CNC Gear Hobber

Hi,

Does anyone have experience please of adding an optical encoder to a vertical mill [this one is an Amadeal] and driving a stepper motor with suitable software and circuitry so as to build a gear hobber. There is a Youtube video on doing this but it is 2010 so I am sure the software would now be out of date and the optical encoder which he built also. Thanks.

Put 'stevenson gear hobber' into Google.

Read and digest everything you find (including the back issues of MEW).

Then you will be in a better position to understand the state of the art and crucially the boundaries/limitations of the method. It is this understanding, more than anything else, that will determine the success or failure of your venture.

Look at the electronic leadscrew thread here and on YT. Same basic principle of electronic gears rather than mechanical gears.

Software and encoders are 'industrial Lego' and are easily replaced.

Thank you I'll look that up.

Please could you tell me which back issues of MEW are relevant. Thank you.

Afternoon John. You can find the electronic leadscrew thread here:

Forum ELS Project discussion

Clough42 ELS Project on YouTube

Cheers,

James

https://www.model-engineer.co.uk/forums/postings.asp?th=75580

John;

If you are referring to Andy Pugh's hobbing videos; it is still very relevant and in use all the time. It's LinuxCNC, which is the base for the Tormach controls now.

You can contact him via the LinuxCNC.org forum, or the mailing list, he seems to be very helpful.

It seems like any optical encoder can interface so long as it has the index pulse will work with LinuxCNC for this purpose.

It's a cost-effective solution, but one that is not off the shelf.

John.

Yes it was the Andy Pugh one I watched. I will try to contact him. Thank you.

Hi, I've not been able to get in touch with Andy Pugh. I couldn't see how to contact him on the linux forum. I've been looking at my Amadeal mill and of course it already has a sensor on the spindle that feeds the rpm back to the control board. Has anyone investigated what this output is and whether it could be used to input to a arduino?

John;

First, check your messages for Andy Pugh info.

If your mill ls like my "King Canada KC20" (sold under different names) then yes, you can send the signal to a computer; it won't give you rotation direction nor does it have an index pulse, but it's great for ensuring that the mill is running at the correct speed, no matter what gear you are in.

I assume this is the video mentioned

Are the teeth on a hob of this type straight sided like a rack style hobber? Is there a correction to the pressure angle on the hob?

Thank you John, got the message. My mill is an Amadeal with the brushless dc motor so I expect it's the same. It's out of warranty so i thought of putting a connector on the side of the control box and taking the output. I wish I had an oscilloscope so I could check what the output is.

Hi

In reply to your opening post.

I have an optical encoder fitted on the quill of my Warco mill when it is set
up for hobbing.I made a split collar that clamps around the spindle turned
in situ that remains in place all of the time ,the drive gear is a close fit on
this collar and secured with 3 screws. You would of course loose the access
to the spanner flats or maybe you have already done so from your posting
of 13/05/2020

(Would it be a good idea to turn up a steel ring and loctite it in place?)

The photo here shows the encoder clamped around the column and gear
being hobbed.The original article appeared in MEW 193 Sept 2012 .
The hobbing unit was designed by Richard Bartlett who makes the Compucut
cnc system ,when i enquired on behalf of another forum member he
still had about 12 of these units in pcb form available.I still have all of this
information available if you are interested.

John

Bazyle- it was the Andy pugh video I knew about, I haven't seen the one you gave me a link to.

John- how many pulses per rev does your encoder give? I am trying to do this with arduino but i would like to know how much the system costs for one already made please.

Hi John

The photo here shows the encoder on the mounting plate,
in the box is a 500 line encoder wheel geared at 2:1 and reading
on the two channels would be 4000 ppr.
Seen here this 2000 line encoder driven in the same way would
have 16,000 ppr,
With this sort of setup it is very easy to get any number of pulses
that you need.
I have had this system operational now for 10 years and cut
hundreds of gears for my own use.You would need to contact
Richard Bartlett to find out if he still has these and the cost .
I will send you a PM with the contact details as this may be
his home number and i don't wish to put this here.
This Syncron system is only the electronics for the hobber
the power supply and stepper motor driver needs to be obtained
additionally as does all of the mechanical parts.

John

Thank you for the information John. Looking at your milling machine it is obviously much larger and more powerful than mine is. The problem I would have with the standard 2 - 2.5 inch diameter hobs is that I don't have slow enough speeds. Mine does not have back gear and the torque just isn't enough at slow speeds. I think ArcEuro used to do small hobs but i can't find them on the site now.

I might fit back gear of course and use the bull wheel to drive the encoder. I had thought of fitting back gear , it wouldn't be too difficult.

Hi John

The Warco machine that i have is an A2F ,Warco no longer sell these,
Chester still do as the 830 VS so you could compare with yours.
They are not all that different mine has an R8 spindle 30 x 8 inch table
i think the motor is 1.5 kw.
I use the hobs that were sold by Arc euro,at the time i started with this
hobbing they had only just started to sell them.Very good cutting tools
its a shame they no longer sell them,i think as the stock run down they
just never got any more ,i think i bought one of the last in around 2015
this 20 DP Myford changewheel size hob is about 50 mm diameter
most of the hobs they sold were around 25 mm dia.
I have under way and for some time a modified version of the hob
relieving attachment that was in MEW 57 page 37 ,some of the
parts here are seen in the photo along with the 20 DP hob as above
shown in the foreground on the left.
This is intended as a part cnc/mechanical endeavour where the cnc
part just provides some automation to the proceedings,there is still
quite a way to go before it is up and running.

I don't hob gears above 1.25 mod / 20dp as i find most of the stuff
i make suits these sizes.

John

Just a quick note that an alternative to a high count encoder on the spindle is a phase-locked loop IC with even a 1 pprev encoder to multiply up the frequency - the CD4046 type chip should do the job. Also I think Joe Noci has built a processor-based system that does something similar in software.

Thanks for all the input. I don't know really how to get over the slower speed problem. I see from my book by ivan Law that he used a Dore Westbury mill which I believe had an epicyclic gearbox inside the pulley. I don't think I could fit one to mine since the pulley is far too small. Hobs on eBay all seem to me around 50 -55 die.