Advice Needed, Converting a Boxford VMC 190

Hi All, I am helping my Father convert a Boxford VMC 190 to use with Mach3.

I am wondering if anyone can help with a few questions I have about this as I am fairly new to the world of CNC.

So far we have replaced most of the electronics with a Pokeys USB, CNC addon and their 2.5A driver boards. We have kept the standard power supply, spindle controller etc. We can now get all
axis moving using the jog functions in mach3 etc. Spindle control is currently using a 10K pot but will convert this to mach control at some point.

Does anyone know how we should be setting up the following?

1 - Steps per mm? - Currently we have the default of 2000 but havent tried to measure this yet. Does anyone know the correct value for this mill based on the pitch of the leadscrews?

2 - Microstepping? - The drivers support all kinds of microstepping but is there a recommended setting to start with?

3 - Motor velocity - Some of the forums say you should hear when this is right but is there a good place to start when using this mill with the standard steppers?

4 - Limit/Home switches - The Boxford has what appear to be inductive sensors on each axis. Are these suitable for use as home/limti sensors and does anyone have any experience with them?

For info CNC control is done using the Pokeys56U with their CNC Addon and drivers. This has a plugin to work in mach3 but seems to work well.

Any info or advice would be greatly appreciated.
Cheers
Martin

Hi Martin,

I cannot help you or answer your questions as I am going to be in a similar position soon.

I have basically bought a VMC190 m/c. All the drives run well in manual, it seems a shame to rip out all the insides and replace them with new boards. I have all the old software with the machine. I am assuming that I can add a RS232 serial socket to my PC so I can communicate with the mill. But what benefits does Mach3 have over the original software? Also, can you get other software that would allow people to run the machine in it's original configuration? I have a auto tool changer on my machine which requires air to run, it all runs at the moment in manual mode.

How did you decide upon the CNC control boards that you bought? Was it through advice on the forum?

I ask because if I have to go ahead with conversion I was looking at the HobbyCNC EZ or Pro chopper Driver board kit, I can see it works off a paralellel port but understand you can just buy a convertor (ie parallel to USB).

Regards

Steven

Hi Steven,

We didn't have the original software and Mach3 seemed to be the popular choice and has a large community to support it etc. I may also give LinuxCNC a try at some point but thought that Mach3 would be a good starting point. We were also reluctant to ripout all the boards but not being able to interface to them made them pretty much no use to us. Also I had read that modern drivers would be an improvement over the ST ones it used. We ripped out almost all the control boards and left the Spindle controller, main power transformer rectifier, cap etc and the Choke for the spindle. We then rewired everything to get a good understanding of what wire did what etc.

Pokeys was chosen as I had a laptop spare that didn't have a parallel port and I had read all-sorts about timings being off with laptops and external converters. I started looking for external Pulse generators that would work with Mach3 and Pokeys was mentioned in a couple of posts. It was a bit of a gamble bit its been pretty easy to get that side of it setup. We use the USB version but there is an Ethernet version too. From what I understand the Pokeys plugin attaches to the Mach3 core so all the steps are counted in the pokeys itself when its running. You can use the pokeys direct with the drivers but we also opted for the CNC addon which adds a couple of relays and also expands the features of the pulse engine to allow more axis etc. It also makes connecting to their stepper drivers easier.

So far we haven't interfaced with the spindle controller directly or with the existing home switches but I plan to take a look at that next. We setup the Stop button to trigger the E-Stop in Mach3. We have since had the machine cutting some parts in Ali which it does a treat although we did have a couple of issues with needing the swap the stepper wires for the Z axis to get the axis going in the right direction (0 at top).
We also need to tune the steps/mm but we roughly did this by clamping a digital caliper in the vice and jogging the tool and adjusting the values. Its a bit crude but it got us to within a few points of a mm which is fine for testing etc.

Would be interesting to see what you go with and how it fares.

Cheers
Martin

1) This depends on 2) combined with pitch of screws, any gearing between motor and screw, and if you're setting up in metric or imperial.

Essentially, most common stepper motors are 200 steps per revolution, so multiply that by your answer to 2) to get your steps per motor revolution. If there is gearing between the motor and screw, you then need to add that into your equation to get number of steps per turn of the screw. You then need to divide the steps per screw turn, by the pitch of your screw to get your steps per unit. Your unit will be either 1mm for metric, or 1 inch for imperial.
i.e. 200 x 8 = 1600 steps per motor rev. I'm going to assume you're motors will be direct connected to the screws, so you still have 1600 steps per screw turn.
Assuming metric and a 4mm pitch screw, you then divide the 1600 by 4mm to get 400 steps per unit.

2) 8 is usually best the compromise. Any more doesn't gain you any accuracy with a stepper system, and less can make things a bit jerky at low speeds, although it may be needed if your step pulse isn't high enough to get reasonable speeds.

3) How fast is your bit of string? Generic guidance is keep upping the figures until things start stalling, then back of a bit to provide some saftey margin.

4) Depends on how many wires the sensors have. 3 or 4 wire, are easily useable provided thier voltage range is useable. 2 wire, bin them and buy new, as they'll be NAMUR output which interfaces will cost you more than new sensors.

Thanks m_c,


I am currently set to 16 on the drivers and it runs fine but will change this to 8 and see how it goes.

The X and Y motors are directly connected but the Z has a toothed belt, It seems to be a 1:1 ration so should be fine. I think i need to measure the pitch of the screws then I can calculate the steps as you described.

The sensors are the 3 wire type and are 10-36vdc so I will get one hooked up to some power and see what the output wire does when it reaches home.

If you get enough speed at 16 microsteps, then there's not really any need to change it. One thing to consider, is microsteps should never be relied on for accuracy, as the stepper position can only be guaranteed to the nearest step. While microstepping, both coils are proportionally energised, with the rotor essentially held between two magnetic fields, so can spring/float (there probably is a better word, but I'm tired!) depending on load.

Sensers will most likely be NPN with an open collector. Are there any numbers on them?
If there is, try googling it to see if there are any datasheets for them, which will confirm what they are.

This post mentions a wiring diagram for the Boxford 190. No reponse to a PM and the user hasn't posted for quite a while.

Interested if someone can supply a wiring diagram to aid conversion of my 190 (Lenze controller type)

Hi Martin,

Sorry for delay in response. I have bought myself a smoothstepper board and just ordered a Breakout board. Looking at the insides of the machine I understand I can retain the steppers and the stepper drivers but need to disconnect the driver control boards. There is one driver control board for X & Y axis and one for the Z axis. I am assuming I can remove these boards and rewire back to my breakout board so I can connect upto my smoothstepper. Looking at the wiring for the auto tool changer it seems to be indenpendant from the rest of the machine so I am hoping to retain this but I shall see.

I am assuming the photos below show the axis driver boards, photo on right is the 3rd axis or Z axis, photo on left shows the 1 & 2nd axis with the stepper drivers board above. If I am incorrect please correct me now.



Attachment 13140 Attachment 13141


Steve

Comparing my 190 to the Boxford 160 lathe that uses a similar stepper driver board as the 190, and a similar MW Controls processor board underneath (in the case of the 160 the steppers are assigned to the x axis, the z axis, and the turret for the lathe toolpost toolchanger rather than X Y Z for the 190).

The Bradford instruments board is possibly also a limit switch interface, the ribbon cable is labelled PL1 fast serial link at its connection to the main processor board and contains very similar components to the main processor board. Comparing the photos of my machine (without a toolchanger) to yours I have a total of 5 wires and a loop on the orange connector, you only appear to have two. Where you have two white wires I have an orange and purple connected to CL5 and CL6 respectively on CONN1 on the stepper board. Suspect these are the clock and direction for one axis.

The additional wiring I have, a 3 core small diameter cable eventually goes through a conduit that leads, I think, to the motor head. That PCB also carries three LEDs L1,L2, L3 attention, limit plus and limit minus respectively.
I suspect these are may be the Z limits, the wiring looks the same as the x and y limits and yours does not have a z limit switch or it does it is implemented in a different way.

Below is a photo of the connector between the processor and the stepper board, at the stepper board end, with the two wires on the end that go to the standalone bradford instruments board

The underside of the stepper board has a factory fitted 'bodge wire' to connect CL6 to pin 6 (step) on the GS-D200S stepper drive on the Z axis. Given that the stepper board is 'universal' there might be some confusion about the allocation of the pins and the silk screen.

The terminal assignments for the 190 should, I think, be as follows:

xd = x direction
xc = x clock
zd = y direction
zc = y clock
cl5 = z direction
cl6 = z clock



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Quote:

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Originally Posted by m100

The Bradford instruments board is possibly also a limit switch interface, the ribbon cable is labelled PL1 fast serial link at its connection to the main processor board and contains very similar components to the main processor board.

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I have the original manual for both the 160 TCL and the 190 VMC, the manual for the VMC says the small board is the 3rd axis microprocessor board.

Do you have yours running with original software?

PS> I may have the wiring diagram for the lenze board

Thanks m_c
All the explanation was awesome :)

Hi M100,

Sorry for the delay with this. Can I ask have you managed to get the Boxford to run using Mach3 without upgrading all the stepper drives? I did look at this but it looks a bit messy trying to tap into the original stepper drives. I have managed to get my machine running by just bypassing the main stepper drive board and installing my own stepper drives in the cabinet. I have disconnected the power from the original board. The Bradford board I believe is something to do with the tool change system (Z axis), although I think there is a sensor on the spindle for possibly height and angle to aid tool changing which I belive could be performed using a macro in mach3 (apparently).

On running my machine the stepper drives keep missing steps (so a circle becomes a spiral), I think this is mainly due to them being really cheap ones off fleebay. I am thinking of upgrading the stepper drives and totaly ripping out the original boards and starting again.

Happy tinkering.

To those of you who have been trying to contact me to get the wiring diagrams. I do still have them but cannot reply to your private messages as your accounts are set to not receive replies!
I do not frequent these forums regularly so you will have to contact me offline. I can be reached on simon (at) byte (hyphen) sized (dot) com

Hi Simon, if you can send me the wiring Diagram of the 190, than this will help me a lot, with the modifications of my new 165HMC. It seems, it has the same controller Board, but for the 4th axe it use the same external board double (but why, it seems, the board can control 2 stepperdrivers) , like in the 190. Today I tried to make a single step with a separate momentswitch, but unfortunately without success. The driver for the tool turret seems the same as from the 125 and 160TCL. Only a DC supply with not many regulations, that stops after each 45°, with a simple NC switch. I have 4 relays and a bigger one for the switch on of the control unit. One is for the doorswitch, the second one switch the spindle motor on or off, i can regulate the controller with the switch on the front control panel. But I don't know, what the 2 other do.
Ok in the meantime I know what are the other relays.
the middle switches the spindle Motor on and the last (near the On relay) changes the direction. The complete machine runs, without any issues in Tipmode.
of the spindle.

Hi Everyone,

I am trying to convert a Boxford VMC 190 using aCNC-USB box from Eding. I found that the output voltages to the motor drives from the boxford processor (xd, xc, zd, zc, cl5 and cl6) and the Eding CNC-USB box to be similar. Since the eding software has some setup functions it is also possible to tweak these voltage vales to match the Boxford processors voltage. While I still haven't checked the spindle voltage levels, My idea is to simply replace the boxford processors pins with the Eding CNC-USB box pins since the signals they both output seem to match. However I am new to this and any advice would be great. By the way do any of you guys have the hardware wiring schematics of the Boxford VMC 190?

Hi Subash,

I am not aware of Edin or CNC-USB. For mine I ended up using a Ethernet Smoothstepper and a PMDX-126 Breakout board. I removed the main processing board but retained the board with e stepper drives on and tapped directly into that. With this I have obviously lost my tool change facility and the ability to use the control panel on the machine but I can atleast run the machine as a CNC machine including spindle.

I need to learn more about how to setup the I/O on the breakout board, maybe then I can work out how to integrate the emergency stop etc.

But overall I believe the best way to actually upgrade this machine is to do what others have done and that is to rip out the whole interior and upgrade the lot. This will unfortunately cost a bit of money if you want Gecko drives etc.

Regards

Steven

Hi Subash,

If you would like to upgrade to Geckodrives then you might be pleased to know we have a special offer giving 30% off basket total. You can find the Geckodrives on our site here

Please use discount code "ccxmas2016". It is only valid once so please make sure you have everything you need in your basket before checking out.

As a member of this forum you can also get 15% discount on all Geckodrives by using discount code "mycncuk" on any future purchases.

Regards
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