saramos

I posted this question in the Question and Answers forum, but later thought this would be a more appropriate forum.

I've been considering getting the CNCShark from Rockler (http://www.rockler.com/c/cnc-routers-accessories.cfm) and was wondering if someone who has one would be kind enough to describe the types of things they have used it for and their impression of the machine.

Thanks

Scott

Campgems

The question is what do you want to do with it? I would think the limited work area would be small for cutting parts from stock balsa or ply. You would want to be able to nest as many parts as possible on a stock sheet, and 36" balsa gives the best flexability. as does 48ply. Also if it is balsa and lite ply you are going to work with, you need a vacuum talbe vs a T slot, although you could add the vaccum table on top of the T slots.

If it is small stuff you are working with, then something like a CNC Taig Mill might be a better fit.

The question though is what do you want to do with it.

Don

saramos

Hi Don,

I'm looking for a tool that will work for a number of projects. Cutting balsa and ply would be one use, but other items I want to be able to cut are fiberglass plate and on occasion carbon plate. I would also like to be able to cut wood plugs for molds or vacuum forming. A current project is to cut parts for the mechanism of a functional leading edge slat. A CNC would be able to cut the curved track I've been designing with better tolerances than trying to cut by hand. I do already have a combo lathe-mill, but it is not CNC. My RC interest is scale, so it could be put to task on two projects I am currently working on, an Airworld ME 262 twin jet, and a scratch build of an F4U-1A Corsair. As mentioned, I would like to make functional LE slats for the 262, and I could use it for various parts for the Corsair. I was hoping to get an idea of what others are putting their CNCShark to use for RC, and how they like the machine. Looking at what is available for a small CNC router, its’ listed specifications seem to represent a pretty good value for the price. If others have supporting or differing opinions, it would be nice to take them into consideration before purchase.

Thanks

Scott

Campgems

Scott, one of the big issues with chosing a setup is what tooling are you going to use. Standard router bits will be eat alive by CF and Fiberglass plates. In addition, they will not make very good cuts. Carbide tools at high speeds are your best low cost answer. Small diameter and high speed spindles are the best. At a minimum, a RotoSaw type motor that will turn about 30K rpm for several hours none stop is what you need. Something that will take 1/8" diameter tool shanks with near zero run out is also needed for these little tools.

I'm not trying to discourage you from your CNCShark, just trying to point out things you need to consider before making the plunge. The CNCShark doesn't come with a spindle motor, so you are on your own there. The recommended motor is what one would use to cut wood signs and such, not a very good choice for precession model work. I didn't look at the specs on the unit, but what you want to look from the basic movement is back lash in each axis. Does the machine have anti-backlash lead screw nuts? Also does the software allow for tool offsets and backlash correction
?
I put together a Taig CNCmill, I started with a manual mill and added the upgraded lead screws, motor mounts, steppers and drivers and power supply. I'm using Sheetcam for stuff like your plate cutting and Meshcam for your plugs. This is all driven by Rhino 3D as my CAD software. The output of Sheetcam and Meshcam goes into Mach3 to actually drive the stepper controllers and handle the back lash issue among other item like limits and home switches. I also have a 4th axis that I can utilize with Meshcam for cutting plugs. Sheetcam is a 2D CAM package. Meshcam will allow you to take a 3D drawing in the right format and cut either a 2 1/2 D product or with later versions utilize the 4 axis for full 3D work. All of this was put together before I jumped back into the RC world again. I was going to make wax patterns for jewelry work. My machine is limited in work envelope to about 12" length which isn't enough for most modeling work I would like to do, IE cutting kit parts. It is capable of doing some very accurate small jobs, but cutting fuselage sides, in fact ribs for 1/3 scale are beyond it'sabilities.

I think youwill find thatthemachine you are looking at isnot going to be able to cut cowlplugs forvery big planes. Try this and see if themachine will handle it. Do a rough sketch of the cowl cross section,the biggest you may want to cut. Then do a rough sketch of the bottom of the router and the extended router bit. both to the same scale.. Play with these sketches and see if you can cut to full depth you need to cut half depth on your plug without the hardware of the machine or your spindle hitting the plug at some point. Also check to see if you have enough Z clearance to take the size plug you want to cut. Ithink that unless you are cutting plugs under 3" depth to center line, you will not be able to do it with a router motor and standard bits. You will need something with a longer reach or a rotary axis for the work.

I guess all this boils down to, establish the limits of what you will ask the machine to do and see if the machine, and the software included will do it or not.


Don

Prop Nut

My Feedback: (3)

Hi Scott,

I do not have a CNCShark, I scratch-built my CNC table (5x9) but you might find more information on CNCzone.com

Here is a thread on that site showing my CNC table.

http://www.cnczone.com/forums/diy-cn...ess_story.html

Also, search the commercial CNC area for info on the CNCShark:

http://www.cnczone.com/forums/commer..._wood_routers/

I do not want to bias you but I have not heard very many good things about the Rockler offering.

Wing ribs cut on my machine:

saramos

Well, I guess I'll find out. I made the purchase on Saturday. I spent a fair amount of time searching the net for any other commercial machines in it's price range, and found nothing that came close to the specs and included software. Hopefully it will arrive on Thursday. Of course, it will take some time to get up and running as this wll be my first experience with CNC. The machine comes with Vcarve Pro included, and I plan to purchase 3d Cut when I get the chance. Some early work I plan to do is to cut some parts out of G10. That should put it to a fairly rigorous test. 3D cutting will come later as I am also new to 3D CAD. I will be using Alibre for the 3D work.

I'll be sure to post on my impression of the machine, though I don't have any type of baseline to compare it with.

Scott

Prop Nut

My Feedback: (3)

Vectric has a great forum community if you have any questions about the software. And there are tutorials on their main page on how to do many tasks. PM me if I can help at all with Vcarve Pro.

Good luck and enjoy!

smithcreek

My Feedback: (25)

Looks good. What bit are you using? Are you double taping to hold the material down?

Prop Nut

My Feedback: (3)

I used a 1/16th 2-flute upcut spiral bit (3/16 cut height 1/8 shank) carbide bit. I have some really good 1/32 bits now as well, they walk through balsa like a hot knife through...well you know the rest of the analogy.

Yes, I am using double-sided carpet tape, it comes in 2" wide rolls and is very easy to work with. I just need to be very careful when I peel the parts up and off the table not to break them.

saramos

Ok, it took me some time to get the machine set up the way I wanted. I still have some improvements I want to do, but on with my first impressions.

First off, I can see that this will be a great addition to my workshop, giving me a lot more options on how to produce parts, jigs, and precision work. I think it's size is a reasonable compromise between work area and floor space requirements. The precision, speed and sturdyness all look good for the cost. I've found a few negatives to the design. The work area is not centered on the table top. It is to one end. This is because the router is not centered in the gantry, and couldn't be given it's size. But this means that when working with pieces that are over about 14", clamping on one end becomes less flexible. The other issue is that the machine does not have an absolute home position. It's zero position is where ever the machine is when turned on. To work around this issue, I added some hairline indicators for the X and Y axis to aid in centering the machine. Another issue is that the table top does not come trued to the head movement. To address this, I used a 3/4" flat bit to plane the surface. The problem again is that the work area is smaller than the table top and the result of planing leaves a recess in the top, and the rest of the table top will need some other method to level it off too. Eitherwise, pieces that are larger than the work area will not lay flat. Also, there are no limit detection for any of the travels, so it is possible to send it code that will run the machine beyond it's physical limits and it will continue trying to travel past the physical limits.

I am going to have an opportunity to try their support as the unit I got has a serious problem that makes the machine unusable. Sometime, when the router is moving in the -Y direction, the stepper motor stalls and the gantry stop while the g-code commands continue to be sent to the controller and the controller continues to send commands to the stepper. If this happens when running a part, it could easily make it useless, and can also cause the machine to run past it's limits.

Enough of all that for now, here's some photos.

Scott

Prop Nut

My Feedback: (3)

Looks good Scott (the sign that you made).

I never worry about absolute zero, as I zero each job to it's starting point (via Vcarve-pro).

You might check to see if the wiring to the stepper motor on your y axis is secure. I had a solder joint break on my x-axis slave (I am using two X axis steppers) and it would act the same intermittently.

Otherwise, congratuations on your new machine. I hope the bugs are worked out and it serves you well in the future.

Here is a Youtube video of a job I cut for a local contractor the other day. He needed some trim made for arched doorways. The job was cut from 1/2 MDF running at 180 IPM.

[youtube]http://www.youtube.com/watch?v=YFEOE825ZqQ[/youtube]

saramos

Thanks for the suggestion on wiring. I'll have to check it out. Looks like a really great setup that you made.

Scott

nh4clo4

My Feedback: (33)

Saramos, V carve is very good software, if you are more familiar on a different cad, you can always import those files in to V carve to write the tool paths. I use a different cad, then use V carve to do the tool paths. If you go to vectrics site and look at case studies for V carve, they used us as a spotlight. Eck Designs.
Ed

saramos

Hopefully, I have the problem straightened out. I found that the zip tie closest to the connector for the Y axis to the controller was causing stress on one of the connector pins. I clipped it off, wiggled the connector a bit, and tested. So far, the problem has not reoccured. Time will tell if this was the issue.

I ran the sign job again with much better results. I ran it as a two tool job. 1/4 straight bit for the large areas, and a 60 deg. v bit for the finish. It is a bit rougher than I anticipated, but still not bad. A little sanding will clean it up.

Scott

Prop Nut

My Feedback: (3)

Hi Scott,

Not sure why you are getting gouging on the v-bit, but it looks pretty regular as if there were an issue on those planes (of movement). Could there have been a buildup of waste material on the slides causing a bumb in the movement? One thing that I do is have a second parimeter cut with a slight inset to take care of any machining marks on my v-carves.

You can get a smoother pocket by using a round bit for finishing rather than just a 1/4 straught bit.

nh4clo4

My Feedback: (33)

MDFproduces alot of resistance to v bits, Did you do 2 passes with the V bit or one? Iusually either set the tool parameters to get 2 passes to required depth, or set the first z high, then resend the toolpath at the correct z so that it only takes a small amount of material on the final pass, It helps to get a finish cut either way on wood, or MDF.
ED

saramos

I was trying to think as to why the problem was happening. All the irregularities occured at plunge spots. I was thinking that perhaps there was so much pressure to cause flexing in the machine to create a bounce back effect.
Also, I ran the v bit toolpath after the pocket/waste clearing toolpath. This means that when the vbit cut the long strokes, it was cutting material on only half the bit. Perhaps that lead to some deflection. I'll run it again tonight and use your technique of a second pass. How much shallower should the first pass be, about .1?

Scott

Prop Nut

My Feedback: (3)

Really? I find that MDF is very easy to cut, regardless of the bit (ok, a bit with no edge would indeed be difficult to cut with, lol) I checked out your website Ed, very nice stuff in the gallery.

Scott, you might also check the nut on the z axis. There might be a bit of slop as you mention that the issue is on the plunge. Check the backlash on the spider gear for the z-axis stepper also.

nh4clo4

My Feedback: (33)

.1 would be a good finish cut, it also depends on the plunge rate, what happens with a v bit is it's diameter gets larger as it plunges, and depending on the gantry, it will push it down, and when it gets to the depth, the material or frame relaxes, causing those irregular areas. I use 1.25 and 2.25 inch diameter v bits, with a spindle, it starts cutting a very small diameter, and goes to a large diameter, which causes a lot of pressure, until it reaches the depth. Whenever I want a perfect cut , I try to use a small finish cut, it takes longer on the machine, but not as much time sanding, or carving out imperfections.
Ed

saramos

Today, I tried a different approach. First, I decided to run the v cuts first. I did the first pass .03 shallow. The second pass took off the .03. Then I ran the pocket to cut the waste. Looks like my 1/4" straight cutter was just a touch too deep, and it left a lot of fuzz. Overall, the results were much cleaner, but there is still a bit of a mark from some of the plunge cuts. Where these plunges are being done, most the material has already been removed. I also ran the feed rate at 90%.

Scott

Campgems

Do you have a touch pad to set the Z height to?

Don

saramos

I've been using a sheet of paper and lower the bit until there's drag on it but won't cut it. How would you use a touch pad?

Scott

nh4clo4

My Feedback: (33)

Mine has an auto z setter. It is a piece of aluminum grounded to the spindle, when you push the auto z button, the router automatically lowers the z until the bit touches the aluminum. When it touches, it completes the contact, and sets the z. If you use a touch pad, you need to mic it, then add that measurement to the start depth. If you are only going to cut parts, then you can eye it, or use your paper method. But when multiple paths are run with different bits, you need an accurate way to replicate the z axis zero. Otherwise the issues you see with the deeper pocket, are difficult to fix. It also helps to zero it out at the same spot, and make sure there isn,t dust or other things in the way.
Ed

Campgems

One other potential cause came to mind other that the Z axis zero. What direction are you cutting. If you are climb cutting part of the pattern and conventional cutting the other part, the stiffness of the machine is tested. Make sure your tool paths are all conventional cutting and that will give you the best finish. If you are cutting grained wood, Climb cutting may be better as you are not going to pull the grain on the surface. If you are using a fine bit to cut balsa and lite ply for parts, the tool path direction isn't an issue as you are making a single pass at depth and the tool is not half in the air and half in the work.

On the touch pad, here is an example.
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INSRHI

You set it on a clean table and slow jog the Z until the light comes on, Jog in 0.0001" increments when you are close. . Reset the Z in the software, Now jog down exactly 1"and reset the Z again and you will have Z zero at exactly table height. Just vary the procedure to give you the Z zero at the depth you want. I is best to work from the table top as you don't want to cut below it, If you use a sacrificial top, then you can work from it and set the Z just below it;s surface.


Don

saramos

Hi Don,

I took a look at my settngs and it is being done as a climb cut. I'll try it as a conventional cut.

Thanks for the info on the depth setting tool. I looked around at a few supplier and Enco was the lowest price by far. I was able to order it plus two composite cutter bits and shipping for less than the other two tool suppiers I checked!

Scott