Thread: J-Head CNC conversion Journal - TONS-O-PICS!!

**damae** · 01-12-2006, 07:14 PM

Right you are! I forgot that you had already posted motor details a while back =)

I'm very interested to see how your pulley arrangement turns out, especially with the encoder mounted to a pulley instead of the motor. The good thing about that is if the belt cogs on the motor pulley, you won't have position loss.

**mxtras** · 01-12-2006, 07:29 PM

Yeah - I am pretty stoked about the feedback thing.

I would really like to get a direct reading off the table instead of indirect through the screw but I think for simplicity, it will be indirect off the screw. The encoder may also be driven by a seperate set of pulleys for a different resolution - don't really know yet, but the way it's designed, I will have a lot of options in the future.

I have a few concerns using the screws, but it's the best I can do right now. Ballscrews are in my future, I am sure.

Scott

**mxtras** · 01-13-2006, 07:07 AM

Well - Tonight was very productive, but not in a physical way. I spoke for 1.5 hours with my control buddy and he managed (unknowingly) to give me a big boost in enthusiasm - not only about the mill, but then entire shop thing. ....long story.

Anyway - I was not able to accomplish much this evening. Nothing went my way early on - some days are like that.

So - minimal pics tonight. This pic shows an indicator in the spindle, resting on the apex of the screw. With the mounting bracket removed and the table completely retracted - so the screw was buried in the nut as far as I could realistically get it - I set a zero. I verified the set up was repeatable and marked the spot on the screw so I could pick up on the same spot each time. I cranked the table out to where I could mount the bracket and checked the set up again - I had .0015" of sag in the screw. I then positioned the bracket and lightly snugged the bolts. If you recall, I had bored the bracket to be a snug fit over the screw, so with the bracket in place, I ran the set-up under the indicator and aligned the bracket so that it positioned the screw back to my original zero point. This will ensure the end of the screw is supported in proper alignment. I adjusted the bracket square to the table and down .0008" - half the clearance of the bored hole to the shank of the screw.

The intention was to be able to drill and ream the pins so that it could be removed and replaced in the future and not lose the location, but not having the reamer I needed pretty much negated all of tonight's efforts. I will just have to do this again after the bearing mount is done.

So - as you can see - the time spent on this project tonight was not too productive. Sometimes you win the moto, sometimes you get hauled away in the meat wagon.

Scott

**joecnc2006** · 01-13-2006, 07:18 AM

what color blue and type of paint did you use?

Thanks, Jow

**mxtras** · 01-13-2006, 08:37 AM

It's Sail Blue Rustoleum.

Scott

**Cebby** · 01-13-2006, 11:37 AM

Scott - I'm caught up with the writeup of what you have so far for this. I will add to it as you progress. Email any of the drawings that you want to share and I'll host them.

Mxtras Bridgeport Custom Lube System and CNC Conversion

**mxtras** · 01-13-2006, 03:49 PM

Many thanks, Cebby!

I see you had a late night! ...or an early morning.....

Scott

**mxtras** · 01-16-2006, 10:15 PM

Well - I had a momentary bout with irrationality but I think it has passed.

I have several ball screws running around (I am a habitual dumpster-diver here at work) and I ran across one this past weekend that I had completely forgotten about.

It is long enough and in perfect condition (visually and smoothness of motion). So I spent more time than I should have looking into fitting it and it's cousins into this project. After looking at everything, I have decided to just buy a retro-kit and be done with it - it's too much effort when a phone call is so much faster!

It will be a few weeks before I can order the ball screws but based on the reaction from the sellers, they will need this time to respond to my requests for information anyway so it might just work out. I will post the results of my reseach either in this very thread or in another thread I started about finding the dimensions for the XY Yoke - that thread is here:

http://www.cnczone.com/forums/showthread.php?t=16538

So - with the lapse of sanity this past weekend, I lost a few precious hours of progress but will likely resume this evening. The plan is to have the ball screws be a direct replacement for the original screws so I am continuing to fabricate the brackets under that pretense.

At the moment, I am still in the hunt for the ball screw kit and related information - see the above link if you have input you would like to contribute - thanks!

More pics and useless text when progress is made.....

:wave:

Scott

**mxtras** · 01-19-2006, 08:48 AM

I had some difficulty clamping the bracket last night and I ended up wasting quite a bit of time, so this evening I went home and grabbed an old magnetic chuck that I had been using in my blast cabinet for the past 8 or 10 years and proceeded to clean it up. The bottom was stoned to remove a few dings and it was clamped down to the table in hap-hazard fashion as clamps and T-nuts are in short supply at the moment. The top surface of the magnetic chuck is in rough shape, but the top surface was fly-cut flat - it only took a few thou to true it up. This chuck was being disposed of at a previous employer because it had been skim cut down to next to nothing over the years of use on a VTL, so it was liberated.

Anyway - the magnetic chuck worked like a champ and the inside surface of the bracket was finally flat and parallel with the opposite side. The edges and other critical surfs were trued up and kissed clean and the bracket was de-burred and tested out.

There are a few more things to do, obviously but short of cutting the excess off the bottom of the bracket - it is pretty much complete for the time being.

Features for a tensioner will be added as well as a series of location pins and tapped holes for the cover. The cover will hold 2 bearings to additionally support the motor pulley and the screw, so the location and parallelism of the cover to the bracket is critical.

The pics show the bracket and motor in position with the table cranked all the way to the left. I end up losing 1 5/8" of travel.

I completed the backlash test of the factory Bridgeport screw bearing and housing with some very interesting, unexpected results. The results will be posted here and in the thread about the yoke when all the data is reviewed and calculated. See previous post for the link to that thread - but the basic data will be here, too - just with less pics and a far more brief description of the test conditions and procedure.....the Reader's Digest version.

That's about it for tonight.

:wave:

Scott

**mxtras** · 02-07-2006, 11:12 PM

Taxes done. When the check hits the bank, I will be ordering ground screws from Hiwin and further progress will be made.

I have been a bit held up lately trying to go as far as I can without the screws and I finally hit a road block or two. The Hiwin screws have a slightly different diameter in one region than the factory screws and I need to run a bearing in that area. So - I will need to modify the screw (or have Hiwin do it - which I am going to inquire about) before I can really continue with the bracketry for the drives.

I have made a tensioner for the X-drive but still have a few things left to machine to complete the X bracket. It would run right now, but it's needs a bit more polish and a top cover to be called done.

The Y bracket is nearly complete but I still have to fab up the tensioner for the belt. I also need to figure out exactly how I want to constrain the driven sprocket to the screw. I can not use a shaft lock collar because the Y screw is only constrained on this end and I have to be able to torque the shaft 'through' the pulley to constrain the bearings to the screw shaft for thrust. I am debating on how to drive the relatively soft aluminum pulley - with a key direct to the shaft, or a keyed, steel hub? To drive with a key, I would have to machine another keyway into the shaft of the screw. I could make a hub with a keyway and drive it from the original Woodruff key location and then add another keyway onto the hub to drive the pulley. I don't think I like the idea of compression on the soft pulley. I need to pick a direction and roll with it. I will probably make the steel hub and jump through the hoops to make the keyways.

I also have a bit of a dilemna - the bracket for Y will prohibit the use of the manual crank handle, so I am left to either make an extension for the screw or omit the handle. I haven't made a decision on this yet. Once the mill is up and running, I will remove the handles anyway, but until then, I am nervous to do so.

Progress report with pics to post soon.

Scott

**NC Cams** · 02-08-2006, 04:48 PM

See if you can find someone in your area who has a BPT EXTRAK and ask to look at their parts/operating manual. If not, contact me off line and I"ll copy the drawing and send it to you.

BPT already came up with the answers to the same issues you're dealing with now and the solution lets you use the CNC and hand drives.

THey have a collet like clamping system that fits inside the CNC drive pulley. Even at 1:2 driving the motor backwards, the force isn't objectionable - the bearing preload of the OEM 6204's generated more rotating torque than the belt drive overspeedin of the motor when hand cranked. However, their screw shaft is a bit longer I think than a manual shaft. Shouldn't be that hard to craft something up that would incorporate hand crank and drive pulley into 1 unit.

Hmmm, just answered my own question/dilemma on how to adapt OTC Hiwin ground manual screws into special ended rolled screws used in my BPT Eztrak.

They drive Y by belt and motor is swung off to the right (facing machine) and nestled down under the table. With cogged belt, we don't have or need a tensioner - it is short and holds plenty of accuracy (we have machined cam masters with it and they are accurate to fractions of tenths).

Ditto that re: lack of tensioner on X axis.

**jdelaney44** · 02-08-2006, 05:27 PM

I don't have a tensioner on anything either, but I do have enough travel in my motor mounts so that I can use a couple different size belts in a jam, if needed, ever. I know, overkill & paranoia. Uh....point being is that I do tension the belts some by pulling back on the motot pulle with a small bar clamp and the tightenning down the motor.

It works fine. You guys have some tension on your belts right? I mean they are at least snug?

I'm asking 'cause I replied with my thoughts above to another post at DIY-CNC where it sounded like they mounted the motor at the calculated centers and installed the belt based on that. They too said all was good. I believe it, it's just not what I would have ever considered possible or wise.

I also have flanges on my pullies so I need some play just to get the belt on.

But, if this works, then it's great input for the future.

Thanks,
-jd

**jdelaney44** · 02-08-2006, 05:48 PM

Scott:

I used a 30 tooth pulley with a shaft lock hub. My assembly process goes something like this. Install all the parts loose, including the belt. Torque the nut to load the thrust bearing. Then tighten up the hub. Then tension the belt.

As for the crank, I had the same worry. Actually I got to a point where I needed to assemble the Y-Drive partially and keep working on parts for it at the same time. So it was either take it apart and put it back every time or come up with a work around.

So...I made an "emergency crank handle" out of a 1/4 20 carriage bolt, some washers, and a piece of 1/2 inch PVC. A picture of it is on my other thread.

http://www.cnczone.com/forums/showth...9&page=5&pp=15

It screws into one of the holes on the pulley hub.

The hub is McMaster part # 6086K13

I left the cover of my drive assembly off long enough to get the CNC working and then I removed the handle.

If the CNC takes a crap on me now, all I have to do is remove the cover, install the handle and I at least can use the machine. I can still re-install the X handle and all the guts on my Z are still in place too.

-jd

**mxtras** · 02-13-2006, 05:27 AM

[QUOTE=NC Cams]..... If not, contact me off line and I"ll copy the drawing and send it to you.[QUOTE]

Cams - sorry for the delay! I have been pretty busy. Thanks for the offer but I got it whipped.

I appreciate the gesture. Many thanks!!

Scott

**mxtras** · 02-13-2006, 05:39 AM

Originally Posted by jdelaney44

....... You guys have some tension on your belts right? I mean they are at least snug?-jd

I need to research this a bit so I don't over-do it, but I imagine the belts should be pretty tight to avoid stretch during accel/decel but not so tight that they 'resonate' or sing. I am interested in some input from others on belt tension dos and don'ts, too.

Originally Posted by jdelaney44

....... I'm asking 'cause I replied with my thoughts above to another post at DIY-CNC where it sounded like they mounted the motor at the calculated centers and installed the belt based on that. They too said all was good. I believe it, it's just not what I would have ever considered possible or wise.-jd

This is what I have done - kind of. I mounted the motor rigidly .010" closer together than the designed CL so I would not risk crimping the belt during installation. I did not know if the designed CL would be super tight or what and I did not have the motivation to do a test, so I chose the somewhat safe route, knowing that I was going to build a simple tensioner to accomodate for wear and initial belt stretch anyway. My top pulley has no flanges. I am installing positive displacement tensioner - not spring loaded. Pics and descriptions to post soon.......had some issues with focus tonight and the pics I had planned to post suck so I need to try again.

Thanks for the thoughts and comments, JD.

Scott

**mxtras** · 02-13-2006, 05:48 AM

Oh - I had to sacrifice my Y dial holder as I could not produce a keyway that long. It is now a drive hub for my top pulley and it also slides tightly into an outboard support bearing. The arrangement works really well.

The entire system is nearly ready to use and I have not drilled a single hole or modified anything on the machine - except the one dial holder as mentioned above. I looked for another on E-bay before I chopped it up, but none were there. I likely will not bother getting a replacement. It looks like the entire conversion of the X and Y axii will be done without modifying the machine at all. This was a goal, but not a design constraint.

I still need a Z axis, but for the intended purpose, I can get by without Z for a while. It will happen later - maybe later this spring. Too much else to do right now.

:wave:

Scott

**mxtras** · 02-13-2006, 06:36 AM

Well - here's a clear shot from maybe a week ago showing the basic arrangement for the Y-axis bracket and the position of the motor - tucked out of the way. This is the only pic that came out reasonably vivid out of the entire batch......if the others weren't fuzzy (auto focus - WTH?) they were too dark (auto flash - WTH?). It's a relatively decent quality Olympus point and shoot digital - and I can screw it up, I guess.

More pics later in the week.

Scott

**mxtras** · 03-06-2006, 05:07 PM

Well - despite the lack of posts recently, this project has been moving along pretty well. I have not been taking photos or posting progress like I used to and for that I apologize. I will post up what pics I have when time permits - my time has been extremely limited lately and I am really struggling to keep from falling any further off schedule.

I ordered ball screws last week from Hiwin - they were in stock. I paid with a credit card and they told me they would ship within three days - that was a bit disappointing. Why does it take three days to ship something you have in stock?? I can order anything from MSC and have it the next day - even without paying for expedited shipping - why can't every company ship like that??

Anyway - I did my homework before deciding which screws to buy and from whom. I RFQ'd all the players in the BP retrofit ball screw scene - I was surprised that many (more than I thought) of the suppliers did not even respond to my request for quote. I guess they don't need the sales.

I put a lot of thought into this while waiting for my tax return and decided that the accuracy of the rolled screws from Hiwin would suffice for my situation. My list of 'needs' is still rather long and for the intended use of the mill I could not justify the additional cost of ground screws to gain lead accuracy. So what if a longer part is .0015" too short or too long - I think I can deal with it as most of my parts are relatively small.

I should have the screws in hand this Wednesday, 3/8. The bad thing is that I leave for Daytona (Bike Week, AMA Supercross) Wednesday night, so the install will have to wait until next Monday - 3/13. As mentioned - I will photo the install and post the exchange for others to reference in the future.

All of the mechanical parts are made to accommodate the new screws - I just need to mask and paint all of the brackets and such. They were fit to the machine but the final assembly and alignment is going to be a very time consuming thing, so they were not installed permanently - this will happen during the final ball screw installation. All the brackets and motors will be fit, aligned and pinned in place.

I need to reduce one diameter on the new table screw by a couple thou and Hiwin said they do not offer that service so when the screws arrive I will look at the possibility of grinding the one diameter on my lathe - but if I can't get make a rigid, accurate set-up then I will have to farm that out and that will slow me down a little. Luckily for me - I have plenty to keep me busy.... (chair)

That's it for now!

:wave:

Scott

**jdelaney44** · 03-08-2006, 04:15 PM

Good to hear. Have fun at Bike Week! I don't ride or anything, but it sounds fun anyway. Probably a lot of work for you.

-jd

**mxtras** · 03-09-2006, 08:24 AM

Sorry for the delays in posting updates. I have been busy and time is very short these days.

This is a control panel I am currently building. I already wish I had done things a bit differently but I have decided to just knock this one out and if it is completely unusable then I will have another go at it. It will likely end up being a little patched together but it will function. Not my best work, for sure but I have to continue with the current version for now.

I will have to add more text at a later date to explain the pics a little but basically - the PC in the cabinet is a completely self-contained controller housing the power supplies and Gecko drives and it runs smaller motors pefectly but the motors for the mill are larger and I am planning to run them off 48 volts, so the compact, self-contained system is no longer. More on that in future posts.

More pics in a minute....

Scott