Here is a list of all the postings Joseph Noci 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: You think you have trouble starting your car on a cold morning?|
Nice One Neil!
There are many utube videos with engine starts as the theme ( some steam as well) - from old aviation engines, tanks, trucks, ships, etc and, for some odd reason, I am hooked on watching them...
|Thread: CNC Lathe Scratch Build|
Well, I believe in treating my equipment with care and that the machines will then deliver the design performance even after I am gone..
I could never feel comfortable going to make something on a machine that is covered in years of grime, chipped by careless tossing of tools onto it, greasy and messy, etc...I clean most of the gunk off the machine at the end of the day - makes it nice to start again the next day, without trying to dig the machine out the swarf and muck...
Just adds to the pleasure of making stuff!
Anyway, thanks both of you for the encouragement - I tend to get lost in the making, and sometimes wonder if the madness is maybe only mine - would rather not foist that on 'conventional' modellers!
Thank You Pete. The build did not start with any major use in mind - the result is limited to what a 5C collet lathe can do and will only work under full CNC, so cannot even be used as a manual lathe - even with electronic handwheels fitted for X and Z. A six station auto-tool changer is in the design stage as well, and the structure is that of a conventional slant bed CNC lathe - the tool approaches the work from behind the work piece so manual operation is a recipe for a crash! Inverting the X infeed direction in the brain, while ignoring the direction in the eye is not easy!
You, and others, will have noticed by now my 'mechanical engineering' pleasure lies not in the building of models, steam (or otherwise) engines, etc - I enjoy building machines, which make more machines!
The lathe is a huge challenge. The build accuracy is not easy to achieve - my mill(s) are a lot smaller than the major parts of the lathe, so a flat lathe bed is not easy to achieve, etc. Since I am trying for better than 0,005mm on machined parts, aligning the lathe axis and headstock is key, and difficult!
Together with the ATC is intended a full C axis and basic live tooling - a milling spindle that can cut in X or Z axis on the work piece, so some additional mechanical challenges ahead.
And then the control software is another mission - there is no commercial controller and software available to control a Lathe with C axis and live tooling - to qualify, there is, but at major prices, for the big CNC names in industry - many thousands of Pounds! Likewise for the CAM software, which will be another interesting exercise.
The intent for the controller side is to use LinuxCNC and 'make' it work - another big journey! That will be the subject of separate topic of posts in due course!
Hope this rather narrow topic is of interest to more folk on the forums and not just taking up server space!
Next Installment on the lathe build..
Most of the major part manufacture for the lathe proper is done - some small items left to do - ballscrew to ballnut mating seals, pulley keyway broaching, etc..
Doing the counterbores on the X axis slide plate / carriage -
Made an under-pin fitting into the mill slot, over which the thru-hole in the carriage plate slips, and then the plate is clamped to the mill table. The endmill, used to counterbore for the capscrew head, is centered over the pin. So, plunge, unscrew clamps, lift plate and slip next hole over pin, clamp and plunge.
The X and Z axis limit switches where a bit of an issue - all the readily available sensors are rather large - mostly the tubular/cylinder style, and make an unsightly fit - so made up some Hall sensors which work very well, and fit cleanly. - these to be encapsulated in epoxy resin.
The headstock is all done - pulled the cheap Indian test bearings out and cleaned all parts, inc the final Timken bearings, oiled and assembled - feels soooo smooth!
19mm collet fitted with a 19mm ground test bar fitted to check runout. Bar is 300mm long, 0.005mm runout at collet, .012 at bar end - need to investigate that...
The small square plate at the base of the headstock, below, is the Z axis hard-stop for homing Z.
Manual collet closer wheel and drive pulley sheeve. Rotary encoder below
Brass button is oil filler with breather hole
The whole lathe alignment is quite a daunting task.
Headstock nod - to bed in Y and Z = using test bar, with an accurate square ( 70mm diameter x 160mm tall Aly bar, squared off at ends) with feeler gauge to test height to bar at collet and test bar end.
Then Z axis slide rails ( front and rear) height to test bar with dial indicator ( as below).
The headstock rotation - using dial indicator on side of test bar and rotate headstock til parallel.
Z slides are parallel to each other to 0.005 / 0.008mm, ie the steel bed width is parallel.
X axis will be done by machining a face and verifying for flatness.
X axis assy fitted and initially squared with headstock face.
More in a week or two..
Edited By Joseph Noci 1 on 14/02/2021 20:49:22
|Thread: Mist Coolant (Fogbuster)|
My flexi-nozzle uses the same interlocking flexi-tube as most the flood cooling systems do - The air supply flows inside that, and also within is a 4mm OD FESTO plastic tube that carries the oil to the nozzle. The base has two entries - one air and one coolant, from the mixer contraption. The base has a magnet undet and can be parked anywhere convenient..
Magnet under base - from a small loudspeaker...the groove around the circular magnet below is where the voice coil used to be..
Coolant inlet pipe fitted - 2nd hole is air inlet.
|Thread: Noga Rotodrive|
I have a few of the NOGA offerings - the large handled kit, a large handled single unit, mainly for deburring edges, corners and sheet edges, and a mini-kit.
To be honest, I NEVER use the countersink capability - I find it awkward and an uncomfortable motion. For CSK deburring, I have some of these:
Ann I use them in a small battery powered drill - that works very well, at slow speed, and one gets the hang of it very quickly - easy to deburr a hole drilled, or apply a more prominent CSK to a tapped hole, etc.
For deburring corners of material, such a milled flat surface edges, or guillotined sheet metal edges, etc, the NOGA kits work well, but I find the long handled types uncomfortable and when doing inside curved edges for example, the need to rotate the tool in a compound fashion while sliding the cutter along the edge is uncomfortable - it requires the whole wrist and fore-arm to rotate, rather than fingers and wrist.
The Mini-Kit is my go-to deburrer ( is that a word??) - very slick to use, quick and easy. Hard to describe the uncomfortable action, but its like whittling a chicken egg sized object with a carving knife versus a penknife...
The NOGA kits I have - this one is new and used maybe a half dozen times - probably won't ever use it again...
This is just a single tool, with spare deburring blades in the handle - gets used when really heavy cuts are needed..
And my favourite: The handle is 80mm long, 16mm across flats
|Thread: Mist Coolant (Fogbuster)|
The point is that you are NOT supposed to be generating a mist - the objective is achieving micro droplets of coolant carried in the airstream.
A large part of success lies in the nozzle. I can turn up the air volume high enough to blow chips out of a groove being milled, without mist developing. The trick is to have a large area of air exit at the nozzle, and to have the fluid exit hole well past the airflow nozzle tip, ie, the fluid outlet tip in my nozzle is about 6 to 7 mm outside the air nozzle outlet tip. That way the venturi effect is almost negated and the fluid is transported down the center of the airstream . The fluid outlet must not be at an air expansion point within the airstream, as it is at that point that a drop in air pressure occurs, and the possibility of atomization arises.
These type of systems should not be referred to as 'Mist cooling systems' - The ones that have earned similar system the bad reputation do just that - generate mist - and that is NOT what you want. If a mist results, very little of it ends up at the cutting tool tip, a lot ends up all over the work area and in your lungs, etc. If mist is being created it is a sure sign of excessive air velocity at the mixing nozzle. The aim is to have micro-droplets of the fluid trapped in the airstream, certainly no mist. If you see fog at all, and it floats about, the fluid has been atomized and that is not desired and hazardous to your eyes and lungs.
I built such a system and posted here about the build - A pressurised fluid chamber with the fluid entering the mixing nozzle where it met with and was entrapped withing the low velocity airstream. It works very well, but only did so once I fitted pressure regulators in both air feeds. A single air line feeds both regulators, with a air solenoid in line, activated by spindle on. When turned off, the solenoid vented fluid tank pressure to air so the fluid flow stops right away. The fluid tank outlet to the flow line is via a needle valve to be able to set fluid flow volume to suit fluid viscosity, etc. - I use only neat cutting oil, no water soluble types, so viscosity plays a bigger role.
The nozzle design was a bit of effort too..
All in all, a bit of a pain to set up, but once running, a pleasure to use.
Don't know how to post a referral to my specific posts on this, and don't want to repeat the whole thing here, but here are some photos..
1 'drop' per sec with air
1 'drop' every 2 sec, with air
1 'drop' every 5 sec
3 drops per sec with air.
Flow stream , no air.
Nozzle. Air flows around it, inside the blue tube in the background. Fluid flows from a small hole in the nozzle tip.
Hol is 0.7mm OD
|Thread: Gear Hobbing computations assistance requested|
John ( Pace), Thank you for the time you have taken to explain and help me along. I have a much better understanding and the concept of not eroding away the teeth with my setup is also better understood. Thanks to everyone who joined in as well - this stuff is not rocket science, but appears so while the fundamentals elude one!
The penny dropped here:
The 2nd photo here is a worm wheel that would be suitable to
Since in my first runs I did erode away the teeth, but realise now that was because my ratios were way out for that tooth pitch and blank diameter - the teeth did not walk over each other, as I thought was happening, but per you explanation above, they simple began to thin out to the point of vanishing...
I am going to make up a handful of scrap plastic blanks , start with the computations and go and experiment to see what actually happens.
John, my application does not require any appreciable power in the transmission - zero backlash is very critical though. That is why I considered a screw thread type tooth profile as appropriate - esp as I can adjust the worm shaft easily to squeeze worm and gear together, forcing the flanks of the teeth of worm and wheel to ride hard on each other, hopefully eliminating backlash. I am also banking on that form providing some protection in the event of things going awry while in motion and the arm being forced into a hard stop - hopefully the worm wheel teeth will just give way..
Before I started with all this, I read through Ivan Law's ' Gears and Gearcutting' - but did not absorbs what I should as I did not know what I did not know... Having read Chapter 7 thoroughly again I have rekindled confidence..
Thank again to all, very much appreciated.
Pete, I believe I understand that. What I would like is achieve some level of agreement between the math and the 'gear' I hobbed. That is after all how commercial manufacturers make good gears! I don't need to be exact, but my gear at 112mm OD after hobbing seems that it should have been around 116mm - fudging is fine, but that is quite a difference. All I want is to obtain the calculated number of properly formed teeth on a sound PCD after machining. If that is a mm out from the calcs, OK, but 4mm is stretching it.
The issue with adjusting the OD/PCD to 'suit' is that its done blind, ie, I start with a way oversize blank and hack away at the periphery till the teeth look good - not very scientific! And then I end up at 112.5mm OD, which is NOT what the maths says it should be - Rather what MY math says is should be - John intimated that my calcs were correct, but the result is not correct! So I was hoping someone can set me right with the math!
Wow, thats all way to much for me! I need to read all that a few times and try understand - I think I have a problem in grasping some fundamental issue here, and so the rest will not fall into place.
I dont quite follow the concept of the 'index' position - If this was a single point cutter, and I indexed the rotary table 158 times around the blank, spending time at each index position to cut the tooth, then I agree, the cutter can only fit into a slot that is one of the 158 index positions.
But in hobbing with a helical hob ( the tap) there are no 'individual' index positions. The only criteria is that a gear tooth crest must always line up with a hob trough as both rotate. Now if the gear blank diameter is too large, the 158 teeth will fit into a shorter periphery ( since the pitch of the hob did not change), and although the hob tooth should then mate with the periphery tooth 1 again, it actually cuts fresh blank - ie, putting more teeth on the blank, in the extra circumference. The chance that when the hob meets the original tooth 1 in the blank, that it mates with it, is pot luck...and so the teeth begin to be cut on top of each other and erode.
That does happen, I watched it many times over 5 or 6 blanks, and only ceases when the blank diameter is correct for that pitch hob.
I believe I understand your comment John:
,the effective pcd has changed along with the profile shape of the tooth which just uses a different part of the the same involute
But does that not only apply if you are changing by one or two teeth, sort of thing, ie, a small change to fiddle the result?
John, then what gets me is - refer your comment:
Getting back to your gear for 158 tooth on a pcd of 116.13 mm the normal od 117.60 mm
I think that these measurements agree with what you have
If those measurements are correct, why did my final gear, with 158 teeth around it, apparently neatly spaced and formed, result in a final blank OD of 112.5mm?
Should that not have been 118.87mm - 2.159mm, ie = 116.71mm??
112.5mm is quite some ways from 116.7mm!
Also, can you please explain where this dimension is taken:
The cut width across the face of the gear at this should be as measured 10.80 mm .
I am battling with this indexing versus spacing thing!
Pete, you said -
That's the point you will not erode all of the teeth because you're not relying on spacing but on indexing. The 4mm error is spread between the teeth but it's not added together to leave a gap at the end. On the first turn you have 158 indexes, on the second turn you have 158 indexes, and so-on. After ten turns you'll still have 158 indexes and each one will be in the exact same place as all the other turns.
Surely that is only possible if the gear blank periphery is divided into 158 equal spaces ( the teeth)? And since these spaces are directly related to the pitch of the hob, we surely have little room to fiddle the space size? And then, to fit 158 indexed positions , related to the hob pitch, equally around the blank, we need to have the blank the correct diameter.
I am sure I will see the light soon..!
Afraid I did not understand that...I realise that with the driven HOB process, you will get the number of teeth, but that number of teeth will only fit properly on a circumference if that circumference is correct...And that is the issue here - I am trying to calculate what my gear blank diameter should be. If the diameter is not correct you simple erode all the teeth down to naught eventually while hobbing..
Jason and Michael, thanks for that. Makes a lot more sense now.
I really thought cutting this worm wheel would be simple, but I am still battling.
I read Andrews post through prior to my post on this, and re-read it a few times this morning, re-looked at my calcs and went and cut another blank - not a success...
Cant see the wood for the trees now.
I hobbed another blank to test again, based on the following calcs, and with the results indicated.
From Michael's reference, I calculate the tap should penetrate about 1.9mm into the blank - (H-H/6).
I chose to cut 158 teeth which gives a PCD of 116.13mm. That 'should' give a blank OD of around 117.6mm.
I prepared a blank off 120mm diameter and started hobbing. I fed in from the periphery , which I think has an inherent problem - the No of teeth cannot fit into the periphery, and can only be correct at the PCD, so teeth started to be over-cut...( see copied text from Neil's post in Andrew's post on worm gears..)
Then fed in to full depth ( which should leave me with an OD of 117.6mm, - in the trough- no?) , but the teeth were still being over-cut or overlapped.
I continued to feed in slowly, and got to a point where now the teeth stabilised and were neat and uniform. I let the hobbing continue so that the blank had done maybe 50 or so rotations - the teeth remained clean and intact.
I removed the blank and counted the teeth - 158 teeth!
That was good, BUT...
I measured the now new OD of the blank ( at the crest of the teeth, but at bottom of the radius as cut by the tap - see 2nd photo) and the blank measures 112.5mm !! Nowhere near what should have been an OD of around 117mm.
158 teeth - counted a few times.
The OD here, across the outer edge, is close to 115mm
112.5mm OD - ???
My tap is a 5/8 BSW for sure. Engraved on the body, and I count 11 teeth in an inch.
I am at a loss!
Copy of Neil's comment:
Edit: thinking about it when the hob first contacts the blank, it's 'natural pitch' will want to cut two extra teeth at the OD than it will cut when advanced to the PCD. Perhaps a way around this is to have the hob fully advanced from the start and make the cut from the side of the blank rather than in from the edge. That way the hob's PCD will remain constant at the required value. Does that make sense?
Edited By Joseph Noci 1 on 01/02/2021 09:37:06
In trying to have a better understanding of the formulae for gear cutting I used some of the various thread form charts for the BSW thread taps to determine thread pitch centerlines, etc. However, something is amiss in these charts - and this seems prevalent in ALL of the BSW charts.
The thread in question is 5/8BSW - the chart gives data in mm.
I am interested in dimension H1.
That should be equal to D minus d3 in the picture.
But D=15.876mm and d3=12.913mm - the difference being 2.96mm, NOT 1.479 as in the chart.
However, 2.96mm / 2 = 1.48mm, close to the chart H1. I do not understand the diagram reference as the dimensions d3 and D are from the thread axis and so the dimension H1 should just be the difference?
Where have I gone wrong?
I am very new to hobbing so do suffer from lack of understanding! I built the electronic control for the rotary table and implemented a hobbing function which I believe works correctly - a duplicate of this setup was built by another member and he used it to successfully make some gears. At least that eliminated any underlying software issues!
So the problem lies just with my understanding!
Pete, if I extrapolate your 1 thou error, for a 158 tooth gear, it give a 4mm 'error; after once around the blank, so I would need to increase the blank diameter or reduce the number of teeth - the latter being no problem. The problem being obtaining said hob - complicated from where I live here in Namibia.. The forces and torque involved in the application are very low, speeds are very low indeed - the wheel max rpm is typically 1rpm, so the worm runs around 150 to 200rpm max. and accelerations are gentle.
The gear is either HDPE or Polyprop. and is quite slippery. I am hoping to achieve very low or no backlash simply by forcing the worm up hard against the driven gear and run it in so that they bed in and mate well, with a little of that very thick silicone 'oil' ( more like a 'solid' treacle!) on the gears.
Thanks John. That all makes sense. Since I have to cut away the existing teeth on the 120mm OD, I think its safest to go for 158 teeth, which gives me the 117.6mm PCD. I have to do some setup though to get my measurement references correct to know exactly where the tap cutting edge is in relation to the pitch line.
John, Thanks for your input. I think I am missing something though!
You indicate PCD=123.4mm +1.5mm for OD + wraparound : I understand your reasoning there, but that's not close to 118mm as you say it is ?( which I had worked out I need for my blank OD) -
If your reasoning is sound, I need to reduce the tooth count by a good few teeth to fit within my 118 to 120mm blank, it seems.
No teeth = (PCD x Pi)/ 1/11TPI .
So for PCD = say 118mm, and 11TPI = 2.30909mm
No teeth = 118 x Pi / 2.30909 = 160.5 teeth.
So I need to choose 160 teeth and that should get me close to a PCD of 117.6mm, and therefore a blank of 120mm should be ok for wraparound, etc.
Somewhere it seems I just messed up the calculations and came up with 168 teeth, but what surprised me was that even in cutting down more and more on the blank - till 112mm OD, I still did not get a balance of teeth into the blank!
I think I need to do it again and be more observant to try see what is going on!
Perhaps I have not explained correctly.
I am not truing to match the existing gear profile - forget that it has 170 gear teeth already on it - consider it to just be a blank disc into which I wish to hob teeth, the shape or profile of the 5/8 BSW hob. I want a final diameter between 110mm and 120mm, with tooth count between 150 and 170 - thats it...The profile will match my worm ' good enough' 'cause that I will cut to 5/8BSW.
I am not free hobbing - I am using a hobbing machine - well, my rotary table and my Hobber controller..
I will take photo's of the actual job and post tomorrow..
I kindly request some help in calculating gear blank diameters for a worm gear I am trying to cut.
I am still busy with my Polar arm 3D printer, which has as drive train a stepper with a 20 tooth gear, and the arms with a 170 tooth gear - 8.5:1 ratio, This is still way to high and the only practical way forward, due to structural implementation constraints on the machine, is to place the steppers at right angles and drive by means of a worm gear. The idea is to hob into the existing 170tooth gear and make a mating worm to drive said gear.
The 170tooth gear is a large model helicopter rotor drive gear, plastic, but tough as nails. The Hob is a re-purposed tap - a 5/6 BSW-11 tap, which I have re-ground on the T&C grinder, to have well raked cutting edges. It cuts the plastic beautifully..
The tap - 11 TPI 'almost' mates with the existing 170 tooth gear. That gear is 120mm OD. I am un-constrained in actual gear diameter as well as actual number of teeth on that diameter - that is taken care of in the printer software.
So, as I am not aiming for s specific number of teeth or gear diameter, this should be easy...Nope....
I have spent many hours trying to work out the match between what I have, the number of teeth I can fit, DP, Addendum, pitch and Base circles, Outside diameters, etc.....I came up with 168 teeth on a Gear blank OD of 118mm.
Some of the constants for the calcs were an intelligent guess though - I do not have such good data on the Tap teeth
I wish to use the existing gear and just hob it to size, so to speak, with the result hopefully being around 118mm OD, and 168 teeth - having cut away all the old 170teeth in the process.
I made test blanks, 200mm OD, and started to hobbit..I stopped with an OD of 112 mm, and lots of missing teeth...
I tried 5 more blanks - set the No teeth to 165, 166, 167, 169, 170 - still a disaster!
I expected to see teeth being obliterated with multiple full blank revolutions while the blank diameter was incorrect for that tooth qty selection, and that tooth erosion begin to cease the deeper I cut, ie, as the blank diameter supposedly approached the correct one. I all cases I approached a final blank diameter of 100 to 112mm (from 200mm!!) with no sign of anything looking to work.
I am not sure how to proceed!
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