Bridgeport Interact 1 mk2 retrofit

04 Jan 2022 20:01 #230793 by NitroExpress577
Good day Members

I have been apart of this community for a few years but this is my first post.

I'm about to throw gasoline on this machine and set it on fire.

I will appreciate any assistance or guidance on my problem

A bit of background on the machine...

I bought this Bridgeport Interact 1 mk2 in 2016 with the idea of retrofitting it with a more modern controller. Being in dark South Africa -we are limited to knowledgeable people and skilled retrofit professionals to contact for any assistance. I got in contact with a friend who is in the same trade as I am (gunmaker) which offered to retrofit my machine with Linuxcnc and mesa cards. Over the years he has retrofitted a number of machines successfully.

We kept the original brushed servos and DC spindle Motor/control card. He recommended the 5i20 , 7i29 for the analog servos and a 7i33ta for the spindle control.

Once all connected, we constantly fried the 7i29 cards - no fuses were blown - random IC's were burnt on the boards. Mesa was very helpful in 2017 and replaced all of my cards at no charge. Again I kept on toasting 7i29 boards - most of the time they were only idling when they popped.  I decided to stuff the machine in a corner and left it till I could figure out a way forward.

In 2019 a friend in the USA sent me a link to DMM in Canada - I contacted them and listed my Mesa Hardware to see if we can keep some of the original Cards and try the AC servo route

They made a recommendation which retained my 5i20 and 7i33ta cards as it is compatible with their Dyn4 Drive and 750W Servo motor.

I proceeded to wire all of the Mesa cards to their hardware as per their wiring diagrams, bench tested the motors using their DMM software and set the drives to Analog input as well as Speed mode (per their instructions)

I performed the DMM Auto tune as per their instructions and connected it to Linuxcnc - started PID tuning as per the Linuxcnc PID tuning (servo) tutorial and got stuck again. When under linuxcnc control/command they perform erratic and very poor, change the input back to windows and using their DMM testing software  - the servo/drives performed flawless and smoothly.

I contacted DMM and they advised met to revert the auto tune settings back to the factory settings - this made things a lot worse in Linuxcnc even after trying to PID tune them.

I only have the x axis connected  to  the machine at the moment to limit any possible interference from other drives ( if there was any)

One thing that I simply do not understand is when I move the X axis in the negative direction it is smooth - if I then move the axis in the positive direction it's jerky and eventually runs away which then triggers a following error.

I have read through this forum where someone had a similar problem - apparently in his .ini and .hal file backlash was enabled . I searched through my files but could not find any activated backlash setting.

Where do I start troubleshooting ?



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05 Jan 2022 15:15 - 05 Jan 2022 15:20 #230871 by Todd Zuercher
I don't know of anyone successfully using DMM drives with analog command inputs with Linuxcnc. There seems to be a delay issue with the encoder translation to quadrature output in the drive. The best solution seems to be to use them with open loop step/dir commands, then they seem to perform fine.
(Someone please correct me if I'm wrong.)

If you want to continue with these with analog velocity commands, your best solution might be to add another true quadrature encoder feedback to use as the position feedback to Linuxcnc, either from linear scales or rotary encoders, so you don't have to rely on the DMM's magnetic encoder's translation.
Last edit: 05 Jan 2022 15:20 by Todd Zuercher.
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05 Jan 2022 17:40 #230880 by tommylight
I got the same impression from reading (a lot) on the net, i also got the impression they do not bother reading feedback and tend to bounce accountability in all directions.
I did write a few lines a while back and got no feedback in any way, shape or form, so just in case here it is again:
Mail 3 of those drives/motors (preferably different types) to Andy, PCW and me,with no strings attached and no NDA.
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05 Jan 2022 19:40 #230887 by OT-CNC
I have an older set of dmm servos on a lathe. I could not get them to work as a closed loop step/dir system with linuxcnc most likely due to the encoder delay and me not knowing how to configure linuxcnc correctly at that time. They do do work fine for me with conventional step/dir input. 
I would suggest, if you just want to get the mill up and running with minimal headaches to just run it in open loop mode. Check with PCW on what stepper board he recommends for those drives. Double check your electrical on that machine in case you got something odd going on with power. You should not be damaging boards if you followed the manuals and wired correctly. All the mesa hardware I have installed so far has been solid. Unless I connected something wrong which has happened. 
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06 Jan 2022 19:34 #230978 by NitroExpress577
Good day Members

Thank you for all the feedback

I rechecked all of my wiring and started to suspect the DMM drive, but before i swapped the drive i first checked the 5v supply from the ribbon cable to the 7i33TA - it measured 4.7v. Not sure if it is too low but proceeded to change the jumper to Aux and wired in 5v as per Mesa manual .

Still had the same problem

I swapped out the DMM drive with a new drive still sealed in the box - did the auto tuning in the DMM software and had the same problem as before.

Only other hardware failure could be the servo motor itself - i did not immediately suspect the 7i33ta card as on the previous setup it was only used to control the Bridgeport spindle drive. (but we will get back to this later)

Due to all my motors already mounted to the machine it was difficult to swapped motors - so i only swapped the 220v  and encoder wires from the y-axis onto the Axis 0 on the mesa 7i33ta

Guess what - same problem. y-axis is acting up.

I immediately knew there was something wrong with the 7i33ta card - moved the x-axis wires to the the axis 1 (y-axis allocation in PncConfig) slots on the mesa card and the DMM x-axis servo motor and drive behaved and operated smoothly - 5min of pid tuning and have them running at 3000mm/min without any following error or erratic behavior.

Made a copy of my .ini file as to not overwrite my PID settings in PncConfig. Changed the Axis allocation with PncConfig - changed some minor wiring and all of the axis are up and running

Now to get back to the 7i33ta 

Upon receiving the retrofitted machine in 2016 - from the first startup i noticed the spindle creeping clockwise when idling - i contacted my friend who did the work/setup and he adviced me the there might be noise issue with the spindle cable running along the 3 phase cable . We rerouted the cable but still had the creep. The spindle was wired to the the axis-0 ports on the 7i33ta, the same ports that caused all of the current problems on the x-axis.

I never tested the spindle on the old setup as we could not get the machine to even move - i suspect that he might have damaged the card when he retrofitted my machine. I will get in touch with mesa and see if the still sell the 7i33ta cards

Hopefully by tomorrow i can start the make some chips

Once again thanks for all the input.

I will keep everyone updated


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06 Jan 2022 21:20 #230988 by tommylight
I am very glad you got it working, also glad it is not DMM .

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08 Jan 2022 17:45 #231142 by NitroExpress577
Good afternoon Members

I'm sorry to report - but no chips

After installing and tuning the drives my Mesa 7i33TA started acting up.

At this point i do not have a clue where to look anymore

If i switch on all the Axis Drives and motor and enable them in linuxcnc - everything is stable. I can jog Y axis with no problems, i Can Jog Z axis without any problems but the moment i Jog the X axis the Z axis goes crazy and runs away. 

File Attachment:

File Name: Ralph.ini
File Size:3 KB

File Attachment:

File Name: Ralph.hal
File Size:11 KB

I have check the wiring - check the shielding etc. the moment i disconnect the Z axis Servo and Drive from the 7i33ta  - the X axis works.

It seems there is something wrong with the Axis 0 and Axis 2 Terminals on the Mesa 7i33ta

I have attached my hal and ini file - maybe something is wrong with my PncConf

I'm out of options at this point

Thank you for the assistance

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08 Jan 2022 18:14 #231147 by tommylight
Almost always that will be wiring/grounding/shielding issue.
In your case, check the motor wiring and shielding and ferite filters.
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08 Jan 2022 20:51 #231169 by NitroExpress577
Thanks will have a look at it again tomrrow

I forgot to mention one problem i had - a few days ago after starting up the machine and testing the x -axis . i ever so often had a tripped touch probe error when jogging the x axis. I do not have any probes installed nor configured in the PncConfig. I figured that it must be the ribbon cable not supplying enough 5v. After I wired in Aux 5v the random touch probe tripping stopped. When i got the touch probe error i also had a Axis2 limit switch triggered error - no Axis 2 (Z Axis was wired in that time)

7i37 is used for all of the home/limit estop etc



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