Faceting machine head assembly.

[Faceting Frank]

Thinking of making a new faceting head for my machine.
Based on a round mast with a round linier bearing for the head assembly to swing on. Linier rail for the base to move back and forth on. Both will help to keep an accurate alignment with the lap regardless of the quill angle.
 Still using the digital gauge, I have to keep accurate recordings of the head assembly position on the mast for each row of facets. Not sure about fitting a digital protractor though. I have a copy of Amateur Gemstone Faceting vol 2 by Tom Herbst, it has 23 pages dedicated to fitting one. OK for getting the initial angle, but not sure about using it as a stop, might just stick with the dial gauge for that. Anyway, will start a thread on it when I start making it.

[JBK]

Will be following, 😊👍

[MakkyBrown]

I use mine as a stop. The new machine I am building I should get back to. I'd not worry about Tom's book to much, the encoder he is using is a bit on the low resolution side. Grab some code of RC or me. Maybe use one of these nice cheap touch screens available now.
Given how you are comp cutting I'd be temped to go with a 10000cpc 40000ppr encoder from USDigital. This is what I have for the new build. They will give 0.009 degree steps. Is it too accurate time will tell

MB

[Faceting Frank]

Thanks for the info on encoders MB. I was concerned about using a digital display as a stop because of the flutter when the lap was rotating. A dial gauge does have some flutter in it, but slowing the speed down means you can look at the top of the needle stroke, where as a digital display is a mess of numbers. Or so I think at this stage, but never used one so could be totally wrong about that.

[RoughCreations]

This is where I usually chime-in regarding encoders and their digital output. Any flutter can be filtered out or smoothed with a simple algorithm in the code, a knob can be added to the display box to change the degree of smoothing on the fly. For this reason and others, an encoder is way more powerful and versatile than an analog dial gauge.
Also refer to: https://aussielapidaryforum.com/forum/index.php?topic=7019.msg61562#msg61562
RC

[Faceting Frank]

The encoder looks very impressive, will look into it in more detail when I start to design the quill assembly and quill support. Have already ordered a lot of parts for the mast assembly, including a 20mm linier bearing in an ally housing, 20mm chromed hardened mast. Thrust bearing for that assembly to pivot on. Still going to fit a digital height gauge to record the linier bearing position for each row of facets though. It works really well and I can go back to any facet and be spot on.

[Faceting Frank]

Finished most of the CAD drawings for the components, but still waiting for some of the parts. Need them before starting to confirm the stated dimensions are correct. Looked at the US digital website, very informative and looking at the prices won't be going for a 40,000 ppr encoder. As I understand it an encoder of 14400 would give an accuracy of 0.025 deg. Would that be right?

[MakkyBrown]

A 10000cpr(40000ppr) encoder would give increments of 0.009 degrees. 90/10000. This is not accuracy, it is more like 10,000 0.009 degree stops(fixed marks on the code wheel). Make sure to get a 3 channel encoder so you can use the index for calibration. Up to you if you get an encoder with a line driver, or without.

MB

[MakkyBrown]

A 10000cpr(40000ppr) encoder would give increments of 0.009 degrees. 90/10000. This is not accuracy, it is more like 10,000 0.009 degree stops(fixed marks on the code wheel). Make sure to get a 3 channel encoder so you can use the index for calibration. Up to you if you get an encoder with a line driver, or without.If you are going lower resolution I am using a 5000cpr/20000ppr encoder (Broadcom or Avago), these were available at Digikey and other stores like Element 14. This might do but not sure if it will be good enough for your comp cutting but price was a lot cheaper than USDigital. But covid stuffed supply of lots of things.

MB

[MakkyBrown]

https://au.mouser.com/ProductDetail/Broadcom-Avago/AEDM-5810-Z12?qs=nm95cbFn36yryX%2Fd2Onjlw%3D%3D

Most stores do not have stock but Mouser still looks to have a few. This is similar or same as what RC and I are using. 5000cpr/20000ppr, with 3channels.

[Faceting Frank]

I can tell by the digital gauge I have fitted to my machine to record the quill support position on the mast that having a 10k CPR encoder would be pointless. I can record the position of facets to 0.01mm, but going back to them after cutting other facets, it would easily be + or – 0.01mm out. So, the realistic accuracy of my machine quill support movement is 0.03mm and that equates to 0.015deg on the quill. A 5k CPR would have increments of 0.018deg.
So, I was looking at US digital E2 encoder 5k CPR with an 8mm hollow shaft to suit my quill shaft. But it says 3 channels on the encoder are optional, but I can’t find on their website where to choose that option.

[Faceting Frank]

Looked that Mouser encoder MB, and the options it comes in, but can't see what shaft they are using. 8mm is mentioned (which is what I want), but it's not saying if it's hollow or not and there are no pictures of any of them that show the shaft.

[MakkyBrown]

From memory that one was for a 6mm shaft. The centre of the code wheel is hollow with an alen key grub screw. Download the datasheet it should have all the info your want. If your shaft is 8mm machine the end of that goes into the encoder 6mm hole.

MB

[RoughCreations]

FYI - see link below to download specification sheet for the encoder used in MB & RC faceting machine modifications:
Download AEDM-5xxx spec sheet

Encoder thread

RC

[Faceting Frank]

Thanks for the info MB and RC. That encoder comes with an 8mm hollow shaft which is good, as it will fit straight onto my machine. So, when I look through their options when placing an order I will be asking more questions.