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Messages - Tool-n-Around

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It likely doesn't matter, but polyrectangles 15,16,17 are up in the air at Z=31

Thank you, good catch. Not sure how that happened. It doesn't show up in CAMotics perhaps because I designated a stock thickness. Not sure if it matters but probably would at some point because my units are imperial and 37 inches would be a bit tall for my 3-axis machine with Z3.75" soft limit!

Normally the x,y zero position work coordinates would be set at an easy position to locate, such as the bottom left corner of the stock, but you have it set to somewhere that looks difficult to establish.

It's was just a familiar dimensional location for drawing features since it made the bores symmetric about the Y and one bore coincident on X.

If you Align the piece to bottom left corner of stock in CamBam then all you need do when it's on the machine is put it in the middle of the table then zero your X and Y to the same bottom left point of the stock.

When I get through fiddling with and get it to run, I'll just drag the machine origin to the corner of the stock.


I haven’t gone away. Just had to step away for a couple days and remove all the sharp objects from my shop! First I must say I appreciate your help and patience. I spoke with Gary yesterday and he is helping as well. Long post but maybe it will click.

I now have six cb files made. Two for this part (base and lid), and 4 others for an air filter assembly, top and bottom feature of the AF base and lid. They all look good in CB, nicely generate the expected tool paths in cb, and simulate well in CAMotics. None of them will run on my machine. I’ll try to stick with this part for now and post the others when I get my machine sorted. I think I have different issues with different parts, and think I still have intermittent EMI issues.

On the EMI, sometimes when I jog, if I hold the jog button, my machine will occasionally throw an error about receiving an unexpected command from the controller and pause. But it won’t (always) alarm or hold and I can usually resume by reengaging the jog. My homing wires as supplied with the machine are neither shielded nor twisted pairs and I think the are 5v signal. If I set my lap top computer in my machine space, even with no machine movement, my touch pad becomes unresponsive until I move the computer. I’m going to buy some shielded cable for the homing switches, check the stepper cable shielding, and replace those if necessary. -Just isn’t worth it.

The Homing and soft limits are in G53 "Machine Co-ordinates" There are what they call workspaces, for you the important one's are Machine c-ordinates and part or work piece co-ordinates. The homing switches being where they are is ok, as this would (after an homing operation) move the machine a convenient place so that you can load and unload the stock unencumbered. Where the co-ordinates are\can be  set to zero in G53 they don't always have to be zero, and could be the tool changer co-ordinates.

This much I understand and have done. Just to save the read back, homing switches are in left rear corner of table and X+ motion to the right, Y+ away from front of table. I home, issue G10 L20 P0 X0 Y0 Z0. Move to a convenient position near the front of the table, issue G10 L20 P1 X0 Y0 Z0 and then G54 (and also G20 to make sure units are correct). I have also tried G92 X0 Y0 Z0 but no matter what, I’m in negative XY machine space. I understand Y being negative because I moved in the negative direction from machine 0, but I don’t understand why I am in X- space when I zeroed and moved in the positive direction.

If you look at the picture I attached, it looks like the controller thinks I have placed the entire part outside the machine space. Am I interpreting that correctly?

In the CB file, I have not changed the Machine Origin from 0,0

By moving my work origin to the right, I can get closer to the machine space but never in it. This has me perplexed because I have a trail file from the machine manufacturer and it positions exactly where I expect it to and runs fine. I also have another file I created that positions and runs through the first MOP but then fails because of the same error 33. I guess it doesn’t like an arc imbedded in the poly line.

I attached a pdf of the console dialogue including the errors after sending the file. That erro 33 I get on other files.

I had and did re-read the Github link so thank you.

If you are using soft limits then you may have to set these parameters: Set your $130,$131, and $132 max travel settings if you plan on using homing or soft limits. It's recommended to enter something approximately close to actual travel now to avoid problems in the future. Note that $130,$131, and $132 max travel parameters correspond to the 'Machine coordinates' parameters in grblControl.

I believe I have these set properly. I did it in USG set up wizard but I can’t jog beyond the soft limits so I think I’m good there. I think you can see it in the attached a pdf (albiet in mm) with the command and response string. I edited out the pages of jog commands but left the (EMI induced?) error.

It's ok for the homing to be where it is at the back of the machine. This position is not the work piece x0,y0,z0. If ok for you to have your drawing co-ordinates XYZ=0 at the lower left hand corner.

I’m not so hung up on the back left being XYZ=0. I figure the important thing is the direction of travel signage is correct because once G54 or G92 is established, it shouldn’t matter other than soft limits, right?

You then place the work piece in the upper right hand quadrant.

This I don’t understand. Why upper right quadrant?

In the picture I've made a blue rectangle in my start up template. This represents the machine work envelope. This is a visual cue for me to place anything outside this area. else you'll hit the limits

Need to learn to do this. Is this same as bounding box?

If a new user fails take this into account and there’d followed the recommended set up for the machine and drawing procedure may not realise that some tool paths can dip in to negative territory triggering the hard or soft limits. I have my soft limits turned off for the grinder and laser, but if you do want to use then then you have to set them in your controller as above.

This may indeed be the case but until I get my head straight and machine debugged, I’ll leave soft limits on. I think I’d have crashed my machine 20 times by now without them.

I do have some thought's about the cad, If you are happy with the terms and conditions for fusion then it would be the one to learn. If you want a “buy once” parametric modeller then there are a few of those too. If you want a free one then freecad is a good choice, I use the linkstage version not the downloadable current version.

I looked at and like Aliebre for CAD because of features and buy to own, but it has no CAM package. I chose Fusion not only because I have a free copy but also because it had a CAM package with a GRBL post.

Here is a pic of the freecad linkstage screen displaying a model that I 3d printed in various sizes.

I certainly like the example you chose.

Thanks again.


Kelly, The front-left corner of the WORK is 0,0,0.   That's NOT the 'home' position.

This I understand. What I don't understand is this: If I jog X+ the spindle moves right and Y+ is away from the front of the table. After I home in the back left corner of the table, when I jog back to the front left corner, the DRO says the position is (-34".xx,-34.yy"). So I understand Y= -34" and change because I jogged the spindle in the negative direction from home just about to the limit of travel, but why does X = -34.xx"?

Isn't machine zero supposed to be where you are homed and work zero where I call G92 X0 Y0 Z0? The origin of my CB part is offset in the stock such that the lower left hand corner of the stock is 0,0,0. Isn't that location what you would expect it to be placed at the G92 command? What appears to be happening is that is indeed the case but because the machine thinks I'm at -34,-34, all the machine work is outside the limit of the work space beyond the far right corner of the machine, resulting in error.

The front-left limit of travel is usually past the corner of the work, in both directions. My two bed-router machines 'zero' at about -9" in X and about -5" in Y from the front-left of the work-piece, assuming a 4'(X) x 8'(Y) sheet of stock.

The advertised XYZ work space on the machine is 35 x 35 x 3.75. The router spindle overshoots the front edge of the table/wasteboard by a couple inches but I could extend the table surface several inches forward beyond the machine framework if I need every inch of workspace travel.


"I'd really like the front left corner of the machine to be 0,0,0 for several reasons with X+ to the right and Y+ away from the front."

That's the correct way to view any CNC machine.  CB is perfectly-capable of making that the origin.  I do -- most of us do.

Most folks don't make the exact 'limit of travel' to be 0,0,0, but pick the spot at the very front-left corner of the work as being that.  Most machines travel sufficiently past both edges of a work-piece in both X and Y, such that there's a bit of 'over-travel' available in order to cut clear to the edges.


That's good to know because I think that means I either have conflicting instruction from the machine manufacturer or I'm misinterpreting the instruction. In my mind, you could home in any corner and as long as the direction of travel was correct, seems like it should be fine after the G92 call, right? But, and I know you can do it with the G54 and up commands, but for the sake of simplicity, if you wanted to intuitively send the spindle to a table position, doesn't it make more sense for the front left corner to be 0,0,0? and if so, dont the limit switches need to be there? FWIW, the machine is supposed to back off the homed position 4mm in each axis after homing.

Still scratching my head a bit.


Hi Kelly.....As your just starting out with GRBL you should consider this plugin below as it'll save you a lot of grey hairs, it's tightly integrated with CB and works well and is really one of those must have plugins if you have an GRBL powered machine.

Happy cnc'ing. Dave

So I read all 12 pages of that, most of which is over my head but gathered it's a plug in that would allow me to run my GRBL machine directly from CamBam via th eplug in, correct?......and it would replace what is now UGS, correct?

I'm a little skittish about doing so but at the same time would like to simplify life where possible. I got the EMI issues sorted but now I'm struggling a bit with the machine set up and may have some XY+- travel convention errors. I posted this at the machine forum but it is pretty thinly traveled. Seems like a silly thing to be hung up on but any help would be appreciated.

I went through UGS set up wizard and tried to cut the demo file that cuts the Mill Right Name/logo and was getting soft limit errors and (air) cutting that didn't occur over the stock. As I recall, I believed the issue was wrong direction of travel designated on the Y axis. I swapped that in the set up wizard and after issuing a G92 X0 Y0 Z0 command with the cutter at the front/lower left corner of the stock, the demo file cuts just fine and still does now. However, now that I have created some of my own gcode files (from CamBam), I'm once again getting soft limit errors because the stock is in a different place than expected by the machine.

All the following reads from the convention of standing in front of the machine. The front of the machine is looking at the gantry from the side of the z-axis rails and router mount. For the avoidance of doubt, my machine homes to the back left corner when standing in front of the machine, because that's where the MegaV assembly video showed the limit switches.  But the beginners guide says when you execute $H the machine will home/move to the back right corner. ??? How can that be if both the X&Y limit switches aren't located there?

So as I'm set up, my machine happily homes to the (my) back left corner. It jogs with X+ being movement to the right, but Y+ is movement away from the front whereas the quickstart/beginner's guide says movement away from the front should be Y- (z- is down and Z+ is up so that is fine).

After I am homed, if I jog the spindle to the front left corner the DRO says I'm at about -34"(x), -34"(y). So isn't the homed location supposed to be 0,0? and Y axis aside, why isn't the front left corner X=0 if movement to the right is supposed to be X+?

The thing I don't understand is, if I issue G92 X0 Y0 Z0 with the spindle at the lower left corner of the stock near the front left corner of the machine, the demo file runs fine with the machine set up as is but doesn't run properly on any other file I download. It wont cut the demo file is if change the Y axis convention to that stated in the guide (Y- away from front). Do I possibly have two things flipped?

I'd really like the front left corner of the machine to be 0,0,0 for several reasons with X+ to the right and Y+ away from the front. First, everything I have drawn and have seen has the XY origin in the lower left corner of the screen with positive X+ to the right and Y+ upward and to me and my brain, that corresponds to the front left corner of the table, with X+ to the right and Y+ away. So to achieve this, would I need to move the homing switch to the front left corner and get the +/_ convention set properly with X= to the right and Y+ away? Would that do it? The other reason is the front left seems to be the most convenient for tool change but I suppose it could always be moved there for such.

I must have the cnc twisties and may need to change my screen name to dyslexia....or is that Lysdexia? LoL.


See attached photo, is this the piece you want to do? What is the model and brand of the piece, to do a Google search.

Yes, but you won't find that available anywhere because I'm the one that made that intake manifold and at the moment, it's the only one in existence. It was cast with the lost foam method and I hand built the pattern with rather crude methods as described here. There are imbedded YouTube videos but you may have to join the forum to see full size pictures:

When I mentioned I don't own a CAD program, it's not exactly true. I have access to Fusion 360, I'm just not at all proficient.....yet. If I had a good solid model, and could make this (see attached and portion pictured on the right) center section in two pieces (top and bottom) instead of the 56 pieces in the current method, the rest of the pattern pieces are straight forward and it would save a lot of time in constructing the pattern, as well as improving accuracy and quality of result.

I might even be able to cut it with CamBam but I don't think I could model/draw it with CB. I'll get there eventually.


Much better with correct tools!!! See attached.


I did download CAMotics after the earlier post in this thread, but when I run the simulation, I don’t get a nice smooth object like yours.

Think I figured it out. I needed to either import the tool list (I need to read up on creating, saving, and exporting/importing tool libraries) or just make sure the tool numbers I add in the simulation match the tool numbers and characteristics of those in the CB generated gcode file.


Another suggestion for you since you want to do both sides of a part and multiple tools. If your router tools won’t repeat on length when you take them in and out I suggest you program the table surface as Z zero and then the top of your stock will be the thickness of the material. Then the clearance plane value will need to be Greater than the thickness (VERY IMPORTANT!!).  All your cut depths will then be positive values measured from the table.

Two reasons you should do it this way. When you change a tool you always set them off the table which never changes. So switching to different height material the tools get set the same. If finished material thickness is important you can surface the top and material variations go away with no calculating or program changes. When you flip the part you good as well.

I'll keep that in mind Gary. I have a zeroing touch plate for the router.


The pic is a screen shot of a Camotics screen, a free simulator. There is a plugin here on the forum that enables you to call it from a CB Menu, It's very handy for developing files, saving a lot of time and catching errors before the file hit's the mill.

I did download CAMotics after the earlier post in this thread, but when I run the simulation, I don’t get a nice smooth object like yours. I attached a couple screen shots and the gcode file which only differs from my previous file by me adding roughing clearance and finish cuts. It almost looks like the simulation used a smaller diameter cutter but I had loaded a .25” x 1.5” cylindrical tool with imperial settings. It was set to medium resolution and when I tried to change the setting to higher resolution it produced a blank, uncut piece of stock? On some simulation I saw run time and total cut length. Doesn’t appear to be available on CAMotics. Is it?

I run Mach3 on the mill and lathe, Both have EMI filters, with GRBL and using USB on my laser cutter and multi-axis grinder I use these cables with a ferrite filter and have no issues with interference (USB wise), so if you have problems with intermittent com's failure between the controller and your Gcode sender then these may help. Dave
Dave, That looks to be a pre-made cable with a 'molded-on' ferrite spike snubber. For Kelly's situation, he should be made aware that those ferrites can also be purchased in a 'clip-on' form to fit existing cables. Lloyd

I do have some clip-on ferrite beads. The problem appears to be associated with the USB cable between the computer and machine controller. If the USB cable touches a stepper cable or anything metallic the stepper cables touch, it produces intermittent coms failures.


hello kelly, Looking at your first poster photo, I see that the surface is uneven! Attached is a mesh file, part of the car engine. Do you have your part's STL mesh file? Armando

Uneven? I drew the part in CamBam and don't own any other CAD program so unless there is someway to do so with cb or CAMotics, no.


Yes your mixing the roughing option and the roughing clearence setting up.ignor the option but set the setting.

Yes I was. I understand now. Thank you.


OK, I obviously haven't tried it for 2D cutting but I'm confused because of this:

The "Roughing / Finishing" setting I never use because as David said it does nothing except with a 3D or Lathe MOP, from the manual "Currently only supported by 3D Profile and Lathe machining operations. "

I thought that meant it wasn't active or available for anything but 3D Profile and Lathe.  ?


I did this file last night so things have moved on a bit post wise, however this may still help.

Thanks for that Dave. Much appreciated.

I'm assuming that you are still using Foam as the stock material and so have not included roughing and finishing mops, which would be required for machining metal.

I'm just using a 1" thick foam board for proofing. The actual part is only 3/8" thick and is a phenolic composite, which is a fair bit harder than most hardwoods. It's also a bit pricey thus the proofing. I'd rather not blow up a piece of phenolic stock if I can avoid it. I figured I could just change the stock thickness when I moved onto phenolic. On the actual piece, I was thinking I'd take Gary's suggestion and overstate the cutter diameter for roughing cuts and then follow with an identical MOP at full height cut on all machined features features. The other reason I was previously asking about order of cut were the features called "slide valve slots". They are cut at .3125 depth but in actuality it would only be .0625" depth of cut if the port was cut first.

As a general rule what you have done by calculating the X,Y offset and using the lower left hand corner at the top of the stock as XYZ = 0 is correct and the way most people would and should do this (you should do this first and if you run into problems) when you have many pieces to cut out and they have different stock dimensions and they must be registered then you can center the work piece’s around the origin of the drawing and indicate the center of the stock on the machine.

Since this part resides and is cut completely within an ample amount of stock, with all machining operations in one set up, I figure precision location of stock isn't that important and I can just draw the machine X&Y on my table/waste board and place the stock about the lines.

I have four more cb files mostly done. They cut the front and back side of two parts. They do need to be positioned precisely but I just incorporated some registration holes in the corners of the stock that locate on registration pegs mounted in the waste board and would be the same for all four files/two parts. Don't know if that is how it is usually done but more on that later.

The last pic is how I organise the tree structure, I separate the mop's into parts so that the parts and mops read from top to bottom in operation order and you don't have to change the optimisation mode, this also facilitates structuring more complex file's using different tool's from multiple tool libraries.

Got it, thanks for that Dave. Where did the solid view of the cut part come from? Can that be generated in CamBam or is it a screen capture from other software? Seems useful for me to discuss parts here on the forum.

Good luck with the gremlins.

EMI problem. I had to reroute a cable. Not sure if it is poor or compromised cable shielding, or weakness in stepper or driver, but for now, sorted....I hope. Had me chasing my tail for a while. Also some problems with soft limit settings. Dont want to turn them off and invite a crash....especially since I don't know what I'm doing....LoL!


OK that's how I originally understood it.

For me, the simplest thing to do is what Gary suggested in the previously linked thread, that being use the same tool path but over state the diameter of the cutting for roughing by twice the desired finish stock cut depth, then use an identical MOP at full height cut with correct diameter cutter designated. To keep them straight name one roughing and the other finish and insure they are ordered properly. Even though the program will think so, no tool change will be required.


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