[tahustvedt]

I'm ready for my new spindle. They are made from scrap aluminum. The bottom mount has dowel pins for easier alignment of the spindle when I need to change spindles. I designed the machine to be able to use multiple spindles without the need for tramming.

The spindle and VFD left China on wednesday, according to the tracking.

[tahustvedt]

My spindle went through customs today, so it might be here on thursday.

Thinking about converting the X to rotating nut. I'll definitely make the rotating assembly, as it seems like fun, and I have most of the materials, but I'm not sure I'll convert the machine, because I will have to hang the stepper under the gantry beam, and I don't like anything sticking down from there and potentially hitting the chip extractor stuff under the table. I don't want to build the stepper into the underside beam either because I'll have to hand cut the holes, and install a fan to keep the stepper from overheating. I don't know what I end up doing. It will cost at least $100 for the two 50x80x16mm angular contact bearings as well, including shipping and tax.

I attached the current state of my drawing. Not sure how I'll make the mounting plate(s) yet, so they're temporary. The rotating assembly has an integrated 62 tooth GT2 3mm pulley, and can be slid onto and installed on the ball nut after assembly and pre-load.

[tahustvedt]

I've turned the rotating part for the rotating nut assembly now, and will cut the pulley teeth tomorrow or this weekend. I'll post a picture of it if I don't mess it up.

I have a new idea for a machine. I'd like to make a small, lightweight, portable gantry with X-rails attached, and provisions for clamping the X-rails to any flat surface. That way I can CNC-cut things out of the machine. I can even clamp it to the gantry beam under my router and cut accurate holes and pockets for a rotating nut assembly. I have a few long 3mm pitch HTD belts that I can use to make a belt rack setup for the X, and Y.

[tahustvedt]

I didn't have any bigger tube, so I had to cut it close. :P Turned out ok. The end nearest the table is threaded 50-1mm, and the pre load nut is locked with an M4 screw.

Attachment 225936


Oh, and the spindle arrived today. Will try getting it to run on its own before installing it. The clamps fit perfectly. The spindle is 79.98 mm in diameter.

[cpr]

I've turned the rotating part for the rotating nut assembly now, and will cut the pulley teeth tomorrow or this weekend. I'll post a picture of it if I don't mess it up.

I have a new idea for a machine. I'd like to make a small, lightweight, portable gantry with X-rails attached, and provisions for clamping the X-rails to any flat surface. That way I can CNC-cut things out of the machine.

Sound as if you should be able to mill into the "short end" of a piece of wood?
Like as if the spindle was fixed horizontally?
This might enable dovetail-like connections?

[tahustvedt]

That should also be possible.

I'm playing with the VFD and spindle now. It worked right away, and after setting the rpm correctly it now shows the correct rpm. The motor speed is controlled via a pot on the front on my Huanyang VFD. What should I set the acceleration time to? I set it to 5 seconds now, and it spins up fine. I don't want it to suddenly fail during ramp up at random intervals.

The spindle is incredibly quiet. There is not much fan noise.

[tahustvedt]

Wow, this thing is so quiet. I'm running a long program now with the spindle at 16000 rpm to see if it will trigger any false limit switches due to noise. Seems to work fine. My debouce is 0. I gotta find something that needs cutting so I can test it under load. I don't have the necessary key to tighten the collet though. I need a 21mm key.

I looked long and hard at the VFD, trying to figure out where to install it and still have access to the display. Then it dawned on me. The display is removeable. I made a new ribbon cable for the display from an old IDE hdd cable, and installed the VFD under the table, with the display poking out from the melamine sheet, right next to it. Works beautifully. The only thing that remains is to install an aluminum channel across the underside of the table for the cable to sit in. Oh yeah, and to adapt the dust shoe to the larger diameter neck.

Don't mind the flimsy castering wheels with tall stems. They will be replaced when I can afford 5" ones. I need the height. :P

Attachment 226204

[tahustvedt]

This makes my old Kress look ridiculous. I had to try running it through some wood. 12mm pass depth in MDF with a 12mm endmill at 45 mm/s and it only pulled 2.5 A and didn't change rpm at all. The impression of power as it plowed through was incredible to me. I have been missing out.

My kress would spark like mad, flicker my lights and stall if I tried that with a 6mm endmill.


I measured the runout with a 1/2" collet and the 12mm endmill. It was 0.04mm. About the same as my Kress. A little disappointing, but no disaster. I'll try with more collets when I get them. I only have 4mm (supplied with the spindle) and 1/2" (from an old er20 shaft project) now, but a full metric set is on the way. I am unable to measure the inside of the shaft with my DI.

[tahustvedt]

I've done a couple of hours of milling in aluminum now, and there's no problem with noise. That was my biggest concern so that's fortunate. It just works.

[tahustvedt]

My electromagnets arrived today. They have 18 kg holding force each at 12 V. I tried one at 8 V and it was very strong. I'll do some testing before I install them so see if they get warm, and fabricate some iron discs for them to hold on to at work, or maybe just find some steel washers.

Attachment 226758

Playing with electromagnets makes me want to build a magnetic sheet metal brake.

[tahustvedt]

It gets quite warm after half an hour, I measure 57,9°C at the warmest. Seems to have stabilized. It will be mounted to an aluminium plate, so that will cool it quite a bit in use though.

[FandZ]

Electromagnet hold down. I like the sound of that. My cnc hobby has turned into my day job and one thing I hate doing is tightening my T-slot hold downs between jobs. I mainly route Oak plywood and I believe it's too porous for a vacuum table. Will your hold downs be able to hold wood down or is it just for steel?

[tahustvedt]

I guess electromagnets can be used as hold downs somehow, but they need very close proxximity to some iron to hold, so It would be a challenge to find a good solution. Yu can get some pretty strong magnets on Ebay. Here's one that's ten times stronger than mine: 12VDC Electromagnetic Lock Magnetic Lock 100 lbs Force | eBay

Oops. Wrong link. This is the one I meant: US Electromagnetic Lock Magnetic Lock 12VDC 180Kg Holding Force | eBay

[tahustvedt]

I installed the electromagnets in the housing and wired everything up to trigger when I close the door.

This is what the magnet looks like when the housing is moved away from the gantry.
Attachment 227086

This is the inside. I made a mounting plate with heat sink fins for it.
Attachment 227088

Here's the mild steel contact pad on the inside of the gantry.
Attachment 227090

There's one on each side of the gantry. It seems to work really well, and triggers as it should. I don't have to think about it. It holds when I start closing the door on the housing. I am able to pull the housing away from the gantry with them engaged, but they hold better than the old permanent cabinet magnets, and it won't matter if they should ever slip a little during use, as they will still continue to hold. While the old permanent magnets could cause jerking forces on the gantry if they let go and reattached as high accelerations, there will never jerk the gantry.

[Bl@ckrat]

whats the length of your X ballscrew ? are you going to change to rotating nut ?

[tahustvedt]

My X ballscrew is 2500 mm (98.4") long. I might change to rotating later. It's working great right now though, so I don't have an immediate urge to upgrade. I have ordered angular contact bearings for the rotating nut though, and will fabricate the parts I need to do the conversion. The most difficult to make parts are already finished.

[Bl@ckrat]

is it a c7 ? where did you get it from ?

i would really like to build a longer machine ... 2.2-2.4 long but only 600-800 wide ... but getting thk rails and ball screws is a mission

[tahustvedt]

Yes. C7. I got mine from here: http://cgi.ebay.com/ws/eBayISAPI.dll...E:L:OU:US:3160

I recommend rotating nut, or maybe going for 25mm pitch for screws this long.


Today I got a new motor from Automation Technologies. A 381 oz/in stepper with 2.8 mH inductance. I can run higher acceleration and speed now. Actually, it will slowly work the housing away from the gantry if I set it as high as it wil go safely. My speeds are now 8000 mm/min in all axes, and acceleration is set to (limited to) 500 mm/s² for the X and Y and 1500 mm/s² for Z.

[tahustvedt]

A short video of the magnet holding the housing in place. The magnets engage as soon as I bring the door down past the horizontal point. I made it that way so that I don't apply any horizontal forces to the housing before they engage.

[tahustvedt]

MY RS485 adapter hasn't arrived yet, and I'm growing impatient. You know you're living in a first world country when having to press a button becomes a problem.

I wired the 10V wires between the VFD and G540, and Mach3 controls the rpm fairly accurately, but I haven't wired the forward trigger yet because I don't have a relay. Can I run the forward trigger circuit directly through the G540? measured the common points on the VFD, and they are not connected to ground. The trigger common will be connected to ground if I wire it directly through the G540 without a relay.

The VFD has two separate commons, one for the rpm control and one for fwd/rev (and various other) triggers.

EDIT: Never mind. I found a relay.