Messages

16

CamBam help (General usage) / Re: Tracing Edges of Surface Files

« on: December 08, 2022, 23:13:49 pm »

Thanks Bob,

I forgot to look under Surface menu (doh!) and flatten would come in handy for the manual method with curve fitting to points. If it's something I've modeled myself, I can generate the bounding regions from my CAD program but when I'm given an .stl, I cannot.

Best,
Kelly

17

CamBam help (General usage) / Tracing Edges of Surface Files

« on: December 08, 2022, 17:21:48 pm »

Is there a CB function for detecting and creating lines/shapes from the edges of surface files? Sometime ago a made this part from a surface file I was given and used the polylines above the surface as bounding regions but I'll be darned if I can remember how I generated them. I did a very similar part yesterday.

To produce the bounding regions I enlarged, hand placed a lot of points along the edges looking down on the surface in XY plane, connected the points with a spline, converted the spline to polylines, and joined up the shape. It worked but was laborious and messy. When I looked at the XZ plane, many of the points I selected on the edge of the surface were assign a Z value, not 0. I had to go into the point table, change all the Z values to 0, and reconstruct the spline and polylines.

I looked at the plug-ins page but didnt see an applicable PI. Is there a better way?

Best,
Kelly

18

CamBam help (General usage) / Re: Switching Drawing Units

« on: December 08, 2022, 16:59:58 pm »

The conversion of drawing units is only necessary if the settings were not made when the drawing was started. This is the case with every CAD, as the file must first be set up. ralf

I'll take your word for that but other CAD softwares handle this much more easily. For example, In Fusion you can simply type the units at the end of the value. For example, if you were working in a file that was modeled with data from imperial/inches, and had metric components to add, you only need to type the unit after each of those numerical entries and they will be added in the correct scale, i.e. working in inches and adding XX.Xmm or vice-versa. This makes it quite convenient to design with mixed units.

In CB, sure, I can model or add components or reference dimensions in units other than the drawing construction, but the size of mm versus an inches means I need to hide everything, contruct the layout in available units, select all, resize, and then display the rest of the relevant features of the work to se how it fits. -Much easier to just be able to add the unit abbreviation after each numerical entry while viewing the entire work space.

I realize CB was developed as CAM with CAD convenience features, and maybe there is a better way in CB than what I have described, but if not, if there was enough interest, it might be something that could be done as a plug-in or future revision.

Best,
Kelly

19

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 07, 2022, 15:07:26 pm »

.....I’ve been trying to get him interested in cnc’ing for years......

Seems like the hook for the young'uns is 3D printing.

I like 3DP. It's very useful for pattern work and smaller investment/shell casting projects, but there's no printable evaporative casting filament that works for, or has any where near the economics, of (machined) lost foam, for the size and nature of parts I make......so cnc it is for me. If I also get some other modest capability out of the cnc router, that's just icing on the cake.

On another front, was advised there would be a 2-6 week delay on shipment of Super PiD due to parts shoratges ....Sign of the times I guess. On the bright side, I should have the motion control hardware for the machine upgrades in hand yet this week. I have an intake manifold project to finish up first but looks like the hardware upgrade may preceed the S-PiD.

Best,
Kelly

20

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 06, 2022, 00:21:28 am »

I do use most of those strategies when it's worth it to do so. I also previously was only conventionally cutting but now when roughing I rip off big DOCs in both directions. For 3D foam cutting, I was cutting at 200in/min, but I wasn't paying any attention to the plunge setting (typically was <60in/min) so dont know how that may have been affecting some of the larger 3D projects, but I have some big(for me) surface area projects on the horizon. When you're making one-offs and have no tool changer, some times it just makes more sense to keep the CAM simple, design for a single tool, and let the machine do it's thing.

I have no delusions about my machine. It is and will always be a hobby machine, but compared to what most call hobby machines, especially for a 35x35x8+ cutting envelop, it's probably better than most and with PiD speed control and the mechanical upgrades, I expect it will be better and expand it's capabilities within the hobby realm. Good enough for who its for....

I think I've bitten off enough for now, unless I must make further controlller changes. A little over a year ago, I'd never heard of a post processor, barely knew what GCode was, and had never written or executed a CAM program of any kind. Now I know enough to be dangerous! LoL

Always appreciate your replies....

Best,
Kelly

21

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 05, 2022, 17:47:09 pm »

Z feed rate (plunge speed) is also set in the G-code. Retract is usually done at maximum (set by the machine config) speed. 'Plunge height' is also an important parameter as it sets the distance above the stock to which Z will move down at full speed and then switch to the set slower plunge feed rate to bite into the material.
Every program which represents a synchronous motion controller, GRBL included, has the task to move the three axes synchronously so that they arrive at the commanded X,Y, Z coordinates at exactly the same time. And it does this taking into account the slowest of the three. So if the Z feed rate is not enough to comply with the faster X/Y drive the controller actually slows down their speed accordingly.  This applies mostly to real 3D engraving of 'organic' shapes when one needs maximum available speed for a finishing pass with a small cutter which could take several to tens of hours.

If I'm interpretting that correctly, that's a pretty fundamental thing I didnt understand, and I can see how that would probably be inconsequential for most of the 2D & 2.5D machining I do, but for 3D MOPs of, as you say of organic shapes, it may mean I was only achieving modest gains (or no gains) in run time reduction by increasing (XY) feedrates without making corresponding increases in plunge rate......depending upon shape. Thank you for that explanation.

Best,
Kelly

22

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 05, 2022, 14:15:00 pm »

Just to be clear, the quoted feedrates (4.5 m/min) was not about what you should set the the rapids to, it was in answer to this question asked earlier in the thread  post 11.

Understood. Also, the available ball screw leads were 4 or 5 (not 4.5) or 10. 5 & 10 have interchangeable interface dimensions.

If your router + backing plate + (carriages or rail) depending on where you have mountedthem is less than 8 Kg then a Nema 23  3 N/m will be fine, if it%u2019s 10Kg then a 4 N/m motor would suffice. If the weight is greater than this then you would have to drop the feedrates and acceleration.

The moving mass on the Z will be <<10kg, probably <10lbs and comparable to that of the existing machine hardware. Compared to the existing machine, the stroke increases from 3.75" to 8"+, the router power doubles, the centerline distance from spindle to beam centerline is slightly less, and the rigidity for the first 4" of stroke should be greatly improved. The only time the machine would ever see the upper regions of the stroke where rigidity could be more of an issue is for cutting foam, so it shouldn't be challenged. I was happy to be able to achieve all that. The height of the entire cutting surface can be repositioned or use of a platform will be used to control the height under gantry and accommodate different active travel cutting rates, but I don't expect to need to change this often as 4" under gantry with 2" cut height covers the vast majority of how the machine is used.

The X&Y axis will remain R&P drive for now. The moving mass on the Y axis will increase more significantly but it has two N23 steppers driving it.

Something to note is that for a Z axis where the travel stroke is short, setting the velocity is not the secret to getting a good performance, it's the acceleration.

I guess in my mind, I was thinking for a given motor torque a 5mm/rev ball screw would have at least 5x the mechanical advantage in linear force as an acme screw that had 5x that lead/rev. I just didn't know how much of the Z-accel was dictated by this and the traveling Z mass versus the stepper motor's internal inertial mass, stepper driver, and controller. Sounds like we're going to find out. I think you'll like it.

I'm not optimistic about being able to access the command lines on the proprietary MillRight control board but that is yet to be confirmed. That could expand this project a bit. Hoping to build hardware over the holidays and have plan of action on this before I pull the existing hardware apart.

Just for my learning, when feed rate is set in a CB MOP, that is just for X&Y axis, and the Z is a calculated/along-for-the-ride as determined by the tool path, correct? Hard to say what Z accelerations will be reuired since it's so dependent on feedrate and profile shape, but if Z cant keep up, it'll just require backing off feed rate, but it's hasnt been a problem to date on my high(er) feedrate foam pattern cutting.

Best,
Kelly

23

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 04, 2022, 12:07:03 pm »

....FWIW I am using a 16x5 single start ballscrew with a Nema 23 type stepper (4.2A max current), a driver Leadshine like on Dave's picture and 1/8 microstepping. This with a heavy 2.2 kW water cooled spindle. Max speed (G0 speed) is set to 2500 mm/min though it can do a bit more. Never happened in my practice to use plunge and retract speed higher than that. 10 mm pitch screws are actually double start with 5 mm pitch between the channels.

Thanks Dragonly, good to know. Think I've got the mechanical hardware sorted out. Will be a few days before I can dig into the machine control. I've got a couple project to complete first.

Best,
Kelly

24

CamBam help (General usage) / Re: Machining Polycarbonate

« on: December 03, 2022, 17:51:23 pm »

Like I said, you'll find conflicting information. Back when I originally selected PC, I just placed a piece an a jar with gasoline and watched how it aged. There was no visual degradation or obvious change to hardness after 6 months.

Best,
Kelly

25

CamBam help (General usage) / Re: Switching Drawing Units

« on: December 03, 2022, 17:36:27 pm »

Thanks for reply, .........I think.

Reading the manual is very helpful. ralf

I did read the documentation but just didn't interpret the last entry correctly, probably because I didnt expect multiple steps being required select and resize everything to merely change the units being displayed and entered. I was expecting a global command and one click. Apparently not in CB. Sorry if the question annoyed you.

K

26

CamBam help (General usage) / Switching Drawing Units

« on: December 03, 2022, 16:24:26 pm »

Sometimes it's the simplest things.

I just want to toggle back and forth between working in inches and mm but when I switch the units to mm in the tool bar, all existing and new dimensions remain displaying and measuring in inches irrespective of which option I select for default on new drawings. What am I doing wrong?

Best,
K

27

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 03, 2022, 13:56:17 pm »

Just changing to a Acme screw and anti-backlash nut will be a huge improvement.

The inexpensive 16x5 and 16x10 are plentiful but knowing what standard you are buying is a bit nebulous. I can probably guess they're lower end rolled screws, just would like identify the ball nut specs preload/clearance.

I’d install a ballscrew, but before you order one make sure that there is enough room for the bearings as this may be the reason that these were selected in the first place.

Design layout work almost complete for Z. I've used a 16mm ball screw which is quite a bit larger to package than the existing screw but not much so compared to a 12mm BS. 

It would be good if you can supply a pic of the drives as some of the cheaper ones have less micro-stepping choices, before splashing the cash make sure that you can get access to the GRBL setup parameters for the millright software, if not then download and install the free LaserGRBL software (not for the laser part) but the GRBL parameter gui is the best and easiest one to use. Once you have changed the parameters to suit the new leadscrew close down the software and use the millright one as usual. If you have access to the command line in the millright  software then you can just type in the command in the second pic. If your leadscrew is 5 mm pitch and you have set the drive to X 10 microsteps  so 2000 steps per revolution, then in parameter $102 set it to 400. = 2000\5 = 400 steps per MM. About 4.5 m|min feedrate about 177 inches\min

This is what I need to understand. Also forgot to check if existing screw is LH or RH. Got some work to do on this and will do some more investigation before I buy the screw.

Many thanks.

Best,
Kelly

28

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 03, 2022, 02:52:44 am »

Thanks Dave, helpful as always but as usual a good part of it is over my head. I'd probably distill it down to I'd probbaly be no worse off than I am now if I changed to a 10mm lead ball screw than the one I have.

Aside from pitch I simply rotated my Z lead screw one revolution and measured the displacment on a scale, not a dial. I just wanted a general idea, but it was very close to 30mm for one revolution, of that I'm certain.

The MillRight literature might say the Z is .5" diameter acme screw buit I can assure you it most certainly it is not. It's very close to 8mm and the anti-balash mechanism is simply a split in the polymer nut preloaded with a cantilever spring. As far as the stepper drives, I dont know. No documentation from the manufacturer is available and no repsonse on their user forum so I suppose as usual I'll just have to open the controller, remove one, and identify it.

Admittedly, I'm out of my element here but I can economically buy a ball screw with a lead of 10mm/rev and was just trying to assess if the stepper could likely keep up at 3x rotational speed to maintain similar linear Z speed and if I could expect to change the Z-motion calibration that much in the machine set up/calibration. It's been a 18 months since I did the calibration and my memory isn't what it once was. I suppose I can just take what I get as far as Z.

If the machine never did anything more than machine foam patterns for me I'd be OK with that and take what I can get for the rest. As far as I'm concerned the upgrade to linear rails is to avoid missing steps due to accumulation of foam debris on the wheels on long unattended run times and any other benefit is just icing on the cake.

I need more Z-axis travel for my pattern work, and frankly wouldn't care if I used as similrar acme drive for my pattern work, but the cost difference compared to effort expended is deminimus, so I figure why not use a ball screw? Sometime it sucks not knowing what you're doing but I've always tried to not let that stop me.

Best,
Kelly

29

Members Machines / Nema 23 Stepper and Ball Screw Lead

« on: December 02, 2022, 16:52:16 pm »

Was looking at ball screw upgrades and concluded my steppers would need to step much faster for the same feed rates on either the rack and pinion X&Y or Z.

The acme screw/nut on my Z has a lead of 30mm. Most of the economical ball screws are only available in 4,5, or 10mm lead. High lead ball screws seem to be much more precious. The lower lead seems like it would be helpful to actuation force and positional accuracy but what determines how fast a NEMA 23 stepper can step when operating within rated torque/load?

For example, if I selcted the 10mm lead, would I just expect to make the stepper calibration adjustment and expect it could keep up with my max X&Y rapids?

Best,
Kelly

30

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: December 02, 2022, 13:07:15 pm »

I hadn't thought about backlash from the racks as a possible source of the poor finish on the heavier cuts/harder materials but that makes sense. I was pretty focused on the wheels as the source, but any displacement there could also affect rack clearance. For now, I think I will stay with the R&P drive on X&Y. For the approach I'm taking to incorporate the linear rails, the X&Y could fairly easily be retrofitted to ball screws in the future. That might help isolate whether I'm getting flex/displacment from the wheels under heavier loads.

As far as cutting foam patterns and foundry tolerances, the accuracy is already good enough. It's really all about speed.  The R&P seems quite tolerant of what little foam fluff it sees, but the rolling wheels are not and cumulatively gather more than the R&P. The new positions of the R&P should also better shield them from debris. Since the Z axis already has lubricated linear bearings, I'm quite confident the additional linear rails and bearings will be tolerant to the foam dust. In use, the existing ones pick up a little foam dust on the wipers which makes them even more effective.

I will definitely use a ball screw for the Z. It is currently has a fairly small acme screw.

Best,
Kelly