I have to confess, my Latin is virtually non-existent!, although it is something I would like to know.
I had to look up your phrase, it is the motto of a school in Oxford and means “no one becomes knowledgeable over-night “.
My phrase (I think) means “ the machine is like a child, all I do is feed it and clean it”
Have not cut much metal, as I am trying to plan my attack (so that I don’t make too many mistakes and have to re-make it), but hope to get more progress this weekend.
That looks a very nice project I will certainly follow the progress.
Kind regards ,
thanks for your kind words.
I must confess that after reading your posts, I found it hard to get some enthusiasm back for my rather inferior machine.
Your workshop must be the envy of many here, me at the top of the list.
I used to own a Bridgeport which was to be the basis of my project, but that’ a long and boring story.
Best of luck with your project, I’m sure it will be something to behold when finished.
(I really like your adjustable supports for clamping)
Last edited by Tweaky; 28-02-2010 at 09:37 PM.
Before starting on the Z axis, I needed to address the issue of positioning the work-piece accurately on the table.
I have to make an upper and lower bearing block for the Z axis ballscrew and cannot mount them together to machine them.
I watched ebay for a touch probe, but with digitising in mind, I decided to go the webcam route (also a lot cheaper).:heehee:
I bought a 1.3Mpixel camera and mounted it in a defunct waterproof cctv camera housing. This has two advantages, the cctv cam. has a C mount zoom lens with an iris control and is of course impervious to swarf and coolant etc.
I made an adjustable mount so that it can be aligned accurately.
After two failed attempts at making a magnetically coupled quick release, I ended up mounting directly to a 3 morse sleeve which I ground a groove into, so that the grub screws which adjust the x and y, also pull the mount to the sleeve.
I am very happy with this, not very pretty (as always!) , but very solid.
I have checked its accuracy many times now and it is always spot-on.
I will be adding a laser at 45deg. to give an accurate height later, an idea I stole from a professional CNC camera costing $650 !
This will enable the camera to be used to measure distances, holes and angles.
Also in the future I intend to use some software to scan an object and create a point cloud for digitising.
Ok so now I can get my work-piece accurately positioned, I made the upper and lower bearing blocks, which house the needle roller bearings for the rotating ballnut.
Ah!, having milled the bearing pockets, I checked the bores and was happy (0.01mm undersize), BUT, I measured the bore at the top and when I tried to fit the bearings.... nogo.:cry:
As Robin alluded to previously, the milling cutter shies away from the work, so my bores were both tapered! ..... bugger.
Spent about two hours with a 1" milling cutter in hand, scrapping the bore to make it parallel... what a pain!
I had used a 1/2" cutter, and ran the code 3 times on the final cut!?
I guess a different method is required next time.
The upper block also houses the two thrust roller bearings and this is closed by a plate, which is also the motor mount.
The bearing blocks mount into a 19mm plate which will attach to the front face of the head. They mount “into” the plate so that the ballscrew is as close to the spindle as possible.
Next I cut the plate, and for the first time clamped the work to the bed.
What a difference! (thanks Robin).
The cuts where sooo much better, cleaner, faster and so much quieter.
And I still have more overhang to remove as I am still using a collet chuck (no metric tools yet for the 3 morse collets).
I was really happy for a few seconds, them I realised that this has severe consequences for my planned 4th & 5th axis, something I guess a lot of you already knew.
Maybe it will work OK with small cutters running at high speed, I will have to wait to find out.
Amazingly the blocks fit snugly and the shaft is in alignment!:surprised:
Next job is to modify a timing pulley to fit over the 37mm barrel of the ballnut, and then cut the depth stop lug off the front of the machine, and fit the assembly to the machine.
Cheers for now
Last edited by Tweaky; 23-03-2010 at 01:13 AM.
Once they start to rub, rather than cut, you can repeat until Doomsday without removing the excess.
If the taper is more pronounced in X it's probably column flex. To flex in Y means bending the column, to flex in X the column acts more like a torsion spring.
Put a dti on it and see how hard you have to lean on the chuck to get problematical movement.
If the taper is even it could be a sloppy quill, does the dti reveal more flexing as the quill extends downwards?
Lots of lube helps keep tooling sharp.
the cutter was a brand new Clarkson HSS 4 flute.
The column flexes as I have said previously, by 2-3 thou with a light pull on the head and 12-13 thou with a more substantial pull, at a height of 12” or so above the table.
Yes, the quill is worse the more it is extended, about 3 thou at max extension and un-locked.
I am not using flood coolant yet as I have not made a tray to collect it, so I am squirting the lube by hand.
I guess I should have expected these results.
I must add that I have not always been using the collet chuck correctly, as I have discovered that the cutter must be screwed into the collet a fair way before it grips the end of the cutter.
I have only learned this after the problem with the tapered bores.
Maybe I should treat this as a training exercise and buy a better quality machine after I have learned how to use this one.
It is difficult for me to have down-graded as I have.
At my previous house, I had a large workshop and had just bought a Bridgeport B2J CNC with the motors removed and was in the process of refitting it, when the house next door burnt down, leaving our rented house un-safe.:cry:
So we had to move and now my workshop is 6` x 4`!
Oh well, se la vie.
Thanks again for your help.
It is a lot more picky on the diameter than ER collets but has better grip in the Z axis.
I got caught out with my first ER chuck, didn't realise you had to fit the collet in to the nose, cost me a collet :whistling:
Getting the right grease on the quill could remove some slop. If you got 10 micron accuracy at the top of the cut that is freaking amazing given the set up. Well worth persevering
I got moved out of the garage by her indoors moaning about the swarf getting walked in to the house. Luckily I own half of a small company so I was able to rent space up on the industrial estate as a business expense. I got 25 square meters for £3k pa, put in an extra floor and turned it in to 50 sq.m
Thanks again Robin,
to say I got 10 micron accuracy would be overstating things somewhat, .... I crept up on it over the last 3 cuts!..... but it was round.
The swarf is a problem, I like the idea of a proper unit to keep the mess in, could go for a bigger machine, a power saw, grinder........mmmm.
I will look into that.
Must finish this one first though, more progress this Easter I hope.
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