Aluminium Framed Router

[Neale]

Drilling into the end, cutting both shaft and pulley, is an established technique but you will find it difficult to do accurately with an aluminium pulley as the drill will start to wander. Also, it's a mistake to drill for grub screws at opposite sides. You are now balancing the force of one grub screw against the other. Much better to drill at 90-120 deg apart, so both grub screws and the bore of the pulley grab the shaft. That might give some useful extra grip. You could just file a small flat on the shaft for one grub screw to bear against?
Good luck - I haven't reached this point on my own machine yet!

[lucan07]

Drilling into the end, cutting both shaft and pulley, is an established technique but you will find it difficult to do accurately with an aluminium pulley as the drill will start to wander. Also, it's a mistake to drill for grub screws at opposite sides. You are now balancing the force of one grub screw against the other. Much better to drill at 90-120 deg apart, so both grub screws and the bore of the pulley grab the shaft. That might give some useful extra grip. You could just file a small flat on the shaft for one grub screw to bear against?
Good luck - I haven't reached this point on my own machine yet!

The pulleys are not aluminium they are Zync plated steel quite solid so I may try a test on the end of one ballscrew I have a small drill stand that I use for holding a tapping aid that I can fix in place with Lube ands patience it should be possible without to much wandering.

[Davek0974]

Drilling in from the end is a good method, if at all possible, drill in and tap a thread - M3 or 4, then fit grubscrews, that way the pulley is secured both directions - axially and radially. You will only get away with it if both metals are similar hardness, my concern is the hardened end of the screw - if one is softer the drill will wander into it.

And yes, grubscrews at 90 or 120 degrees only, never opposite and only two screws, always file/grind a flat on the shaft for at least one screw, better still drill a little divot the same size as the tip of the screw.

[lucan07]

You will only get away with it if both metals are similar hardness, my concern is the hardened end of the screw - if one is softer the drill will wander into it.

The shafts will be harder than pulleys, I could Dremell a half round into shaft and use mill to match this on pulley would not be identical in all honesty but should be close enough to be able to run a M3 tap. Alternatively with opposing grub screws would I be better to drill through shaft completely and use a split pin

And yes opposing grub screws an amateurs mistake lesson learnt will remember that once is a mistake twice is stupid!

Decision made I had seriously under estimated how hard the ballscrew material was going to be.

Significant flat ground on one side and loc-tite to ensure grub screws stay put will be my plan of attack for now, just dremelled first one and grub screw replaced by an allan head A2 stainless machine screw should be sufficient to prevent rotation and lock pulley in both directions.

[lucan07]

Got ten minutes to inspect the plug on X axis and it had a problem caused by old age and drugs, I got older massive doses of steroids prescribed eyesight went to crap, some plonker managed to rotate pins by 90% when soldering late the other night, easily fixed glad I didn't use a 6560 for this build the driver would have gone pop and I would be soldering a new TB6560AHQ IC into the board and tales of magic smoke would be told.

[lucan07]

Bit of progress made over the weekend sorry to say weather was nice so my bikes took most of my free time been neglecting them too much lately they need riding and I need the exercise getting old, London Surrey 100 end of July and Box and Neath hills are both killers if you are out of shape and practice. However fixed problem of slipping pulleys before it occured, a bit of testing/tuning first cuts a few slats of 25mm mdf which I have decided to use for first sacrificial bed, had a selection of 2020 off cuts laying around from printer builds etc so using these for clamping t-slots gives me 5mm to skim as needed. Using 6mm Router bit 1st DOC 3mm 2nd 6mm 3rd 12mm MDF using 12000rpm and 1500mm pm feed no problems with cuts. I have used a BOB I was given I think its a cheap chinese import and I appear to be having occasional problems, axis will refuse to operate in one direction, jogging a different axis then frees the original axis to move as required so another BOB on its way, double checking wiring next on to do list, all wiring is CY shielded cable currently all mounted in small pc tower case whilst waiting for cabinet to arrive so may just be everything to close for comfort. VFD is mounted well away from everthing else.

[lucan07]

A little googling indicated that problem may well be with me using opto isolated Bob to feed opto isolated drivers but this was not conclusive, however a post on Mach3 forum got the same answer from on of the Mod's Tweakie who I class as a reliable source so hopefully new bob without opto isolation will solve my problems with axis stalls.

[Davek0974]

I have the same setup and asked the same question to a lot of suppliers - the answer was that using opto isolators to drive opto isolators was no issue at all and is very common as it protects both ends of the system.

[Clive S]

A little googling indicated that problem may well be with me using opto isolated Bob to feed opto isolated drivers but this was not conclusive, however a post on Mach3 forum got the same answer from on of the Mod's Tweakie who I class as a reliable source so hopefully new bob without opto isolation will solve my problems with axis stalls.

I have not seen Tweakie post but I am pretty sure that using double opto's won't make any difference to an axis refusing to go in one direction or the other. I would check the cables for loose connections.

[lucan07]

I have not seen Tweakie post but I am pretty sure that using double opto's won't make any difference to an axis refusing to go in one direction or the other. I would check the cables for loose connections.

post in question attached with reply had seen this mentioned elsewhere all other cables checked have replaced Bob alone and problem is now solved, in short if not problem on occasions why did tweakie come up with response straight away without opto bob or drivers mentioned, why did non opto bob solve problem?

Re: Router/Mill Design & Build « Reply #12 on: May 02, 2016, 06:30:42 AM » Bit of progress made over the weekend sorry to say weather was nice so my bikes took most of my free time been neglecting them too much lately they need riding and I need the exercise getting old, London Surrey 100 end of July and Box and Neath hills are both killers if you are out of shape and practice. However fixed problem of slipping pulleys before it occured, a bit of testing/tuning first cuts a few slats of 25mm mdf which I have decided to use for first sacrificial bed, had a selection of 2020 off cuts laying around from printer builds etc so using these for clamping t-slots gives me 5mm to skim as needed. Using 6mm Router bit 1st DOC 3mm 2nd 6mm 3rd 12mm MDF using 12000rpm and 1500mm pm feed no problems with cuts. I have used a BOB I was given I think its a cheap chinese import and I appear to be having occasional problems, axis will refuse to operate in one direction, jogging a different axis then frees the original axis to move as required so another BOB on its way, double checking wiring next on to do list, all wiring is CY shielded cable currently all mounted in small pc tower case whilst waiting for cabinet to arrive so may just be everything to close for comfort. VFD is mounted well away from everthing else.

Tweakie.CNC Global Moderator Offline Posts: 5,716 Super Kitty.

Re: Router/Mill Design & Build « Reply #13 on: May 02, 2016, 07:18:20 AM » Nice work sir. Let's hope that changing the BoB cures the axis one way problem (issues such as this can occur when using an opto-isolated BoB feeding into an opto-isolated driver). Tweakie.