First build. Old equipment + new technology= FUN???

All things related to the Centroid Acorn CNC Controller

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mikecowhey
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First build. Old equipment + new technology= FUN???

Post by mikecowhey »

Alright So this is my first post on the forum so to start with . Hello all... Here is my official build thread.

To start with I picked up an Acorn controller and a stepper motor kit so that I could use my old decrepit manual combo machine as a learning tool with the intention of eventually upgrading to a larger more capable machine in the future, at which time I will move the full CNC conversion from where it is now to its new home with a more proper ball screw conversion on the table. This probably wont happen until sometime next summer at the earliest, I am working on having the carport converted to a garage so that needs to get completed first before I add any more toys...

The current setup as it sits
The mill
Shoptask 1720, old and very worn out not really worth much as a mill, probably better as a boat anchor but being used as a learning tool so that when the new mill is purchased it will hopefully (but not likely) take less time for the conversion. the Ways on the bed are so worn out on the bed that when tightened to where there is little to no lateral play in the table it reduces the usable x movement from 17 inches to about 3. Directly under the mill head thankfully, outside of those 3 inches your arms have to look like Arnold Schwarzenegger from his prime days to turn the handle and get any movement out of it...

Drive hardware
An inexpensive stepper kit that is highly overpowered for the conversion in work but only because I am planning on this hardware going on a mill at least 3 times the size of what I have now. 1650Oz steppers, 60VDC power supplies and individual drivers. these are connected vie the way Shoptask originally set up their machines for CNC conversion using toothed belts and pulleys. I know this is not ideal but I do not want to spend the money on a ball screw conversion on this machine, If I do anything with this in the future I will more than likely mill the top off of the saddle and get an XY table to bolt onto it and eliminate the worn bed from the equation. all this of course being commanded by an acorn controller in a large PC case converted to house all of the electronics.


stepper kit was purchased from CNCMOTORIII on ebay
stepper motor model number 85BYGH450C-012B, these were suppose to be a dual shaft motor but those were sold out so I got the single shaft equivalent
stepper driver model number DQ860MA
each stepper/driver kit came with a 350W 60v power supply and a breakout board, the break out board is still in the box.



Still in work
I need to manufacture a drive belt tensioner system witch I think I have figured out I just need to manufacture the parts. and some of the other misc. components like limit/home switches and this monstrosity should be up and running.

Sorry for the lack of photos. I will get some uploaded and attached to the thread this weekend as soon as I have a chance. Until then have a great evening and see you all again soon.


Here is the link to the google photo album where I will try and dump all the photos in general, I will add links to specific photos to things that pertain specifically to a question or relative to a specific thread as I post them down below.

https://photos.app.goo.gl/LtwH7kGTBfoSRLZH8


Mike
Last edited by mikecowhey on Sun Sep 18, 2022 3:34 pm, edited 1 time in total.
ShawnM
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Re: First build. Old equipment + new technology= FUN???

Post by ShawnM »

Welcome Mike and good luck with the conversion, it'll be a great learning experience for when the new mill arrives. Definitely start a Google photo album so we can see what you see and help suggest things along the way. Check out B&B Manufacturing for tensioners and all the belting supplies you might need. https://www.bbman.com/

Also, be sure and list or photograph your drives and motors so we know what you are working with.

Again, good luck with the conversion, you wont be disappointed with Acorn in any way, it's the best and most versatile DIY controller on the market.
mikecowhey
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Re: First build. Old equipment + new technology= FUN???

Post by mikecowhey »

Sure thing, I will do an edit on the original post as I ad pertinent information. It was late last night when I made that post so I will definitely get photos this weekend once I have a chance to get back out and spend a few moments playing with the toys...

One quick question on this build. I have been trying to read up on limit and home switch wiring/setup strategies and am a little confused. I apologize if there is a thread already covering this (type in limit switches in the search bar and a lot of results come back), but which is better/more proper a setup. Having physical limit switches and home switches or eliminating the limit switches and going with just home switches with software limits? Aside from less wiring/easier physical setup what is the advantage of the later, or are there any real benefits from doing it this way? I currently have switches mounted on the mill they are not yet wired in and can be set up either as limit or home switches and I am trying to figure out if I should set up as either home or limits, or add a couple of more switches and run both.

Thanks
ShawnM
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Re: First build. Old equipment + new technology= FUN???

Post by ShawnM »

Hi Mike, as for home and limit switches, you'll find users in both camps. Some want limit switches at both ends and some use only home switches and soft limits. I'm in the second camp as I only use 3 home switches and then software limits to set my travel distance. Soft limits have never failed me in the 3+ years I've been using Acorn on several builds. It's simple and effective. A professional machine will have home/limit switches at both ends.

You should also determine if you plan to home the machine manually or let Acorn home it automatically to the switches. Once again, there are users that do both. I let Acorn home my machines automatically to the home switches at start up every time. Both my routers and plasma table are setup this way. This will help determine if you need home switches or just limit switches. They can be setup either way in the wizard.

Then comes the issue of wiring them in series or parallel to one Acorn input or wiring each switch to it's own input. As you can imagine wiring each switch to its own input if you have one at each end will eat up nearly all the 8 inputs on the Acorn and you'll need to add the Ether 1616 for more inputs/outputs for other signals. Again, you'll find users in both camps here as well and a professional machine will have each switch on its own input.

There are diagrams from Centroid on how to do both so have a look at the various schematics here.
https://www.centroidcnc.com/centroid_di ... browse.php

It's really up to you and how you want to wire it and what makes you feel all warm and fuzzy inside. :mrgreen:
Gary Campbell
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Re: First build. Old equipment + new technology= FUN???

Post by Gary Campbell »

Most of the guys that feel a need for a limit switch in every direction of travel came from weak open loop steppers that lose position often running on hobby grade controllers.

Even with the same drive mechanics the Centroid controller will perform better, lose steps less and when setup properly, travel limits decel the machine before the hard stops.

I setup all my machines with provisions for a homing (only) switch or sensor for every axis.
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ShawnM
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Re: First build. Old equipment + new technology= FUN???

Post by ShawnM »

I'm with Gary on this and as I mentioned only have home switches with soft limits on each axis. I can run one of my routers at 650 IPM to the end of the table and Acorn will decelerate it and stop at the soft limit every time. My plasma table with Clearpath servos runs at 1200 IPM and I can drive it at full speed to the soft limits and it stops exactly at the soft limit every time. But again, do what make you feel comfortable. I like to keep things simple 'cause it just works.
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Re: First build. Old equipment + new technology= FUN???

Post by mikecowhey »

So really then there is no real advantage/disadvantage to either way of thinking. Basically comes down to preference. In that case I will probably go with home switches and keep an eye on how the system preforms. I presume the necessity to home the machine regularly would just be to set the machine back to a predefined "start" position so that the soft limits and machine travel capabilities are kept within the machines physical boundaries. I have access to a CNC Plasma table and it is rarely homed for that reason, normally we check machine squareness about every week or after it has sat for an extended time. The limit switches just keep us from running the gantry into things it shouldn't hit. Also, the limit switches on the plasma double as home switches.
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Re: First build. Old equipment + new technology= FUN???

Post by tblough »

Soft limits work on an open-loop control like the Acorn ONLY IF the axis drives have an error output and it is properly connected to the Acorn. If you loose steps for any reason, soft limits are useless.
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mikecowhey
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Re: First build. Old equipment + new technology= FUN???

Post by mikecowhey »

tblough wrote: Thu Sep 15, 2022 9:10 pm Soft limits work on an open-loop control like the Acorn ONLY IF the axis drives have an error output and it is properly connected to the Acorn. If you loose steps for any reason, soft limits are useless.
Gotcha. My stepper drivers do not have any error feed back capability so the more logical choice would be to use physical limit switches and manually home the machine when not in use or before a job, which ever i feel like doing. At least until I figure out if I am having issues with loosing steps or not.
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Re: First build. Old equipment + new technology= FUN???

Post by Muzzer »

It also depends on the nature of your machine. A reasonably large powerful machine could become damage (or cause it) if it tried to move beyond the axis limits. The 2 machines I have that were built as pukka CNC from the factory (each over 2 tonnes) both have limit switches at each end, so I followed that lead. Having said that, it must be acknowledged that our Acorn systems are not quite in the same league as modern professional machines in terms of functional safety etc.

If you allow your machine to be jogged before it has been homed (which is possible in Acorn), you can easily drive the axes against their hard limits. This is a fine test of their mechanical robustness and of course many conversions have motors with very high stall torques. Limit switches at least give you some protection against this risk, even if it is generally only likely to happen during setup and commissioning. Speaking as someone who has seen this happen on all 4 of my machines....
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