12 lathe interface. Is there a post processor for fusion 360 which works straigtht away?

I will keep updating the build but it should be much quicker than the DTM320 build.

[martyscncgarage]

Looking forward to watching your progress. Keep in mind, you may have to "Tune" the PID settings for the DC Brush servos, I assume there is a software utility that came with your drives?

Marty

[Commotion]

I have the software for tuning the drive. It’s similar to the ac servo drive except some of the functions u can change in the software on the ac drive like read high/low for enable, direction etc u have to pull the cover and change a jumper or dip switch. The closed loop gain and damping functions and selecting the ppr is done in the software.

[Commotion]

Well I got a version 3 acorn board mounted up. I have the 24/5v power supply for the acorn and step/dir signals and also the 48v power supply for the servo drives. I tested it out with the one servo drive connected to the z axis. I found the carriage makes an ordinary noise when rapiding back and forth. I also took a stab as the turns ratio as I had no idea what it was. I guessed 2mm as I had a feeling it would be acme screw like the x axis and I was correct however I discovered when determining this that although the pitch may have been 2mm the helix wasn’t even. On the indicator if I moved it 1mm it would read 0.98 mm, move it one more mm and it would read 2.0mm, move it one more mm and it would read 2.98mm and would keep repeating like this for the extent of the indicator. That may have been helping to induce the rattle in the carriage. My z axis on the mill also has an acme thread and I am spinning it faster than it was intended and it also make a cyclic rattle noise so it could just be the way acme threads are.

Anyway I stripped it down to see how I could fit a ball screw. I designed up a bracket and decided to have a go at making it on the dtm320. I think it turned out well and what’s more it fits in the frame and looks like it’s going to work. I ordered a 12mm ball screw and nut and will turn down the journals on the ball screw to replicate the acme shaft so it fits in all the existing bearing blocks.

I’m still waiting on second servo drive, vfd and spindle encoder. I have a new belt for spindle motor and have machine up a motor mounting bracket but made a mistake so need to adjust and make another one.

Some pics:

[Commotion]

Small update: i found out what that single board PC was which was originally fitted to the PC160. Its an advantech PCM-3370. unfortunately too slow to run the acorn as that would have been cool since its so small.

http://download.advantech.com/ProductFi ... t_ed.1.pdf

I had a bracket laser cut and mounted the ac motor to the frame. The longer belt i bought for it was too wide so i popped the guide rings off the pulley and machined up some new ones which allows the pulley to run the wider belt and pressed them on.

I also mounted up the quick change tool post i was given with the lathe.

Cabinet is pretty much layed out minus the missing parts I am still waiting to arrive. i had notification that something will be arriving tomorrow. Will be either VFD, encoder or servo drive. either way i should be able to make some more progress tomorrow night. i hate waiting.

[martyscncgarage]

Looks good so far.
Remember to follow the G320X instructions (Geckodrive also has a video I believe) on setting up your drives and motors.
Post video/pictures of your progress.
Be sure to use the DB25 port on Acorn

[Commotion]

here is a picture of a little something else i have started to flesh out. i have been thinking about building a mill from scratch even before discovering the acorn and getting the hercus mill has allowed me to get my head around the control side of things but after the lathe is properly up and running i will start building this:

Its a baby horizontal mill with 150 table. i have been recently working on the way cover designs so im free to adjust the structure to suit. once thats locked down i will order the plates to be laser cut and start fabricating it then machining it. i have the ball rails for the table but would need to order the rails for the vertical axis.

[martyscncgarage]

here is a picture of a little something else i have started to flesh out. i have been thinking about building a mill from scratch even before discovering the acorn and getting the hercus mill has allowed me to get my head around the control side of things but after the lathe is properly up and running i will start building this:

HORIZONTAL MILL.PNG

Its a baby horizontal mill with 150 table. i have been recently working on the way cover designs so im free to adjust the structure to suit. once thats locked down i will order the plates to be laser cut and start fabricating it then machining it. i have the ball rails for the table but would need to order the rails for the vertical axis.

Interesting. Start a new build thread if and when you get going on it.

[Commotion]

The VFD i ordered finally arrived so i was playing around bench testing it like i did with the one for the mill. i couldnt find the same VFD as i used on the mill so i took a gamble and tried this KCLY brand drive. i could find very little on the internet about them and was hoping like heck it came with a manual as i couldnt find any diagrams or manuals online.

According to the manual its a vector control drive which i have no idea what that means but i set it to that option as opposed to frequency control. all i know is im running the same 0.30KW motor that i had in the mill before upgrading and i could hardly spin it above 80Hz in the mill with the other VFD and even then the rpm would wander. in the lathe all connected up with the belt it spins straight up to 120Hz and holds the rpm steady. i even tried it on 180Hz and it would get it up there but couldn't hold it so i set it back to 120Hz. so far im pretty impressed by the drive. Luckily it did come with a very thick and well written manual and it turns out there are a huge number of parameters that can be set and adjusted of which about 1% i understand what they do. Next step is to mount it in the cabinet and connect it up to the acorn.

I am having some issues with the servo drives throwing a fault after running a sample program for a bit. On the pawn program it normally last until the finishing operation then the drives fault. unfortunately as much as i try i cant get the tuning software to communicate with the drives. i can plug the cable into my ACS drives and they talk fine so it musnt be my cable or comm port settings. i have contacted the seller to see if they have any contacts for tech support. i just want to see what the error is so i can look at addressing it.

[martyscncgarage]

Sensorless vector control on a VFD attempts to keep torque the same at all RPM ranges.

Re: your drives/motors. Certainly sounds like a motor tuning problem to me. Especially if you get further into the program before faulting.
Is it happening when taking the finishing pass on the pawn?
Did you calculate your max feed rate of your machine?
How did you come up with the max rate?
You have to calculate how fast the motor can turn given the voltage fed to it. Let's say for simplicity's same your DC brush servo spins 1500rpm at max voltage of 120vdc. You have a ballscrews at 5tpi with a pulley reduction of 2:1. So it takes 10 revolutions of the motor to turn the screw 1 inch. Divide 1500rpm by 10 and you get 150. Add a safety margin of .85 or 150*.85=127.50 inches per minute for your max feed rate setting.

Just something to check.
Marty