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View Full Version : My comical CNC lathe story and does anyone have experience with gang toolposts?



Rob
26-08-2016, 07:37 PM
Here is the basic time-line leading to my question... I had an idea to make some things but I knew very little of machining. Did tons of study and realised I will never know enough but didn't give up (stupidly or not I don't know yet). Decided CNC was most in line with what I wanted to do and got some quotes for others to prototype and produce my designs but that didn't work out. After much searching (and begging for loans) I bought a refurbished Orac cnc converted to Mach3 with a home-made auto tool changer. Learning curve (everything) so steep I wanted to just jump off a cliff so many times but stubbornly carried on.

After many trials and tribulations such as needing to change the foreign language half-broken laptop computer it came with and stuff that I won't mention because I know how stupid it will make me look (oh, you have to twist the EM button to reset it?) I have got to the point of manually using the keyboard to jog the tools to make some things. Not the way it was intended, but I have at least now made something and know a lot more about Mach3 and the lathe. Still long way to go with the 2d/cad/cam stuff. Thinking I'll just use the wizards at first.

The immediate problem is the auto tool post constantly slipping out of alignment. For plastic is was fine but lately I have been trying brass and it slips a lot. Maybe I am sometimes feeding it to fast and/or cutting to much depth at one time and this wouldn't be a problem if using the lathe as cnc? I took the changer apart and can see how a couple of set screws hold the tool post alignment gear with the axle, I don't think this is a rigid design. Also the little transformer looking motor that changes the positions is constantly heating up quite hot even though I'm not using it. So I am thinking to change the auto-changer for something else. First I thought about using a quick-change tool post but then I remembered seeing someone had an arrangement for multiple fixed tools on a plate and found out this is commonly referred to as a "gang" tool arrangement. Lots of videos on YouTube for this style of tool holding. I am only going to make small items and from what I've seen I think are non-standard (?) boring type tools that do things like external grooving/parting etc... the number of tools on the Orac could be easily enough to do what I want given the cross travel distance.

Having said all that, does anyone have any experience using a gang tool holder/plate type set up? I see these tool holders can be made specifically to hold regular and modified boring tools directly or they are made to hold multiple ER collet chucks which in turn hold the tools. A company in the States that makes gang tool holders is Omniturn, but maybe someone knows of sources in the UK?

Cheers
Rob

m_c
26-08-2016, 09:51 PM
I ran some gang tooling along with a QCTP (Quick Change Tool Post) on my old connect lathe.

I had mine setup to take three ER collets. Details of the setup can be found at http://www.machsupport.com/forum/index.php/topic,20153.0.html

There are plenty videos on youtube for ideas, but the big limiting factor is X-axis travel.

Personally, I'd see if the tool changer could be made reliable, as manually changing tools continually gets quite monotonous.

John S
26-08-2016, 10:23 PM
Rob,
Do you have photos of the tool changer.
A lot of these did look home made even though they were made by the manufacturers. They used to have a tiny 24v DC motor and it spun to work the worm and wheel [ very crudely made] and went past centre, then reversed onto a ratchet and the motor stalled but then it dropped the voltage to around 9v ? to hold it on the pawl.

Billythefish
26-08-2016, 10:31 PM
New user, hi all!

Some stuff I have learnt with an emco pcturn55:

drop mach3, use linuxcnc.

probably your auto changer will work fine (mine does). Post pictures and i can comment more...

gang tooling will also work fine.

You need a milling machine to make tools for your lathe...

cheers,
john

Rob
27-08-2016, 08:26 AM
Hi, thx for both replies. I made a video to send to the guy who made the toolpost (youtube link below). His English is limited so I did repeat myself a few times and also I really had no proper idea what I was talking about :) Since then I started to take it apart and found I was completely wrong in that the two set bolts are in fact the ones that are used to adjust the gear position and which I have adjusted numerous times now. It works for a while then slips.

The motor voltage drop would explain how they solved the tool from bouncing up and down, I was wondering about that if the belt would hold it with tension from the motor. The motor is also getting very hot though which worries me.

Anyway, the video still shows the changer quite well so please have a look and let me know what you guys think. I'm pretty sure he did make it himself and well done to him, but I just don't know what to do to about this slipping. Plus the motor is getting very hot.

https://youtu.be/mpLcjtrQ3pA

Cheers
Rob

PS: I haven't got to the point of using the Orac with g-code yet, only using the manual jogging. I'm hoping to ask a friend who used to work with cnc lathes to explain the basic Mach3 turning wizards to me when possible as the cad/cam process is a bit daunting right now. I can't even understand (yet) how the different types of homing works. I'll get there eventually.

As much as an auto tool changer is a nice idea, I still like the idea of a gang tooling arrangment. Also, this man, (maybe the forum knows him) made a really nice tool post https://www.youtube.com/watch?v=IfYLgENFvIk

John S
27-08-2016, 12:55 PM
Rob,
Won't get a chance to reply in full until tonight but once the bolts are adjusted you really need to cross drill it and fit a dowel to stop the slipping. Also make two decent thick washers up instead of the off the shelf punched out ones that will never tighten correctly.

It looks to be reasonable made but the direct belt drive frightens me. It really needs to go thru a worm drive so it can't drive back.
Something like this.

http://www.stevenson-engineers.co.uk/files/tool%20changer.jpg

Rob
27-08-2016, 08:30 PM
Thanks for having a look John. I was also thinking to drill it through and put in a dowel pin, but long term if more tools are added it might end up needing lots of holes. Actually I might do that in the short term until I can get a gang tool arrangement. I dont even see how the individual tool height can be adjusted without using shims or something. I just don't like this thing, such a hurdle and I haven't even got to the cnc part yet, rofl.

John S
27-08-2016, 09:18 PM
If the tool plate and ratchet have been machines accurately they it should all stay in line. You have guessed right and yes you do have to shim tools up to get on centre.

Where are you based ?

One problem with gang tooling is that the Orac doesn't have a great travel in the X axis to get different holders on.

Short term, if the bearings on this tool changer are OK and not got loads of bag in them is to replace the ratchet wheel with a wheel that has 8 ? holes in it and use a detent pin to locate it after turning by hand, like the example you linked to on YouTube.

Rob
28-08-2016, 12:33 AM
Well John, I just had a long look and play about with the auto-changer and think you are right that the best way forward is to get one of the tools aligned the best I can, tighten the set bolts then drill though the first piece and partly into the cog gear, then use a dowel to secure that position. Then any other tools can be adjusted with shims.

The gang tool idea, you are also right. I could maybe get 4 tools on there but I can see it's a major endevor. Forget it for the Orac.

As for the bounce back of the wheel when the lever is on a cog gear, well, the original belt and motor hasn't shown not to work yet so I will still have an auto-changer if that works. If the motor doesn't hold it steady enough, then I have a second plan to cut out the auto changing part and use rubber bands from a hook on the casing and for each tool change I'll hook the bands over a tool on the other side effectively pulling the wheel in the opposite direction. Sure, cowboy way of doing it but I don't have a machine shop and live in the middle of no-where in rural Scotland. Came up from England to do a bit of gold panning and decided to stay, lol. Accent is Canadian, moved to UK 1990.

While looking at this toolpost I also played around with the homing controls, didn't go well. I'll have to sit down this week with the Mach3 pdf instructions and go through it. Bit by bit. Also I would like to see if I can actually get the auto-changer to change a tool, I can't figure out how to do it yet.


Thanks for your thoughts and suggestions on this, I think I can get this thing to work. Happier than yesterday :)

m_c
03-09-2016, 12:48 AM
drop mach3, use linuxcnc.

probably your auto changer will work fine (mine does). Post pictures and i can comment more...


So changing controller software will fix a mechanical problem?

magicniner
03-09-2016, 11:35 AM
So changing controller software will fix a mechanical problem?

Ah, but for some Linux is more of a Religion than a tool for a job, it's mystical properties, not revealed to non-initiates, can solve not just mechanical problems but also cure coughs, colds and pimples on the makewater!

:D

i2i
03-09-2016, 02:49 PM
changing to linux will not sort your problem, all that will do is to give a massive headache.

Right getting on to the real problem, the simplest way to cure this is to lengthen the "pawl", this is the rectangular part that catches on the rachet wheel. Similar tool changers to this have an adjustable end stop for the pawl which sets the tool position relative to the centre line of the lathe.

Or you could raise the whole tool changer to match the centre line, but this may give your tools a bit of positive rake.

I'll pm you my mobile number if you need a chat.

Tom.

Rob
04-09-2016, 08:07 AM
changing to linux will not sort your problem, all that will do is to give a massive headache.

Right getting on to the real problem, the simplest way to cure this is to lengthen the "pawl", this is the rectangular part that catches on the rachet wheel. Similar tool changers to this have an adjustable end stop for the pawl which sets the tool position relative to the centre line of the lathe.

Or you could raise the whole tool changer to match the centre line, but this may give your tools a bit of positive rake.

I'll pm you my mobile number if you need a chat.

Tom.

Hi Tom, thanks for the reply, haven't checked in for a couple of days...

The linux/mach3 debate, maybe one day I'll have a proper cnc machine such as a Hass that comes with dedicated software but until then I'll stick with Mach3 because at least I have learnt to use the jog buttons, lol, yes I have a long way to go. The home/referencing thing is doing my head in right now. Then there is the offsets, then actually getting a wizard to do something, then fingering out how to string them together. And that's just the software! How to find where to buy cutting inserts that go with the tools I have, %&%$&% if I can find them even after calling the UK office of the manufacture and them sending me on a wild goose chase. Ok, too much pouring out my frustrations with this lathe/cnc steep learning curve, it's all fun, on to the auto-changer...

This thing is a bad design in my opinion, I am not a pro but if I was to design it, each individual tool would have an adjustment of a few mil either way up and down without having to use a shim of some sort. The paw that clicks into the ratchet wheel on this thing has two Allen bolts which are loosened to adjust the wheel and tool face relative to the work piece but only for one tool so the rest need shims if not aligned up naturally. The problem is not really aligning the tool, it's keeping the alignment where it is once tightening the bolts. This is why I will align one of the tools then drill the two parts and put a dowel pin in, at least then they will not move out of alignment, I hope.

I think this auto-changer problem has been figured out, it's the Mach3 software that is the headache and really need help with. The manual is good but there are some confusing things about the referencing/homing I don't understand (yet). Step by step. If I can get past this basic cnc stuff then hopefully I can get using this lathe properly. It is a nice lathe overall and hopefully it will do what was intended until I deserve a better one.

Cheers
Rob

m_c
04-09-2016, 01:24 PM
If the turret has been machined correctly, then all the tool slots should be at identical heights, so you shouldn't need any shims as long as you are using the correct size of toolholder.
Regarding inserts, post up any numbers on what you have, as there are only a few different basic shapes of inserts for lathes, unless the holder is for something very specific.

Referencing a lathe in Mach, depends on if it has homing switches or not. If it doesn't have homing switches, then personally I'd add at least one on the X-axis, as that is the most critical axis.
However, in a nutshell, without homing switches, all tool offsets are taken as on offset from your master tool. At startup, you take a test cut with the master tool, measure the cut, and enter the size into the DRO, so Mach then has a known reference point.
If you have homing, then you don't have a master tool, and all tool offsets are an offset from the home/reference position.

Where about is middle of nowhere?

John S
04-09-2016, 02:00 PM
Where about is middle of nowhere?

Anywhere north of Watford Gap.

Rob
05-09-2016, 03:53 AM
If the turret has been machined correctly, then all the tool slots should be at identical heights, so you shouldn't need any shims as long as you are using the correct size of toolholder.
Regarding inserts, post up any numbers on what you have, as there are only a few different basic shapes of inserts for lathes, unless the holder is for something very specific.

Referencing a lathe in Mach, depends on if it has homing switches or not. If it doesn't have homing switches, then personally I'd add at least one on the X-axis, as that is the most critical axis.
However, in a nutshell, without homing switches, all tool offsets are taken as on offset from your master tool. At startup, you take a test cut with the master tool, measure the cut, and enter the size into the DRO, so Mach then has a known reference point.
If you have homing, then you don't have a master tool, and all tool offsets are an offset from the home/reference position.

Where about is middle of nowhere?


John is right, middle of no-where in my case is far north of the WG, a rural village in Scotland. Went to look for gold and got stuck here.

I was wondering if there was a tool insert standard. I have some Tizit tool holders:

sdncn 1212 m11, Ceratizit stock number 221870
sdjcl 1212 H11, Ceratizit stock number 7068521200
sdjcr 1212 f09 , Ceratizit stock number 77343

For the parting tool I bought a new one which I can get inserts off ebay for instead of trying to finding the Ceratizit ones.

I don't understand what you mean by correct size of tool holder. The holder is the turret slots in the wheel, there are no individual adjustment. The adjustment on the cog wheel adjusts them all at the same time, it would be impossible to line them all up this way.

What you say about the referencing/homing is pretty much what the mach3 manual says also, but I don't know how to determine if there is a homing switch or not. The original manual for the Orac says there are homing switches, so maybe there is. I can understand generally what your saying and the manual, but I'm finding it confusing on some points like I don't know how to test if the homing works because it seems to need a cutting program to run, or maybe not, this is the confusing part. Once I understand how to make this work then it's just getting the wizards to work. Getting closer.

There is one program I really like, it's Denford's 2D quick turn cad/cam for turning as it's really easy to use being made for teaching in schools, but it's 168 and it's not possible to try the code first to see if it works with Mach3, although it does say it can save a .tap file. Anyway, I'll use the wizards first to learn and then hopefully move on to some cad/cam software.

Clive S
05-09-2016, 09:37 AM
The original manual for the Orac says there are homing switches, so maybe there is. Rob Some good clear pictures of your lathes might be helpful in determining what and where the switches are if any.

m_c
05-09-2016, 07:19 PM
I'm based near Edinburgh, but am occasionally in various corners of the country, and if I happened to be near wherever you are, I'd be happy to pop in for an hour or so.

There is one main standard for lathe tool holders, however there are also some manufacturer specific types, but they tend to use non-standard codes.
The key bit of info are the letters, as they tell you the insert type, toolholder style, and orientation. The numbers that follow are the shank size. Then the final code is the insert tolerance/size.

A SDNCN 1212 M11 takes a DCMT 11T3 insert
The SDJCL/R are left and right versions of the same tool, however the left hand version takes a DCMT 11T3 insert, whereas the right hand takes a smaller DCMT 0902, however 0902 is not a common size, so you'd be better to buy a new holder.
www.shop-apt.co.uk (http://www.shop-apt.co.uk) is a reasonable source for tools and inserts.

What I meant by tools lining up, is provided the tool disc/holder and the ratchet has been machined correctly, once you have one tool at the correct height, they should all be at the correct height when in the cutting position. If you're having to adjust the height of individual tools, then something is not right.
When I bolt a tool into my turret, I don't have to adjust it's height. If the height is wrong, then I have an alignment issue and all the tool heights are wrong.

If homing is working with suitable switches, when you click the Home (I think, it's been that long since I've used Mach 3, it might actually be Set Home) button for the axis, the corresponding axis should then carry out a homing routine.

Rob
05-09-2016, 07:44 PM
Rob Some good clear pictures of your lathes might be helpful in determining what and where the switches are if any.

Good idea, I'll take a few pics :)

Rob
05-09-2016, 08:34 PM
I'm based near Edinburgh, but am occasionally in various corners of the country, and if I happened to be near wherever you are, I'd be happy to pop in for an hour or so.

There is one main standard for lathe tool holders, however there are also some manufacturer specific types, but they tend to use non-standard codes.
The key bit of info are the letters, as they tell you the insert type, toolholder style, and orientation. The numbers that follow are the shank size. Then the final code is the insert tolerance/size.

A SDNCN 1212 M11 takes a DCMT 11T3 insert
The SDJCL/R are left and right versions of the same tool, however the left hand version takes a DCMT 11T3 insert, whereas the right hand takes a smaller DCMT 0902, however 0902 is not a common size, so you'd be better to buy a new holder.
www.shop-apt.co.uk (http://www.shop-apt.co.uk) is a reasonable source for tools and inserts.

What I meant by tools lining up, is provided the tool disc/holder and the ratchet has been machined correctly, once you have one tool at the correct height, they should all be at the correct height when in the cutting position. If you're having to adjust the height of individual tools, then something is not right.
When I bolt a tool into my turret, I don't have to adjust it's height. If the height is wrong, then I have an alignment issue and all the tool heights are wrong.

If homing is working with suitable switches, when you click the Home (I think, it's been that long since I've used Mach 3, it might actually be Set Home) button for the axis, the corresponding axis should then carry out a homing routine.


Thank you so much for this info, lots to learn. I will check out the link for tools.

For the tool turret alignment and the homing issue, to make this easier I will make a short video tonight showing what is happening and post it tomorrow.

One other thing, do you or anyone reading this know what equivalent grease to use for the Orac headstock and zerk nipples? I bought some "slide oil" for the bed and screws from ebay so that's covered. I know the grease is some sort of lithium hydroxystearate grease, but anyone have advice on this as I see various ratings like "EP2" and other ratings on ebay. What is good for a headstock?

Here is part of the manual's lubrication instructions:

Add grease sparingly to the Headstock bearings through Grease Nipples at back of
Headstock. GREASE: ALVANIA No3 or SPHEEROL AP 3


I live in Crianlarich, Stirling. People only travel through here at as fast as possible, there is even a new by-pass, lol. If you're ever travelling to Oban or Fort William way some time in the future it would be a pleasure to meet you and get some advice. Please let me know a couple of days in advance so I'm not off somewhere.

Rob
16-09-2016, 01:36 AM
I think I found a limit switch, not sure, hopefully I can get some pics on here soon. One thing I noticed is when in manual there are various options for homing but in auto there are only two, no idea why.

Another thing I tried is to get a simple wizard to do something (a groove) but no result. It's so confusing and I can't find documentation for all the little things it tells me is happening. If I could just get a wizard to make one move it would be fantastic.