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View Full Version : CONVERSION: Re-Built a used CNC mill machine to the point of 80%



dudz
18-01-2013, 12:00 AM
I bought a second hand Machine from a French bloke some time ago. I was correctly advised on this forum that for the amount of money I was about to spend on buying it, I could otherwise build my own instead. But having no previous exp with building these machines, I decided to buy the used machine and change what had to be changed as and when it was needed. (I wish I had listened to your advise in the first place, but my mistake has taught me alot).

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Firstly, The router....I tried polystyrene, wood, and Aluminium....The Aluminium was difficult to get any good results with so I ordered a Chinese 2.2kw water cooled spindle and controller. Then I had to get a Z plate made to hold it and had to buy a spindle holder from US ebay. The Chinese holder was rubbish from ebay.
After trying a few jobs with wood, I found the spindle pushed so hard that the cutting bed began to bend like a banana !. It was a vacuum bed with only 4 drilled and tapped mounting holes. So I ordered a piece of aluminium 470mmX300X25 from ebay for a new cutting bed. I used "Emachineshop" and "Cambam" to create the counter-bores , mounting holes and 6mm holes for clamps then tapped them by hand. With my new Chinese spindle and endmills the machine "just about" managed to create the cutting table. Although I did have alot of messing about with large G-clamps to hold this down.
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I was quiet pleased with this.
Next was supported rails ( new cutting table already designed to take new bearing blocks ) Again Chinese from ebay.

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I have not replaced the Y axis rails with supported ones, as I feel that these are sturdy enough over the short distance that they span.
I measured the squareness from the profiles against the ballscrew on the X axis....It ran 16mm out over 850mm !! , what with this and the bent vacuum bed, I really don't think the previous owner and builder could of produced anything good. I checked the ballnut, and the bearing seal is squashed on one side because of the runout. I may have to replace the ballscrew / nut and mounts soon. It runs but gets a little stiff in places (at each end of the ballscrew).
I decided, that the machine just was not rigid enough, so I ordered 45X45mm and 90X45mm profiles and corner blocks from German Ebay. I clamped it all together today. I think it is a vast improvement. It is all as square as I can get it with simple spirit levels, and metal working squares ( I have no gauges yet ). The table needs a slight skim to make the bed perfectly level, but it is only 2mm out over the whole bed length at the worst. The only thing I cannot check (lack of gauges) is the squareness from the spindle to the bed. I have seen a "Pro tram head square" on ebay ; 01 Pro Tram Bridgeport Head Square Knee Mill Spindle CNC Router milling endmill | eBay (http://www.ebay.co.uk/itm/261145086295?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649) , I don't know if there is a cheaper way to check this accurately ??
I have robbed a pump from my fish tank for the coolant for the spindle.
I feel I now have a machine that is capable of milling Aluminium. Alot of wasted money from buying a bodged machine, but I think i am almost there.

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Web Goblin
18-01-2013, 06:23 AM
To be honest I think you will still have problems getting a decent depth of cut in aluminium. The gantry frame looks a bit weak to be able to take the cutting forces without bending. How much clearance is there between the spindle and the bed? It looks quite large from the photo.

dudz
18-01-2013, 09:20 AM
I don't intend to use fast feed rates, and never plunging. I have tried to get as much clearance between the spindle and the bed.(150mm) . If I can get 1.5mm of cut on each pass (and I'm sure I will) then that's great. The Y rails are 25mm thick over 500mm ish. I never had a problem with the gantry before I beefed it up. In fact using a plunge, the spindle would push the original bed down so hard it would bend near the ends and the X axis 25mm unsupported rails would bend without the gantry moving at all. The weakest point is the Y axis rails IMO. I will find out soon enough. I don't care if a job that should take 10 mins actually takes 40mins. I just want accuracy. The next step will be to put a 5mm plate behind the rails and change them for supported ones, but that's if I get any problems.

JAZZCNC
18-01-2013, 02:53 PM
I don't care if a job that should take 10 mins actually takes 40mins. I just want accuracy. The next step will be to put a 5mm plate behind the rails and change them for supported ones, but that's if I get any problems.

I think you'll find that while it may well cut at 1.5mm DOC the finish will be rubbish and the machine will quickly feel the affects and start to suffer with accuracy.

If you want accuracy and quality finish then you'll need to beef up the frame and Z axis or take shallow DOC.!

martin54
18-01-2013, 08:27 PM
a sheet of composite board & you could box that all in nicely to contain swarf with that frame you have added, or if you want a clear finish a sheet of polycarbonate. Be easy enough to make one side or end a door for loading or just removable panels all round.

dudz
27-01-2013, 10:42 AM
Thanks for the reply's so far. Panels are a good idea. As for beefing up the frame, I thought I'd already done that ??.
I am going to add more corner plates between the profiles and add a aluminium plate behind the Y rails, but apart from that I don't see what else would beef it up apart from welding the profiles together !

dudz
18-02-2014, 09:09 PM
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Just ordered Supported Y and Z rails and new ballscrews. Making a new Z axis with 20mm thick Alu plates. Should be done in around a month.
I have done 1.5mm passes in 7075 and 6082 Alu now with good results. Hopefully I will get slightly better finish on my parts when its all done.Although Im pleased so far. I have added more extrusion under the X rails since this photo, and that gave me surprisingly less tool marks on my jobs.

dudz
08-03-2014, 07:58 PM
Y and Z plate almost finished..........

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EddyCurrent
08-03-2014, 08:12 PM
Looks quite straight forward when using supported rail, that might be the best solution for those without much in the way of machinery or workshop facilities.

dudz
08-03-2014, 09:47 PM
Looks quite straight forward when using supported rail, that might be the best solution for those without much in the way of machinery or workshop facilities.

Yep, probably is...but I for one could not have marked or drilled the holes accurately enough without the CNC I already have. My pillar drill drills egg shaped holes, so I do all my counter-boring and through holes on my machine.
Kind of like people with 3D printers, they make parts for more 3D printers !

The machine I have gives very good results but lacks in perfect smooth edges. So hence the new axis.

dudz
19-03-2014, 01:21 PM
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EddyCurrent
19-03-2014, 07:09 PM
Looks far more substantial now with the supported rails etc. those are some meaty motor mounts.

Lee Roberts
20-03-2014, 04:35 PM
Looking much better dudz!

dudz
20-03-2014, 05:44 PM
Thanks :beer: