Thread: Bridgeport Power Feed 6F & 8F Upgrade/Enhancement -- Soliciting Input

This is my first post here -- if this is inappropriate or belongs in another forum, mods please let me know. DISCLAIMER: I represent only myself and Pumpkin, not any other mentioned companies (e.g. Bridgeport, Minarik).

PART I.

Last year as part of my company's (Pumpkin) buildout of a modest prototyping shop we purchased a '77 Bridgeport Series 1 2J mill with a Sony Millman DRO and a Bridgeport 6F power feed (x-axis). The Millman worked, the 6F did not (though it was mechanically in excellent condition).

As part of a moderate overhaul of the entire machine, I tore down the 6F unit, both mechanically and electrically. This is a very nice piece of machinery from the mechanical perspective -- no point in getting rid of it if it can be saved. I refreshed the motor w/ new bearings & seals, and a thorough cleaning, and repainted the whole unit. Then, I decided to upgrade its electricals to a more modern setup, because i) it wasn't working and ii) the front panel had seen better days.

Quite a bit of work / thinking has gone into this so far, so I will cut to the chase and show you where we are:

N.B. This is a real picture of the first-generation prototype unit and some things (especially the control layout) will change in the final unit. But overall, it's quite representative. The motor is off to the side so that we can test it separately.

My company is considering turning this effort into a Upgrade/Enhancement Kit for BP 6F & 8F owners, and I'd like to hereby solicit comments to glean how much interest there is in Pumpkin offering such a product.

First, some economic realities (taken from eBay and various reputable replacement parts vendors):

• A fully rebuilt 6F/8F unit with the original parts (I presume this means the SAECO controller board) is e.g. available on eBay for $1600.
• A Servo Model 150 replacement is around $600. You would remove the 6F or 8F altogether and swap the model 150 in ...
• Replacement limit switches (two per unit, a common point of failure) are ca. $30 each.
• Repaired circuit boards are around $180-$230 each, either repaired or new.
• A replacement potentiometer (for the speed setting) is $37 each.
• The rapid-traverse button is $38 each.
• The front panel is $30 each.
• I dunno how much a motor rebuild / replacement is ... ours just needed a disassembly and cleaning, and I chose to replace all the bearings and seals as well.

In examining all of the 6F's electronics (i.e. the front panel, its switch gear, the fwd/rev selector switches, and the drive electronics), I observed several areas where I felt the unit would be improved if newer components were used. The current upgrade has:

1. All IP66-rated (i.e., "splash resistant") switchgear and fuse holders on the front panel. All of the switches combined cost less than the old RT switch.
2. A much larger rapid traverse (RT) button, with substantially greater travel, all contributing to a more positive feel when engaging the RT.
3. A more ergonomic potentiometer.
4. An LED power illuminator is incorporated into the DPDT power switch (the original had a neon lamp, I think).
5. Dual front-panel fuses for 115V or 230V operation.
6. A thicker front panel (0.090" vs. 0.060") to better withstand flexing.
7. (IMO) Nicer / more legible / more "international" pictograms of the various functions.
8. Very-high reliability sealed roller-tip rocker fwd/rev switches (Pumpkin uses the same switch family in the satellites it builds). At less than $10 each.
9. A three-dimensional cam that positively actuates the fwd/rev switches for long life and positive actuation.
10. Some other electrical features I won't go into right now, that are linked to the use of Minarik and compatible drives.
11. The ability to accept SCR- and PWM-type drives in the industry-standard MM footprint (e.g. Minarik MM23001C (SCR), Minarik MMXL10-D240AC (PWM), and others).
12. The ability to run a compatible drive at 115VAC or 230VAC.
13. Higher-quality internal wiring.

I also sourced a high-qualiy Teflon-based valve seal to aid in reducing and/or eliminating the oil leakage problem that occurs when gearbox oil leaks down the selector shaft into the fwd/rev switch area.

None of this upgrade requires any permanent modifications to the 6F or 8F itself -- it's all a parts swap. Apart from the custom parts that Pumpkin makes (front panel, fwd/rev switch mount, fwd/rev switch cam and drive mount/heatsink), all of the parts are readily available direct from various sources, in onesy-quantities, should a replacement ever be required. Also, if you don't like the default color scheme (green RT button and blue power switch), you can choose from a wealth of other colors (white, red, green, yellow or blue).



PART II.

So, why might this upgrade be of interest?

1. The front panel upgrade is nice to have because the switchgear is of high quality and has improved layout and ergonomics.
   
2. The fwd/rev switch and the Teflon seal improve a weak point of the original design, namely that oil would leak down and affect the fwd/rev switches.
   
3. The biggest improvement, however, is the ability to use more modern drive electronics, with attendant possibly better performance and reliability (and low prices). For example, the original SAECO unit had adjustable min speed, max speed, IR comp and current limit controls. The Minarik drives have these settings, as well as adjustable accel and decel controls. The Minarik MM23001C is $107 directly from Minarik, has an unconditional 12-month warranty, and has a 60:1 speed range. Their MM-footprint PWM drives have a 100:1 speed range, though they are more expensive.

PART III.

So, at this point we will be finishing up the development of this unit, running some final tests on our mill and comparing it to another, working, original 6F unit, and offering this upgrade kit for sale in some form or another. And that is where I would like to solicit some comments from the community. I'm interested in:

1. Feedback re the front panel.
   
2. Which option is of most interest? Option 1) A kit that contained only the Pumpkin-built components, and you'd have to buy all the other components (mainly switchgear and drive) on your own, using a Bill of Materials from Pumpkin, and wire it all together yourself; Option 2) A kit that contained all of the components, pre-wired, and all you'd do is remove your old faceplate and drive electronics and replace it with the new one; Option 3) A full-service offering where you send the head unit (maybe even complete with the motor), and we retrofit everything.
   
3. Feedback and questions re any other issues of interest.
   
4. Opinions on whether the 6F & 8F as upgraded above are competitive with e.g. a Servo power feed.

Frankly, option 1) above is likely to be most affordable, and most profitable for Pumpkin as well. Given that Pumpkin is in California, with high labor and indirect costs, the other two options might be too expensive for most potential customers. So I'd love to get a feel for how much people would be willing to spend to upgrade and enhance their 6Fs and 8Fs.

Thanks for listening,

--Andrew

And here's a pic of the inside of the gearbox of the same unit -- now you know why the unit hasn't been filled with oil yet

You can see the Teflon valve-stem seal in place, and that we applied a sealing epoxy to the circumference of where the selector shaft guide enters the bottom of the main casting.

I also refinished the selector shaft to ensure a good match to the valve stem seal.

The horizontal spring that holds the dogs away from the hypoid gear when the selector is in the central (off) position is not present. It connects between the drilled pin visible just below the red knob on the left, and the downward-pointing pin with a keeper groove on the right. The dogs are just behind the selector shaft.

The selector shaft's radial travel is limited by a spring-loaded plunger that lives in the top middle of the cover with the oil level glass in it ... you can see the detents that the plunger goes into at the top of the selector shaft, still inside the gearbox housing.

--Andrew

Truly amazing work. I am in awe. Makes me wish I had a 6f on my Bridgeport. Good luck with the venture. Given the current demand and supply for 6F and 8F parts and complete units, I imagine that your version of the 6/8F will go very far.
Steve

Andrew,

I like what you have done there. Nice work!

I've got an 8F and learned from others about making 2 "weep" holes in the bottom of the electronic enclosure. Taking a the bottom cover off and checking for leaks goes a long way to improving the longevity.

IMO, both the 6F and 8F feeds are superior to Servos and far better than the imports. Your price must reflect that. You have to be priced cheaper than a Servo and competative to the imports. I think that you need a modified Option 1. All parts need to be included in your kit along with good instructions. Very few would have the time to go to 6 different vendors and ordering parts. We want everything at once so we can put the drive together over a weekend.

Just my $0.02
JR

Ah, great, some feedback!

(One reply for whatever reason didn't show up, so I'm taking the liberty of addressing its points as well):

Nice work, I really like the look of the front panel, although I find the graphic for the rapid traverse unnecessarily cryptic. Just label it "Rapid Traverse". Plus the big button just looks too much like an e-stop. (I am nit-picking).

I prefer the larger, mushroom-style RT button because it's easier to activate and IMO it forms a "shield" that will resist ingress of cuttings, etc. into the switchgear better than a smaller button. BUT, the nice thing about the switches we chose is that they exist in many different flavors. Here's a pic of a black-on-Al panel, with a smaller RT button (note that the smaller button looks a little lost with the 10/0-10 pictogram above it):

One reason to offer it as a kit is so that people can choose what style and color actuators they like ... but it might make more sense to offer just one "configuration", and tell people where they can get the switches, in case they want to change them. The problem here is that the volumes are likely small, and it costs us money, the more different variants we offer.

As to RT vs. pictograms, other have said they prefer Rapid Traverse as well ... maybe we can accommodate both styles. I'm trying to be as "international" as possible, keeping the English text to a minimum, for a broader possible market.

Price-wise, thats a tough one. Bridgeports are sort of a support machine anymore, not really so much a profit generator (obviously there are exceptions). I think they would compete well against genuine Servo brand drives if a rebuild on a customer core could be done for close to the same or less than the cost of a new Servo brand unit. Kits may sell well also.

Others are repeating this ...

Truly amazing work. I am in awe. Makes me wish I had a 6f on my Bridgeport. Good luck with the venture. Given the current demand and supply for 6F and 8F parts and complete units, I imagine that your version of the 6/8F will go very far.

STJ7780: Thanks for the compliment, but to me, there's far more amazing work going on in these forums where old machines are being resurrected, etc. I love product design, human interface issues and component sourcing, and so I thought this would be a fun project, that might sell as well. I am definitely interested in more feedback on who (still) has 6F & 8F drives, and who is willing to keep them going and/or upgrade them.

I've got an 8F and learned from others about making 2 "weep" holes in the bottom of the electronic enclosure. Taking a the bottom cover off and checking for leaks goes a long way to improving the longevity.

JRIowa: Yes, I have some ideas to address that as well ...

IMO, both the 6F and 8F feeds are superior to Servos and far better than the imports. Your price must reflect that. You have to be priced cheaper than a Servo and competative to the imports. I think that you need a modified Option 1. All parts need to be included in your kit along with good instructions. Very few would have the time to go to 6 different vendors and ordering parts. We want everything at once so we can put the drive together over a weekend.

This is very helpful advise. Sounds like something between $400 and $700 is what people might spend to overhaul / upgrade their existing 6F/8F.

What I'm not clear on is how much of a "project" people will tolerate. The guy who has a BP +6F in his garage is probably willing to make a weekend project out of it, once he has all the parts in hand, whereas a commercial shop with multiple units (do such shops exist? Or is it all CNC?) wants a minimum of downtime. My concern is that the way the 6F/8F are made, it is inherently labor-intensive in terms of fitting this upgrade. Mainly, in assembly / disassembly, and doing the wiring. I suspect the internals of a modern Servo-brand unit are all on one PCB, thereby simplifying its design and keeping the price low.

Are people willing to cut wires to length, crimp spade lugs on them, and then follow a good installation manual? We could even provide a roll of wire and the terminals, but people would have to have a crimper, cut the wires to length, strip and crimp, etc. ...

Also, it seems like a lot of folks who are "resurrecting" BP Mills in their garages, etc. are capable with wiring (after all, they installed PCs or VFDs to run the BP's 3-phase motor), so I'm thinking / hoping that the real cost of the wiring is born by the end-user in the form of their time ...

Oh, while I was at it ... I setup a microphone to compare the noise from the 6F motor, when driven from a Minarik MM23001C (SCR) drive, and when driven from a Minarik MMXL10-D240AC (PWM) drive. I used the same field drive each time, and set the armature voltage to 70Vdc. Here's what I got, in the frequency domain:

SCR drive is in light blue, PWM drive is in pink.

You can see 60Hz and 120Hz pretty clearly. In the 700Hz-2.5kHz region -- which I assume the human ear is very sensitive to -- there's much more going on with the SCR drive than with the PWM drive. And, you can see the PWM drive operating at it stated "over 16kHz" frequency (pink peaks).

Subjectively, the PWM drive seems a bit quieter. This was all done with no load, btw.

Anyway, PWM drives are more expensive, but are reputed to be quieter, and because of their better form factor (1.05 vs 1.3x of SCRs), wear brushes less.

Though I'm trying to learn all I can about buying a used Bridgeport Mill, very nice work.

Is there any update on this?

I would be interested in a conversion or even a parts list and source.

Progress:

1. We're closing in on the final iteration of the front panel and legends.

2. The cam is being designed -- hope to send it out for fab within 10 days.

3. We've acquired another PWM drive (KBE) and need to test it.

4. We fabbed an initial bracket for holding these drives in the location where the old SAECO unit went ... we'll be finishing up a drawing and sending out for quotes over the next 10 days or so ...

There's still some more work to be done (e.g. testing against a working, all-original 6F, and product photography). I expect that we should have it all wrapped up around end of September.

--Andrew

Nice job, nice idea, sounds like you need at least 2 options:

a. for the shops without down time or the home machinist that is not confident enough, rebuilt/updated unit for money and working core exchange.

b. for everyone else, bag of parts and instructions

Third option if you have the time and desire.
c. rebuild/update service, buyer sends their unit, you rebuild and update. Similar to option a. but with extra charge for doing it based on a schedule, vs. pulling one from a shelf you updated as you had time.

Just some thoughts,
Rich C.

I'm very interested in this mod. For the record, I prefer the "bag of parts and instructions" option.

Thanks for the feedback -- Keep it comin'!

Progress report:

1. Switch Cam: The first usable cam has been tested, and works nicely when integrated with the SCR-based drive, but we feel that the "dead zone" in the center was too narrow. So on to the next cam.
2. Front Panel: Still converging on the right layout ... getting closer.
3. Switch PCB: Nearly done, waiting on cam to be finished, as the cam affects the locations of the switches on the PCB.
4. Drive mount / bracket: This will happen after the top three items are done.

--Andrew

I'm with 310 Guy. I changed to a servo when power supply went bad but really liked the 6f better. Waiting to see how this developes. tommie

Progress report:

1. Switch Cam: The second cam has a much better dead zone. Was 3D-rapid-printed as a test unit. A couple more units are now being made in different materials for testing.
2. Front panel: No activity.
3. Switch PCB: First articles out for fab, now that cam appears to be complete.
4. Drive mount / bracket: No activity.

--Andrew

Just a bump to see if OP has made any progress

Yes, some progress being made .. specifically, the first switch board PCBs are in, being assembled for testing, and the first "production" switch cams are coming in soon as well ...

--Andrew

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Status Report / Update:

1. Switch Cam: I had an enlightened moment and now see a better way to do the cam than before ... The plan is for the new cam to be smaller and to provide three functions: direction switching, inhibit, and braking resistor. The latter is new with the new cam.
2. Front Panel: No activity other than beginning final production artwork.
3. Switch PCB: First article (proto) back and built validates various concepts, but will be revised again for the new cam.
4. Drive Mount / Bracket: Designed, going into proto production. Supports various MM-footprint drives (SCRs and PWMs).

I also had a long discusion with one of the drives engineers to validate my approach and ensure that this design addresses the concern that the simple (and affordable) drives that this will support will not be damaged from the reversing operation. Put simply, the motor needs to stop before the operator reverses direction. This was likely true with the older SAECO drive as well. Since these are not fancy 4-quadrant drives (or better, AC drives), this design labors under some restrictions due to the use of a large DC motor. I think that this design will prove to be a well-executed ugrade given the constraint of sticking with the original motor. IOW, this upgrade has features to enable motor reversing and to protect the drive if you are abusing your 6F/8F and rapidly sending the table back and forth

On the subject of price, ths upgrade will most definitely be offered as a kit first ... customers will have to purchase their choice of compatible drive (SCR or PWM) as the only major "outside component". That's due mainly to the fact that we cannot come close to offering the drives at prices comparable to Internet pricing, and we are trying to keep the end-user price as low as possible.

--Andrew

Status Report / Update:

1. Switch Cam: Now on v6 of the cam, very happy. Still have to find the best way to have it made in qty.
2. Front Panel: Out for another revision so as to improve wiring access to the various terminals.
3. Switch PCB: Rev F is finalized, now out for fab.
4. Drive Mount / Bracket: Finalized, out for quote.

--Andrew

Thanks for the update. I am watching with interest, ready to order when available.