new cnc not running as fast as advertised.

[eugene thomas]

The problem is 3d finish. I tried cutting stuff as slow as 100 ipm and still not look good.

[Brad Shipton]

Mind sharing a picture or two? The signs I have made have turned out good in my mind, but most of them have been freebe gifts, so I have not given it much thought. James and a few others do a lot of this, and you might get their attention.

[Bruce Page]

The problem is 3d finish. I tried cutting stuff as slow as 100 ipm and still not look good.

What size radius cutter are you using? Is it new, is it sharp? What RPM? How much step over in your tool path? Are you running a roughing TP before the finish TP? These factors can make a big difference in cut quality.

[Ross Moshinsky]

The problem is 3d finish. I tried cutting stuff as slow as 100 ipm and still not look good.

I'm confused. Is your issue the rapids or the machine not working properly? One is an entirely seperate issue from another. Also I have no idea how much experience you have with a CNC, but it takes time to find the right settings that give you good results. 3D machining is a time consuming process that requires careful consideration of bit type, design, and material choice.

[eugene thomas]

Well I was not happy with the company listing speeds cnc can't reach but it morphed into the cnc not cutting 3d way I think is exceptable. I can't load images from phone and in Florida till next week. But the files trying to cut where all cut good on old cnc.

[Gary Campbell]

Eugene...
Both of the issues that you list are available to change within WinCNC settings. It is important to know how to tune your machine to get the best operation for the types of files that you cut. It's unlikely that any two combinations of machine, material, file type and bit are the same.

[Ross Moshinsky]

Eugene...
Both of the issues that you list are available to change within WinCNC settings. It is important to know how to tune your machine to get the best operation for the types of files that you cut. It's unlikely that any two combinations of machine, material, file type and bit are the same.

To add to this, rapids are a bit like listing the max specs of a vehicle. While your vehicle might have a top speed or a max tow limit, the vehicle is not designed to be driven at max speed or tow at max limit. You can do it on an occasion but it's definitely not designed to do it all the time.

I wouldn't be too concerned about the rapids. Get the machine setup right and producing and then judge whether you're happy with the machine. If it doesn't produce, then you have every right to complain, assuming your expectations are reasonable.

[Leo Voisine]

The problem is 3d finish. I tried cutting stuff as slow as 100 ipm and still not look good.

The finish on the 3D cutting is not a function of the cutting speed as much as it is about HOW you are doing the cutting.

It's more about process than speed.

Good quality, very sharp cutters
Step over amount
Depth of cut
Material being cut
Geometry of cutter
How well the machine is trammed
How the material is being held in the machine

Also, what is the definition of "good"

I can get really good 3D cuts with my programmed feedrate at 350 IPM or at 35 IPM.
It is not likely that the machine is going to move at the programmed feedrate anyway, because of acel and decel.

With rapid moves, the only time you get any real benefit from full "pedal to the metal" speed is when the rapid move is a long distance.
If the rapid move is an inch or so, the machine will not reach full speed anyway, again because of acel and decel.

[Ted Reischl]

About rapid travel speed:

Most machine manufacturers spec rapid speed as both axis driven at the same time on a 45 degree angle.

So think about it, if each axis can move at 800 IPM then both running on 45 will produce about 1.4 X 800 IPM combined speed.

Let's say you are at 0,0 and you program G0X20Y20. Each axis moves 20 inches, but the combined distance along the 45 degree is 28.284. So the machine is actually moving much faster than the individual axis.

[Gary Campbell]

Ted is right. Many even use the "theoretical" speed that the machine could move. Its a shame that many mfgr's just don't post the speeds that the machine can actually run at, on a day to day basis, but they don't, and its not necessarily their fault.

Consumers buy on specs. They really don't know much about those specs, and seldom will they need a machine that will run those specs but they buy on specs.

Forget CNC's. Take a Corvette. Few will drive one over 80mph. Yet if the factory uses a speedometer that only goes to 100, sales will decline. Proven fact that the same car with a 200 mph speedometer will sell more units than if it had a 100 mph speedometer. Sad, but true.

[eugene thomas]

I think company that built my cnc use the ""theoretical" speed that the machine could move". I get better results now by running the spindle rpms at 16000 for 1/8" ball nose when cutting hard woods and the manufacture sent me new coupler for z axis, old coupler was not a good choice for cnc. they changed some of the set up in the driver files also.. In the specs they state use "1200 Oz. Micro Stepper Motors" but only use them on the 2 y axis motors. I still need to buy new motor for the z axis so that when get all the bugs worked out I can run z axis higher than 150 ipm (tech form company told me if run faster than 150 it could lose steps) but they want $400 for it so will look for another source first.

Thanks for all the help though, feeling lot less frustrated than was month ago about this .

[Gary Campbell]

Eugene...
In many cases simply putting on a more powerful stepper without changing the drives reduction ratio will not increase the axis' speed. Before I plunked down $400 for a stepper I would like to know what rpm the current one would be running at when at the max of 150 ipm. Is there a counterbalance to offset any of the Z weight?

I have seen some machines where fine pitch lead screws were used on the Z, resulting in higher than desirable Z motor rpm, which caused lost steps. Slowing down the Z, which worked fine for machining type operations, required 3D cutting at such slow rates that made the product unviable to produce.

Have you checked with other owners of the same brand/model? Are they experiencing the same issue(s). Sometimes batting issues like this around in a forum discussion brings up some good solutions from more experienced users.

[eugene thomas]

20161228_104130.jpgI posted picture of my z axis. I bought the air assistthinking it worked same as last CNC but now think they just use it to keepspindle from dropping down when power is turned off, if wanted to install theatc on cnc could use for that but THAT is not going to happen. Told meshould be set and 2 or so psi. I could have saved some money and justused block of wood. the stepper motors are interchangeable because the z motorwas originally on the x axis but dropped the z axis motor when changing out thez axis coupler. I could push the x axis when under power. Thecnc looked at before bought this one had same issue crop up not longafter looked at his CNC. after new motor, no more of an issuein the X axis. think when all done I will have over $800 on getting thisnew from factory CNC running way should of from factory. Think if mymain job was a lawyer instead of boiler plant operator the company would havebeen fixing the problems at their coast instead of mine.

[Gary Campbell]

Eugene...
Sorry, I just realized you had a ShopSabre machine. Apparently there are people there that do not take kindly to my comments to their owners, especially when it appears they have perceived issues. Therefore I will not make any more comments on this thread.

[Mark Bolton]

The air balancer is there to counter the weight of the spindle effectively making it as close to weightless to the Z axis motor and screw as possible. I cant say I have any idea what your beef is with the air balancers job was i.e. "same as last CNC". Did the air balance on your last CNC do some other fancy operation? Reading through the entire thread you've not posted any data about how the machine is not performing at spec? Its hard to make any sense of any of it. Your machine was likely shipped with a more reasonable rapid in the Wincnc.ini (smart on their part). If you want to go in an dial it up to the max have at it. But as has been said, you'd better be on your game, and there with a stop watch, to run at those speeds. I run mine at 1200IPM rapids and its hair raising.