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Author Topic: MB concave build  (Read 2896 times)

FlashGP

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Re: MB concave build
« Reply #15 on: September 12, 2019, 05:43:07 PM »
Thanks Makky.

I have used both a stationary splash pan and one bolter to the oscillator.  The stationary one is better as I can rest my hank on it when cleaning swarf off the cutter and it does not continually flex the drain hose.  A piece of 6.35mm copper aircon return pipe soldered to the splash pan makes a nice  point to plug the drain into.

My first splash pan made from a piece of 2 inch copper pipe and fixed to the oscillator hit a large piece I was cutting parrallel concaves in when I was cutting the facets on a large rectangle (abt 3.5cm long)
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #16 on: September 29, 2019, 09:34:47 AM »
Built the control box, tested.Going to have to change from stepper to geared?? dc motor with encoder. Stepper is just too noisy. Just need to find a motor.

Rusted

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Re: MB concave build
« Reply #17 on: September 29, 2019, 07:01:50 PM »
Makky I presume you mean the motor to control the back and forth motion.
I wondered about the noise from the stepper.

I may be able to help you with a little 12v motor from a teleprinter. top quality motor. I may also have one with a little worm drive on it so you can just hook up a crank.


MakkyBrown

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Re: MB concave build
« Reply #18 on: September 30, 2019, 08:00:34 PM »
Hi Rusted,
Yes, back and forth motion. If I can get a motor/gearbox running at roughly 200rpm, with an encoder on it I should be able to oscillate how I was planning with the stepper. 
I have a motor here with an encoder and worn drive on it, just need to find the plastic gear it that drove it and it might do. 
Thanks for the offer, have you many?  I wouldn't want to take a motor you have earmarked for another project.
CheersMB

Rusted

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Re: MB concave build
« Reply #19 on: October 01, 2019, 07:59:41 AM »
I will have a look at what I've got today.
Have you considered a windscreen wiper motor, very robust and have a decent gearbox. Also window winder motors might be worth looking at.

Rusted

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Re: MB concave build
« Reply #20 on: October 01, 2019, 10:16:48 AM »
Righto, I have dropped a motor in the mail it should reach you in a few days.
I tested it and it seems to turn at around 1 rev per second, may be a bit fast so chuck a resistor (or pot) in series and have a play.

I cut your Supernova design in CZ yesterday, wowsers I have never seen a gem with this much sparkle, it's unbelievable.
« Last Edit: October 01, 2019, 10:20:44 AM by Rusted »

MakkyBrown

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Re: MB concave build
« Reply #21 on: October 01, 2019, 10:53:01 AM »
Cool, I'll have a play in it.
You certainly like the harder to cut designs :), great to hear Supernova is nice in CZ.
How is your encoder going?, send it down if you want and I'll get it going and write some basic code you can work with.
CheersMB

Dihusky

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Re: MB concave build
« Reply #22 on: October 02, 2019, 07:03:35 PM »
Looks a seriously cool rig, seen a couple of custom ones and a friend had his at the AFG meet. Do you think the lock up plates will be enough to stop the quill flex?

The two I've seen use a lateral stop system beside the quill, one had a fine adjustment on it and being hard against the quill there was zero flex when cutting. Both machines allowed the quill to move vertically and the quill was held firmly against the stop when cutting.

FlashGP

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Re: MB concave build
« Reply #23 on: October 03, 2019, 07:30:33 AM »
Hi Dihusky, I am currently building another quill stop as the stop needs to be able to move in 2 directions to allow for changes in mast height as the angles change.  The ajax thread used with stepper motors has an 8mm travel per revolution and is too course for the fune adjustment needed to perfectly allign the cutter to the quill. 

The new stop is being based on 2x10x20mm aluminium box sliding inside a 2x25x15 box.  I have cut a 6mm thread and plugged the end of the small box with JB Quick and tapped it.  All I need to do is make a backlash eliminator and I'll have a fine adjustment for the plane of rotation of the mast head.  The other two axises don't need a fine adjustment.

I'm eliminating play with 3x10 mm bar and two adjustment screws, similar to the plate used to remove slop in dovetail slides.  It'll also act as a brake once the position is set.

Regards
Glash
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #24 on: October 03, 2019, 09:31:40 AM »
Looks a seriously cool rig, seen a couple of custom ones and a friend had his at the AFG meet. Do you think the lock up plates will be enough to stop the quill flex?

The two I've seen use a lateral stop system beside the quill, one had a fine adjustment on it and being hard against the quill there was zero flex when cutting. Both machines allowed the quill to move vertically and the quill was held firmly against the stop when cutting.
Thanks, it locks the pivot solid. I think it should be ok without the stop, I'll find out anyway. A slight bit of flex might be helpful cheating when polishing. :)

FlashGP

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Re: MB concave build
« Reply #25 on: October 03, 2019, 06:10:28 PM »
Hi Makky,

Have ypu included a fine adjustment to allow you to truely allign the quill to the verticle plane bisecting the cutter.

I found 0.01mm increments are required.  Especially if cutting concave steps.  If not perfectly alligned, the boundary of the two concave steps is on an angle and will not line up with a standard step cut on each side of the concave.

I noticed this on the blue topaz I posted to facebook.  I added steps to the end of the 6 mains on an Australian star that I cut because when concave cutting the angle needed to meet the girdle is different.  They all had tilted boundaries.

I'll be using a test step cut as an allignment tool for the next competition stone I cut.  If not perfectly alligned the boundary will tilt when the angle is changed for the next step.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #26 on: October 03, 2019, 07:38:51 PM »
Hi flash, I am adding horizontal fine adjustment. I am thinking of using an alignment plate that goes in the collet, then adjusting horizonally. I will not have z axis adjustment atm(other than a bit from the oscillation carrage). I need a new faceting head/mast that is on a slide.

FlashGP

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Re: MB concave build
« Reply #27 on: October 04, 2019, 07:43:45 AM »
Hi Makky,

Why not put a couple of linear beatings under the cutter assembly and move it when you change mast height.

Regards Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #28 on: October 04, 2019, 12:02:12 PM »
Hi Flash,
With the gemmasta as soon as I lift/lower the mast height on the pole I have to re align I don't think the linear bearing will help. In the future I'm thinking a new facteting head, with linear height adjustment and on a slide.
With the gemmasta when doing steps, I thinking of pulling the handpiece off and making an allignment tool that goes on the shaft the handpices comes off, this will match up with another alignment tool in the concave machine collet.
I have ideas for alignment tools that will work a little different to what Ultratech does.The other possibility is using a hard stop and aligning against that after changing height.
Cheers
Andrew

FlashGP

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Re: MB concave build
« Reply #29 on: October 04, 2019, 06:29:27 PM »
Hi Andrew,

I guess I hnow what you mean, the Gemmaster mast is about 8mm offset from the center line running down the Quill.  This is what threw Clarrie and lead to him making a stand alone concave machine.

If you centre the cutter and the Quill with a Gemmaster mast, then raise the mast, you create a narrow triangle with the verticle plane centered on the oscillation of the cutter.  This offset pivots the cutter off centre as you raise the mast from horizontal.

But once you have locked the C axis of the Quill in the same verticle plane as the C axis of your cutter, you should be able to raise and lower the mast and just have to move the cutter in and out without having to readjust the mast stop.

Regards
Gordon
Yours Sincerely
Flash (Gordon)

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