# Avid cnc troubleshooting



## Bieser

Ok so I bought a used 4×8 avid cnc.

It took me a while to get all the setting correct as far as motor tuning etc. I think I am pretty close.

I sketched up some basic cabinet sides in vcarve and it started cutting all my dados etc then on the final pass where it would be cutting out the actual parts away from plywood it took a strange cut path on its first time around then came back on a different path. I looked at my tool paths. No reason it should have done this. Any thoughts?


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## rtbrmb

I am no expert- I do own a small CNC Shark (sold by Rockler) that I have owned for almost 8 years.

The two times I have had this issue;

One time I had some small scraps on the back side of the CNC that the gurney was running into & stopped it from going on its designed path…..once that happens it can't recover to the original path

The other time (last year) the issue was a failing/failed controller. I scratched my head with that & even bought a used controller off e-bay…same results. Once I upgraded to a new controller ($500) all the issues were solved. Even though my CNC was about 7 years old at that point- the controller technology was about 13 and very outdated in computer years (no chance to repair it at that point).

Is it possible that any of the cables are being pulled taught and not allowing the router to complete it's path?

Hopefully this helps.

Bill in MI


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## Mike_D_S

Well it may not be the case, but my guess would be insufficient clamping and feed speed too high/rpm too low.

This assumes the parts are shifting which may not be the case. But running too fast without corresponding spindle rpm can generate significant side force.

Have you done a basic chip load calc for your feed speed and bit?

Also does your design have tabs included to keep the parts stable during the final pass?


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## Mike_D_S

Other option is it may be losing steps on long cuts or transits.

You can poor boy test that by setting up a tool path to drill four holes in a big rectangle maybe three feet apart by five feet long. Drill the holes on the first pass then repeat on the same path four or five times. If your losing steps or have some mechanical issue the after a few passes the holes will be getting reamed out some as you lose position accuracy. If you can make four or five laps in the same run with the holes being perfect circles then I'd look other places than the mechanism/steppers.


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## MadMark

As it was being cut free it shifted in the holder. Leave a couple of ties to hand cut for final release. This will keep the cutout from moving.

Alternately you overdrove your servos and lost steps.

Try not to cut too close to an edge. Narrow edges are prone to blowout.


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## Bieser

This is all new to me. Today I figured a few things out. I bought this machine used. So far I ran a 4 hole test for square and it was off, I calibrated the steps and the square was spot on, however after cutting a spoil board I ran a grid for vacuum clamping and found the grid was out of square again. I am wondering aside from adjusting the gears on the tooth is there a better way to adjust for square on the avid setup? I don't have homing switches, after looking at the back of the internet maybe that would help it stay square. I have ran the x axis to its rubber bumper limits and then hear the gear skip a tooth and wonder if that is whats causing me to go back out of square? Sorry for the basic questions again I am a computer illiterate cnc beginner.


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## Mike_D_S

Anytime you jump a tooth on a geared belt setup you're going to be off. The machine position is essentially inferred from the stepper motor. The motor moves a step and the software assumes the machine moved by the equivalent distance based on the mechanical setup. If the stepper moves and the belt jumps a tooth, then the real physical position of the machine doesn't match what the computer thinks it is.

Homing switches will definitely help with keeping you from hitting the mechanical stops which is a definitely on the list of things not to do. They can also help with setting a repeatable zero. There are also x/y touch off setups that you can use the get a repeatable zero.

But if you aren't running into the mechanical stops and still getting off track then you may have a bad stepper, bad wiring, or a questionable controller. When you realize its out of square, does it does it keep drifting further out of square or does it change in sudden jumps?


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## Bieser

Mike, Thanks for all the info. I noticed tonight that maybe I did not have the tension on the springs set tight enough on the one side. I could fairly easily push it to the next cog. I am going to go down and reset everything tomorrow and give it another try. Is the way you square this machine up best is by making sure your on the same tooth on the gear? Any fine adjustments must be made by adjusting the track? I think I am going to have to get some homing switches.

I have not figured out how to set limits which I suppose would stop the machine from running out to the bumps? why do you need homing switches if you have limits in place?


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## Mike_D_S

You don't specifically say, but I assume you followed the leveling, gantry and tramming documentation from the Avid CNC site?

Limit and homing is really the same function on the zero side of the machine. It's the same sensor, just performing different functions at different times. When the machine is actually running and cutting they are in "limit mode" to keep you from running off to the mechanical stops.

When you're actually homing the machine, they serve as known reference points on the physical frame.

If you think about what I said about that the computer only knows how much it moves the steppers and determines the position of the axis based on adding that motion to the last known position. So when you first turn everything on, the computer doesn't have a last know position and doesn't know where the machine physically is. So the home process moves the machine until it gets detected by the zero side limit switches. Since those limit switches represent a known physical position, the software now knows where the machine is.


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## Bieser

Ya I have been through the website, The problem I am having is they are setting up a pro machine with sensors where mine doesn't have any of those so its pretty vague on squaring without the sensors


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## MadMark

The zero and limit switches are just small mechanical switches at the four sides of the machine. Most any type of switch will do. Small lever switches or even push buttons can be used. Mounting is more of an issue than electrical characteristics.









Classic lever switch is a little over an inch long


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## Bieser

Ya looks like I will need to get some, it seems like this would make things easier


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## DS

OP, you've received lots of good advice here so far.

I would recommend following the setup instructions for a new machine from the avid website. This will ensure there isn't something amiss in your physical setup. 
Whenever I get any new tool, I like to spend a lot of time to carefully set it up properly to ensure I will get the best performance that tool is capable of. I am known to completely disassemble bandsaws, planers, table saws etc, and put it back together with better tolerances than the factory. (Some might consider this excessive, but I like reliable tools)

Also, check your controller settings as well.
if you attempt to overdrive your motors by having a too aggressive acc/dec setting, you can stall a stepper or skip a tooth. Both of these things are bad. Compare your current controller settings with the factory defaults to see if something is extreme out of range.

Since the X axis is driven with two motors, if one side skips or stalls, this creates the out of square issue. Homing should reset square as it relies on the calibration of the left and right switches to set square on the machine. (Calibration of square is covered in the docs on the website)

If you continue to get out of step, there is something else wrong. Like you said, the tensioner might be loose, belts could need replacing, feed rates could be too aggressive, etc.

Also, the folks at Avid have been fairly responsive to any issues with their machines. You might try calling them and they could walk you through the issues you are having.

I wish you all the best with your new-to-you CNC.


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## DS

> Ya I have been through the website, The problem I am having is they are setting up a pro machine with sensors where mine doesn t have any of those so its pretty vague on squaring without the sensors
> 
> - Bieser


Also has 293 pages of standard machine setup

Lots of setup instructions for standard machines here


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## Mike_D_S

DS has the right idea. Treat it like it's a pile of parts and walk through the new machine setup. This will get you back to "factory" condition and you may catch a few things along the way.

Also, just to clarify OP has the 4×8 so I think this the is the right link for the standard machine setup instructions.
https://www.avidcnc.com/support/instructions/standard/4896/instructions/

Also, don't be afraid to email the Avid people and ask for any documentation for your machine.


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## Mike_D_S

Going through the standard machine instructions it still calls for limit switches. If you don't have any (and assuming the previous owner didn't remove them) then the machine may be one of the older kits.

I think contacting the Avid CNC guys may be really helpful.

I see they offer the current proximity sensor kit as a separate add-on. Depending on which controller you have it may be a pretty straight forward installation.


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## Bieser

Ya I believe I have an older machine, I cant see where it ever had them. I tried getting a hold of avid but it seems like you send and email off to them and they get back to you. Hopefully I hear from them beginning of next week. Thanks for all the help you will probably see me around this forum a bunch as I get my feet wet with this.


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## Mike_D_S

Provided your controller will support them, I'd recommend the proximity switch kit upgrade. Being able to home the machine in all three axis to get started makes life a lot easier.


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## MadMark

Once zero has been set issue a G0 X0 Y0 Z0 to return to origin at end of job.

Limit sw's aren't normally needed once origin has been set. If your gantry is hitting limits your gcode is bad. Use MACH3 or some such to check your tool paths before cutting.


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## Mike_D_S

Yep, limit switches in limit mode are basically emergency stops.

On the subject of zeros and referencing the workpiece, I rigged up this positioning jig which has been very helpful when setting up cuts as it provides consistent square positioning with a known position for the corner of the workpiece. Basically I picked up some aluminum tube and some rod that fit the inside of the tube fairlywith minimal clearance but easy to slide in and out. Then I clamped down a sheet of MDF and drilled holes through the MDF and into the spoil board big enough for the rod in the pattern I wanted. I lifted the MDF sheet and opened the holes up on a second pass big enough for the tube to go in. After glueing in the tubes in the spoil board and the rods into the sheet, I chose the zero position for the jig and then cut a straight vertical and horizontal cut through the MDF to create the squared edges.




























I have a small gcode program to run which sets the machine to zero based on which of these positioning jigs I have set up (i have them for the top and bottom corners).

I have a couple of things I make which require rotation or flipping the workpiece to do operations on both sides. These have been a lifesaver as you ensure that one corner of the workpiece is always lined up with the current machine zero.

I'd recommend setting up something like this to any hobby CNC'er as it made my life a lot easier.


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## Bieser




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## Bieser

Looks like I have a gecko drive g540. Wondering about just getting some switches and installing on my machine. My little bit of research says it should work with this setup? Probably set it up with some lever switches? I see the cylinder type sensors also. Maybe those would be better for fine tuning?


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## Bieser

Something like these?

https://www.amazon.com/Taiss-LJ12A3-4-Z-Inductive-Proximity-Detection/dp/B073XDKM9S/ref=sr_1_50_sspa?dchild=1&keywords=proximity+sensor+normally+closed+2+wire&qid=1612629843&sr=8-50-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyWlczOEJDRDNTVUtNJmVuY3J5cHRlZElkPUEwOTQ4OTM3MUtTREY4MlBLTThXNSZlbmNyeXB0ZWRBZElkPUEwMDE4ODcwMlI5MUpBWlNJUEpHMCZ3aWRnZXROYW1lPXNwX2F0Zl9uZXh0JmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==


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## Mike_D_S

Bieser,

The ones you link are rated for 4mm detection for steel (note it says iron, so steel alloys may be less). For aluminum I'd expect this to be significantly less than 4mm. One of the answers on the Amazon listing says for a small aluminum piece it had to make direct contact to be detected.

As a homing system they may be ok, but as limit switches you want enough detection range for the machine to start decelerating prior to hitting the stops.

While I'm generally a cheap ass, this is one area where I would expect to spend a little $. While you probably don't have to go to the Avid package price, don't skimp too much on the switches. A good home position is key to good cuts and cheaping out now may result in wasted material later.

If you want to go cheap, then the answer is micro-switches like these. These are the ones used on my Probotix machine.


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## Bieser

Does anyone know a better way to get a hold of AVID? I have shot off several emails with no reply. I cant seem to locate a phone number of this company.


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## Mike_D_S

No idea on how to contact them, but can you give a little more info on the testing you have done?

The details may help suggest some additional steps to take. I think it would be good to understand a little better what kind of issues your facing.


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## DS

I bought some parts three weeks ago and got a call when they filled my order to verify the address.
It might be hard to find that number now. Sorry.


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## DS

From the website contact us page;

Want to contact us by phone?
We're always happy to speak with you on the phone to answer any questions about our parts and your specific machine build!
We want to put you in touch with the right person to answer your questions and our engineers are usually out on the floor working with machines, so to ensure we can give you the best possible service please send us a message above letting us know you'd like to talk. If you'd like a call back just give us your number and a good time to contact you, otherwise we'll e-mail you back to set up a call.
We're located in North Bend, Washington (close to Seattle) in the United States, which is in the Pacific time zone, currently UTC/GMT -8 hours.


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## Mike_D_S

Hey Bieser, you have any luck getting the Avid sorted out?


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## mpsprunger

The proxes detectors whether NPN or PNP have to match the other NPN or PNP , they cannot be mixed


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## Bieser

I did get ahold of them. Took a little bit to get connected they are sending me the necessary parts. Maybe I'll get that up and going next week


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## Mike_D_S

Glad to hear it. I was doing some cutting work on my machine yesterday and I was wondering if you made any headway.


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