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I've done worse, not on the large hadron collider scale perhaps, but whaddya do? Personally I remind myself that it's business and in business you always start from where you are now.Quote:
Originally Posted by Ross77
OTOH, being business I do get to buy the cloud of smoke pre-tax and reclaim the VAT :whistling:
I understand your pain :nope:
Seems like ages since the last post but finally managed to find some workshop time and have made quite a bit of progress. bolted the headstock to clamping collar, fitted new bearings to the spindle and modified the belt guards. just need a new belt and stepper drivers and it should be good to go..... :smile:
For now I have decided to use the original 1 phase motor as a test. I think it will be better to just get it working and then upgrade parts if needed.
I've also been wondering if I should take off the steppers and refit the hand wheels so I can check that it works as a manual mill. anybody agree?
Nearly there, should be making chips at the weekend, :dance:
For the sake of my sanity and desire to get this working I've put the homemade drives on hold and splashed out on some PM542's from Gary. very nice drives no buzzing or crackling like the other ones.
Just need to fit the limit switches and get used to mach 3 now.
Look's nice and purposeful :)
Love the drill-table monitor stand :LOL:
yeah I like it :smile:. its got to be one of the most over engineered monitor standQuote:
Love the drill-table monitor stand :LOL:
:dance::dance::dance::dance:It works..............not finnished by any means but milling Al under Mach 3 control...
Its happy cutting 0.5mm deep in Al and seems to have a 0.02mm resolution (probably change when I cut a bigger test piece)
the surface finnish is quite good, not very good pics tho. I think the mill is a little out of tram (if thats the word) the cutter is leaving small ridged as if each pass is sligtly semi-circular.
Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.
You could try adjusting the tension of the base mounting bolts; on a small machine like yours it might flex the post enough to correct the tram. Are the semi circles left by the cutter the same side when machining left to right and right to left? If the side swaps (i.e. the cutter is only cutting on the leading edge, then it could be the whole machine is flexing with the cutting load) lighter finishing cuts should fix it.Quote:
Is there an easy way to fix this? as I can only think of shiming the X-Y table but that will be a nightmare.
BTW the correct way to test the tram is with a DTI mounted on arm a few inched away from the chuck, so it can be rotated aroung the table (use a parallel between the table and the dti to even out irregularities in the table surface)
The bottom of the groove looks like something has come loose in the tool chucking.
The sides of the pocket look like a tool which can't decide if it is rubbing or cutting. Maybe a tool cutting uphill that is flexing to remove the allowance for the next pass.
I think you have other things to fix before you start worrying about tram :naughty:
Also 0.5mm sounds awfully light.
cheers didnt think of adjusting the pillar :redface: I'll have to check the cutting again to see if its flexing, before i go adjusting anythingQuote:
You could try adjusting the tension of the base mounting bolts; on a small machine like yours it might flex the post enough to correct the tram. Are the semi circles left by the cutter the same side when machining left to right and right to left? If the side swaps (i.e. the cutter is only cutting on the leading edge, then it could be the whole machine is flexing with the cutting load) lighter finishing cuts should fix it.
I'll try that then, I've seen the dual gauge ones and always asumed you need both gauges to cancel the error, Duh..Quote:
BTW the correct way to test the tram is with a DTI mounted on arm a few inched away from the chuck, so it can be rotated aroung the table (use a parallel between the table and the dti to even out irregularities in the table surface)
I think thats from when i tested the repeatability on the z, it produced a different cutter pattern for half the length but is the same depth.Quote:
The bottom of the groove looks like something has come loose in the tool chucking.
Im sure your right, :cry: I was just so happy it was finally working. the other point is that I only have the single phase motor running at 1:1 so the cutter might not be quick enough.Quote:
I think you have other things to fix before you start worrying about tram :naughty:
Or, maybe, too fast :eek:Quote:
Originally Posted by Ross77
Irving may disagree with this next bit :naughty:
There are published tables for cutting speeds but there are also tables for chip loadings. If you go for the official cutting speed the feed rates have to increase in proportion to keep the chip removal rate and up goes the side loading.
I simply don't have enough iron in my round column mill to hold against the side loading and smaller tools don't have enough meat to avoid bending. I reduce the revs and feed rates dramatically, I may be wrong but it works for me.
Get it wrong and first the tool digs in removing too much, then it rubs for a bit before the next dig in. Surface finish goes to pot.
When a tool starts to rub, rather than cut, it introduces a bending force. You can go around the finishing cut until the cows come home without fetching it to size. Increase the hole cut size to get past the rub and Whammo, you've cut oversize.
The trick is to rough out and leave an even excess all the way round the job then get the revs and feeds right on the finishing pass. Ignore the tables, find out what works on your machine. Even then the problems may come back when you change direction.
The routers of aluminium cut uphill, but they are usually making pretties rather than working to tolerance.
The millers of aluminium have a lot more rigidity in the system so they have can afford to cut downhill, meaning the tool shies away from the finished size rather than in to it. This does mean removing the backlash. If you compensate for backlash in the software you can't afford any side loading on the tool which can move the slides, a severe restriction on feed rates, and hence, spindle revs.
You must be a mind reader I was just going to ask about the tables for speeds and feeds........ Is it not worth me knowing what it should be so I can work back? where can i finf these tables?
I'll have to check the flexing, The quill was hardly down and the bit was 10mm dia, 20mm long in a ER32 collect chuck so I hope it wasnt tool flex. And im not sure how i can slow the spindle down without a major redesign and a shorter belt. I was hoping to check it worked properly before I bought a 3 phase motor.
Certainly shallower cuts and plenty of cutting fluid improved the surface finnish, just how noisy should a rough cut be??? maybe I'm erring on the side of caution.
I'll have to refresh my memory on up hill and down hill milling. I always thought that learning how to use it would be harder than making it :oD
Here are cutting speeds, milling is second table down, calculator below.
http://littlemachineshop.com/Referen...tingSpeeds.php
It suggests 1600 rpm for 10mm in aluminium. Personally I'd go for about half that. If the suds gets diverted for a moment by a fixing bolt, I prefer it if the tool doesn't go red hot :whistling:
My mill came with a 2hp motor but no way on God's green do I want to put anything like that down a small cutter, it's just too much. I replaced it with a 1hp on a digi phase inverter and I never work it hard.
How noisy should it be? Any loose fittings on a bench mill will rattle. The cutter should make cutting noises, if it becomes noisy that usually means you've lost the tool tip.
Thanks once again for your advice, It definetly looks like I just need to learn how to use it..........The mini mill beginers guide was quite useful too, its suprising how much you read and then forget :heehee:
Ive ordered some 2 flute ali cutters 3,4 and 6mm so i can keep the speed up and find the right feed. Hopefully get there in the end.......
Ok cutters arrived today, tryed the 6mm one and what a difference. 3mm deep cut in one pass with nice clean sides and no burrs on the edge. not sure on the cutting speed but the velocity is set at 400 mm/min. but the feed rate said 18mm/min I think . still need a bit more practice with mach.
You where definetly right Robin, I think I,m getting closer to the machines capabilities, althougth for what it is I'm more than happy with how it performed with the 6mm cutter. I'm sure that I can improve on the 3mm depth with a bit more tuning.
now its cutting clean edges It appears to be 0.3mm out, not sure if this is a step unit error ( had to round up to whole no.) or backlash. When I first tested it under no load I was getting 0.02 accuracy, is it possibly that the machine is still settling down? I dont think it can be machine flex as i was only typing the G-code line by line so it would have plenty of time to straighten up before the change in direction. I wont be to happy if the delrin nuts need constant attention tho...
Quote:
Originally Posted by Ross77
3mm deep sounds about right for a 6mm tool, so does 1420 rpm suggest you experiment with feed rates.
Measure the backlash, find out how much of the 0.3mm is accounted for. Perhaps a man has to ask himself, is Delrin better suited to free rolling gantry style machines?
I spent a lot of time and money removing the backlash from my machine, if I could have done the same with a plastic nut it would appear somewhat futile :whistling:
Robin