Bridgeport Manual to CNC Conversion...

[BMSTECH]

I have just completed my quill feed and seems to work fine. Check out my King Rich mill CNC conversion.
Cheers,
John

[davek0974]

Nice job, thats a tidy fix for the quill drive

[mactec54]

Thanks 2:1 then

Z axis...

It looks like I have four options here...

1 - Drive the Quill direct from the bolt point where the depth gauge mounts at the front.
2 - Drive the manual lever shaft on the right side
3 - Drive the power-feed clutch shaft on the left side
4 - Drive the knee lift

Points -
Option 1 seems to be the most common but adds a lot of bulk to the front of the head and costs a little Z axis travel.

Options 2 & 3 are similar, both will suffer from the rack backlash but option 3 is the neatest one, backlash can be reduced with the clock-spring.

Option 4 is a contender I think, it gives a massive 300mm Z travel, but suffers from stickiness and has backlash in the bevel gears. The force is reasonable - I measured my one and if my figures are correct, it needs approx 1Nm to lift the knee based on the handle length of 160mm and 6kg force on that handle 6kg / (1000/160) = 0.96Nm. The backlash is a factor but the Z is usually used to plunge or position - both of these are done in the positive direction so maybe backlash does not matter here?

Thoughts?

There is only one of your options that is satisfactory for these mills doing the Quill mod is the best, using the knee creates a lot of ware on the column which were not designed to be used at CNC speeds, very low fee rates would be ok with the knee, but would be very slow for the machine process, some do the Knee and the Quill, and use the Knee just for positioning

Doing the Quill does not have to be difficult here are some plans from the Zone, this is one of the better ways to do it, and quite easy to do

http://www.cnczone.com/forums/bridge...ve-design.html

http://www.cnczone.com/forums/bridge...ing-forum.html ( Plans Here )

[davek0974]

Thanks, I am just exploring the options after looking over the mill with a tape measure

Those plans will certainly help but i'll likely go with an option that does not need the housing being split, motor drive on top.

Will motorise the knee later on just because hand cranking it is a *****

[mactec54]

Thanks, I am just exploring the options after looking over the mill with a tape measure

Those plans will certainly help but i'll likely go with an option that does not need the housing being split, motor drive on top.

Will motorise the knee later on just because hand cranking it is a *****

Yes it does not have to be mounted like that, there are many options for mounting the top support plate, you can remove the gearbox cover on the side of the head and mount from there, all the gears would be removed or disabled anyway

[davek0974]

Ok, so the front mounted screw is the most popular, 1605 or similar seems to be the way.

The motors I am looking at are 750w AC servo, I was thinking of just ordering a set of three as the price is really good and the smaller motors (for the Z) seem to cost more.

My main concern here is having 750w of motor and probably 2:1 drive on the Z axis, transmitting all its power through the one bolt into the front of the quill. Is there a way to help prevent damage - motor current limiting etc on a servo ?

Are things like table & quill locks removed as well?

[mactec54]

Ok, so the front mounted screw is the most popular, 1605 or similar seems to be the way.

The motors I am looking at are 750w AC servo, I was thinking of just ordering a set of three as the price is really good and the smaller motors (for the Z) seem to cost more.

My main concern here is having 750w of motor and probably 2:1 drive on the Z axis, transmitting all its power through the one bolt into the front of the quill. Is there a way to help prevent damage - motor current limiting etc on a servo ?

Are things like table & quill locks removed as well?

The motor you can control, normally in your software,with Acceleration and Velocity settings, plus the Drive has safeties, for over amp voltage etc, they will trip before, it would break or damage the bolt, the quill lock you can remove the whole thing, but it can also be useful to take up any clearance in the quill housing, I would remove the little handle/lever on it though, and just use it finger tight, the X & Y axes yes just put a plug in those, unless you need to do the same as the quill

[davek0974]

Many thanks, will get to pricing stuff up now..

[davek0974]

Has anyone here replace the BR2J vari-speed sheaves and belt with a timing belt and fixed pulleys - for VFD drive???

Would it be stock parts - pulleys and taper-locks etc?

1:1 ratio?

[eman5oh]

I already have the VFD on my mill and am looking to do a 2:1 pully set as described here Bridgeport Boss 5 retrofit - Pirate4x4.Com : 4x4 and Off-Road Forum I have a Teco 2HP VFD on mine and if I had it to do over I would have used a 3 HP VFD. The 2HP motors I believe were conservativly rated at 2hp and will trip my 2 HP VFD unless the limits are turned up. The accel and decel are slow as well, won't make much difference on a honby machine but will cause trouble if you want to tapping to work properly as I do.

[mactec54]

Has anyone here replace the BR2J vari-speed sheaves and belt with a timing belt and fixed pulleys - for VFD drive???

Would it be stock parts - pulleys and taper-locks etc?

1:1 ratio?

I started doing this around 20 years ago, here is a photo of one I did, this is very modified Head, that is 5" shorter than the standard Bridgeport Head

[mactec54]

I already have the VFD on my mill and am looking to do a 2:1 pully set as described here Bridgeport Boss 5 retrofit - Pirate4x4.Com : 4x4 and Off-Road Forum I have a Teco 2HP VFD on mine and if I had it to do over I would have used a 3 HP VFD. The 2HP motors I believe were conservativly rated at 2hp and will trip my 2 HP VFD unless the limits are turned up. The accel and decel are slow as well, won't make much difference on a honby machine but will cause trouble if you want to tapping to work properly as I do.

Yes you should alway have a higher rated VFD than the Motor it is driving,more so when using Single Phase up to 2Hp more is the norm, you would need a Braking Resistor, for doing Forward /Reverse Taping

The one in the photo above has a 5Hp VFD on a 3 Hp motor, and does Rigid Taping, with zero problems

[eman5oh]

Yes you should alway have a higher rated VFD than the Motor it is driving,more so when using Single Phase up to 2Hp more is the norm, you would need a Braking Resistor, for doing Forward /Reverse Taping

Yes, things you learn the expensive way..... I was hoping to save others an expensive lesson. The VFD I used is rated 2HP while using single phase input, but it does not perform well and has no provsions for a braking resistor. The replacment will be a 3 HP unit with a braking resitor.

[mactec54]

Yes, things you learn the expensive way..... I was hoping to save others an expensive lesson. The VFD I used is rated 2HP while using single phase input, but it does not perform well and has no provsions for a braking resistor. The replacment will be a 3 HP unit with a braking resitor.

Teco are a good VFD what model do you have, I have not seen one that does not have the feature to add a Braking Resistor

[davek0974]

Thanks guys,

That cut down head looks sweet, not sure i'll go that far though Are those Poly-V pulleys and belt?

I'll have to dig deeper but it looks like its just a matter of removing both sheaves from the motor and using a taper-lock pulley and then removing the top sheave from the spindle and using a custom mount pulley? Also making the motor adjustable for tension?

Maybe a small ratio increase from motor to spindle?

The vfd I have is very happy and has braking resistors fitted, I can do tapping on it but now use a tapping head.

[mactec54]

Thanks guys,

That cut down head looks sweet, not sure i'll go that far though Are those Poly-V pulleys and belt?

I'll have to dig deeper but it looks like its just a matter of removing both sheaves from the motor and using a taper-lock pulley and then removing the top sheave from the spindle and using a custom mount pulley? Also making the motor adjustable for tension?

Maybe a small ratio increase from motor to spindle?

That is how a lot do them, Yes Poly-V belt 8 Rib is ideal the photo has a 6 Rib, but others I did went to 8 Rib, for motor tension, if you calculate the correct belt length by the pulley Dia you don't need much adjustment, I only slotted the motor mount,you have to draw it up and then adjust the pulley Diameter to suit the belt

[eman5oh]

Teco are a good VFD what model do you have, I have not seen one that does not have the feature to add a Braking Resistor

It's a TECO L510 2HP https://www.google.com/url?sa=t&rct=...R60cvFCyTZdYbw

[mactec54]

It's a TECO L510 2HP https://www.google.com/url?sa=t&rct=...R60cvFCyTZdYbw

So your one has the Braking Resistor already built in, so may need some parameters set to activate

[eman5oh]

It has a braking transistor, it does work but will trip if I set the decel to less than 5 seconds and have the spindle spun up to 4200 rpm. I am hoping once I remove the vari drive parts and put in fixed pulley it will have less inertia and the braking will work better.

[davek0974]

Eventful morning....

Did some paying jobs, then started messing with the BP, it turns out I have the 1.5Hp / 1450rpm motor and top speed is 3500rpm although the vari-speed won't turn past 3000 or below 500 so I'm guessing something is wrong inside the head for a start.

I tweaked the VFD a bit, luckily the front panel pot was still programmed as speed source - it was just set at 50Hz.

After a few tests I finally set max to 100Hz and min to 15Hz, it was on default 25-75Hz.

The head was then wound to 1450rpm so it was at 1:1 ratio. Using the VFD this gave me a range of 430-2860rpm in high and 52-346rpm in low.

I made a test cut on one of the batch parts I was making earlier - these are moly steel and use I use a 1/2" HSS tool at 450rpm, I'd made loads so I knew what the machine sounded like when running them and there was no noticeable difference. With the tacho on the spindle while cutting the speed dropped from 450 to 420rpm but the chances are it did that anyway.

There are some issues up top as the sheaves are flapping like hell at speed.

I think a fixed conversion at 1:1 might be worth doing rather than repair the sheave bushes etc. At least that will give me the most of my meagre 1.5Hp at the spindle rather than lost in the pulleys.

OR, Is a servo motor torque really linear from zero to rated speed?? I.e. will a 1.5kw AC servo really give me 1.5kw or 2Hp at 100rpm AND at 3000rpm or have i read it wrong??

Would I be better off just fitting a 1.8kw AC servo motor for the drive and connecting at 1:1 ratio??

If it was correct then I would have full power from 1 to 3000rpm at the spindle - sounds ideal.

Would this play well with my upcoming CSMIO/A CNC conversion - would Mach give speed control and correct rpm readout??