Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: olf20 on August 30, 2017, 06:03:25 PM
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I want to be able to identify various places on my mill
table for different projects. I don't want to connect in
any way.
I also do not want linear scales. I have dual shaft steppers
and I want to mount encoders on the x and y axis so I can
move the table to a exact location, then go about my machining.
Ebay has 2 and three axis digital readouts, but I"m not sure which
encoders would be the right ones. I have contacted one of the
suppliers but have not heard back from them.
http://www.ebay.com/itm/2-Axis-Digital-Readout-For-Milling-Lathe-Machine-With-Precision-Linear-Scale-Hot/252862032164?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D45729%26meid%3D21c7301be2ee4acaa337ff9a4f0bd02a%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D322514107578&_trksid=p2047675.c100005.m1851
Have any of you done this?
Care to share particulars.
olf20 / Bob
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Hi,
that read out is made for a particular linear encoder. You will have to match the linear distance travelled per count to one count of your rotary encoder.
If for instance one linear scale count is 0.01mm then you will have to arrange a rotary encoder to match... lets say you have a 5mm pitch ballscrew
direct coupled to your stepper then the stepper will rotate (0.01/5)*360 which is .72 degree. Thus your one count is 0.72 degree or (360/0.72)= 500 count per rev,
therefore your rotary encoder must have 500/4=125 lines. I don't recall seeing an encoder with that unusual number of lines.
It may be some of the 'programmable' magnetic line encoders could offer the flexibility to specify some unusual number of lines. The only ones I've seen locally
have been worth BIG BUCKS, like $800 each!
To be honest I think trying to match a linear scale to a rotary encoder is going to be a real battle.
Perhaps ask the manufacturer of the readout if it is possible to 'reprogram' the readout , that I suspect would be a lot easier than the reverse.
Craig
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I have email the supplier, but have not heard back yet.
I see what you are saying about matching the encoder
to the display.
Thanks for your help!
olf20 / Bob
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Can you not just use Fixture Offsets G54--G59 0R G54.1?
Nick.
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Yes I could, but I wanted something absolute
not connected to Mach. It's not a big problem
just something I was thinking about.
Manufacturer responded that their system
will not work with rotary encoders.
Thanks for the replies.
olf20 / Bob
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Hi Bob,
I think that it would work with a rotary encoder its just that rotating 'one click' on your encoder may mean you readout increases by .125mm say.
If the readout is to be useful then the actual distance travelled when your stepper rotates 'one click' has to be identical to the readouts increment for
'one click'.
You could certainly do it with an Arduino or similar. Are you electronically inclined? I thought about it last night and wondered whether an Arduino could
'translate' your rotary encoder to the same as the readout expected from its matching linear encoder. But then thought well if you are using an Arduino why
bother with the readout at all?
You can probably tell I have given this a little thought because I wanted a similar thing for my mill. My inclination at that time was to use linear differential
voltage transformers as the sense elements. As my experience grew I cam to realise that while my Mach mill doesn't have encoders or LVDTs provided the steppers
don't lose steps, and they don't unless I crash it, then Mach IS THE SAME as the readout, ie I don't really need an independent system at all.
I soon found other ideas and projects to absorb me rather than pursuing this one down a rabbit hole.
Craig
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Thanks for the reply Joe. I just don't want to leave Mach on
all the time. This solves one problem, and the other is quick
reference to several setups when not using Mach.
Thanks for your reply.
The manufacture just email me back and said they do have
the rotary encoder for the display.
I might be in luck after all.
Thanks
olf20 / Bob
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Bob,
Let use know how things go as I may be interested.
RICH
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Well I got a reply from the Supplier.
" sorry for the delay reply.
No problem, please see the attached picture, it's the rotary encoder for milling machine.
You don't need to reset the readout, the SDS6-2V can recognize the rotary encoder automatically
But your milling machine must have the place to fix the rotary encoder.
The price for the rotary encoder is US $146.
Should you need any further help, please feel free to let us know.
Best regards and have a nice day."
I'm investigating other encoders to find a cheaper one.
But at least we know something is out there.
Will post back when I find more.
olf20 / Bob
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Hi,
I don't understand:
But your milling machine must have the place to fix the rotary encoder.
Attached? How? It is like some sort of quasi linear encoder?
Craig
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I emailed them back to confirm the mounting and
signal (I hope). I told them that I had double shaft
steppers.
Waiting
olf20 / Bob
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Let us know how things go.
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Latest reply. Maybe someone can make some
sense out of this?
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Does this help ?
Tweakie.
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Yes it does! How did you do that?
Thanks
olf20 / Bob
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Here is another encoder / display. This one will keep
the reading when powered down. I'm doing a lot of
two sided machining. This would help in making sure,
and resetting the machine for proper alignment.
http://www.ebay.com/itm/1-ft-Length-Wheel-Encoder-Support-Counter-Grating-0-1-ft-Display-Meter/322371257324?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649
Also the price is right.
olf20 / Bob
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Hi,
the resolution of the display in the link is 0.1 foot and an accuracy of 20 thou? Does that sound right?
Craig
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Here is the spec on the encoder. The unit can be calibrated
to users needs, according to the seller.
Encoder:
Resolution: 600 p/r
Power source: 5-24 VDC
Shaft: 6mm Dia, 15mm Length
Size: 40mm Dia, 37mm Length
Output : A B 2 phase output rectangular orthogonal pulse circuit,
the output for the NPN open collector output type
Maximum mechanical speed: 6000 R / min
response frequency: 0-20KHz
Cable length: 1.2 meter 4-core shielded cable
olf20 / Bob
Vcc: + power, V0: ground ,Connection color is clearly marked on nameplate ,
A B 2 phase output must not be directly connected with VCC, otherwise,
will burn the output triode.
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Hi,
how does using this rotary encoder differ from using linear scales? Worse this encoder is differential, when you turn it on it will have no
idea where it is until you reference it.
From your description of what you wanted you'll need an absolute multi turn encoder or absolute linear scales. Both are available but prices start
at $700 not $70.
Craig
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Bob,
I tend to agree with Graig and you may want to see what is available in linear scales.
I have scales from Shooting Star Technologies on my mill for over 10 years and they still work great.
Not glass scales but they serve the purpose.
Also consider some kits as you just solder components to a board and then choose what you'll use as an input.
Friend uses it a lathe and it is cheaper to do than Star or others that provide hobbiest scales.
I still use both my mills manually so the linear scales are like mandatory.
You can save money by using Mach to be a measuring device for locations and if some screen work was done
you can do as you want for info and save money. BTW, it's a PITA to use a stepper'd driven cnc manually as there is no
feel to the mill. I know it defeats your purpose of not having to turn the PC on, but, turning on the pc or turning on the scales
are not much different from a lazy point of view.
Just something to think about.
RICH
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Rich, Craig points well taken. I will rethink all this and do
some investigating of linear scales. Being basically lazy
I was exploring options that are out there.
Thanks for your time!
olf20 / Bob
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Bob,
Have look at "Shumatec" for display kits. Our's are really old and still working.
I don't use mine anymore but a friend is still using his on his lathe after 10 years.
I'll see if I can get more info. Can do a three axis machine for around $250.
RICH
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Did you build the boards or did you purchase them
already populated?
Thanks
olf20 / Bob
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Got the kit which had all the components, the board, and a case with the mask. Just had to solder the components to the board and cutout the case for the mask.
RICH