Light Machine Corp. Benchman XTr (retrofit)

14 Nov 2013 17:18 #40814 by MacGalempsy
Last year, I got the bug to put down the XBOX360 and pickup a hobby that would get my butt off the couch. After reading a few articles about 3D printing, my mind was made up that it would be great opportunity to bring excitement to the boring graveyard shift. Dreams of designing and making custom pieces distracted me from anything else. Everything was print this, print that. Surprisingly, the loving girlfriend (now wife) was cool with the idea. About the first 2 months after the first parts order, the printer was up and running. Another 2 months, the results were finally decent enough to be able to model an item in Google sketchup, convert it to STL, and print the object in ABS plastic. No matter how much I try, print results are typically mediocre. It did not take long to aspire to getting a CNC mill, at that time mainly to make better printer parts. So, the search for the mill started back in about May 2013. The main place looked at was EBAY, there is a lot of stuff that goes through the market and its not like CNC mills are everyday items to find on Craigslist, or the newspaper. They had Big machines, small machines, etc... but nothing seemed to jump out and scream "THIS IS THE ONE!" After a summer of slow searching (due to vacations and the busyness of getting married), the search was rekindled around late August-early September. By late September,a BenchmanXT with 4th AXIS and ATC came to market, but no controller card to tie it all together. A call to Light Machine Corp revealed the ISA controller card was no longer available and that they wanted $14-17K to retrofit the controller. The guy Issac over there sent over a readily available quickstart manual, but never replied to further questions or phone calls. It seems as thought the company MO is be a douche bag to perspective clients. The manual did slip up and mention the missing ISA card is a NEXTMOVE card circa 1999. Quick searches revealed similar cards were still priced over $1000, but nothing would guaranty the card was the right one. After chatting with the guys on #LinuxCNC, they convinced me that the Mesa 5i25/7i77 combo was the way to go. So, I decided to pull the trigger on the machine, and figure it out along the way; praying for help along the way ;) The machine is now in my possession, and this is where the saga begins....

This archive is written by a NOOB for NOOBs, with hopes that the real pros can help with tips and clarity, while at the same time reducing the mystery that encircles retrofitting a CNC mill with a Mesa 5i25/7i77 combo. This article will begin with a breakdown of the machine components, then move onto wiring and controller programming. Hopefully, when it is all finished the machine will be fully operational and ready for the second half of the process, making stuff.

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14 Nov 2013 17:58 #40817 by MacGalempsy
Breakdown of the components:

The BenchmanXT is an enclosed vertical milling center that comes in a variety of configurations (see link). My configuration is the one with a 7.5k rpm spindle, 20 tool ATC, and rotary 4th Axis. I will list the components by system, then link make the appropriate links the corresponding data sheets. Data sheets were the key to determining the wiring layout. Especially on the encoder wiring where there were 5 tan lines coming to the mainboard. One of the best tools for researching old stuff is The Way Back Machine, which is an archive of just about every website build ever. Looking for the impossible, try searching WAY BACK MACHINE in your favorite search engine.

Virgin Wiring

XYZ DC Servo System
Servo Amplifiers - Copley Controls Model: 800-469 (looks like 4 4122 on a single plate)
Servo Motors: X/Y - Litton DC brush servos LW30 Z- Litton DC brush servo LW50 (now owned by MOOG)
X/Y/Z Encoders - Tanakawa TS-5412
Powersupply - 230v AC =>48V dc 15A toroidal transformer/rectifier/choke combo
z-axis brake -

A DC Servo System
SMW 5C-RT rotory table
DC servo - Magmotor Corporation c33-H-075X
Encoder - DRC TK731
AC Spindle System
Allen Bradley Ultra 100 series digital drive DDM-019
Allen Bradley TL-series AC Servo w/ encoder

ATC System
4 Pneumatic valves - SY3120-5L0Z
Pneumatic Actuator and 2 endstops - lifts/drops ATC on tool change
Pneumatic Actuator and 2 endstops - slides ATC in/out from under spindle
Pneumatic actuator and 2 endstops - lifts/drops tool in and out of collet
Pneumatic actuator and 1 hall sensor - open/close collet
carousel motor and gear - HPC (model???) 24V
carousel encoder - BEI H20EA-37-F28-SS-500
PSI gauge for 90PSI trigger
external buttons
-platter up/down
-index platter
-drawbar clamp/unclamp

cycle start
cycle stop

Safety features
endstops on X/Y/Z min/max limits
front door lock/switch Moeller AT-02-24DMT-zbz

Coolant sump and pump - not sure which model, need to open it up.

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14 Nov 2013 18:21 #40820 by MacGalempsy
Running through the wiring took the better part of 5 weeks, but was very well worth it. For the minimum, I was able to get a label maker and go to town. A handy gridded notebook made transferring notes to the computer much easier, and is a good reference when trying to remember the slightest details. A good notebook will have dated entries, and be reviewed prior to beginning a day of cataloging.

Before removing connections, attempt to power up the device to determine if everything works. It will save you a lot of time to narrow down the list of components that are functioning properly before trying to connect them to the board. Perhaps a machine was for sale is because it is broken, figure first what is broken so you can order replacement parts and not have to wait on the mail.

1) individually label each wire coming from the MAIN and ATC controller boards. Document where they plug into the board (mainly in case we had to put it back together).

2) describe and photograph each plug and individual wires. try to be as systematic with descriptions, listing gauge, color, connected device, port descriptions of corresponding devices, etc.. The more thorough you are now, the less time you will have to go back to the wiring harness when it comes to making connections.

3) when reviewing corresponding devices, write down the manufacturer name, brand, part numbers, date of manufacture, etc... this will help when searching for technical datasheets.

4) after completing the catalog process, remove the obsolete mainboard and atc controller, its time to move on to the next step.

An example: for the mainboard, I started at the top left and labeled that harness M1, I know it has 3 wires that are red, white and black and it goes to servo amplifier #1.

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14 Nov 2013 18:44 #40821 by MacGalempsy
Powering the main breakers

The main power this system is 230V 20A. I was able to make a jumper from a 3-prong laundry dryer cord and a L6-20P plug from Home Depot. The jumper plugs into garage until a dedicated line can be run from the breaker box. Ultimately, no jumpers should be used when the machine is fully operational.

The power system is divided across 10 breaker, with 2 breakers per set (5 sets total).
1 Main - 15A - black and white - power in from the 230V wall connection and to PSU1
2 Op Station - 4A - out to PSU2
3 Servos - 3A - power to the DC Servo tranformer-rectifier-choke PSU system
4 AUX - 3A - to 9V transformer for the halogen light (unused at the moment because halogen bulb is replaced by 24v 7W LED.)
5 Spindle - 10A - connected to RELAY1 for power to the inverter, when key switch is on, there is power to the relay, thus triggering the drive power.

The most difficult part, and nerve racking was working the DC servo loop to make sure it was wired correctly. By making a call to the guys at Toriod, they gave me the wiring specifics and we got it setup right the first time (without any trips to the hospital!) Result - 70V DC 15A whoop!

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15 Nov 2013 21:10 #40840 by andypugh
Thanks for doing this detailed write-up.

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07 Mar 2015 18:44 #56531 by MacGalempsy
Well, it has been a while since the last post, so it is time for more of the write up. Since the machine is almost finished, I will review the VFD then move on to some other parts when there is more time to do so.

The VFD in this Benchman XT is an Allen-Bradley Ultra 100 Series Drive.
Link: Manual

The ULTRA software took a few tries to find the right edition, but the biggest pain was finding a computer with windows95 to pull the printout that is attached to this post. After that was done, I later came upon a touchpad that is mentioned in the manual on ebay for $30.

The interesting things here are 1) the spindle can be toggled between torque and personal EEPROM mode, which I think works out to velocity mode.
Input1 on the PDF is set for Drive Mode Select: Active = Torque Mode, Inactive = Personal EEPROM
Output1 on the PDF is set for Disabling Fault Active = Fault

There are several additional Digital inputs and outputs, but they are not used in this configuration. After I get the last few necessary electronic items to get the spindle going, I can elaborate upon request.

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08 Sep 2015 01:49 #62212 by dynamyte24
I have a Benchman XT, however it is the model with a 45K rpm spindle and 12 tool ATC using ISO 10 toolholders.

My machine is functional using the original software, on an old Dell Optiplex WIN NT4 computer driving the NextMove card.
But I want to have an alternative should the PC or the NextMove (which sits in an ISA slot) go belly up in the future,
so I'm gonna be watching this thread.


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07 Oct 2015 07:32 #63527 by steve_a
Hey! I have just acquired a Benchman XT for a high school robotics club. I bought it knowing it was not working and I just got it in. I plan to attempt to do a repair but if that doesn't work, I will do a conversion. The unit I got is a basic 5000 RPM but with a 20 tool changer. I'm not sure if it has flood but I will look at it closer later to see if that is installed. If not, it looks like an easy installation so I am pretty excited. I worked with an old EMCO and did a conversion and added a few cool things with Linux; a Z touch off and X and Y axis zero. The experience taught me that a solid base is necessary for CNC. This is relevant because we have a Chinese built SIEG X3 type mill that we converted to CNC. It works OK but the basic unit was not build for the precision of CNC so the results have always been iffy. I chose the Benchman because it is US build. I was also looking at German and I would have looked closely at Japanese but I've soured on Chinese quality. Anyway, the unit supposedly has a bad Automatic Tool Changer card, but I doubt that is the real issue. I looked at a picture of a board someone had posted and it is just a glorified interface card. That's actually a bad thing because it made me suspect the motion control pca, which is a very hard to find and pricey unit. If that is the problem than a conversion is a certainty.
Can anyone tell me if they can initialize the motion control board if the unit is disconnected from the computer? I still need to have a 230V socket installed so I have not done more then inspect the unit.
I will post my progress and relay what I learn. I have 9 tool holders and information on where to acquire more if anyone is interested. If I decide to do a conversion, I will offer the remaining control boards cheap! I also look forward to input from anyone else who is attempting to revamp their Benchman. It is an elegant looking machine and looks amazingly like a Haas!
Today was move in day and I unpacked everything so I hope to have pictures and more information in the near future.


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13 Oct 2015 22:46 #63754 by MacGalempsy
Steve, Congrats on the new toy. It is taking a while for me to complete this, but a lot of that is the steep learning curve. Instead of picking up the LMC collet holders, the decision was made to use Tormach compatible collet holders from DARKON ( and make new ATC holders. It was a lot cheaper to go this way than buying the original tool holders which were more than $100US each. With a 20 tool changer, that's $2K just to get going. The Darkons were $500US for 20, and the aluminum stock was about $40. I am in the last stages of getting the 4th axis, spindle and ATC up and running. Once it is all done, I cannot wait to put the back panel up, push it against the wall, and get to cutting stuff!

I am curious if you guys running the factory software have been able to come across PID values for the X/Y/Z axes?

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13 Oct 2015 22:51 #63755 by MacGalempsy
Steve, if you need troubleshooting help, hit me up in #linuxcnc. I am not the best, but am pretty sure we have the same machine.

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