Gantry flex

[Frunple]

My question is how are those things selling for that kinda price if it's all plastic??!!
You can make your own, for a lot less, out of aluminum.

[martin54]

My question is how are those things selling for that kinda price if it's all plastic??!!
You can make your own, for a lot less, out of aluminum.

It's obviously not all plastic but yes guessing from this post there is far to much, why the price well the Company that are making them probably have high overheads & obviously still need to make a profit. Yes you can build one yourself BUT not everyone is capable of doing that & even then if you want to do it properly you need the right equipment to do that or be able to find someone that can produce those parts for you. If you are self building you don't look at costs costs as Company does, most people don't look at their time as a factor & Labour costs for something like a router will be high, plus you probably don't have the same costs when it comes to renting/buying workshops, insurance, Tax & everything else that goes with running a business lol

[ger21]

My question is how are those things selling for that kinda price if it's all plastic??!!
You can make your own, for a lot less, out of aluminum.

Because most people starting out in CNC don't have any idea of the actual quality of what they are getting, and the importance of rigidity. And the majority of them don't want to build their own machines.

[Frunple]

Wasn't really asking. The answer is obvious.
Just pointing out the waste of money on these machines when it can be done for a whole lot less.
And there's nothing hard about building your own, and nothing special needed to do it.

[FixitMike]

My question is how are those things selling for that kinda price if it's all plastic??!!
You can make your own, for a lot less, out of aluminum.

The machines are basically plug and play, and come with VCarve. I was making a sign the day after I put the machine together.* It comes with a controller that handles the work of converting G-Code to the electric pulses required for the stepper motors, instead of using your computer, so a computer glitch will not ruin your job. The graphical interface (control panel) is easy to use. You do need a computer for the interface and, of course, to run VCarve.

If you subtract what you have to add for software (VCarve plus Mach3 or other) for other machines, the Sharks are quite affordable. The rigidity is a problem only if you are trying for high accuracy and high speeds. For hobby use they are quite adequate, in my opinion.

*Disclaimer: I have 20 years background using CAD programs for machine design, so learning VCarve was quick for me.

[Steve Misher]

FixitMike is correct:
The sharks are not a production machine. If you cut slow, you will get a nice cut.
When I had my HD4 running, it cut out the pieces I needed, but when I tried to speed up my cutting of parts, they were not consistent from part to part unless I slowed down the feed and speed rate. I got a bad one and that is why I returned it to Rockler and got the Axiom. Next Wave had the control box and other components in for repair more than I had the machine. Between the flexing and electronics, I just couldn't get it to run correctly. The Axiom is much heavier duty than the Shark and every part I cut out is exactly the same as the first. It also cost more than the Shark, but I was so frustrated at that point with the HD4, I just bit the bullet and spent the extra money.

[martin54]

Wasn't really asking. The answer is obvious.
Just pointing out the waste of money on these machines when it can be done for a whole lot less.
And there's nothing hard about building your own, and nothing special needed to do it.

There speaks a person who is obviously quite handy & use to getting on & doing things them self

To some it would be extremely difficult to do, some simply don't have the time, there are those who have plenty of money & would rather buy plus a whole lot of other reasons, as Mike has said the machines are plug & play & very easy to get up & running. To you ( & me) money can be better spent elsewhere but for some it seems the easiest & best way to get started with CNC

I started to build my own machine but then one came up as a non runner at a price I would have been silly not to take, just ripped out all the old electronics & replaced with modern electronics & was good to go, I was an engineer in the Royal Navy for 20 years so for me yes it was an easy job, I have a friend who doesn't understand the first thing about them, soon as he has a problem he calls me

[MDHunt]

Ok, I moved the gantry down to the lowest position available and lost almost available inches in the Z axis. I also slowed the inches per minute as well as the plunge rate to pretty slow speeds (20 IPM feed rate and 5 IPM plunge). I also changed the depth per pass, adding more passes.
The results were better, but still not perfect like I would expect a CNC machine to do (the drill holes were still slightly elongated).
I am already running the spindle at 18,000 rpm for a 1/8" end mill.
I guess I am going to have to look at the aluminum bracket on Next Wave as suggested.

I also emailed next wave and got this for a reply.

1.) If you have the gantry set at the highest position, try lowering the gantry by using a different set of mount holes. The shorter the gantry height the less flex.
2.) Look at how far your router is extending through the router hanger bracket. Like the gantry the longer it is the more flex there is. Raise the router up.
3.) Slow the Inches per minute of travel down especially on larger bits.
4.) Change the depth per pass to add more passes to your project.
5.) Run you router at a higher speed.

1 and 2 will result in the gantry having less flex. 3-5 will result in taking less force to do the work, resulting in less flex.


I'll give these suggestions a shot tomorrow and post the results.
Thanks for the help!

Paul, yes, there is a small amount of flex in the Z axis when I press on it with minimal pressure. I don't want to damage my machine, so I don't do it with much force. When I am drilling or carving, what should be a straight drilled hole, is elongated along the Y axis by a small amount and the drilling depth is less than it should be.
Steve, when talking about the Z speed, are you referring to the plunge rate?

Gantry would have to be very weak to flex that much on a drill pat ... does it flex when you press on it?

Could the material have lifted off the table during a drill cycle?

[martin54]

At that kind of feed rate I am surprised your not burning the holes running at 18,000 RPM, I would be running a lot slower than that even with a single flute 1/8" bit. You can up your plunge rate, at a feed rate of 20 ipm I would set the plunge at the same value.
Have you tried using a drill bit for the holes rather than an endmill ? Might give you better results but it does sound like the machine needs to be made a bit stiffer

Have a read through this thread about using a drill bit as opposed to an endmill for holes

http://forum.vectric.com/viewtopic.php?f=2&t=28905

[wmgeorge]

Can you get your money back?