Professional machinists are involved in a highly competitive business. They need to eek out every drop of productivity they can. Recently on Practical Machinist, someone asked where to get the best feeds and speeds chart, which produced quite a bit of discussion from the readership. There’s a lot of wisdom on that board. One individual, who grinds and sells cutters for a living flat out said no such charts are possible because they don’t convey enough information. I agree, charts are limited to just a few variables while our G-Wizard Feeds and Speeds Calculator considers over 50 variables. It would take many pages of charts to convey the types of calculations it makes in chart form.
Here was the response I gave as a post:
I’m with CarbideBob.
To get good feeds and speeds, you need two things: a good calculator and calibration.
As some have said, the calculator will get you a starting point. It performs an even more important role though, which I’ll come back to in a second. First, let’s look at this idea of calibration.
Calibration means bringing the real world experience and data into the equations that the calculator uses. A feeds and speeds calculator…
2011 was a great year for G-Wizard sales, but 2012 has so far trumped it. Sales are off to a great start. We’re in spitting distance of being able to double our installed base, so we decided to enlist your aid in the process.
At some point in the second half of each month, we’ll take stock of how the month is going and whether we think we can achieve our goal of doubling the sales from the same month last year. Based on that assessment, we will offer a limited number of 15% off coupons you can use to purchase a 3 year subscription of G-Wizard. Just go to the G-Wizard purchase page, click the “Buy G-Wizard Now” button, and when you get to the shopping cart enter the “15OFF” in the coupon code. Be sure to choose the 3 year subscription. The offer is good whether you’re a new customer or just renewing your subscription.
There’s only a few of these coupons given each month and when they’re gone, they’re gone. If you miss out, you’ll have to wait and see whether the following month merits more coupons. For this month, we only need a few extra sales,…
Let’s assume you have a working CNC machine that you’ve just acquired, but that you know very little about CNC. Let’s further assume it is a mill and that you will primarily be focused on cutting metal. You’re probably ready to start milling custom chopper parts, build a tool changer, or maybe scratch build a Colt 1911 handgun. With CNC, you can build almost anything and you’re chomping at the bit to get started on your pet projects.
Not so fast! Remember, you just got the machine and you’re a beginner. You’re not ready for those projects yet.
Here are 10 things you should focus on to maximize your chances of becoming quickly successful:
1. Buy Some Decent Cutters
Don’t get the package of assorted sizes of imported Chinese cutters of indeterminate quality. You don’t need the solid green unobtanium aerospace cutters from Men-In-Black-Cutter-Supply, just get some decent cutters from a reliable source that has reasonable prices like Maritool.com. Try for a name brand, perhaps one that’s on sale at a supplier like Enco. Knowing you have a reasonable cutter eliminates a whole bunch of variables that govern your…
I’m in the middle of painting panels for the flood enclosure I’m building for my mill and wanted to pass along a mini-review of the Harbor Freight HVLP spray guns I’ve tried. I started with them more expensive one they sell, #93305:
Not such good luck with #93305…
To be honest, I didn’t have very good luck with the 93305 model. Seems like no amount of adjustment would prevent it from working fine for a little while and eventually spattering to much paint out the nozzle which dripped down all over everything. I followed the instructions, I Googled the heck out of other’s instructions, all to no avail. This model pressurizes the paint can, and I’m convinced it’s pressure regulator that sits on top of the can was defective in some way and too much pressure was forcing too much paint through the system. My unit was also older than the one pictured and had a metal gun instead of what looks like blue plastic in that picture. Steer clear of this model!
A quick order early in the week landed me another model to play with for the weekend. This was the #94572, which includes two gravity-fed guns (no…
Release 1.630 is a minor feature release:
– We’ve added buttons so you can go to the correct web page to Purchase G-Wizard as your trial is running out or to renew your subscription if it is running out. It’s also easy to see how many days are left on your trial or subscription as they draw to a close.
– Added a button to the “Search KB” popup to show all entries.
– Re-evaluated the Rougher Endmill performance and upped the feedrates for it.
– Added 4 user-defineable fields to the Tool Crib so you can track extra information of your own choosing. One customer wanted this to be able to track the quantity of particular cutters he had on hand. To use it, click the “Optimize” button and you can name the fields. All cribs use the same field names. The 4 fields are scrolled all the way to the right.
– Cleaned up some rounding issues for the Bolt Circle calculator.
– Fixed a bug in tool deflection calculations where we had assumed the body of indexable tooling was made of carbide instead of steel.
– Fixed a problem with CSV exports of Tool Cribs and CutKB.…
Starting the week between Christmas and New Year’s, CNCCookbook began doing quite a few transformations to give the site an overall facelift. We revamped our menus and merged the WordPress blog into the main site (it had been a separate site during most of 2011). In addition, we’ve redoubled our efforts to publish more quality content. The results have been rewarding as our traffic is way up. I’m pleased to announce we now receive well over 1 million visits per year, and that we have over 10,000 of you on our mailing list. For comparison, our traffic during January 2011 was 58,000 visitors versus 104,000 in January 2012–a 79% growth rate.
That’s quite an accomplishment, and we’re very proud of it.
For comparison, here are some measures of annual unique visitors by Compete.com:
Compete works by sampling an audience of 2 million to see which web sites they visit. It’s a pretty large audience, but the numbers are more representative of relative volumes than actual volumes. Nevertheless, we can see that CNCCookbook is moving up through the ranks of machining websites quite nicely.
I like to use larger pictures (the site’s standard is 800 wide) so you can see the details. People these days have larger screens too, except when they’re on an iPad or something similar. When I did the update to our blog recently, I used a WordPress theme called “Boldy” that is a fixed width theme, and it is optimized for 1024×768 screens. Because of that, a lot of the photos were getting cut off on one side. So, I spent a few hours today rewhacking the theme to produce a variable width version that can expand to fill a larger screen.
Ahhhhhhh. More elbow room!
This new variable width version doesn’t have everything just right yet, so I will probably tweak on it some more, but I decided it was worth rolling out. Besides, I need it for the post on Vacuum Tables that follows!…
I’ve been interested off and on in vacuum fixturing for quite a while. My brother is in the design stage of a big CNC router table, and wants to build in a vacuum table capability. I had been dimly aware that it is also applicable to CNC milling operations on metal, but hadn’t really delved into it too much. Then I came across a great article showing how to build a vacuum table over on the MicroSystemsGeorgia web site and it was the impetus for several hours spent researching this method of fixturing.
Here is the table design by Chris Kokourek that got me going:
Here is the vacuum table mounted on the VMC table. That outside groove was done with a 1/8″ ballnose and is used to hold rubber cord that seals the edge. The round vacuum ports are milled 1/16″ deep and each one has a hole in the center leading to the passages behind…
Here is the vacuum pump. It takes compressed air (20 CFM) and uses a venturi to generate the vacuum. In addition, it tries to silence the noise a bit. Not cheap, but some of these are available on eBay!
Here are the air…
“Corncob” Roughers are endmills that have serrations on the flutes to help break up the chips. You’ve probably wondered what the advantages are for these, so I thought I’d put together a post and talk about them a bit. These roughing endmills are only useful for roughing as the serrations leave tracks on any walls machined on the workpiece. So, unless you don’t care about those tracks, you’re going to need to put up with a toolchange to a finishing endmill and another pass to finish your part. Because of these extra steps, it’s reasonable to wonder about the value of these endmills.
What do they do that regular endmills don’t? There are at least two strong benefits to these endmills.
Their first advantage is that they often seem to minimize chatter. If you’re hogging hard and getting chatter, try one and see if it doesn’t go away. The configuration of the teeth with the serrations changes the characteristics of the vibration and can often move the frequency out of the critical zone for chatter. For more about these sorts of effects, see our Feeds and Speeds Cookbook chapter on chatter.
The second advantage for these roughers is they can…
Let’s start out by saying this article is not about troubleshooting a machine that isn’t performing correctly. There are cases where seemingly innocuous commands to a properly set up and adjusted CNC machine do not result in the moves that were commanded.
How can that be possible?
The short answer is that this is caused because there are many approximations and assumptions made every step of the way from your conception, to CAD drawing, to CAM program, to G-Code, to Trajectory Planning in the Controller, to the Servos or Steppers driving the axis, to the leadscrew and other components driving the table, and so on. There are various techniques that are used to minimize these errors, but it is useful to be aware of their sources, so let’s look at a few of them. This diagram includes a few examples of each:
Sources of CNC Position Error…
From Conception to CAD File: CAD Errors
In your mind’s eye, you see a very pure shape. Circles, cylinders, smoothly flowing lines, all with infinite precision. The CAD program has to render these notions with more limited means. Perhaps it can only represent lines, and hence arcs and circles become a series of…
If you’ve been reading our blog for very long, you’ll know we’re fans of John Grimsmo’s knifemaking videos. In them he uses a little hobby mill to make custom parts for knives, which he sells to collectors. There is a lot of fascinating and useful information in them, but beyond that, they’re just fun to watch if you have a few minutes and any interest at all in knifemaking. Here is John’s latest video which covers a variety of topics:
In this video he’s working with some Swedish stainless that is well thought of for making knife blades called “RWL34″. The blade design itself is interesting, and John works through a couple of problems he encountered working this tough material, including breaking an endmill due to excessive deflection. He uses G-Wizard to figure out how to reduce his depth of cut to keep deflection within allowable limits and shows all of this in the video. It’s a pretty long video (over half an hour), but he has a lot of detail to show folks about how he approaches his work.
Given how expensive good cutters can be, a tool like G-Wizard can pay for itself pretty quickly if it helps…
This is an amazing project and video I saw recently on Hoss’s 3D Printer thread over on CNCZone:
3D printing an alien skull in high resolution…
There’s not a lot of information available about how this printer works, but there is a blog with some interesting pictures:
Whistle done in typical RepRap melted filament style…
A whistle done in 50 micron resolution with this high resolution 3D printer…
A ball 3D printed in high resolution…
As you can see, the resolution with this technique is much much higher than the typical hobby-class melted filament 3D printers like RepRap.
Apparently the process involves photo-reactive resin (resin that is cured by light), and they use DLP projectors to create the layers one 2D slice at a time. Imagine a glass-bottomed tank full of resin, and a glass plate on the Z-axis where a normal mill’s spindle would be. Lower the plate to the bottom of the tank and project an image of the 2D slice onto the bottom of it through the bottom of the thank. The resin is cured by the light, and it takes 5-10 seconds for the layer to harden. Move the head up by the layer thickness (50…
Tired of cutting air to see whether your g-code program is going to work?
We just added a new chapter to our G-Code Tutorial that shows how you can use a G-Code Simulator like G-Wizard Editor to help diagnose your part programs.
Lots of good info there about what a good g-code simulator can do for you. If you haven’t already signed up for the free G-Wizard Editor/Simulator Beta Test, now is your chance. Sign up and then use GWE to go through our G-Code course.…
One secret to productivity on the mill is to use as much of the envelope as you can. The more parts you pack onto the table, the more it can get done without assistance while you work on something else. When it comes time to pack a bunch of small parts on, the ubiquitous vise is not the right tool. Instead, consider something more like this shopmade pallet system as seen over on Practical Machinist:
16 parts all neatly held by Mitee-Bite’s “Pit Bull” clamps…
The Mitee-Bite Pitbull’s have a sharp edge that jams the part against a stop on the other side as you tighten the socket head. They’re prefect for this kind of work. Mitee Bite offers a whole line of different edge clamping products worth checking out.
This particular fixture is also part of a shopmade pallet system. A pallet is an interchangeable plate. There is a base mounted on the table, and one or more of the pallets. By using pallets, you can drop a bunch of parts on the mill table, machine them, and them remove them all as a unit. Putting parts on or off the pallet can be done while the machine is…
Here’s a great video from the Eclectic Angler showing his fixture for making the side plates for a fly fishing reel:
Love the use of the toggles to make it easy to pop a new workpiece into place. Note also the pins that position the workpiece at the top and left before the toggles are applied. Ideally, you’d like to use a combination of pins that does not “over constrain” the part. Ideally, that would mean two pins at the top and one on the left.
Because the three pins at the top over constrain the top edge. It only takes 2 points to identify a line, and he’s using three. Two points at the top and one point on the left would be the ideal way to build a fixture like this, but his is working extremely well as you’ll see from the video.
Check out the Eclectic Angler’s site: some very nice reels if you like fly fishing. He even sells books if you have a desire to build your own reels.
Disclosure: Michael is a G-Wizard customer.…