Aussie Lapidary Forum

LAPIDARY => Gemstone Faceting => Topic started by: MakkyBrown on August 27, 2019, 08:28:30 PM

Title: MB concave build
Post by: MakkyBrown 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.


(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-270819202115.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9092)
(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-270819202015.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9091)
Title: Re: MB concave build
Post by: Rusted on August 28, 2019, 07:41:47 AM
That is just beautiful Makky, superb workmanship.
Title: Re: MB concave build
Post by: MakkyBrown 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.

(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-290819221748.png) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9093)


Title: Re: MB concave build
Post by: MakkyBrown on August 29, 2019, 10:45:35 PM
opps just realized I need to add a larger hole at end of slot.
Title: Re: MB concave build
Post by: MakkyBrown 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.

(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-020919191849.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9095)
Finished base.(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-020919191933.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9096)
Will fit the motor unit to it tomorrow.


Title: Re: MB concave build
Post by: MakkyBrown on September 02, 2019, 07:31:21 PM
Underside of base(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-020919193022.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9097)
Title: Re: MB concave build
Post by: MakkyBrown 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.

(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-030919175056.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9098)
Title: Re: MB concave build
Post by: MakkyBrown on September 04, 2019, 08:00:10 PM
Made faceting head lockup parts.
(http://aussielapidaryforum.com/forum/gallery/9/thumb_5704-040919195700.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9100)
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.
(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-040919195558.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9099)
Title: Re: MB concave build
Post by: MakkyBrown 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.

(http://aussielapidaryforum.com/forum/gallery/9/medium_5704-100919220036.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9101)
Title: Re: MB concave build
Post by: Rusted on September 11, 2019, 06:52:03 AM
I don't know about Tin, but Pewter is readily available at Op shops very cheaply.
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: MakkyBrown 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
Title: Re: MB concave build
Post by: MakkyBrown 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.
Title: Re: MB concave build
Post by: MakkyBrown 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.
Title: Re: MB concave build
Post by: FlashGP 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)
Title: Re: MB concave build
Post by: MakkyBrown 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.
Title: Re: MB concave build
Post by: Rusted 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.

Title: Re: MB concave build
Post by: MakkyBrown 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
Title: Re: MB concave build
Post by: Rusted 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.
Title: Re: MB concave build
Post by: Rusted 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.
Title: Re: MB concave build
Post by: MakkyBrown 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
Title: Re: MB concave build
Post by: Dihusky 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.
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: MakkyBrown 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. :)
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: MakkyBrown 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.
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: MakkyBrown 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
Title: Re: MB concave build
Post by: FlashGP 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
Title: Re: MB concave build
Post by: Faceting Frank on October 05, 2019, 03:49:51 PM
I don’t know much about concave cutting attachments, but I do know the quill is going to have to travel in a perfectly vertical trajectory as you alter the angle. If it doesn’t then it will be moving to the left or right of centre as you alter the mast height.
 My mast is the same as Ultratech. But what I had to do to my machine to get the quill 90deg to the lap and allow me to cut the stone in the picture from 90 to 20 deg. Keeping all facets aligned without using the cheater, is to have an adjustment for the quill pivot, altering this by trial and error till I got it right.
(http://aussielapidaryforum.com/forum/gallery/9/medium_120565-051019154526.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9111)
(http://aussielapidaryforum.com/forum/gallery/9/medium_120565-051019154257.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9110)
Title: Re: MB concave build
Post by: FlashGP on October 06, 2019, 09:10:17 AM
Hi Frank,

Pretty much the same issue, but the cylindrical cutter on a concave cuter adds two more dimensions of error. 

With a flat lap on an ordinary faceting machine, the plane through which the quill pivots must be perpendicular to the top of the lap and the plane through which the stone sweeps across the lap must be parallel to the lap. 

The vertical quill pivot plane on the concave cutter must still be perpendicular to the top of the cutter, but it must also be in the same plane as the centre of the cutter as it travels back and forwards.  If it is parallel to that plane, then the facets will be off-set, that is when at 96, they may be cutting as if set to 2 or 94.  This is because the stone is no longer sitting on top of the cutter, but part way around its circumference.

If the mast is off-set (as in the GemMaster) and this is not compensated with the Quill positioning, the cuts will be tilted on the stone.  It's why you need to be able to adjust the position of the cutter relative to the quill so it is perfectly aligned.

regards
Gordon
Title: Re: MB concave build
Post by: Faceting Frank on October 06, 2019, 12:35:05 PM
I’ve looked at the whole of this thread now and realise my comments would have already been thought over.
Don’t know if you guys could put a digital Vernier to use. I have one on my mast and use it to keep a record of its position on different rows of facets, or individual facets on some comp. stones. Allows me to get back to any facet with absolute confidence I’m spot on. Bought it at Hare & Forbes part number D667.
(http://aussielapidaryforum.com/forum/gallery/9/medium_120565-061019123249.jpeg) (http://aussielapidaryforum.com/forum/index.php?action=gallery;sa=view;id=9112)
Title: Re: MB concave build
Post by: FlashGP on October 08, 2019, 08:35:17 AM
Hi Frank,

I use a Facetron on which the mast pivots.  The mast passes through the aluminium block that is the body of the faceting head.  As a result it would require a fair amount of engineering to mount a digital vernier. 

But because my protractor is permanently calibrated and runs off a crank and odometer, I have added a 1/100th degree scale besimide the tenth wheel.  This plus the dial indicator allows me to come back to the same height after changing angles.

Because I use laps of varying thickness, it is probably easier to use this setup than a digital vernier in the mast.

Regards
Gordon
Title: Re: MB concave build
Post by: FlashGP on October 08, 2019, 08:38:38 AM
Hi Makky,

About your reallignment issue with the concave cutter on the Gemmaster.

Thinking it through, you may have to add an adjustment to the pivot lock so you can compensate for the offset of the quill.

Regards
Gordon
Title: Re: MB concave build
Post by: MakkyBrown on October 08, 2019, 10:21:52 PM
I plan to cheat a bit flash if I have too and use the pivot of the concave cutter assembly to help with the alignment. :) Maybe i could make an adjustable 0 indicator.
I am about to start focusing on book volume two, I have 80 designs to work though, start test cutting and formatting and remove a few with the aim of having 60 really good designs I am happy with for book volume 2.So concave machine will be on hold of a bit until I get on top of the book. :)I am really happy with how most of the new designs render and can't wait to cut them  ;D
I'm thinking it will be better than volume 1.
CheersAndrew
Title: Re: MB concave build
Post by: FlashGP on October 09, 2019, 12:08:45 AM
No worries, I'm looking forward to seeing volume 2. 

I showed Volume 1 around or local facetors group meeting on Sunday, a number of the members were impressed.

regards
Flash
Title: Re: MB concave build
Post by: Giel on October 20, 2019, 05:27:53 PM
I have been away from the forum for a while, and my own concave build has been on hold.

I just wanted to say: Awesome build Makky!!!  beers
Looking very professional, god I wish I had a neighbour like you with a cnc machine and a lathe.

Also thumbs up to Frank for the faceting machine, that's the best homemade machine I have seen on the internet!
Title: Re: MB concave build
Post by: FlashGP on October 20, 2019, 10:17:35 PM
Hi Giel and Makky,

I hope you are both entering at least the concave cut stone in the Australian Facetors Guild 2020 annual competition.

I didn't enter the concave stone I was cutting as I alligned the concave cuts to the wrong guide facets so the pavillion was2 index stops off allignment.  Mrs Flash scored the stone. 

There was 1 concave section entry in 2019, not bad as it is a new section, but I would like to see more entries in the the 2020 comp as I believe the 2 optional sections (the concave cut and the Open Challenge) add interest and encourage diversity.

I cant enter the 2020 comp as I am one of the organisers.
Regards
Flash
Title: Re: MB concave build
Post by: Giel on October 20, 2019, 11:04:46 PM
Quote
Hi Giel and Makky,

I hope you are both entering at least the concave cut stone in the Australian Facetors Guild 2020 annual competition.

hahaha, that would be fun, but my new faceting machine has yet to arrive, my concave build is going slow as I am not a machinist and have to wait months for parts. Above all, I am spending it all at the moment on the new machine and laps.  :)
And I consider myself a bit of a beginner, and I'm dutch.

But in time I will enter if possible.  beers



Title: Re: MB concave build
Post by: Faceting Frank on October 20, 2019, 11:15:18 PM
Barry Chapman was the only entry in the concave section.
Title: Re: MB concave build
Post by: FlashGP on October 25, 2019, 07:33:05 PM
Hi Geil,

I know about going slow.  I built my concave cutter from bits from Banggood.  Direct coupling the collet holder to the motor with one Thou shims to centre the collet holder on the shaft has given me more accuracy than a 150mm extension shaft mounter on bearings.

Anyway, you only have 7 more months to complete your machine and submit your entry, plenty of time to finish the concave machine.

Regards
Flash G
Title: Re: MB concave build
Post by: Giel on October 25, 2019, 11:26:45 PM
Quote
I know about going slow.  I built my concave cutter from bits from Banggood.  Direct coupling the collet holder to the motor with one Thou shims to centre the collet holder on the shaft has given me more accuracy than a 150mm extension shaft mounter on bearings.

Maybe I should let go of the idea to make it perfect....
Just build it and get cutting, I will probably modify it later on anyway.
I have a collet holder that fits the motor and I also have an extension shaft with bearings so both options are available.

Quote
Anyway, you only have 7 more months to complete your machine and submit your entry, plenty of time to finish the concave machine.

hahaha, amping up the pressure..... ;D

But seriously, if possible I will enter. (never entered a cutting competition before though)



Title: Re: MB concave build
Post by: MakkyBrown on October 26, 2019, 08:15:29 AM
I'll enter aswell Giel. Just build it is the best approach, as you'll probably find unexpected issues you will need to change.
CheersMB
Title: Re: MB concave build
Post by: Giel on October 26, 2019, 08:36:37 AM
Quote
I'll enter aswell Giel. Just build it is the best approach, as you'll probably find unexpected issues you will need to change.

Yeah I know that I will probably run into unexpected issues, I already am while building it: I need to find a metal worker in the area for some parts, need to find a nerd to help me with the dc motor and driver, because stepper online will not answer my emails.
slowly but surely I am getting there.
Title: Re: MB concave build
Post by: MakkyBrown on October 26, 2019, 09:41:53 AM
Quote
I'll enter aswell Giel. Just build it is the best approach, as you'll probably find unexpected issues you will need to change.

Yeah I know that I will probably run into unexpected issues, I already am while building it: I need to find a metal worker in the area for some parts, need to find a nerd to help me with the dc motor and driver, because stepper online will not answer my emails.
slowly but surely I am getting there.
I might be able to help with the motor.
Title: Re: MB concave build
Post by: Giel on October 26, 2019, 07:04:31 PM
Quote
I might be able to help with the motor.

I finally have an email from stepper online and I just ordered the cables to hook it up to the computer.
I think I will manage in the end, if I dont I will let you know. thanx for the offer!

First my idea was to use a brushless dc and threaded rod for both motions (swivel and positioning). But I cannot make it myself as I dont know much about electronics and programming.
Brushless dc mode 1: for swivel action, needs a speed control and  a circuit for polarity change every second or two. The time of
                                polarity change needs to be adjustable also.
                   mode 2: for positioning, needs a very slow and precise rotation so I can position the mandrel and lock it down.
So that would mean two motors, and circuits, one for each slide table. This way I could also use a V-wheel.
I really like the idea of a V-wheel for cutting large stones that are relatively flat, with a few V-grooves on the pavilion you can still have a great lively stone. (great when you have big but flat rough)

If I cannot find someone in town who can help me with the above, I think I am going the easy way on the machine.
I have a "12V DC 100 RPM High Torque Gear Box Electric Motor for Speed Control" that I will use for the swivel action.
I will use a threaded rod for the other slide table to adjust the position of the mandrel by hand. But that means I can only use cylindrical mandrels for now. So it will only swivel in one direction instead of two, and positioning will also be in one direction instead of two.

Hope this makes sense.



Title: Re: MB concave build
Post by: MakkyBrown on October 26, 2019, 07:55:04 PM
Hi Giel,
You are welcome to my code and wiring diagram for my controller. I am using the key pad to stop/start/directions/ and speed for the dc motor(with collet holder)
The oscillation motor where I was planning to use the stepper. I'm changing to a worm drive using a dc motor with an encoder on it. This will be controlled from the same control box as the main dc motor. Key pad will be able to stop/start oscialtion, and control oscillation speed, start position and stroke length.If you have not used arduino before it is great and lots of sample code out there to steal etc.
But didn't you purchase a driver box for the bldc motor?? You should be able to just wire a pot to it for speed control if it is like some of the others I've seen.
CheersMB

Title: Re: MB concave build
Post by: Giel on October 26, 2019, 09:55:17 PM
Quote
But didn't you purchase a driver box for the bldc motor?? You should be able to just wire a pot to it for speed control if it is like some of the others I've seen.

Yes I did, and I will be using a pot for speed control as you describe.
I think I did the wiring correctly, but apparently I have to set the whole thing up connected to a computer using brushless dc software to get it going. And to modify it with the softare so it can be used with a pot.
I have all the parts but I did not order the cables needed, as it was not mentioned on the website, I ordered those this morning so I have to wait for those to arrive.
I think I will be able to get the motor for the collet holder going.

Title: Re: MB concave build
Post by: FlashGP on October 28, 2019, 12:29:17 AM
Hi Giel,

I just used a small 30rpm 12v motor from Banggood.  It is tiny and looks like a motor from a model, but it is geared with a worm drive and  works better than a 2w turntable motor from a microwave oven, safer too.

I made an arm that fits on the worm drive  out of some 10mm square rod drilled and tapped with my bench drill.  The taps are 5mm threaded holes and I cut and filed that part of the  arm o 5mm thick using a hacksaw and file.  The holes are offset and spaced at 15, 20 and 25mm from the centre giving me adjustments for the length of travel.

I then bought a male and female tie rod ends from Banggoood and connected them, one end to the arm on the motor, the other to a post on my base plate of my concave cutter.  Polarity isn't important for the oscillator,  the rotary motion of the arm pushes and pulls the cutter head equally well in CW or CCW rotation.  It looks a bit like a steam engine crank.

I just use a 12 to 36v 775 motor from banggood.  It does 3500rpm at 12v, 10,000 rpm at 36v.  With small diameter cutters, 3500 rmp is about OK.  I wouldnt use a slower motor, it takes too long to cut.

Switch mode power supply is the way to go.  They are cheap and have 110/220v terminals and 12v and ground terminals on the 12v side, plus an earth terminal.  They are about 1/4 the cost of a traditional supply and pack more punch.  I bought a 25amp supply for about $35 Australian.  It would have cost me about $300 for the 2 transformers needed for the same current  for a traditional supply.  I went big as the price difference between a 10A and 25A supplý was only $10.  I figured if I needed bigger motors, I would already have the power supply.

The basic circuit is, mains in to the switch mode supply, with the Active Brown wire, rumming via a switch.  Two 12v wires 10A to from the power supply, one each to a pulse width modulator (dc speed controller). One set of wires from each pulse width modulator to a 4 pin plug, both motors are fed via this plug so I cant mix them up.

The small motor is controlled with a 10A PWM, one direction only, that cost about $4.  The big PWM can handle up to 40A at up to 50v.  It cost about $12  from Banggood.

next supply I make, I'lllhouse in an old computer case or CD case from the recycling shop, the plastic electrical box I bought cost me abput $50 and everything was a tight fit.

lastly, put a 47ohm 5w resistor across one of the 12v outputs.  Thiskeeps the switch mode supply under load when the motors arenot turning.  It is supposed to make the switch mode supply run better.

Regards,
Flash
Title: Re: MB concave build
Post by: Giel on October 28, 2019, 02:41:29 AM
We think alike Flash, I have made something similar as you describe for the swivel action.
I have a 12 V 100 rpm motor with a speed control, with a "swivel block"
Made the black block on the 3d printer, It has a threaded rod running through, a square aluminium plate runs through the block connected to the arm. When I turn the two nuts the aluminium plate slides up and down, that way I can adjust the swivel length. (just need to print the turning knob and fit it over the two nuts.)
(http://aussielapidaryforum.com/forum/gallery/9/48179-281019022446.jpeg)
(http://aussielapidaryforum.com/forum/gallery/9/48179-281019021708.jpeg)

I also have DC motor for the mandrels, 3500 rpm, already have the speed control and power supply.
I have almost all the parts now, looking for a metal worker in the area to make the aluminium plates as I cannot do that myself.
Title: Re: MB concave build
Post by: FlashGP on October 28, 2019, 08:33:54 AM
Hi Giel,

Necessity is the mother of invention.  Yours looks a bit nicer than mine,  maybe I should buy a 3d printer.  Rej (Gem Cut Studio) Poirier madr his faceting machine using one.

The neatest oscillator I have seen is on the VJ, it is two disks with a ball bearing race and offset locators that screw to the machine's platten and the base of the cutter housing.  But this is way beyond my capability using silversmithing tools and a bench drill.