# Building first CNC router controls cabinet

#### ryanjg117

Joined Nov 3, 2017
26
I am looking to build my first CNC router and will be using a commercially available kit from Avid. I'm planning to buy just the mechanicals from them (extrusions, gantry, motion) but build my own electronics cabinet and source my own VFD and spindle. Part of why I want to build my own cabinet is because I would like to use Clearpath SDSK servos rather than steppers, a Centroid Acorn controller, plus I would like to learn a thing or two along the way. I have only built smaller electrical cabinets in the past, one of which housed a small VFD and that's about it.

Fortunately, Centroid includes a schematic for their Acorn used in conjunction with multiple Clearpath servos (schematic attached). I'm not great at reading these... yet.

Also fortunately, I met someone online who built this very configuration into his own cabinet - Acorn controller and Clearpath servos - driving an Avid router. He was kind enough to share pictures of the finished cabinet. Unfortunately, he didn't go off a bill of materials or anything that would help me get started. I believe he ordered just about everything from FactoryMation and Mouser. Looks very clean to me and I really like the bulkhead connectors - would like to do the same there.

I'm wondering if it's possible to build a bill of materials based on these pictures and the schematic? I know what many of these components are (controller, servo power supplies, VFD)... It's more the stuff on the periphery (fuses, breakers, contact blocks, NEMA enclosure) that I'm not too familiar with yet.

How would you recommend I get started?

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#### jpanhalt

Joined Jan 18, 2008
10,935
It seems your suggestion might work to an extent. However, I would start with the schematic you have and add everything else that is needed. Then getting a BOM is easy. If you use an electronic CAD program, a BOM is usually just one or two clicks. If not, you can manually go through the paper design and check off the parts.

Eventually you will need a complete design, so no time is wasted in that approach.

#### DNA Robotics

Joined Jun 13, 2014
596
I would think the cabinet is the last thing to build. As you create your CNC machine one section / axis at a time, lay them out on aboard. When you get everything working, arrange it as neatly and logically as possible. Now you have dimensions to build or buy a cabinet.

Joined Jul 18, 2013
21,995
How would you recommend I get started?
I have built control cabinets as part of my occupation, and first I would recommend obtaining a copy of NFPA79, there is an older copy out there on the web.
When sizing an enclosure, you always end up about 10% too small! Unwritten rule!
What that enclosure is missing is wire duct, Panduct etc. Also main enclosure disconnect
Draw up or obtain a suitable schematic of the design per NFPA79
Always use stranded control wire conductors using proper colours..
Mark all conductors at their termination points.
Place fusing - disconnect etc at the top, followed by heat producing items such as transformers.
Ensure to set up a star point grounding system termination plate that includes the service ground.
Labeling of ind lights P.B.'s etc. E_Stop P.B. require a yellow background (circle -square etc).
The enclosure shown is missing most of the above.
Just a few for starters off the top of my head.
Max.

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#### KeepItSimpleStupid

Joined Mar 4, 2014
4,373
It kind sucks. No wire duct. I used 18 AWG with the lower stranding, which I think is 7. This make it flexible and stiff. both desireable.

This company puts a lot of the available stuff in one place, but the quantities are too high. Here, https://www.automation24.com quantities are resonable.

I found accompany to get reasonably priced wire (US) in 100' put ups. One problem, they are the manufacturer. Stock is minimal. You may have to wait (1-2 months) for a particular run. At the time, they had a $50.00 minimum order. Wire will cost an arm and a leg. Wire ferrules are useful, but not as necessary for reduced stranding wire. Look here, www.winford.com , for some useful DIN rail stuff. Most of my network stuff at home mounts o DIN rail TS-32 is the most common. Guess, I used J-rail for my first project - don't. It does come in aluminum and steel with and without slotted holes. The enclosures are usually flange mounted and have a 1/8" removeable aluminum plate in the back with some gap. You can drill and tap to mount various devices, wiring duct and the DIN rail. Very few screws should be needed. I prefer Idec stuff. I wasn't happy when I had to replace hyndreds of AlCO switches with Idec because of a stupid re-design. They trap heat to the lamp with an "o-ring" sealing the lamp. That was like$20.00 USD * 400 switches.

24VDC is the usual cabinet power. I happened to use 24 VAC for my first panel back in the 1980's. It was still working 10 years ago.

You can label the indicators I used with printed transparency film or clear labels from a labeler such as a Brother p-touch under the lens, For that reason, I use the rectangular lenses.

One company makes a plate with various penetrations e.g. Ethernet and others. You don't have to cut the wire.

The terminal blocks are wierd:
they come in 1/2 terminals
then sides the same size as the terminals
then oversize sides - partition plates
and end plates. (2 required)

The come in multiple layers. Ground only.

There are jumper bars. These can be wierd. You can say buy a 10-way bar and cut it, but don't expect to use five 2-way bars.

It makes sense for power to come in at the top with some sort of disconnect. It becomes much easier to work in alive box when you can disconnect power and gravity works for you.

There's another usefull technique where you wire the connections to the outside world immediately to a terminal strip and then cross connect.

You can have a piece of instrumentatiion with one connector with analog in analog out, digital in, and digital out.So you wire the instrumentation to a set of terminal strips, then pigtail the analog outs to the analog out card, the ins to the analog in card etc.

Then you have to replace the PLC with a new model. So, you just replace the cross connects.

#### ryanjg117

Joined Nov 3, 2017
26
Thanks all. Going to dive into NFPA79 soon. Is there a good software program for laying out a panel like this?

Joined Jul 18, 2013
21,995
I found that wire such as THHN/TEW/MTW can fill up a duct pretty fast so for much of the the low current demand circuits I use TR64 control wire.
The insulation is rated OK but the OA dia is less.
Max.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,373
I don't have time to look for it, but here's the company http://brimelectronics.com/brimpx-1.html, Be nice to them. There should be an 18AWG wire with two different strandings,. You want the lower one. it's probably MTW for Machine Tool Wire.

Joined Jul 18, 2013
21,995
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#### soyez

Joined Aug 17, 2020
51
I am looking to build my first CNC router and will be using a commercially available kit from Avid. I'm planning to buy just the mechanicals from them (extrusions, gantry, motion) but build my own electronics cabinet and source my own VFD and spindle. Part of why I want to build my own cabinet is because I would like to use Clearpath SDSK servos rather than steppers, a Centroid Acorn controller, plus I would like to learn a thing or two along the way. I have only built smaller electrical cabinets in the past, one of which housed a small VFD and that's about it.

Fortunately, Centroid includes a schematic for their Acorn used in conjunction with multiple Clearpath servos (schematic attached). I'm not great at reading these... yet.

Also fortunately, I met someone online who built this very configuration into his own cabinet - Acorn controller and Clearpath servos - driving an Avid router. He was kind enough to share pictures of the finished cabinet. Unfortunately, he didn't go off a bill of materials or anything that would help me get started. I believe he ordered just about everything from FactoryMation and Mouser. Looks very clean to me and I really like the bulkhead connectors - would like to do the same there.

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I'm wondering if it's possible to build a bill of materials based on these pictures and the schematic? I know what many of these components are (controller, servo power supplies, VFD)... It's more the stuff on the periphery (fuses, breakers, contact blocks, NEMA enclosure) that I'm not too familiar with yet.

How would you recommend I get started?
yes of course it is feasible to do so

#### mcardoso

Joined May 19, 2020
187
I've done 3 CNC control panels over the years and they have turned out increasing nicely. If I were to do a fourth, I'm sure it would be even better than the last. I do design engineering for industrial automation as my day job, so I have a lot of panels I've built there. Here are a few tips (some are also mentioned in previous posts):

AutomationDirect
I like AutomationDirect for my home building endeavors. They are fairly priced and are good quality. They also have free phone support which is really awesome.

Circuit Protection
One of the biggest issues I've seen with home designed electrical cabinets (I was certainly guilty of this when I started) is lack of proper circuit protection and wire sizing. This is all about fire prevention and it is especially important in your own home. You'll need to familiarize yourself with NEC and NFPA79, mostly about breaker/fuse sizing and wire ampacity, although it is good to know the whole thing.

Wires are sized such that a a short circuit anywhere in the circuit will trip the upstream breakers/fuses before the wire can melt. Breakers and fuses are used to limit current downstream so smaller wire may be used. For example, I have a 240V 50A breaker in my home subpanel feeding my CNC mill. There is 6AWG wire going from that breaker into my cabinet which supports 55A. Once in the cabinet, it is shared among different breakers. In one example there is a 2 pole 20A breaker. The 6AWG enters the top of the breaker and 12AWG exits the bottom. I can now use 12AWG in my panel because any short circuit will trip the 20A breaker before the 12AWG wire melts.

I typically use circuit breakers and stick to the Class C trip curve. Other trip curves work better with big motors or resistive loads. You'll want to stay away from supplementary breakers unless you know how to use them. Obviously the code books are huge, so I'm glossing over about 99.9% of the information, but that is a start.

Disconnect
You should add a circuit disconnect between your incoming line and the primary breakers. This gives you a rugged power switch and a means to safely deenergize the panel before opening it. Most will lock the panel closed when power is on and have a cheater button to open the panel if needed. This is good so you don't forget power is on and reach into the panel. That's easier/more common than you think.

It also provides a Lock Out Tag Out (LOTO) location. Even at home, I lock my panels off when working on them. Here is the one I usually use for home projects:

Cabinet Size
As mentioned above, give yourself lots of "extra" cabinet space when purchasing an enclosure. Chances are that you will use it all. If you are not designing the panel in CAD, use masking tape to draw the cabinet size on the floor and manually lay out your components. Make sure to add wire duct and leave 2-3" of space on both sides of the duct to get your fingers in there to work.

You'll be surprised how much space you really need. My 4 axis CNC control with steppers was 24x24x6" and was way too tight. My 6 axis CNC control with AC servos was 24x36x8" and was still really tight (although a lot of that was the size of the servo drives).

Wire Duct
Again, as mentioned above, buy wire duct and use it! It makes your panels look super clean even if there is a mess tucked inside. I prefer the 1x3" size with narrow fingers. Don't be afraid to cut fingers off to pass larger cables into the wire duct. I'm obviously referring to the wire duct "fingers" lol.

Ferrules
You really should buy some ferrules and a cheap crimper. These go on the end of every stripped wire and do two things. First they keep your conductor strands from fraying, and second, they add extra insulation so there is no exposed conductor where it lands on a terminal block. Do not solder with these. Link (no affiliation and I've not tried this one):

https://www.amazon.com/Ferrule-Crimping-Tool-Kit-0-08-10mm²/dp/B07PJK2VNT/

This is a personal preference, but I like to add bulkhead connectors to all connections leaving my panel. This definitely adds expense, but makes cable management outside the cabinet much much easier. Cheap "aviation" style connectors are all over ebay, or you can get more robust and high quality connectors too.

We use MIL-DTL-D38999 series connectors constantly at work. The smaller sizes aren't too outrageous in price. These are the highest quality pieces of electrical hardware I have ever held.

Wire labels and schematics
Even if it is all a hand sketch, you have to make some kind of schematic and label your wires. At work we label by sheet and line number in the schematic, but at home I just number sequentially. Heat shrink wire labels (fits label makers) are the best, but I use Brady wire marker cards at home. It was a small investment, but I bought numbers 1-100 and haven't run out of labels after 6 years.

Power and Signal segregation
Your AC power and especially VFD outputs should be routed as far away from DC signals and power. They absolutely should never mix in the same wireway. You'll need to incorporate this into your panel design from the beginning.

DIN Rail Components
Most of industry standardized on the 35mm DIN rail for mounting components. You can get almost any component to fit on one of these and it is the most space efficient way to build your panel. Parts are typically thin and tall so they can be stacked in high density. You run a wireway above and below the rail to place your wires into as you build.

Terminal Blocks
Interconnections are easily made through terminal blocks. These are placed on a DIN rail and pass the signal through. I typically place them before any connections leaving the panel and between controllers and end devices. They are also a great place to put your meter on for troubleshooting. Here are the ones I like to get for home builds:

Don't forget to get the accessories like end barriers and jumpers.

DC Power Distribution
Leave space after your DC power supply to put a bunch of terminal blocks jumpered together for power distribution. I like to do 10 DC+ and 10 DC- as a start. Don't forget fuses immediately after the DC supply.

If you like machining, check out hobbymachinist.com. There are a bunch of us CNC guys over there and it is very friendly and casual.

Here is my latest panel. I'd change some things with the knowledge I have now, but I'm pretty happy with it.

Edit 10/13/2020: Corrected wire ampacity

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#### shortbus

Joined Sep 30, 2009
8,179
. I can now use 14AWG in my panel because any short circuit will trip the 20A breaker before the 14AWG wire melts.
Did you mean to say that? To my knowledge, a 20Amp circuit requires 12 gauge wire. Or has the NEC changed over time?

Joined Jul 18, 2013
21,995
NFPA70 (NEC/CEC) and NFPA79 "Industrial control enclosure wiring" state you cannot use a smaller cable than that provided by the breaker/protection current.
I do CNC retro fits for a living, so have to conform to the above standards.
Max..

#### mcardoso

Joined May 19, 2020
187
Did you mean to say that? To my knowledge, a 20Amp circuit requires 12 gauge wire. Or has the NEC changed over time?
Whoops, that's my bad. I live in the 90*C column at work. I should have triple checked. 12AWG is accurate for 60*C conductors and terminals. I will edit the original post.

#### ryanjg117

Joined Nov 3, 2017
26
@mcardoso - Your post deserves five likes, but I can only grant one.

One question: you mentioned "Always buy the subpanel with your enclosure and build on there." Are you stating the sub-panel should be outside this main enclosure? In other words, I can't (or shouldn't) run the supply line right into the main box? Or are you saying the enclosure should have a back-panel that I can mount everything to, and then drop in when complete?

On a related note, my shop is on its own panel separate from the house (its a detached shop) with 200a service. It's not a subpanel, it's a second panel I have to pay the utility company extra for each month. I already ran 10/2 romex and installed 30a 2-pole breakers before I drywalled the shop, but in hindsight probably should have gone with a thicker wire as most ampacity calculators tell me I'm going to be limited to 30a given my wire size and length of run.

I know it depends on the components I select, but is it realistic to build this cabinet with a 30a supply limit? I believe I'm going to require 1 or 2x IPC-5 power supplies to drive the 4x Clearpath SDSK servos, a VFD to drive the 2.2kW spindle, and Acorn for the controller.

Joined Jul 18, 2013
21,995
The ideal is to have everything under one disconnect and enclosure.
Drop down to 120v if needed inside the enclosure, remember to re-refernce any secondaries to set up a neutral.
For a larger machine, you should have 240v supply if in N.A..
Max.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,373
One question: you mentioned "Always buy the subpanel with your enclosure and build on there." Are you stating the sub-panel should be outside this main enclosure? In other words, I can't (or shouldn't) run the supply line right into the main box? Or are you saying the enclosure should have a back-panel that I can mount everything to, and then drop in when complete?
I'll comment. The enclosures (wall flange mount) have an optional thick aluminum panel that can be removed. It doesn;t mean, you ever will. As soon as you add a connector to the enclosure case, all bets are off getting the panel back out. the initial holes can be drilled and tapped while in the back of the enclosure, BUT doing it when its not mounted is much easier. In one enclosure, I drilled two holes to mount anoter DIN rail. I think.

You should as was recommended, use a row of terminal strips at the entry points and cross connect from there.

It should be easy to disconnect power and usually you require a disconnect within like 3; of the machine.

The control panels I did had a 15A 120V service and the largest loads were ten 10W solenoid valves. I had 3 fuses. One for the panel and one for the valves. My panel required a key for power and it was always in the panel. It was removed when the system should be "tagged out" which was very rare. 2-3x in 10 years.switch

The 60A 3 phase stuff we had a work had a disconnect on the equipment and a wall plug. Not the best, because you can't really tag it out, but it did have a key to get into the equipment enclosure and a key to operate.

The 90A 3 phase stuff had a wall disconnect. It also had a breaker on the equipment panel and a key lock.
switch
The equipment that had a 208 200A single phase feed had a disconnect coupled to the panel door. I never had to go in that one.
switch
The 3phase motors had a control enclosure on the wall with fuses, 3 phase protection, overload relays. They were purchased as motor disconnects. The three phase protection and 120V isolation xformer and fuse was added. In order to open the pan;e, it required a screwdriver interlock.

Here https://hoffman.nvent.com/en/hoffman/Disconnect are some interesting enclosures.

But you can put a disconnect on the backing board and have the actuator protrude through the panel. Example: https://nemasupply.com/collections/...able-disconnect-switch-baco-metal-short-shaft

Research Arc Flash

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#### mcardoso

Joined May 19, 2020
187
One question: you mentioned "Always buy the subpanel with your enclosure and build on there." Are you stating the sub-panel should be outside this main enclosure? In other words, I can't (or shouldn't) run the supply line right into the main box? Or are you saying the enclosure should have a back-panel that I can mount everything to, and then drop in when complete?
I was referring to the sheet metal panel which can be purchased separately and mounted inside your enclosure. This lets you build some of the panel on a bench, and gives you something besides the back of your nice new enclosure to drill into.

I typically bring the supply into my enclosure directly and use one of those rotary disconnects mentioned above as a main power switch. External disconnect boxes are a bit overkill for this IMO. If you are concerned about good lockout points, you can buy a lockout bucket which goes over the plug on the power cord to prevent you from plugging it in.