Need help understanding spindle specs

[Chelmite]

I have a shopbot desktop with an HSD spindle.

The spec plate has two sets of numbers for the HP for 3 sets of speeds:

For example for 200 Hz /12K rpm:
hp 0.88(1.15)

What are the two hp numbers?

Thanks,
Chelmite

[Brady Watson]

1.15 hp = @ .86 Kw

-B

[Chelmite]

Here's the full table:


V(+-10%) 220 220 220
Hz 200 250 300
rpm 12000 15000 18000
kW 0.65(0.85) 0.65(0.85) 0.50(0.60)
Hp 0.88(1.15) 0.88(1.15) 0.74(0.97)
A 3.2(4.2) 3.2(4.2) 2.6(3.4)

So, I get that there are two sub-columns for 200Hz, but what distinguishes the two sub-columns? I can't choose 3.2A over 4.2A, can I? Does the difference have something to do with 60Hz vs 50Hz for the power main? If so, which column is which?

Thanks

[Brady Watson]

Yes, I believe that is a 50/60Hz (line input freq) difference between the numbers.

What number does the VFD display when you crank the speed dial all the way to the right? 250? 15000?

-B

[Chelmite]

It says F300 when cranked up fully.
So, if that's for 50/60Hz, which number is for 60Hz, the number in parentheses or the number outside the parentheses?

[ssflyer]

Damn, I have to look it up. There is a setting in the vfd to display rpm...

[adrianm]

From the docs it looks like each 100 on the desktop display is 6000rpm so F300 should equate to 18,000 rpm which sounds about right as the maximum speed of the spindle to me.

[scottp55]

I keep this right next to spindle.

[Chelmite]

I get the relationship between the Fnnn display and the rpm (multiply by 60). What's the difference between the numbers on the spec plate that are inside parentheses and the number in front of the parentheses? (See table above.)

[Brady Watson]

F300 should equate to 18,000 rpm which sounds about right as the maximum speed of the spindle to me.

Yes - It is...18,000 Max. Ignore the nameplate on the spindle, which says 200Hz etc. This was a small oversight since that little spindle is used in other applications where for safety reasons, the RPM needs to be limited/de-rated to 12,000 RPM max. It is good to 18k so no worries.

-B

[Roy Harding]

For the MOST part, I set the spindle speed at 12K (200 on the dial), and adjust X/Y movement speeds for the individual bits appropriately.

I found that I'd often forget to change speeds when I changed bits - but having the appropriate X/Y speed in the tool database meant that I never push a bit to the breaking point.

[Chelmite]

Hi. Does anyone have an answer to my original question? For a given RPM (12000, 15000, or 18000) what is the HP of my spindle according to the specs on the side of the spindle? E.g., for 12000 rpm (F=200), the spindle label says 0.88(1.15). So, is the HP 0.88 or 1.15?

I'm trying to input the HP/rpm curve in to GWizard to compute the speeds & feeds for my bits & mills. When I assumed that the HP was 1.0 across all speeds, the ShopBot head ended up stalling while it was cutting in the X direction and losing track of where it was. Thinking that it was at X=1.0" when it was really at X=15", the ShopBot then cut through the middle of my workpiece instead of the left-hand edge of the design. I've heard that the problem is using the wrong HP in the speeds & feeds.

[adrianm]

Best to call ShopBot directly for something like that I would think.

Are you sure it's HP you want? I would have thought the torque curve across the RPM range would be more useful.

I've never needed to know the HP or torque of my spindle to work out the correct feed rate. RPM's and chipload is enough.

Are you cutting metal?

[scottp55]

Steve, Admit I'm a newbie(3 months) to the Desktop but confused how feeds and speeds would have anything to do with location unless you're pushing so hard it's missing steps(hasn't happened to me yet). Was unfamiliar with gwizard but after watching their blurb still don't understand how that would affect it. What are you cutting,with what,and what are your settings?

[Brady Watson]

Hi. Does anyone have an answer to my original question? For a given RPM (12000, 15000, or 18000) what is the HP of my spindle according to the specs on the side of the spindle? E.g., for 12000 rpm (F=200), the spindle label says 0.88(1.15). So, is the HP 0.88 or 1.15?

I'm trying to input the HP/rpm curve in to GWizard to compute the speeds & feeds for my bits & mills. When I assumed that the HP was 1.0 across all speeds, the ShopBot head ended up stalling while it was cutting in the X direction and losing track of where it was. Thinking that it was at X=1.0" when it was really at X=15", the ShopBot then cut through the middle of my workpiece instead of the left-hand edge of the design. I've heard that the problem is using the wrong HP in the speeds & feeds.

0.88 hp.

As Adrian mentioned, hp is generally not part of the chipload calculation - Only move speed & RPM are really pertinent - and depth of cut.

My advice would be to put the chipload calc away until you can get the tool cutting without using it. It is very difficult to adhere to recommended chiploads for various reasons, such as inadequate hold down to resist cutting forces, the design is very convoluted with a lot of starts & stops around turns etc. Chipload values are for production - in order to maximize tool life. If you aren't doing production, it is of little use.

If you are cutting aluminum, you should be using a single flute spiral-o upcut bit @ 1.2XY and 13,000 RPM as a baseline. If cutting wood, a good general speed would be 1.5 to 2 inches per second XY, and 13,000-15,000 RPM. If you are burning - reduce RPM or increase feed rate. If it is bogging down or stalling, then slow down feed rate or increase RPM.

LISTEN TO THE TOOL - and adjust accordingly. This will make you a way better machinist/operator than plugging in numbers from some calculator.

-B

[Chelmite]

HP matters because, if you calculate a theoretical rpm and feed rate for your bit, and your spindle doesn't have the power to make the cut, the spindle will stall. I'm not running production, but, if I can get the SB to finish a step in 1 hour instead of 3 hours, I consider that a win. I don't know what you guys do when a job takes more than 20 minutes. I can watch for only so long before I get bored, and I don't want to leave the machine in case something goes wrong.

I'm cutting wood. Did I "LISTEN TO THE TOOL"? Of course. But by then it's too late, because it's cutting the workpiece. I listened to the bit as it was cutting. It sounded way different as it stalled and then tore through my workpiece. I stopped it 3 inches into its detour. Fortunately, nobody was listening to ME when the SB cut through the middle of my nicely routed workpiece. Anyone listening to me would have been able to tell that I was not pleased. (3 of the steps, with different tools, speeds, & feeds worked beautifully. The 4th step, that should have been a trivial outline for the design ended up trashing the work.)

I use a feed & speed calculator so that I get the maximum throughput without hurting the work or my tools. But, the feeds & speeds calculator is only as good as the data given to it. Without the proper HP at the different r's per m, it used the (Marketing) HP (1Hp) as the limit, which I now know it can't achieve. I was running the tool at the theoretical speed of 18,000 rpm and feed rate of 240 ipm, assuming it had 1 HP to back it up, when in reality, at that rpm, it's only 3/4 HP.
(See http://blog.cnccookbook.com/2011/11/01/taming-an-unruly-spindle-power-curve-with-g-wizard/ for more discussion.)

By the way, bradywatson's terse answer of "0.88 hp" didn't really answer the question, because (a) it didn't explain the difference between the spec'd numbers inside and outside the parentheses, (b) a previous answer hinted that the difference between these two spec numbers had something to do with the line supply frequency, but didn't say whether this was substantiated, or which number was for the 60Hz supply. I now realize that in my question "the spindle label says 0.88(1.15). So, is the HP 0.88 or 1.15?" I failed to say what line frequency I was using. It's 60Hz.

[Brady Watson]

A number of experienced users have given you valuable advice.

If your idea of gratitude is attitude, then I don't think you are going to get much more help.

-B

[bleeth]

10-4 bw........

[Roy Harding]

H... I can watch for only so long before I get bored, and I don't want to leave the machine in case something goes wrong.

I'm cutting wood. ...

I was the same way at first. Once I got used to it, though - I carry on around the shop doing other tasks while the ShopBot does its' thing. I bought the thing to save me time - and no time is saved if I'm standing there staring at it.

[bleeth]

Once you get used to it doing it's thing it's like watching paint dry.If you're spending the time it's cutting watching it every second you are missing the whole point of owning it. While it works, you should be doing other work, therefore increasing productivity, not just ability.

[Chelmite]

I'm sorry. I didn't intend to offend. I've been trying to get an answer to my question for 3 days, so I tried refining the question. I tried to point out what info I was needing and made constructive suggestions about what was lacking. Asking clarifying questions is not attitude. It shows that I care about the answer and respect the person enough ask him for information.

Then it turned into a discussion. Discussions are great. We all contribute something and all get something out of it. I documented my info source on HP & speeds to help others and show that I'm not just making this stuff up.

At no time did I put down anyone, other than make a joke at my own expense. Sometimes the humor is lost in the land of text. I didn't mean it to be offensive.

[adrianm]

What type of wood are you cutting? What pass depths? What type of tool?

240ipm seems very high for a desktop to me. As far as I know that's as fast as a desktop can move so you're right on the limit. I wouldn't push my PRS Alpha with a 2.2hp spindle that fast in a lot of materials.

The CNCCookBook articles are aimed more at machining metal than they are at wood users. Nearly all of the variables they mention just confuse the issue.

With wood just start slow and start upping the speed until the finish deteriorates or some part of the machine starts to struggle. You're then in the ballpark and you can fine tune from there.

Bear in mind that atmospheric conditions, different batches of the same type of wood and the newness of the cutting tool used will all effect the speeds you need to use.

That's where using your ears comes into as Brady said. As those variables I mentioned change you'll hear the cutter struggling or even under working and you'll be able to adjust for the situation.

It's not an exact science where you can type in a bunch of figures and it will tell you exactly what you need to do. It's a learning process between you, the type of work you want to do and what your machine is capable of.

[scottp55]

Steve, I very much agree with Adrian on you maybe pushing the envelope to much. We are doing prototypes that are being passed around New England so quality is most important and finishing is very time consuming compared to cutting. I can run faster than I do, but I'll have to run the piece twice because of the finish and bit deflection and I'd rather run it once slow than twice fast. Always check your bit temp after a new wood or cut(should be room temp). Mainly cutting sugar maple ,but out of our 20 bits very few like faster than 1.7 IPS and most do best in the 1.1-1.5 IPS range(most of our bits smaller than .2") and none like faster than 16K. Fastest is 3 IPS for surfacing routine at 12K. Run the same routine again and you can hear how much bit deflection you are getting. Again watch your depth of cut.
When running a new wood or new bit that is significantly different than anything you've done before and you're worried, I've found the people here on the forum very helpful(do a search first, as I've found most of my questions have already been covered-A google search is sometimes more helpful finding stuff than a forum search). At some point you WILL need the people here. I've seen 2 guys stall my Unisaw(hop hornbeam slab), that doesn't make it a bad machine. I do recommend you lose the gwizard for a couple months. I hope any of this was helpful, I ramble, Brady is succinct and VERY pertinent, Different styles. scott