JDs BP J-Head CNC Conversion Blog

[jdelaney44]

Yay! It's done. This a.m. I elongated the bolt holes on the link. Made a couple of trips to OSH for nuts and bolts, and oh SH*&! I forgots, and got it put together. Assembly went kind of like this.

1.) The sides went on first and were left loose on the transmission studs. Also the bolts to the struts going back to the tranny studs were left loose.

2.) The ball screw to quill link was installed on the quill and tightened down good & tight. Check the quill for free running. No scrapes, good.

3.) Put the bearing blocks on the screw and insert the screw & block assembly into the sides. Bolt up loosely.

4.) Bolt the quill link to the ball screw. Turn the screw by hand to make sure there are no problems along the entire travel.

5.) Turn the ball crew until the quill is fully extended, link all the way down.

6.) Tighten the 5/8" nut under the bottom micrometer depth stop indicator lug.

7.) Turn the ball screw until the quill is fully retracted. The ball screw nut will be at the top.

8.) Tighten everything else up.

9.) Install the pulley, thrust bolt on the end of the ball screw, the motor mount, motor, tighten up the belt.

10.) Apply power and watch it run!

11.) Think - Hey, I did that!

12.) Drag your significant other into the garage to watch as she / he looks at you as if you are nuts.

Thanks,
-jd

[DieGuy]

Originally Posted by jdelaney44 Drag your significant other into the garage to watch as she / he looks at you as if you are nuts. Thanks, -jd

This is a daily occurance the my household!

Nice job!

[Hood]

Looking good JD, great to hear its working fine as well, just hope mine does when I get it finished. Not had a chance to get anything done to mine the head started making lots of horible noises mid week and think the bearings have gone. have a spare bridgie and have been swapping the head over this weekend, man they are heavy, even with the motor and belt housing removed.
Hopefully next week will see it completed, geckos are scheduled for arrival tomorrow so the scrap drives I have in now will be removed.
Look forward to the rest of your conversion.
Hood

[jdelaney44]

The motors I have are 100V Reliance Micro 100 series. The temp power supply I made is 33V. My final supply will be 56V. So, I have been concerned about the torque.

I decided to use a 3 to 1 reduction based on a couple of "rule of thumb" statements I have seen out there.

So......I decided to lock the quill down last night to see if I could measure the flex in my drive. No go. The motor pushed the quill right out of the lock. Then I put my plastic shot filled mallet under it. It squished it down a good 1/8". So....there is plenty of torque using a 100V motor at 33V with a 3 to 1 reduction and a 5 TPI ball screw. Once I get to 56V there should be no problems.

Thanks,
-jd

[lerman]

My understanding is that the speed is proportional to the voltage. The torque is proportional to the current.

So, running at a lower voltage will reduce the maximum speed, but should NOT affect the maximum torque (within some limits). Obviously, if the voltage is too low, it cannot drive enough current into the motor, but that is not usually the case.

Ken

[jdelaney44]

So here are some drawings of how I've envsisioned the X-Drive on the Bridgeport. These are exploded.

I did pencil and paper for the Quill. But after making several errors I think I could have avoided, I decided to invest the time with the CAD. I think in the long run it'll be faster.

You'll see a four bolt pattern on the inner and outer plates. Thisis for a couple of bearing blocks. There will be a 5/8 in. shaft that goes through those to a coupling that will join that to the ball screw. When I replaced the ball screw I got the one to go with the existing Bridgeport power feed. I did not want to disable the ability to put the machine back into the condition it was when I got it. Again, incase the CNC craps out I want to be able to use the machine to make repairs if needed.

The drawings don't look great in the browser. You might want to download and open with something else. My Turbo CAD's save as to JPG is less than great. I'll keep working on it.

Thanks,
-jd

[Hood]

JD hows your X and Y going????
I have got my Z completed and working and have actually made some money with it Will be a while before I get my costs covered but what a machine, still got limits to fit and cables to tidy but hope to be moving workshop soon so might wait until then to do the snagging. Also I am a very untidy person as you will see from the pics so I feel at home wth things being half finished
You can see my x y and z pics HERE

Hood

[jdelaney44]

Hood, I started the X today. Should have it done tomorrow. Going well. I'm trying to get the Y done by the fourth. I've got some personal stuff hitting the fan right now so that's slowed me down quite a bit. But, so far so good.

Thanks for the links. Looks good. Glad to hear it's working good too!

-jd

[Hood]

Look forward to pics of your finished X and Y. Today I hope to get my limits fitted so I will be happy to leave it alone and get on with other work while the Bridgie does its stuff.
Hood

[jdelaney44]

Here are the pics of the X-Drive. Just about ready to mount. Note the shaft. I have a screw designed for the Bridgeport power feed so I am making the x-Drive to fit that.

-jd

[jdelaney44]

Some more on the X-Drive construction.

(as always please pardon the spelling and typos)

The CAD exercise helped a great deal. I have previously just been slugging it our with pencil and paper. I use TurboCAD 11 (TC). Just got the upgrade in the mail yesterday. I've decided that CAD programs are a matter of personal choice. The 3D operations in TC make sense to me. They also have what, to me, is a pretty intuitive control for sizing and dimensioning objects. I haven't tried them yet, but the auto dimension features in 11 are supposed to be better. The dimension features in 10 allowed me to quickly set up the dimensions you see in the clips above. I need to reload those too. Just notices I managed to load the same drawings like four times. Nuts.

These drives are aluminum since I am not as concerned about the rigidity as I was on the z-drive. Actually I over killed on the z-drive. More on my observations there later.

So this time around I decided NOT to surface the stock like I have been doing. My rationale was a.) I see a lot of other people getting away without doing that, b.) the belt stretch should probably soak up and deviations created by the inconsistent plate thickness, c.) I can shim the drive and the motor to get perfect alignment if it does become an issue, and d.) I am using flanged pulleys so the belt coming off should not be a problem, and and e.) the material deflects when you surface it anyway so the true gain is really very questionable.

Still everything coming off the bands saw had to be squared up on the edges. I do this by picking the best looking side and putting it down in the vise. Then I mill the one edge sticking up with either a 0.5 or a 0.75 end mill. Then I flip it over and do the same. This time though I'm checking dimensions as I go. I currently over size the stock on the saw by about 0.25.

Once I have two sides parallel, I clamp the piece flat in the vice using a couple of steel parallels to hold it at the top of the vise. I got a set of these for $99.00. 0.5 thick by 6 inches long.

Once clamped I run the side of the end mill along it in the Y direction. One deep cut to get it close and and then one or two finishing passes to get it pretty. I have taken to running the finish cuts at about 0.002, dry no coolant, with the rpm at about 1500. Now turn it over and do the same this time working to the final dimension.

This go round included a run to Harbor Freight to get a set of 12 inch calipers.

Six finished parts one paperweight. I'm getting better! - This time the DRO was being squirrelly. I had to recalibrate it. Unfortunately I did not discover this until after I made the motor side plate and checked the dimensions. Everything grew by about .002 / inch. In the 12.75 inches of the plate everything looked perfectly proportional and accurately spaced. But it was WAY off by the time you got to the end of the plate.

I debated for a long time about not fixing the DRO for the balance of this build. It would be wrong, but it would all be the same wrong, right?

Well, then I figured if I ever want to make spare parts or retrofit something in there I'll be fighting these odd dimensions for the rest of my life. Forget that. So I remade the motor side plate.

The slots for the motor mounts screws are 1/4 inch. They are 2 inches center to center of the end radiuses. I did this to give me a lot of latitude in belt sizes. You never know when things break if you can get what you want, when you want it. This Just In Time world we live in doesn't always work out so good!

To cut those I plunged, slowly, the 4 flute HSS end mill all the way through the 0.5 at one end and ran it to the other end with the power feed at about .75 ipm. Real slow. I actually adjusted it by ear. When I heard a smooth cut I kept that speed. Oh, The end mill was in the collet right up to the top of the flutes. I got way too much chatter with it sticking out any more. The slots came out OK. They are smooth and the ends don't have too much of a deviation from what I will call recoil. Coolant was used, yes.

The slot for the motor shaft was made by running the same .25 end mill around the perimeter. I hand calc’ed the end points and used the DRO to tell where I was.

Note that I zeroed the DRO using an LED edge finder. It was zeroed at the upper left corner of the part, same as my drawing dimensions so I didn't get confused half way into the operation.

Note on using the edge finder. When I got it, the directions said not to have the machine turning when you used it. That made NO sense to me. I think they must mean high speeds.

I know I have about .0025 of runout in the spindle. So what I do is turn the spindle at like 10 rpms (using the VFD to slow it down). Then I crank the part over until I just get a little blink out of the LED as it grazes the edge. The tip of the finder is .20. So then I know I am .101 - .1015 or so away from the edge. This offset is then set in the DRO for X, repeat the process for Y. You now have a pretty good home setting in the DRO. I say pretty good ‘cause nothin’s perfect ever.

Hmmm……To make this better, I need to really put edge finder in the collet and mark the position somehow so I can get it in the same spot every time. Re-check the total runout periodically. Then use the same collet, the same edge finder, all lined up the same way every time. And make sure the R8 tapers are spotless of course. If I get a dog hair in there I’m off by .002.

So lets see. Do all that, then put in a three jaw drill chuck with a stock #10 drill bit in it and pray for +/- .005 as that wobbles around. Hmmmmm. Such is life.

See posting this stuff helps work things out!

The big deal is turning the spindle slowly and looking for the LED flash. That gets me a lot closer to compensating for the runout.

The back side was easier as it just has holes, no slots.

Then came the drilling of all those screw holes. Decided to use 10-32 x .75 screws. I thought that was going to take forever. It took about 45 minutes per big side and 15 minutes for the small sides. A #10 drill was used for the front and back plates where the screws would countersink flush.

I settled on drilling a line of holes, and then going back and counter sinking that line. At first I thought I might get lousy countersinks. But the machine and DRO seem to be holding +/- .002 or better so that's no problem for a drilling operation at all. So I drilled on side of holes, change to the counter sink bit, and went back to where I started that line, then went 90 degrees along the next side etc... I did get away with not locking the table as these were small holes with little chance of enough force being developed to move the table while drilling. This was done with an regular three jaw 0.5 in drill chuck on an R8 arbor. Cheap Chinese one. I need to get a Jacobs, they work so much better I can't even describe it. Actually I have the chuck for the late, just need the R8 arbor for it.

So now for the short sides of the box. Ran out of 0.5 plate, so I switched to some 0.375. The holes are slightly offset to make the outside smooth given the original design called for 0.5 through out. No big deal. Drill the holes as before just with a #21 drill this time for the 10-32 tap.

Tapping was accomplished by chucking the tap into my 1/2 VSR Milwaukee drill. Nice drill, lots of torque. Very carefully used the drill motor to drive the tap in. Reversing when the resistance got too tight. About 1/2 a turn to relieve the chips. Took some time, but not as long as it would have hand tapping them all. This also required that the tap be allowed to find it's way square in the first couple of threads. Which worked pretty well as long as I eye balled the drill to be square to the part. Some day I'll be able to afford a Tap Matic. Still, no busted taps this time. Yay!

Now everything is square, slotted, drilled, countersunk, and tapped. Assembly time! Much to my shock and awe, it all fits and ALL the screws go in easily. (The sun shines through the clouds as the organ plays and the choir sings for a miracle has truly just occurred! ) (Ok I just HAD to use the banana icon, sorry)

The only problem I found was that my pulley is hitting the bearing block on the inside, so just put the block on the outside and problem solved. I may still see if I can work that out somehow.

Onto the Y-Drive CAD drawings............

[Jamf2]

Congratulations.

Thanks for documenting what your doing. It has been very helpful.