Machsupport Forum
Tangent Corner => Tangent Corner => Topic started by: cjmerlin on August 15, 2006, 03:39:33 PM
-
Hi, Is there anyone out there who uses a Denford Orac with a toolchanger fitted. I have a tool vibration (chatter) problem and all attempts to sort it have failed.
I've been a (hand) machinist for some years but being new to CnC causes it's own problems as well but all the different speeds and feeds i've tried fail to stop it.
I've checked head bearings, tightened gib screws, toolchanger bearings, tool height etc,,
I'm using a TPUN (triangle) type insert tool and when cutting down a shoulder on a bar, the tip cuts fine until it gets to the end of cut and sets in heavy chatter.
I've tried other insert tools and the same problem occurs.
If anyone would like to add their words of wisdom it would be gladly appreciated.
Many Thanks..
-
Hi,
is the tool a 90 degree approch type. e.g. if you touch the tool on the face of one of the chuck jaws, can you see the back edge of the tip touching the jaw.
for CNC turning you are best using 93 to 95 degree approch tools. Or you can lock the tool in at a very slight angle so the back edge of the tip is clear of the work.
Graham.
-
Hi Graham, Thanks for your reply. My problem started when I recently bought the machine and fitted with insert tools. The toolchanger sits directly on the cross-slide and the tools are inclined upwards towards the chucked material at about 3 degrees. Having this chatter problem and thinking that the tool position is wrong I have made a spacer plate to raise the toolchanger so that the tools are level (90 degrees to the bed)
After doing this and setting the drill tool positions at exact center i find that my turning tools are now too low and there is no more adjustment. On this machine the tools are shimmed on top and the tool set screws are underneath the tools. Not quite a good idea in my book.
As this problem still persists I have ignored the settings for the drill tool positions and concentrated on getting the current insert tool correctly aligned.
It is level and at center height, well just a tad above just in case there is a bit of flex when cutting.
The finish when cutting is good although the side of the shoulder shows radial lines due to the chatter when turning into the shoulder.
I thought about your comments and this morning I went to check it out, pointing the tool as far as the set screw allowed to give a larger side clearance has produced helical pattern on the work and the side of the shoulder looks like a golf ball. Chatter still persists.
I must mention that the workpiece is 16mm dia and protruding 30mm out of the chuck.
I have cut longer stock with a center at the end and the chatter is alot less and at times none existent.
I have used the same tool on my Clarke hand-lathe with good results and no chatter so I'm still thinking there is something wrong with the Orac machine
Any ideas are welcome.
Kind Regards.
-
Hi,
have a look at the chuck it may be warn and only gripping on the back of the jaws (see picture)
You can check this with a feeler gauge while gripping a hard lump of stock, a milling cutter shank would work well
make sure the jaw is gripping all the way along the stock and see if you can get the feeler in the front edge between the jaws and the stock.
if you can then its new chuck time.
Graham.
-
Hi Graham, Thanks for your info, After checking and double checking all possible things it could be you're right it's the chuck. It's one of those cheap Chinese one's and I tried yesterday to true the jaws up but I found they were soft jaws and I work with stainless steel alot so I have ordered a new one which is a TOS make and comes with a certificate. It's also supplied with hardened inside and outside jaws.
That should solve my problem and I can get back to normality again. 8)
Thanks again for your help. :)
Kind Regards
John
-
dear sir
i have a denford orac with the tool changer i found out that the motor driving the turret was not strong retracting the toolholder against the stop so i took the motor off and put a manual crank to turn the toolholder i know it does not help when you have a lots of parts to make but i only make short runs and it does not vibrate any more
-
Hi cjmerlin have you tried using a tip with a smaller tip radius, so to stop the increase in load when you get to the shoulder
Tony
-
Hi Tony, Yep, I use 0.4mm radius tip, Thanks for the suggestion though. I knew there was something not right with the machine when I put a HSS tool ground correctly (no radius) and tried that. Still had the heavy chattering. I removed the chuck and put a clarkson collet chuck in the spindle taper with a piece of 5/8 bar in it. No chatter what so ever. Guess it's the chuck then!
The main thing that threw me was the fact that the tools in the toolchanger are angled upwards towards the stock at about 3 degrees. Thinking that due to this, the tools will rub under the cutting edge, if set to the correct height so you can face to the middle of a bar the tool is not at a tangent to the centre if you know what I mean.
I have tried putting a plate under the toolchanger and adjusting the setscrew to get the tool height right and the tools level which is a fight between the drill tool center positions and the lathe tool positions.
I have found that in order to get the right positions and the tools level and the drill positions correct, I have run out of shimming clearance and all the tool positions are a bit low.
This has made me think that the toolchanger on the Orac is not designed specifically for the machine and is a bolt-on extra.
Not having any pics to look at I can only assume that the sloping tools situation is normal for this machine.
I must say that in using it, I have found no problem in cutting material.
A quick thanks for Marcel's info, I have checked for this and although the toolchange is dog slow, It stops solid on the ratchet with no play at all.
If anyone can give me more info on the toolchanger setup (or pics) I would be gratefull.
Kind Regards.
John
-
if you want plans for the orac toolchanger i can send then to you
marcel
-
Hi Marcel, I do have a plan for the toolchanger, drawing number TP110. It has a spacer plate underneath the main body, item TP110/16. which is designated for the Orac and not the Easiturn 3.
It does not give any dimentions though. If I knew what the thickness of the plate was it would be helpful.
I have tried a 6mm plate but it doesn't give enough shim clearance for tools. I've tried a 5mm plate but still the same problem.
The thing I have noticed is that with a 6mm plate the tools were level, eg parallel with the bed. if I used a thinner spacer I will be getting back to sloping tools again.
Are your tools parallel or sloping upwards.
Kind Regards
John
-
hello
my tools are parallel it will work better this way if your tools are sloped you will have a hard time putting them center of your parts and your bushing for drilling will be off centered .
marcel
-
Hi Marcel, Thanks for that I guessed as much. Trouble is, When I bought the machine I was given the original single tool holder so I am guessing that the guy purchased the toolchanger and fitted it himself.
I shall try and get it sorted by a bit of trial and error until I find the right thickness for the spacer plate.
Kind Regards
John.
-
john
my plate mesures .198 inch if you want a real fast method take a lot of printing paper mesure put it under your toolholder and see how it goes it is the fastest way .
-
Hi Marcel, Thanks for that. I'll check it out tomorrow.
Kind Regards
John.
-
Hi John
Only just found this thread - use an Orac with a toolchanger at work quite often. You shouldn't get any chatter problems - we have used it for 1mm deep cuts in EN24T steel and they came out beautifully. You mention shimming the tools - with a tipped tool the tip top should be level with the top of the tool body. With the packing plate in you set one tool to the correct centre using the adjusting set screw and then the rest should be fine - this should be pretty close to horizontal.
If I read it correctly you are missing the plate and having the toolholder at about 10 degrees of angle to get it on centre? Am I right? Might know someone with a toolchanger in pieces so I can try and get a drawing of the plate if you like.
Gotta go - limit switch problems on my mill :(
Cheers
Dave
-
Hi David, Thanks for the info, I'm just waiting for the new chuck to
arrive and time to fit it. I made a plate to bring the toolchanger
up. I now have the drill positions correct and my insert tool needed
0.4mm packing. I guess this is right, I would have liked a bit more
space above the tool as sometimes I use tools made from HSS stock and
after a few regrinds especially with parting tools they'll end up
below center.
What's the largest radius insert you have used on the Orac.
Kind Regards
John
-
Hi John
I presume you are going to have make a new backplate for the chuck? You may want to put the old toolpost on for that as I had to make a special toolholder to step the tool out far enough to machine the plate. Ours had a damaged power chuck on it when we got it so there was no backplate available.
On the toolchanger front we don't use any packing at all - when we do use HSS you just have to be very careful grinding it! If you actualy want to know the largest tip radius it is 6mm - a round nose profile tool! That tool did a hell of a lot of working making long slender specimens and the only time we had chatter was when we ran the spindle too fast. Normally I think we run .4 or .6 tips - depends on whats lying around at the time!
A friend of mine has a toolchanger for his Orac which when it arrived refused to work - a strip down revealed that the grease inside had solidified preventing the motor from turning anything!
I presume you have physically tried moving the front (tool) plate back and forth and checked the tightness of the 3 screws that hold the plate on ? There is not much to really go wrong inside them!
Cheers
Dave
-
Hi David, I'm planning to use the old back plate as it has plenty of thickness, just machine off the old location step and turn a new one. I have made a tool that fits in the tool changer and has enough reach to do the job.
I've over hauled the tool changer completely. Well, tightned everything up and adjusted the bearings. I'd like to sort a better motor as the toolchange is dog slow. I thought it might be better using a stepper motor like the Boxford toolchanger.
You dont happen to still have the power chuck do you?
-
Hi John
I've been building the controls for a friends Orac toolchanger. We're also thinking of swapping the motor for a stepper - probably a 17 frame and use a 555 timer to generate step pulses and simply toggle the direction line. I don't think there are any major issues with leaving the stepper pulsing away while its stalled but I need to do some further research into this. The big question is what torque rating to go for.
The power chuck is still around somewhere - unfortunately its in quite a few pieces with a smashed front plate as somebody drove the tool into it before it was put into store! It's not great as the air supply comes up the spindle so you can only put about 2 inches in the chuck - i.e the depth of the chuck.
Cheers
Dave
-
Hi David, Leaving the stepper pulsing away while stalled will drive you mad after a while. The one on my Boxford uses a stepper and when it reverses back onto the stop it still pulses for a second or so creating a very loud buzz that vibrates through the whole machine.
The ideal situation would be to use a small microcontroller to do the job and connect to the serial port leaving more printer port pins available.
Other than that you could use a couple of 555 timers, one to provide the pulses and use the position sensing gear already in the toolchanger and then another activated when you toggle the direction line to give say a 3 second reverse onto the stop. A powermax ll stepper with 2 amps per phase on a L297-298 setup driving the worm gear direct would be ideal.
Same about the power chuck, I've seen similar on ebay and wondered why anyone would want to use a power chuck if you cant run a bar through it.
Kind Regards
John
-
Hi John
As it happens I'm going down the RS232 front! I've got an AVR microcontroller that does all the work, Mach sends a code to it, the AVR does it's thing monitoring the sensor states and switching motor outputs and then returns a selected tool to Mach to ensure the correct one is selected. Only had it on the bench using switches but it seems to work ok so far. Now waiting for my mate to rebuild his toolchanger so I can start testing!
Cheers
Dave
-
Hi, Well I got the chuck and after a few problems I fitted it, It has reduced my vibration problem about 50%. Now the vibration is just the tool and not the whole machine.
I have made a video which is about 10 meg and can be downloaded here, www.jtechdesign.co.uk/orac/lathe3.mpg
Please note the video and sound my not match exactly as I had to do them separately.
I've used different tools at different heights to the center and they all do the same to a lesser or greater degree, The only difference since I changed the chuck is the shoulder of the piece shows no chatter marks and looks well turned.
I'm starting to think that it may be something other than the machine it's self.
I have noticed that there is a delay before the retract from the cut allowing at least 5-10 revs of the spindle before retracting.
On my Boxford it retracts off the cut immediately
I'm wondering if, because the tool is just sitting there, it is just rubbing on the radius of the tool nose.
Why is there a delay between commands, I'm turning only using G1 and G0 commands.
Could it be that I'm using a 800mhz computer and it's just not quick enough?
Any idea's are welcome as I am almost at whits end.
Kind Regards
John
-
Hi John
Just had a look at the video - firstly have you tried dropping the spindle speed - we had a chatter problem and found that dropping it cured the problem.Can you give us an idea of speeds, feeds, depths of cut, diameters, material etc?
Secondly - headstock bearings? Have you checked them - do they need tightening?
Thirdly do you have backlash enabled? If so Mach will dwell as it applies the backlash to draw the tool out - from memory you can set this as a % of the max feedrate. Also if you are running with no backlash have you got constant velocity enabled?
I may be able to try the same test on the one at work-allthough that has the original control system in it.
Cheers
Dave
-
Hi, I've tried several speeds and feeds, the current program is below.
Headstock bearings? I've thought of that and tightened the end nut as tight as I could, I lost 200 rpm off top speed and It made no difference to the problem. I've since loosened it off one tab notch although the top of the headstock still gets warm pretty quick. I have tryed checking for radial play, cant perceive any.
I have listened to the spindle at 1000 rpm taken the front cover off the headstock to reveal the bearings and I can hear this sound (www.jtechdesign.co.uk/orac/SPINUN.wav)
You can just hear the races jingling in the background, I don't know if this is an indication of wear or not.
I've taken backlash off totally today and it made a slight difference to the delay.
I had been working in dead stop mode and changed to con-velocity and this has made no difference.
I'm working in stainless steel but I've also put the same diameter 5/8" in free cutting steel and although it's less pronounced I still get the same effect.
Cheers for the reply.
John
part code
--------------------
G18 G90 G94 G80
M09
M06 t0101
G0 Z0.00
M08
M03 S1100
G0 X17.6 Z0.8
F200
G0 X15.6
G1 Z-34.9
G0 X17.2 Z-34.2
G0 Z0.8
G0 X15.2
G1 Z-34.9
G0 X16.8 Z-34.2
G0 Z0.8
G0 X14.8
G1 Z-34.9
G0 X16.4 Z-34.2
G0 Z0.8
G0 X14.4
G1 Z-34.9
G0 X16 Z-34.2
G0 Z0.8
G0 X14
G1 Z-34.9
G0 X15.6 Z-34.2
G0 Z0.8
G0 X13.6
G1 Z-34.9
G0 X15.2 Z-34.2
G0 Z0.8
G0 X13.2
G1 Z-34.9
G0 X14.8 Z-34.2
G0 Z0.8
G0 X12.8
G1 Z-34.9
G0 X14.4 Z-34.2
G0 Z0.8
G0 X12.4
G1 Z-34.9
G0 X14 Z-34.2
G0 Z0.8
G0 X12
G1 Z-34.9
G0 X13.6 Z-34.2
G0 Z0.8
G0 X11.6
G1 Z-34.8974
G0 X13.2 Z-34.0974
G0 Z0.8
G0 X11.2
G1 Z-34.8762
G0 X12.8 Z-34.0762
G0 Z0.8
G0 X10.8
G1 Z-34.833
G0 X12.4 Z-34.033
G0 Z0.8
G0 X10.4
G1 Z-34.7664
G0 X12 Z-33.9664
G0 Z0.8
-
Hi John
This doesn't seem right at all - is the chatter only at the shoulder or on the whole length?
Do you get chatter with all tools - tipped and HSS ? We had a problem where we had some tips that were slightly different and we couldn't get them to cut as well.
Presumably gibs etc have also been checked?
The previous work I have done in EN24T was at around 1000RPM, 50mm/min feed and upto 1mm cut with no coolant - this was on pieces around 12mm diameter.
I pass your video on to a couple of people and see what they think.
Cheers
Dave
How long do you estimate the delay to be? Seconds?
-
Hi David, I've started new topic in the main Mach3 forum as I think my problem is with the software/computer rather than the machine. The chatter only occurs at the end of a cut, The machining is actually very good until the end. This is happenning with all tools I've tried. Changing the chuck has reduced it from vibing the whole machine.
I have noticed that at the end of the cut when I command a G0 rapid off (about 0.5mm) just to clear tool, The machine just sits there for about 1 second before moving.
I have changed the G0 rapid to a G1 instead and this has reduced the problem by about 50%. Now it is at a level which doesn't offend my ears.
I presume that the delay I am experiencing is not due to software but my computer which is only a 733mhz.
I'm hoping to upgrade it to 1.2-1.4ghz and hope this sorts my problem.
Cheers
John
-
Hi John
That was my suspicion but it can be difficult to narrow things down - I showed the video to a friend and he made the following comments :-
"Clearly it starts to chatter when the feed/spindle speed is reducing suggesting
that it chatters when the tool load is reducing.
I would suggest he uses a tip with a smaller tip radius. What tip style is he
using? Bear in mind that some tips are designed to be set over or under centre
and will cause chatter when set ON centre.
What spindle speed is he using? It looks to me like 20mm diameter so I would
suggest a small lathe with a tipped tool would need to be run at 600 - 700 rpm.
Is the bed of the machine level and tightened to a beafy bedplate? My
Colchester used to chatter like hell until I carefully levelled it up.
A few ideas at least."
With regards to computers, my mill runs on a 1.9Ghz machine with backlash and the only delay is when the backlash is taken up as would be expected, apart from this it barely stops in 'dead stop' mode.
What version of Mach are you running? Have you checked the Pulse frequency and the 'time in int' values in the diagnostics?
Cheers
Dave
-
Hi Dave, I'm running mach3 at 25khz. I've tried 35-45khz but that just crashes the computer.
I can't find the 'time in int' value you mentioned but the step pulse is set to 0 in motor tuning. I'm using Gecko's for the drives.
I can understand what your friend was saying, I'm still guessing it's the speed of the computer. The tip I was using in the video was 0.4mm radius TPUN type and the material is stainless 5/8" bar, I've tried altering speeds and feeds from 700rpm to 1200 rpm and all the tools I've used including an HSS one I ground myself make the same chatter at the end of the cut. I say chatter, It's more like vibration like the tool is rubbing that ends up as chatter. Noticing that there is an obvious visual delay between commands whereas my Boxford with it's original hardware/software will run the same program with no discernable delay at all has led me to assume that this is where the problem lies. The tool is sitting there rubbing the stock until the next command is executed.
Because my computer is a Compaq in order to upgrade I have to buy an adapter from China to fit the later processors.
I'm hoping this will cure the problem.
Cheers
John
-
Hi again, I have had a good idea, I have spent all afternoon configuring a copy of TurboCnC to work on the machine and I've run the same g-code. I have no problems at all with TurboCnC running, in fact I would say the machine is a lot smoother and quicker with no waiting between commands. Running in a Dos environment has some benefits.
So now I have the answer. Is it a Mach3 configuration problem or Mach3 itself or because I'm running a 733mhz computer. By the way I have no other software running other than Mach3 on Win 2000.
Cheers
John
-
Hmmm - sounds like you've got the problem narrowed down. Probably worth running this past Art and see what he says.
Cheers
Dave
-
John - as a thought, have you tried reducing the lookahead buffer size? I'm not sure whether this will make a difference but may be worth a try!
Cheers
Dave
-
Hi Dave, Sorry for the long time between posts. Great comment, This was the last thing I thought of, I reduced the lookahead buffer which reduced the delay a little but still having the problem.
I finally got my cpu and heatsink for the upgrade. The problem upgrading began with the size of the computer. It's a small form factor desktop Compaq EN which resides in the box space under the lathe and because it fits so nicely I would have had problems to find a newer computer to fit. I decided to upgrade the existing 733Mhz processor, relying on Ebay and alot of info hunting I found I could upgrade to 1400Mhz Tualatin cpu providing I had a converter socket for the differing voltages.
Well I ended up buying a 1266Mhz chip, big difference pricewise £20 or £60 for the 1400. Waited for the converter to arrive from Hong Kong and planned what I'd be doing before everything arrived, I'll upgrade the bios before doing anything else to it.
The next problem once the bits arrived was finding that once all the parts were assembled the heatsink was a tad too tall as the hard drive has to fold back down over the cpu to get the lid back on.
I trimmed the heatsink with the trusty linisher and mounted the fan on the side. I crossed fingers and switched on, Success! Booted first time and once convinced the heatsink was doing it's job I fitted the machine back into the Orac.
Once into Mach3 I took advantage of the highest kernel setting without a crash and setup a program to run.
I found immediately that the 'end chatter' problem I had miraculously disappeared completely and the delay between G1 then a G0 command is hardly noticeable.
I guess the moral of this is,
Just because you can load Mach3 on a slower computer than recommended, It isn't necessarily a good thing!
Many thanks for all your advice and I hope this post will be helpful to others
Kind Regards
John
-
Hi John
Good to hear that you've got it sorted. It's an interesting problem as you must have been somewhere in a 'grey' zone where you didn't lose steps but were running below optimal. With the Kernel speed I think Art suggests not to run it any faster than you need.
Cheers and well done
Dave
-
Hi Marcel I notice from your post you have a plan for the Toolchanger for the Orac as I have been unable to pick up the Genuine tool changer I was wondering if I should set about and Fab one Drawings would greatly help if the offer is open to others .
Regards Mike
-
here it is
-
Hi, Is there anyone out there who uses a Denford Orac with a toolchanger fitted. I have a tool vibration (chatter) problem and all attempts to sort it have failed.
I've been a (hand) machinist for some years but being new to CnC causes it's own problems as well but all the different speeds and feeds i've tried fail to stop it.
Hi CJ,
I would be grateful if you could share your schematic hook up of your Orac. Its much the same as my Starturn 5 and I would like details of home and limit, encoder output from the spindle and of course the hookup for the toolchanger.
Van you help?
Thanks
I've checked head bearings, tightened gib screws, toolchanger bearings, tool height etc,,
I'm using a TPUN (triangle) type insert tool and when cutting down a shoulder on a bar, the tip cuts fine until it gets to the end of cut and sets in heavy chatter.
I've tried other insert tools and the same problem occurs.
If anyone would like to add their words of wisdom it would be gladly appreciated.
Many Thanks..
-
if you want plans for the orac toolchanger i can send then to you
marcel
Hi Marcel,
I have the Denford Starturn 5. I think it's the same toolchanger as the Orac. Can you tell me how you hook it up to MAch3. I use a CNC4PC breakout board.
Thanks
George
-
I'm sorry if multiple messages are coming in covering the same request. I haven't got the hang of posting yet.
I'm desperate for help with my Starturn5.
It works with it's original LCB3 controller.
I would like detailed info on the hookup of the Limit switches for X & Z axis. Also if anyone has succeded in getting the auto tool turret changer woking I woul like to have some hookup shematics.
The Denford forum is great and the guys are very helpful but I'm finding it a bit of a jungle right now with so much conflicting information.
I'm using MACH3 with a CNC4PC C11 board on my flatbed 3 axis router and would like to use the same electronics.
Any help at all would be most welcome.
Kind regards to all
George