[kensbey]

So my "brilliant" stand design to allow the coolant tray to slide under the frame my have soem issues.

So far i have just been doing manual milling with the machine, and there is quite a lot of vibration happening due to a lack fo rigidity in the frame. This is resulting in pretty poor surface finish and some chatter.

Repost of an earlier pick for reference:


I think i need to add some vertical legs directly below the mill, but this completely ruins the possibility of a simple slide in tray underneath. It's possible that some extra struts running off to the side would help as well, but probably not as much.

[pete from TN]

I would suggest that you definitely add more bracing under the machine itself. If you wanted to you might be able to fabricate two large troughs under each side of the mill in those openings. Make them have a ledge that they slide into from the front and then you can build a dual trough chip tray setup that will allow you to just brush or blow the chips off the machine into the troughs and then once your coolant drains out of the troughs into your resorvoir you can just slide the trays out the front and dump them into another container for disposal. My new VMC is setup kind of like this actually, there are two perforated trays on each side of the base of the mill with two hinged slides that guide the chips down onto the chip trays and the coolant runs down thru the perforations into the troughs below them which are tied together with a large diameter tube. The pump is in the back of one of the troughs seperated by a large screen effectively making another chamber to keep crud out of the pump. You could accomplish much the same setup and believe me having the ability to remove the chips in a tray like that is a much welcomed advantage. You could also install your resorvoir in the center area under the mill itself and make some quick release hoses that go to the troughs....The enclosure I build for my old RF45CNC was solid bottomed and I had to reach inside there to clean the chips out which is a PIA and getting in behind the machine is also a *****. With two large removable trays you could access the machine with them out and have a much easier time of cleaning out the chips when you are done machining. Does that make any sense?

I would probably put several square tube supports underneath the machine itself and skin the top of the stand under the machine maybe beveling the edges of the sheet down into the troughs on each side. Wish I had done something like this on my build but hindsight is 20/20 they say. Good luck with your build man the little RF45's are a capable machine for their size and once CNC you can have a lot of fun with them. If I find a good deal on a used one somewheres I would buy another one for sure to complement my VMC....peace

Pete

[Robin Hewitt]

there is quite a lot of vibration happening due to a lack fo rigidity in the frame. This is resulting in pretty poor surface finish and some chatter.

Have you tried moving it off the stand and cutting?

Is it the stand or is it you?

[kensbey]

Is it the stand or is it you?

hahahahaha yes some of it is definitely my poor manual machining skills, but on some cuts the whole machine (including the base) is moving. Because its low, i work kneeling in front of the machine on a pad. i'm often leaning against the frame and can feel the movements.

That being said, i'm sure when it's cnc and more linear in speed then it will be a little better. But i'd really like to get the stand more ridgid cause otherwise there will still be movement when the cnc cuts are close to the natural frequency of the stand.

@ pete,

yeah i'm starting to think that i will have to do this. i was sorta thinking about a U shaped tray to wrap around the mounts under the mill, But i think your idea is much better

i will probably make a cover thats slanted on top that fills the whole area in front of the mill, covering the motor and stuff. and then put the coolant tank and pump behind the mill.

also, i havent done much with flood coolant, any tips for enclosure design? does it need to be sealed or breathe when its not in use? how long does it last? any particular materials to avoid?

[Robin Hewitt]

i havent done much with flood coolant, any tips for enclosure design? does it need to be sealed or breathe when its not in use? how long does it last? any particular materials to avoid?

Soluble oil slowly seperates out the oil, you get great blobs of it floating, it's called tramp oil, then it starts to rot. I let it breathe and change it 2 or 3 times a year.

It will fill the ways on the bed then start spilling out, usually at the ends. If you can contain it on the bed with splash guards you can fit hoses either end of the bed and take it straight back to the tank. Best if it doesn't reach the screws below. If you can, mount the return hoses so you can blast air down them and you don't have to panic when the swarf blocks them. I have a filter bag in the tank around the return lines because any gunge gets stuck in the 1/8" nozzle.

The simplest splashguard is a sheet of plastic standing in an unused tee slot.

It you don't have a spare tee slot you either bolt to the sides or do something clever. Neodymiun magnets are handy, if you insert them nearly through aluminium angle you can pinch a soft rubber cord onto the bed and any iron residue that sticks can be wiped off.

A wet dry vacuum cleaner with a nozzle that fits inside the tee slot is useful.

You will need a flow control doo-hickey or things get real messy real quick. The oil will escape, a little all the time, a lot occasionally.

[kensbey]

Thanks robin, all useful advice. I don't really want to enclose the table itself as i plan on building a big perspex enclosure around the whole mill, sliding doors, etc. Also, some of the projects i have planned will need to hang over the side of the table a bit.

i already have expandable covers to keep coolant off the ways and screws, althought i may end up replacing with sliding aluminium ones at some point.

increased spindle speed is the another i have to think about, the std 1600 rpm pretty much ruins the chance of good surface finish with anything less than a 16mm cutter.

[Robin Hewitt]

increased spindle speed is the another i have to think about, the std 1600 rpm pretty much ruins the chance of good surface finish with anything less than a 16mm cutter.

Nothing wrong with 1600 rpm, I rarely go that fast, don't let folk cutting metal with routers confuse you, you are milling. There is a limit to how many horse powers the tool can carry to it's tip so big feed rates to match big rpm are not a good idea. You want to see swarf not dust coming off it.

The trick to a good finish is understanding that the tool will bend. You always cut down hill so the tool shies away from the finished surface. On the roughing out pass you leave metal for the finishing pass. Leave too much metal and the tool will bend too much on the finishing pass and leave you oversized. Leave too little and the tool will never engage the surface for a cut, it will simply bend and rub.

If you try to remove one thou with a small tool in iron it simply will not happen, if you start deepening the cut it will ignore you until you reach a viable cut when it suddenly takes a big swallow of metal and leaves you undersize.

Avoid pure aluminium (1050) like you would the plague. If you get the feeds a tiny bit wrong it will start to extrude rather than cut and your tool will break.

Back to the coolant. You are going to have to drill holes to let it out of the bed, you may as well fit return hoses under the holes. Sooner or later your coolant stream will hit the chuck and fly out sideways. If you don't have splash guards close in then everything will get covered, your steppers will start to steam your bearings will start to rust, it gets in everywhere. I strongly suggest you catch it as soon as possible.

[kensbey]

So i ordered some angular contact bearings from VXB. They were pretty cheap, so i'm not sure how they will turn out. I have seen some others on the forum here use them. The price of proper ground matched pairs is far beyond my budget and probably beyond the accuracy limit of the machine anyway. instead i will be attempting preload with Shims, which is really going to be quite a trial and error method for me.

Should i be attempting to measure preload? what have you guys done on these sized mills?

[arizonavideo]

You set preload with the nut so you should not really need a shim but the A/C bearings are a bit shorter so you might need to add a shim to keep the nut on the threads. This is a good place for a hard and flat part.

The retainer has a lock ring and you can end up between two points and you might want to add a shim if you have one. It does not need to be supper thin only allow you to end up at a different point on the threads.

Preload is a bit tricky because the top bearing will not slide to release pressure if you over tighten and try to loosen it up some. If you get it too tight and back off you need to smack the top of the shaft to release the shaft tension and get the proper feel of the preload. You need to protect the shaft. I use some soft aluminum.

What is proper preload is hard to say exactly but too loose will allow for slop and too tight will run way hot or destroy the bearing. Without a seal in the lower it should get warm to slightly hot after 20 min or so at 1000 RPM or so. If its cold your preload is too low and if if you can't keep your hand on it hot then it is too hot and too tight.

I just did mine again last week and before I had them a bit too tight but this time they are just right. Hot after a hour at 2500 RPM but I can still hold my hand on the lower bearing housing.

You want NLGI#2 grease. I'm using Mobil Synthetic Grease Mobilith Shc 100.

So far so good.

PS Their is two small holes in the lower bearing housing to allow a driver to push out the race.

I don't see a belt drive. If your running at the stock speed the stock bearings are fine just add new grease. The TRB run hot when new but should cool down after break in. If not just loosen the preload slightly.

[kensbey]

haha my mistake, i really should be specific. I am talking about angular contact bearings to hold ballscrews.

Thanks for the info tho, will come in useful when i do a vfd later.

[TiagoSantos]

Mr Wizard's CNC Cookbook has a section dealing with AC bearing preload in detail.. I'm not sure that many of us bother that much with setting it that accurately on the ballscrews. I'm tightening mine until I can't feel any screw backlash but the bearings still rotate easily. I should really play with getting the shims in there just right, as I'm sure it would make the bearings last much longer.. but they're cheap and I'm lazy!

[kensbey]

Yeah this is what i figure.. at $13 a pair, its really not worth it to spend hours upon hours just to prolong their life a bit. Maybe later if i get everything else done and still not happy i'll shell out for some ground pairs.

[ChrisAttebery]

I don't know if you got your stand issues squared away, but I built a similar stand for my RF-30. I used 2"x3"x.125" tubing for the top and 2"x2"x.125" for the legs and lower cross members. I never had any issues with it.

To me it looks like the top of your stand is too light for the machine. I would try to beef it up if possible.

Good luck,


Chris

[kensbey]

Got the X axis nut mount almost done. Pic shows test fit with one nut.

[bricks007]

Hey kensbey, hows the conversion going? Ive had the same machine for a year now and now going down the cnc path. Ive seen a few hm46 threads but they seem to stop mid way, would be good to how you went with it...

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[kensbey]

Hi brick007! Thanks for the interest. I actually got married and then spent 6 months living and working in Germany. It was awesome fun but unfortunately put the mill on hold for a while. We recently got back to Australia and have moved into a new place with a bigger shed, which means the conversion is back in motion. Not a lot yet, but expect more progress over the next few weeks!

Kensbey


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[headsmess]

sorry to do a lazarus post, but what happened with this project?

i just got myself a hm46 with the cnc plan in mind gotta love the nasty "decorative" scraping job

and as it weighs in at 318kg (600+lb!) it calls for a fairly substantial, ahem...bench lucky theres a stack of old lintel irons sitting here waiting for such a job

might be time to make a lil crane for the shop too!

oh wells. i guess i start my own thread now. i got one ace up my sleeve though... my lil x2 cnc machine!

[kensbey]

sorry to do a lazarus post, but what happened with this project?

i just got myself a hm46 with the cnc plan in mind gotta love the nasty "decorative" scraping job

and as it weighs in at 318kg (600+lb!) it calls for a fairly substantial, ahem...bench lucky theres a stack of old lintel irons sitting here waiting for such a job

might be time to make a lil crane for the shop too!

oh wells. i guess i start my own thread now. i got one ace up my sleeve though... my lil x2 cnc machine!

Hi headsmess,

Yes i am still alive.

We recently bought a house, so I have been tied up with moving etc. It has meant there hasn't been a lot of mill progress. I have almost finished my Y axis ballnut mount, but that's about it.

Having an X2 sounds like a big advantage! I thought that cutting all my parts for the conversion manually would teach me some basics of milling quickly, and it has, but it certainly makes it a slow process.

Go pick yourself up one of those engine hoist thingos from supercheap like this. I have found mine to be invaluable. It is strong enough that you can put lifting straps around the head of the mill and lift the whole mill/frame/bench together if you need. Will make life easier when you need to take the head off too.

Thanks for the thread revival, I need to get back onto this project haha.

kensbey