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Hello All:

I am new to the forums and wanted to talk about my machine that I just built – maybe get some advice.

First, I have a fairly good background when it comes to CNC machines. My first machine was a Joe’s CNC that I built probably 10 years ago. It was a great Big Box store build. I used it for a long time to get familiar with machining. That machine first ran Linux CNC, which I loved. Having developed with Arduino, I moved over to GRBL after a couple of years.

Our family business has a couple of laser cutter/engravers that I love to use. I also have a couple of 3D printers.

I decided to get back into milling machines and saw the incredibly awesome MPCNC (thanks, Ryan). I also saw the LowRider which I have parts printed out for (but I will be reprinting for V2).

My MPCNC is a 24" x 24" machine (sorry about the units, I am American). I run it using the Dewalt DW660. I am using conduit for the rails.

I use a Woodpecker (GRBL) control board. Having a couple of 3D printers, I am familiar with Marlin but I love GRBL. I love the fact that I can change settings on the fly and there are less settings in config that all seem to do with 3D printing instead of milling. I don’t plan on using my machine for printing. Maybe in the future, I will print out a drag knife and purchase a later.

I am all for advice and I am learning a lot still. I don’t get offended easy so feel free to pile on criticism with any post that I write. I am learning quickly that I need to have a speed control on the 660 (smoked a bit).

I am experiencing a couple of problems in addition to speed control. First, the machine stutters as it moves. I think I have done a fairly decent job on alignment. I am thinking the rails might be a problem because the stuttering only happens in specific places.

Also, my wire management is a nightmare right now. That will change soon when I extend my motor cables and add drag chains. That should help things out quite a bit.

Other improvements will include dust collection, and a touch plate.

My main purpose for the machine is using it to cut plates for other machines, and gifts. I would like to put together a LowRider for cabinet work. I am sure there will be a thousand and one uses once I get back into this again.

Excited to be part of the community and look forward to meeting many of you.

Blaine Edwards

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Welcome to the crew, and back to CNC!

 

More details. A single flute at a normal pace 8-15mm/s should not smoke. Two flutes could.

So many things this could be, too many commands at once, improper speeds and rapids, arcs, you are using GRBL so I am not going to be of much help here. Maybe your settings, steppers, drivers, gcode. Probably not your rails.

 

 

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Thanks for the reply. I was using a double flute HSS 1/4" upcut endmill (it is what I had on hand). At 30,000 RPM (I believe that is the rotational speed of the 660), it is going to burn. I just bought a dimmer switch and will be installing and reducing speed to just over half. I need to get a tachometer to get an accurate speed reading. In the meantime, I will play around with it.

I have more bits coming and I will experiment.

I saw your initial feeds and speeds. but if you do have any suggestions on settings/bits for ply (that is mainly what I am going to be cutting), I will take it gladly.

I will play around with settings and see if I can tame the beast.

 

Thanks again for the awesome designs and the support.

 

Blaine

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Thanks for sharing. I use grbl, but it’s not terribly common around here, so I only know how to solve the problems I’ve had with it (which have been few). I use mine with a raspberry pi, and I run CNC.js on the pi, so I can connect and control the machine from another device through wifi.

I’ll be interested in your progress with any additional features you add.

w.r.t. stuttering, is it skipping steps, or just slowing down, then speeding up? When you say it happens in the same place, is that with the same gcode or with any gcode (or just manual movements)? If the grbl (or Marlin) board is “starved” of commands, it can stutter. I think this is Ryan’s first thought. So if it’s in a corner with really high resolution points in a particular gcode file, then the gcode points are very close together, and the CNC machine is checking them off faster than the gcode sender is sending them. I’ve seen this due to either very dense gcode (with lots of little movements, and high feed rates) or because of a bad connection (like a poor quality USB cable). I know in CNC.js, there is a visualization for the size of the planner buffer, and if this gets to zero, then that’s bad. If it’s happening when you just move 100mm in one direction, then it’s not that problem.

Where I disagree with Ryan is that he won’t be much help. :slight_smile:

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Appreciate the thoughts.

This is the setup that I have going as well. I have used bCNC in the past but I think I will stick with CNC.js presently. bCNC is great for milling circuit boards because of the mesh bed leveling feature. I haven’t looked to see if that is available on CNC.js.

The issues that I am experiencing with the rails is more friction related. I have moved the machine by hand it will normally “stick/stutter” in certain spots.

Thanks for the info on the buffer. I never knew that was a feature.

Blaine

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Loosen the tension bolts, if that is the case, they are extremely over tight.

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I’m giving cnc.js a try. I have the desktop version. It seems you have to unlock it to do anything with it. When I click on the unlock button it doesn’t do anything. I’m oblivious missing something here. How do I unlock it?

 

Thanks for your help.

Ryan

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Unlock usually means, kill the power to the steppers. That way that are not locked in place.

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The latest versions of grbl need a reset before you can do anything (v1.1+?).

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The issues that I am experiencing with the rails is more friction related. I have moved the machine by hand it will normally “stick/stutter” in certain spots.
 

Ok. For me, I had a bent rail, and a stepper not running on my first power up. So if you are moving it by hand pay close attention to where those stutters are cause they could be every so often, or though a section. Every so often, check tension and through one area, check your rails. Also some cheap bearings will get weird chatter at the rpms we use.

Then maybe you have under-tentioned? But even so a bad bearing need be replaced. They might cause a random stutter. Can’t guarantee that cause it’s a totally different application I seen this in.

The guys should correct me if I’m wrong but you might have something in moving it by hand. Try isolating the assembly from the steppers by dropping the belts. If studder goes away, refocus on one side at a time.

Isolate and find the studder. Bearings can be funky sometimes. None of your issues may be bearing related, but your by hand statement kinda says non electronic. Maybe it’s the stepper itself. Or your wiring.

Just as an example of how it could be your wiring if you moved it by hand, move your stepper with all wires clear. Moves nice right? Now make contact with all four leads. Now you can feel an increased detent.

Last note, if you feel it seemingly on both x and y axis it’s more likely in the center carriage, coincidentally this is easily over tightened.

Lots of options. There’s more but since you felt it by hand, try the powered down ones first.