Here is a list of all the postings michael jones 16 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Warco WM18 milling head shake ( technically spindle is precessing) when plunge milling a blind slot.|
Hi all it's mjj here.
Thank you all for your comments. All very interesting and entertaining. Before making my initial post I had emailed Warco suggesting I take my machine to them for them to examine. I have now recieved a reply and they have accepted and with the possible offer of a replacement machine waiting. So here's thumbs up to Warco. I would be happy with just replacement parts if that.s all required. What's mutually fair is fine by me. If I can help prevent this problem happening to others all to the well and good full marks to Warco.
Now returning to as many comments as I can . Firstly taking note of one persons reply about checking if any was loose . Well before embarking on trying to find some sort of gib adjustment comprise I gave the machine a quick once eye scan. Whilst not loose I did find that the milling head has tilted by about 3 degrees. Also attempting to put it back i fond that the holding screw for head swivel detent was totally loose so that I was unable to retract the pin. It looks like vibration has made itself known. Prior to this problem occurring the head was at 0 degrees for certain. I haven't had any recent crashes of a cutter or ER32 collet chuck since I ditched using those huge clamps from one of those 52 piece clamp sets. Ditching them in favour of some home made clamps and a more than half decent machine vice. Now the direction of tilt was such that it would favour the long cutting edge of the slot drill so this will have some bearing on matters. Most likely making the hole larger and promoting more shake.
I would agree with many of the later comments. In many ways I've based my actions on past experience .....The only exposure to milling was in training and thus that on industrial machines. I had that I had made due allowance for the size and quality differences in the machines. I can't think that I have been trying to push things too hard by seeking to get high metal removal rates. However I would accuse myself of going perhaps too gently. Well at least I my Myford super7. My mind boggles at what some claim to achieve and struggle to get tipped to cut anywhere half decent ... too reluctant to push it too hard I guess.
My original posting apart from the obvious was to get some kind of proper handle on what I should or not expect from hobby time machines I guess. Perhaps as one of you suggested the unlearning phase.
On a lighter note since someone mentioned Cinncinnati machines , back in the late 60's / early 70's the company had one of their numerical controlled drills installed, i think it must have been hydraulically controlled.
On commissioning day news spread through the company like a wild fire . While the commissioning engineers stood around watching the large paper tapes whirl into action as one pressed the go button. The machine sprung into life only make very load bang it tried to drill a large diameter hole from the bottom of an 18" by 2 foot cast iron casting! Ooops could well have been one of the first instances of the realization that there are different definitions of what sign should be used to describe axis movement.
Thanks again all for your comments.
To reply to the latest post. Hind sight is a wonderful.thing . I probably just too happy with the performance in the first instance to try every aspect. The rods used were fully ground ( 0.4997" measured at various points on the circumference and along the the bars ( approx 6^ long so they take an average ).
I have emailed Warco but have not yet had a reply.......I have tried phoning but the tech' phones are just too busy.
Many thanks for taking the trouble to assist.
I think the last post has almost hit the nail on the head. Except in my instance Blind Freddy was recovering from a Friday lunchtime binge and day dreaming about a weekend binge with his mates! It appears to me that these tapered gib thingies can't hold the head securely on their own with out some support from the locking screws. My guess at the moment is that since the gib thrust is applied from the ends of the gib strip a degree of buckling of the gib may be allowed to take place that allows the head to move about on the dovetails. Looks like Blind Freddy was given the freedom to fashion the dovetails on the column and possibly the milling head as well. My impressions at the moment is that the angled part of the dovetail looks somewhat convex rather than flat , even where the possibility of wear if any is unlikely to have taken place. But I really need to investigate this aspect further.
I had considered using the quill to apply feed in the first instance but I am re aqauintting myself with the art of milling and also I am exploring the envelope of performance / abilities of this machine. ( My only exposure to mechanical engineering was a year spent in basic training at the onset of my career some 50 + years ago. You couldn't call basic these days as we covered every aspect from foundry work through to metal spinning , sadly though we didn't get time to do any gear cutting or hand scraping. So I'm a bit rusty.) Thinking that the quill would add additional length to the cutter and there by add another variable to the exercise.. it's certainly discovered a major limitation. The same goes for first drilling under sized holes/ slot to start in the first instance.
To answer a few questions , the material was BMS. As for the cutters , the first two I used were from one of those boxed sets I think I possibly bought from a reputable trade stand at an exhibition but one of the others was from a cutter purchase from Arceurotrade and two would you believe were industrial throw outs long since past their supposed life with tip cutting edges freehand sharpened by myself on the bench grinder! The last were done in a fit of frustration and an element of try and see approach. Surprising they cut very very freely compared with the purchased items . I expected head shake and hence the first plunge to form the slot to be far worse ...... not the case there was no difference. So it's down to the mill.
I guess my main problem is having spirits raised by my satisfaction with the machine up until this issue and of course be encouraged by the fact that some gifted people have been sucesful in converting this type of machine to CNC. ( Which was one of my main aims.) Now has painfully been dashed on the rocks.
Once again thank you all for your kind assistance. I think i'll go off and see if I can find a comprise adjustment for the gib. I might also consider fitting some setting screws to the head to limit limit the freedom of the gib when the standard locking is loosened.
Oh by the way does anyone know what the angle of the dovetail should be?
Regards all . mjj
Hi . Would welcome advice on this vexing problem please.
I have a WM18 mill which was purchased last October at the Midlands exhibition so is still just about in warranty. I am awaiting a reply from Warco but would like to know if others have experienced anything similar. I have been using the mill until now for simple surface machining and occasional drilling operations which the machine quill was used . All these operations involved milling with the main column locked. I have also machined a few through slots which were started with a suitable drill. All these operations were successful and I have been very pleased with the machine up until the start of last week. When for the first time I attempted to create a enclosed blind slot which by necessity needed to be started by plunge milling into the work piece with a 5/16" slot drill.. ( Both table axis's and quill locked , column unlocked and used to feed .) Horror of horrors .When the cut started the milling head quite visibly moved causing the machine spindle to appear to ir move in a circle around it's true axis.. The hole produced being visibly larger than the cutter by approximately a millimeter! The work piece is now wrecked but I thought it wise to continue to form the intended slot.. The column was then raised and locked to allow a suitable depth of cut and the X axis unlocked and machining commenced . This latter operation progressed with no issues. However overall the slot is somewhat keyhole shaped , no way as intended. Since the cutter was brand new and I was a suspicious of it's end gashing I order other cutters from different sources and repeated the exercise on scrap material. All progressed with similar disaster. Observing that the milling head body was shaking by about a millimeter when applying the plunge into the work , I decided to progressively apply the column locks bit by bit . Eventually the head movement subsided to a acceptable level. However at these settings considerable amount force is needed on the column hand wheel to apply any cut. Surely this cannot be right. By my consideration the machine has had insufficient use to have worn an appreciable amount.
I made a phone call to Warco regarding the gib strip adjustment and proceeded with gib adjustment. On adjustment of the gib so as to limit the head shake to a total of 3 thou of an inch ( where column movement is quite stiff) I find that further up the column this slackens of but at the very top it is impossibly stiff one needs the biceps of 4 African elephant thighs to move it. Mmmm I proceeded then to make some measurements of the dovetails on the column and find alarmingly that there is approaching differences between top and bottom of about 5 thou ! .....not good. Whats more on close examination of the top of the column reveals a serious machining defect, the surface grinding of the right hand dovetail seems not to have reached that far and the initial machining is seen to be very uneven , the ground surfaces seem to be unworn elsewhere.. No wonder I cannot adjust the gibs correctly and very much doubt whether they were in the first place.
What I would like to know is am i asking too much of a low cost machine in expecting it to be able to slot drill a blind enclosed slot and what sort of level of run out at the spindle should I reasonably expect.. Also what should the dovetail angle be it looks non standard to me. From my industrial training days many years ago was a bread and butter job for a vertical mill. Having read of model engineers converting this model of machine to full CNC my mind struggles to see how if their machines were like mine to start with.. Am I doing something wrong , have I overlooked something?
When I purchased this machine it was with the view to follow their footsteps but not now , I feel very dejected.
Any thoughts or advice would be appreciated.
m j j .
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