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Author Topic: MB concave build  (Read 3942 times)

MakkyBrown

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MB concave build
« on: August 27, 2019, 08:28:30 PM »
Here's a couple of pics of where I'm at with the build atm.
Need to pull the collet holder off and shorten shaft.I'm planning on using my gemmasta faceting head and modding to lockup the pivot.





Rusted

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Re: MB concave build
« Reply #1 on: August 28, 2019, 07:41:47 AM »
That is just beautiful Makky, superb workmanship.

MakkyBrown

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Re: MB concave build
« Reply #2 on: August 29, 2019, 10:21:43 PM »
Thanks Rusted, coming together ok. Making use of scrap alloy I've collected.Designed the base will cut it tomorrow. Have shortened the motor shaft, need to make a few clamps etc. Then onto the electrics.





MakkyBrown

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Re: MB concave build
« Reply #3 on: August 29, 2019, 10:45:35 PM »
opps just realized I need to add a larger hole at end of slot.

MakkyBrown

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Re: MB concave build
« Reply #4 on: September 02, 2019, 07:25:57 PM »
Far out, mental note do not try and lap a big bit of alloy flat by hand, setup and surface in mill. The stock had a bit of a bend in it.
Got the plate true but it took me way to long, I suppose it was good exercise.


Finished base.
Will fit the motor unit to it tomorrow.



MakkyBrown

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Re: MB concave build
« Reply #5 on: September 02, 2019, 07:31:21 PM »
Underside of base

MakkyBrown

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Re: MB concave build
« Reply #6 on: September 03, 2019, 05:59:21 PM »
Getting there, finding a few small stuff ups. Like only 75degrees of pivot not the full 90 as it hits on mast slide base. Should be able to fix or will need spacer under pivot plate. Then I can't see myself using it much at 90degrees anyway. Using a 1mm polycarbonate spacer on the pivot and it is nice and smooth.

« Last Edit: September 03, 2019, 09:28:59 PM by MakkyBrown »

MakkyBrown

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Re: MB concave build
« Reply #7 on: September 04, 2019, 08:00:10 PM »
Made faceting head lockup parts.

One piece has 1mm clear polycoarbonate on it, the other has a white 3m acrylic spacer. I glue the space on but had to pull it off and move it a bit to make the clamp work. As pictured locks the head up really nicely.


MakkyBrown

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Re: MB concave build
« Reply #8 on: September 10, 2019, 10:03:17 PM »
Currently building the control box. Need to find out where I can buy some tin to make mandrels.


Rusted

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Re: MB concave build
« Reply #9 on: September 11, 2019, 06:52:03 AM »
I don't know about Tin, but Pewter is readily available at Op shops very cheaply.

FlashGP

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Re: MB concave build
« Reply #10 on: September 11, 2019, 01:33:27 PM »
Hi Makky,


you can use bearing alloy, but brass works well.  I have a re-purposed tap spindle for one cutter.  The others are brass inserts over which annealed copper tube has been pressed and glued in place with Locktite 262.


Aussie Sapphire may have some Polymetric mandrels left with 3/th shanks.  They were too big for my ER11A collets (max 7mm, but should work with ER16A collets.


I'm also considering buing some 1/4 inch and 6mm brass rod from the local brass supplier.  It comes in 3.6m lengths.  I figured I could make the 1/4 rod into new dops and cutters, and the 6mm into thread for more accurate adjustment than the current threaded rods I am using that were designed for stepper motors.


regards
Gordon
Yours Sincerely
Flash (Gordon)

FlashGP

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Re: MB concave build
« Reply #11 on: September 11, 2019, 08:12:19 PM »
Andrew,

How do you find the lower linear bearings on your cutter?  I wasn't sure if they would have more slop than the linear bearings that run on the round rods (like those in your carriage for the motor.


Is that a CNC cutting head motor attached to your collett?  If it is how do you find it?  John Broadfoot had suggested a CNC motor, but they were 400W, it seemed a bit of overkill that would require a second power supply for the remaining electronics.

If you lower where your oscillator assembly pivots for angles by 30mm, you would have room to undercut the base a little so you can get 90 degrees.  I'm looking at that for step cuts.  The theory being that they would increase the range of angles that the side facets would reflect at, increasing brightness of the cut. 

The added benefit of lowering the cutting head assembly, is that you can then get 0 to 90 on the Quill and have a little spare for big stones.  It may make fitting the splash tray easier.

regards
Gordon
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: MB concave build
« Reply #12 on: September 11, 2019, 09:14:23 PM »
Hi Flash,
The lower bearings have no play, they are even a bit stiff as I may have a very slight curve on one of the plates. They are best best linear bearing cheapest option catagory about imo. But I didn't like the idea of using them with constant oscillation so used the rods for that. I plan to change out the bearings on the rods for plastic. The replacements I purchased had too large an OD.

-Splash pan I will be bolting onto the motor frame and will move with the osilcation. 
-At 0 degrees(like cutting a table) the centre of the dop is about 18mm[Edit just turned the mast around 180degrees have heaps now] short of the centre of the pivot. I have 60mm of fully adjustable oscillation so that shouldn't be an issue and will make my mandrels fairly long. I have enough mast height for clearance.  I think it's already got 0-90degrees everywhere except the horizonatal pivot(stufffup) that I might fix of just leave it as I'm not sure how often I'd be cutting at 90 degrees. Need to either cutout a bit near the protractor of put a spacer in.
-Motor is the one salvaged off an old hp printer, 6mm shaft, I shortened the shaft so hopefully that reduces any flex.
-I've sorted the mandrel materials and will be making up some molds.
I need to make up an alignment plate that fits in the collet.
Atm I'm just going to finish it and use it no major mods unless a fundamental issue appears.
CheersMB
« Last Edit: September 12, 2019, 12:44:55 PM by MakkyBrown »

MakkyBrown

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Re: MB concave build
« Reply #13 on: September 11, 2019, 09:18:04 PM »
I don't know about Tin, but Pewter is readily available at Op shops very cheaply.
Good idea on the pewter. :) I'll remember that and might try it at some stage.

MakkyBrown

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Re: MB concave build
« Reply #14 on: September 11, 2019, 09:20:33 PM »
Power supply I plan on using is an old laptop charger does something like 19.5v at 12A. Stepper will run at 19.5V, DC motor 12v, and 5V for everything else.

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