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

Bump. Any progress?

Originally Posted by 310 Guy

Bump. Any progress?

Yes!

Status Report / Update:

1. Switch Cam: No new news.
2. Front Panel: Latest (sixth?) revision is back in, this appears to be the final arrangement, maximized the room for internal wiring w/connectors, now working on final artwork. Improved the cutouts so that e.g. the fuse holders don't rotate any more.
3. Switch PCB: In fab, waiting for first articles of this final version of the PCB.
4. Drive Mount / Bracket: Was challenged by how to couple the heat from the drive into the 6F/8F's casting ... on the original unit with the SAECO drive, the PCB is screwed down tight "flush" against four bosses in the casting, and the rectifier/SCR heatsink is nearby. The only conduction from the SAECO PCB's ground plane to the casting is via these four bosses. To use modern drives and have access to their adjustment potentiometers with the bottom sheet metal cover removed, the drive has to be "deep" inside the unit, hence the need for a bracket. So I was struggling with how to couple the drive's heatsink not just to the bracket, but to the casting as well. A little creative sourcing and now I think we have a good solution. We are currently verifying that another, later 6F's casting has the same internal dimensions, and then the bracket (revised to handle this heat coupling issue) goes into fab. The drive+bracket is shock mounted, thermally couples well to the casting, and uses explicit grounding lugs to ensure a good ground throughout the system. Plus, all these drives have a larger heatsink than the original, and there's the additional mass of the bracket as well.

So far, there have been no nasty surprises on component pricing, etc. I still need a source for the cam, though we could 3D-print the early ones at Pumpkin.

--Andrew

Status Report / Update:

1. Switch Cam: See Switch PCB, below.
2. Front Panel: Minor tweaks were made to make the wiring easier to do -- components were shuffled around a bit. Not quite ready to go to final production. No longer a perfectly symmetric arrangement, but much more manageable from a production and wiring standpoint.
3. Switch PCB: We finished v7 of the cam, and did a run of Switch PCBs ... everything works great .... but we found that the labor associated with connecting the switches to the switch PCB (they are screwed down against the Switch PCB, and operate parallel to the plane of the PCB) would make the whole thing cost-prohibitive because of the labor needed to wire the switches to the PCB. This was a bummer moment. So, after some time, we figured out an alternate way to do this, which requires a different cam. We are close to the new cam, and will then proto up the Switch PCB, test again, and be ready to go. In all cases, the cam still does all the things we wanted, but the new switches-on-PCB scheme requires 1/10 or less of the labor to assemble, and then will help keep the price down.
4. Drive Mount / Bracket: Brackets were fabbed, received, and work great. Accommodate three different drives (SCR + 2x PWM) nicely, with provision for coupling the heat to the body of the 6F, and for a braking resistor if desired. Rubber isolated mount to handle dimensional variances in the castings. All mounting fasteners are captive stainless studs. Did I mention that I'm very happy with this part?

I know it would be sexier if I posted a video of the unit running right now, but I don't want to have to field questions that will relate to the prototype, when the production version will differ somewhat, albeit with the same performance.

Also, a few more tidbits: The 6F drive that we are using is S/N 81xxx, attached to a '77 vintage Series 1 2J. Also, I have access to another BP 6F (S/N 61xxx, I just found out today, you have to look from underneath to see it) on an '87 vintage Series 1 2J. I had noticed -- but had not thought too much about it -- that the BP schematics / overview illustration was different from mine ... and the difference between the 6F B & 6F C electrical innards wasn't really jiving with what I was seeing (I thought I had a 6B). To make a long story short, it turns out that my (older) BP mill has a 6F C power feed attached to it, and the younger, '87-vintage BP mill has a 6F B power feed attached to it! So, I have been designing to retrofit the 6F C. Now it's all clear. It looks like anyone with a 6F B will have to swap out the clutch shaft for one from the 6F C (e.g. Clutch Shaft - Industrial Control & Automation, Inc) in order to do this retrofit. 6A users are likely out of luck, as there's not enough room to handle these electronics, and the front panel is different and smaller. It does not currently appear to be possible to utilize the 6F B's clutch shaft, because of the angled end down near the switches.

What makes it stranger is that the motor on my unit is not one that matches a 6F C -- at least, not what you get if you buy parts for the 6F C motor. Its brush holders are different from what you can buy online, it has no rear plastic "cap", and the rear cap on the motor is completely round in diameter, without those square areas where the brushes are. Additionally, while the rivets are present, there was no name plate on this motor. We ended up completely cleaning it and replacing the bearings and seal, and then we also replaced the (apparently unobtanium, looks-like-they-were-made-from-bakalite brush holders (that are electrically connected via screws) with the modern 6F brush holders (that are soldered to)). I felt I had to do this because with the old brushes, the motor sounded different and worked slightly differently going in one direction compared to the other. With the new brush holder and brushes, everything is perfectly symmetric.

Lastly, the original electronics reversed the field, whereas the new electronics reverse the armature and leave the field on at all times. This means that you have roughly 100W (90V field voltage x ca. 1A field current) of continuous power dissipation in the motor housing. Recently we left our unit on but not turning, with the motor detached from the 6F housing, and it stabilized at around 105deg F. So no big deal, it's like having a 100W light bulb there when the unit is on but no cross feeding occurs. Of course when the motor is attached to the 6F housing and the 6F housing to the table, the thermal mass is much greater, and the motor will stay cooler.

So, right now I am waiting for an intern to finish up the new cam, then we'll test the system again, and can then talk about making the whole thing available for sale.

So I apologize that this is taking longer that I wanted, and that 6F B users will have to source a 6F C clutch shaft to make this work.

--Andrew

Did you say you would have the kit ready yesterday. That is when I need it.

Now seriously, I have a dead 6F on one of my mills, I have a Servo on one of the other mills. No complaints, but I do like the layout of the 6F much better. I would be interested in a kit if reasonably priced. Right now I am looking at replacing the board with one of the Minarik Model MM23001 Boards, without doing any upgrading of the other items. But probably should be leaning that way. So that leaves the door open.
Keep up the good work. BWP

Originally Posted by bwp

Did you say you would have the kit ready yesterday. That is when I need it.

Now seriously, I have a dead 6F on one of my mills, I have a Servo on one of the other mills. No complaints, but I do like the layout of the 6F much better. I would be interested in a kit if reasonably priced. Right now I am looking at replacing the board with one of the Minarik Model MM23001 Boards, without doing any upgrading of the other items. But probably should be leaning that way. So that leaves the door open.
Keep up the good work. BWP

As I mentioned in my previous post, it's taking longer than I anticipated to develop a cam that would make this upgrade price-competitive .. I plan to 3D print the new cam (v9) this week, and then create a new switch board for it.

I do have a complete, assembled, working prototype unit that uses the too-expensive-for-a-real-solution cam, for the MM23001. I would be interested in getting feedback from a "real" user, in return I'll sell this unit at a discounted price. I'll PM you with details, let me know if you're interested.

Oh, BTW, this assumes that you have a 6F C (with the longer clutch shaft) ... if not, you would need to replace the 6F B's short clutch shaft with a longer one. No solution for a 6F A, sorry. I presume it's a drop-in for an 8F, but I'm not entirely certain yet.

--Andrew

When is this upgrade kit available?
wd74

Originally Posted by bwp

... Right now I am looking at replacing the board with one of the Minarik Model MM23001 Boards, without doing any upgrading of the other items. ... BWP

About ten years ago, I replaced a burned out Bridgeport board, with a Minarik board, as you are planning. The description still can be found on the web. Here is one place where it is referenced: BRIDGEPORT 6F (See posts 7, 8, and 9, for descriptions and photos.)

This system still is working on my Bridgeport at home.

-Jon

I just ordered a minirik power supply I would like to know what kind of micro switches did you replace the originals with?

wd74

Originally Posted by WD74

I just ordered a minirik power supply I would like to know what kind of micro switches did you replace the originals with?wd74

The switches we use are lever arms with rollers at the ends -- this type of switch was never used in the 6F/8F, so it wouldn't be appropriate.

You can get many different kinds of switches from Electronic Components Distributor | DigiKey Corp. | US Home Page . No minimum order, though they do charge extra for shipping when the order is under $25.

--Andrew

Originally Posted by WD74

When is this upgrade kit available?wd74

Not yet known ... the first cam we designed was beautiful but would have made the upgrade kit cost $1000 ... the second cam is more practical, but put too much stress on the switches ... we are currently working on improving the third cam ...

--Andrew

Ah ... here we are nearly a year later ... what's the status, you may ask?

Short form: Prototype is on our BP Mill, works very well. Some small issues need to be resolved before we invest in the parts for the first production run.

Long form: We've been through many, many revisions. PCBs are on Rev L, faceplate is around the 10th revision, cam is on revs Q and R (!). I'm very happy with the ergonomics, the Minarik drive (when the various adjustments are done properly) has lots of torque, rapid traverse (>40ipm) and overall speed range (ca. 1ipm to 30ipm) match the original, no permanent changes to the unit, etc.

Secondary benefits: the teflon seal on the selector shaft is really keeping the electronics nice and dry, and you can switch pretty much willy-nilly from left to right through center/off without having to worry about crashing the gearbox -- that's because we make use of the inhibit function that the Minarik and other drives offer (this is one of the functions of the switch cam). IOW, operation is perceptibly smoother overall than with the original design.

I've been bouncing the performance of our retrofit unit off my design partner, who has an original 6F drive on his BP, and I've now reached the point where he's willing to admit that it is better / a step up from the original, which is one of the design goals. But it took a couple of extra design efforts to reach that (for example, rapid traverse was just "max dial speed" in the early versions, but now it's around 30% faster, and that had to be done via field weakening, which was not one of the original design goals).

This has been a side effort and has taken so much time due to its many revisions ... but I suspect it will be ready for sale before the end of the year. It won't be cheap, but it will be worth it.

--Andrew

Bump. Any progress?

Yeah, it's been a while ... on the backburner.

One problem we were unable to resolve to my satisfaction was that the PF lever would not "snap back" to the middle when hitting the travel stops. Since we want this to be a perfect drop-in replacement, that's a bit of a sticking issue. I have an idea on how to resolve it, and may be able to work on it in the coming weeks. But we're still a ways away from release, as I feel this must be resolved.

--Andrew