Electronic Lead Screw Project

Phil,

UK delivery yes, but don't be surprised if it's shipped from China.

Generally, I find that if the sellers address, towards the bottom of the eBay page on the left hand side, is in China, that is where the item is likely to be posted from. I have been caught out many times like this. Sometimes the items arrive on time, but mostly they don't. I am waiting for bevel gears and a few other things at the moment that were supposedly posted from UK stock. Two weeks overdue so far.

Paul.

Neophyte,

Yes, I've had the same problem but this came pretty quick.

Sometimes they have stuff sent from China, keep it in stock and then put a UK postage label on it to send out but if they have non left they don't tell you but just wait for it to come from China.

Very frustrating!

Pekkka, I had forgotten about that git hub list. Thanks!

Phil. That seems better than waiting from a China delivery for the encoder, but the one I have found on eBay is a bit light on specification

You can change the pulse count because clough42 gives the information in the video about getting the software he rings two important bits of data, the no of pulses and the tpi ( pitch in metric I seem to remember). Only viewed it once

Ah... there’s two postings unseen on this page!

just got got to get all the components before I really start

Edited By Zan on 28/11/2019 18:24:46

Hi Roy

Between my other large list of other jobs I'm in the process of fitting one to my S7.

I'm trying very hard to squeeze the stepper motor into the change gear casing at the LH end of the machine.

Brian

Two PCBs/Kits left to go but I need an address from Nigel Taylor 2 and confirmation/payment/address from LesT

I've tried PMs but so far no answer, please PM me ASAP

Phil

Brian

Yes, avoiding the need to cut a hole in the gear cover looks like the main installation issue . I suppose the motor could be mounted sideways with some bevel gears in the drive but it's very messy. Had you thought of putting the drive at the other end, e.g. with the motor behind the bed and a belt drive to the lead screw?

Roy

What will happen with backlash in the leadscrew if you are using a rotary encoder are you using a linear scale to measure the actual length moved?

David

I will be mounting the motor at the tailstock end Drawings available from Jeffrey.co.uk. Just select the below n google it ......Im not sure doing the modification to the leadscrew bracket or putting the thrust bearings in will be really required as I intend to leave the gearbox in position. At some time in the distant future, the electronics may fail and all the units will be obsolete. I may buy a second processor and led&key board and program both when the whole system is up and running

Myford ML-7 lathe CNC conversion - Part 1: Leadscrew

david, any rotary encoder will only be fitted to a servo motor, otherwise the clough42 system is open loop if a stepper is used.  The encoder in the system is for synchronising the leadscrew and spindle, it’s mounted at the headstock

i am also considering adding a separate arduino system to stop the saddle ar two exact points, at the start an end of its movement and linked to the encoder z to give spindle sync.  This will be similar in principal to the meek and cleve leadscrew dog clutch system

Edited By Zan on 29/11/2019 09:48:19

Edited By Zan on 29/11/2019 10:02:54

The encoders from U.K. seem to be expensive or lacking in data  information pre sale . I want one with a z output for syncing so it mabe a China hobby, but clough42 says I also can’t find a 1024 here, most are 600p/r

” I used a 1024-pules (4096 count) encoder (Omron E6B2-CWZ6C).
Choose an encoder that runs on 5VDC with open-collector outputs.

so does anybody know if this is an npn or pnp device? Or doesn’t it matter ?

The led n key board. Ebay.  Look for .......  

8 bit digital led tube tm1638 key display module for a real arduino te 289 ab.

Price £4.71. From Edinburgh 3 day delivery

Edited By Zan on 30/11/2019 22:07:13

This one appears to have all the right numbers: https://www.ebay.co.uk/itm/NEW-E6B2-CWZ6C-OMRON-Rotary-Encoder-E6B2-CWZ6C-1024P-R-5-24v-100kHz-6000r-min/312836056462

... but I would appreciate a ‘sanity check’ from someone conversant with these things.

MichaelG.

.

Edit: fixed the link ...

Edited By Michael Gilligan on 30/11/2019 22:29:07

Thanks for that Michael, but the Link doesn’t seem to be working, but I’m having real problems with my router at the moment. I was editing my last post. Look at the led board info

Sorry, Zan ... Clumsy arthritic old fingers

I’ve fixed the link now.

MichaelG.

That looks just the ticket! And Looking at the spec it looks ok to me, but I’m no expert

But the lead time is terrible it’s very similar to the ones I’m looking at, with 3 weeks projected delivery  but at the moment it can take 10 mins to load a page to view it and others. So I’m in no hurry at the moment.

Looks like the main bits will cost. the order of £100

Edited By Zan on 30/11/2019 22:46:56

Michael, I'm not an expert either but clicking on the Ebay link in the encoder line item on the Clough42 web site takes me to something with what looks like an identical spec. Not worth ordering anything else and risking problems for the sake of a couple of weeks in my view. The big ticket item is the stepper motor and controller.

Zan, thanks for the link, looks like very comprehensive description of the mods. For reference in full (sorry I don't know how to make it clickable), it's:

http://www.jeffree.co.uk/pages/ml7-cnc/part-1-files/myfordcncpt1.htm

Roy

.

Cheers, Roy

Here’s your **LINK**

http://www.jeffree.co.uk/pages/ml7-cnc/part-1-files/myfordcncpt1.htm

MichaelG.

I thought it might be useful to post a couple of photos of the business end of the Z axis CNC conversion of my S7, which was inspired by Tony's articles but is simpler.

This is the screw drive itself. I didn't do any machining on the bracket as it already has two machined faces. I used needle roller thrust races either side of the bracket, probably from Arc. They have machined cups facing towards the bracket to align them and keep the dust out. There's a spacing collar with a grub screw on a flat machined on the leadscrew, then the pulley - I can't remember now but the collar may be loctited into the pulley. Not visible is a nyloc on the pulley that sets end float and preloads the bearings.

This is the back of the bed. 20mm aluminium plate bolted to two of the 0 BA (?) screw holes in the bed, 1/4 plate bolted to that with slots to allow tension adjustment. Crude but effective. Note I'm using a size 38 stepper for torque, didn't try a size 23 but better safe.

I have to say that I don't see the attraction of an ELS when for not much more work you can have full CNC with supported commercial software, but hey.

John.

That is about what I was going to do, I showed the cnc conversion to illustrate another approach. I don’t think cnc on a hobby lathe is worth the trouble, we do so many individual tasks using different setups on mainly one off items, that it ain’t worth the trouble. I’m doing the els project to make the lathe quieter. Now I’m mainly using tipped tooling at high speeds, the noise from the gearbox train is too much for me so I tend to drop the speed and loose the effective benefits of the tooling.

I was also going to fit a rev counter, although I have a vdf control and a graduated dial, it is not clear to view the actual speed especially when changing belts from fastest spindle speed to slowest for increased torque etc. I will be using a bigger control box than clough42 as I will put the vdf remote controls in it as well to tidy things up. With this system it can all be done in one. I did explore just using an arduino but sorting the coding timing was too much for me.

Roy

i came to exactly the same conclusion overnight and ordered it first thing this morning! If you look at the postage details low down in the info, the lead time is a lot lot shorter than in the listing at the top!

To add to Michael's answer, the CWZ6C is the NPN Open Collector version. If you want PNP Open Collector, buy the CWZ6B. (Can't think of a good reason for buying PNP as the PNP encoder has reduced performance.)

Open Collector is an output convention that expects the attached controller to hold its input line at logic HIGH. This is typically +5Vdc provided by a connecting a high value resistor (>1k) from the input pin to supply. An open collector encoder signals by pulling the input line down to logic LOW by shorting the computer's input pin to ground.

NPN and PNP switch in the opposite sense, thus NPN HIGH is PNP LOW and vice versa. The microcontroller can be programmed to work with either, but, if building a project with someone else's code, easier to follow their instructions!

The same encoder is available in a form that signals by outputting a positive voltage rather pulling the line down to zero. (CWZ3E). Again, the microcontroller can be programmed to work with this convention, but small code and circuit changes would be needed.

Similarly, the CWZ1X signals in RS-422A, which is designed to drive long twisted pair cable - an unnecessary complication in an ELS project.

All the models come in a range of different resolutions making it necessary the check the specification carefully before buying. The lowest is 60 pulses per revolution, the highest 2000. Look for mention on the label or sales literature first for the encoder ID, "E682-CWZ6C" and then find its pulse rate. This will be a number like 1000P/R, 1024P/R or 2000P/R and may not be immediately obvious. The encoder has several makers. I don't think it matters.

Datasheet here

Dave

Edited By SillyOldDuffer on 01/12/2019 13:07:19

Thanks for that, Dave

Hopefully the one I ordered is correct.

MichaelG.

On the question of "CNC on hobby lathes", I think the view that it isn't worth the trouble is to mistake how CNC gets used in practice. Almost everything we do can be reduced to turning parallel, facing, boring, and tapering. Every one of those can be done with a CNC wizard. No need for a ball turning gadget, just another wizard. Any thread you want? Got it. And then you can use CAD/CAM, or generate your own g-code to produce mathematically defined profiles. To make the best use of it CNC does force you to have a system of repeatably mountable tools and calibrate their offsets, but once you have that it's so much easier. Want to face off and turn down a bar to a known diameter? Switch on the lathe, home X (once per session), put the stock in the chuck, mount the desired tool, find the end of the stock with my end finder, launch the wizard, insert the dimensions, and run. No more feeding to the shoulder being careful not to overrun, stopping to measure every so often, forgetting how many cuts you have applied so you scrap the part, trying to take that final last shave off to reach the right diameter.