Shop Holmes

[Duuuuuuuude]

I'm a little disappointed that there wasn't any drifting involved.

[JohnRobHolmes]

I've got traction with those rubber tires!

[Duuuuuuuude]

Then I'm a little disappointed there wasn't any tire smoke.

[JohnRobHolmes]

Maybe next time. This is actually a toy for my kid to ride in, not for me

[doublej]

A 1 link would be easier with the tight spaces. And less work.

[JohnRobHolmes]

We are now getting into the custom engraved bologna and hot dog market! After playing around with my little 3w lasers, I knew it was time to step it up to a 50w one. Not sure what to burn first!

[binaryterror]

Get a video of that in action! Those things are cool to watch.

[JohnRobHolmes]

How about a custom marked porksteak for now?

[JohnRobHolmes]

I was pondering milling and routing tonight and wanted to collect my thoughts.


When selecting a tool one must ask, "What am I trying to cut, and what is my max headspeed?" Those are the two first questions on tool geometry, although just going by manufacturers recommendations normally guides a tooling purchase. Once headspeed is set, the feed rate will determine chip loading. Chip loading must be enough that the tool is not rubbing, but not too much that the machine or tool cannot handle the load.


It has to be assumed that workholding and toolholding rigidity is taken into account, and it turns into more art than science when learning. Ive found my turning center can't mill as aggressively in aluminum, it isn't as stiff as a regular mill since it is designed primarily for lathing. By listening to the cut, inspecting the finish, and inspecting accuracy, the machine happy zone was found. Because of the maximum headspeed limit of the current live tools, higher flute counts have to be used to prevent tool breakage while getting decent production rates.


For CF and other composites on the mini mill or a gantry, a diamond pattern (aka roughers or double cut) solid carbide routers seem to give the best results. With a strong vacuum on the cut, the burr is a good workhorse- my current favorite with plunge cutting IMCO | SB-11 Cylindrical Shape End Cut Bur - 1/8" diameter - 1/4" shank - 1/2" loc - 2" oal - double cut . 1/8" size is my standard, and if no burrs are available I will grab an uncoated 4 flute and spin it as fast as possible. As long as the tool is kept cool it will stay sharp for a very long time. Freeze the panels in the deep freeze and cut cold for 2 to 3 times tool life increase. I was tipped onto this by another machinist and it works, the brittleness of cold makes the structure chip better. If we cut composites often I would build a gantry inside a deep freeze, supposedly if everything is cold the tool life and job speed can go through the roof. The limit is airflow to cool bit and pull swarf , and rpm to keep chip loading per rev proper as feed rate increases.



Conventional VS climb milling is also something to consider. The small taig is so flexible that I don't get advantages from climb milling unless it is merely a finish pass, and it is difficult to tell the difference. Machine flex changing the part size is more noticeable with climb milling. On the Mazak, finishes are easily noticeable as better with climb milling on the rough cut or finish cut. There is more material being removed on the Mazak, so the clean ejection of chips is more important.

[JohnRobHolmes]

Running tranny outputs the last few days. Tool life is getting better. Had my finishing insert last 2052 parts and over 100 minutes in the cut before it came loose and chipped. Shoulda gone through tools this morning and checked tightness since the machine temp cycled. Previously was feeling good to get 30 minutes from an insert.

We are learning that most tolerance drift is due to material temp this time of year. The bar and spindle runs about 100f today. Room temp is 83f. A room temp bar takes a few cuts to get stable, almost 0.001" drift. But if we let them sit in the sun and hit 100f it is equal to the last bar within 0.0001. Neat.


Gonna run these until Sunday and then it's time to swap to UAV and sensor d outrunner motor housings.

[JohnRobHolmes]

Bouncing between the lathe and laser today, my right hand man had to take off at noon so I get to double up. Four motors per output seems to be about right on timing. I shoot for a 0.0003" tolerance window on the output critical dims.

Lathe is making the first half of the regular scx10 tranny spool outdrive. Lightening is done in the second op.


Laser is etching a new trailmaster sport- 5000kv type

[BigSki]

I was at a training seminar today to get "up to speed" on the new 60v brushless outrunner motors that DeWALT will be using in an upcoming tool line. All I could think of was how long until you decide to build one for yourself!

[JohnRobHolmes]

I've had both drill and dremel tool designs for years, once we get some imbedded controllers finished it would be easy and cheap.

I've heard the outrunner dewalt is using is pretty sad compared to even hobby grade stuff. It's like a sealed can quality in brushless. Low grade mags, low grade lams, low copper fill, poor torque density. Maybe they have a high dollar version in the pipeline?

[Duuuuuuuude]

Originally Posted by JohnRobHolmes

I've heard the outrunner dewalt is using is pretty sad compared to even hobby grade stuff. It's like a sealed can quality in brushless. Low grade mags, low grade lams, low copper fill, poor torque density. Maybe they have a high dollar version in the pipeline?

Consumer grade blows goats.

[BigSki]

Originally Posted by JohnRobHolmes

I've had both drill and dremel tool designs for years, once we get some imbedded controllers finished it would be easy and cheap.

I've heard the outrunner dewalt is using is pretty sad compared to even hobby grade stuff. It's like a sealed can quality in brushless. Low grade mags, low grade lams, low copper fill, poor torque density. Maybe they have a high dollar version in the pipeline?

They have a few different versions of everything... The ones that I saw at the seminar looked to be of a good quality. As usual in commercial business, there's plenty of trade offs between quality of parts and profit margins. We had the chance to see some of the magnets, along with the test data in regards to the 'knee' area of the max load vs. demagnetization w/ different magnet types. They are using some of the Neodymium Iron Boron (NdFeB) magnets in the outrunner motors.

They did some testing with Samarium Cobalt (SmCo) magnets, but the cost put these out of reasonable usage for a consumer product. I'd personally love to see what you would come up with if they approached you to make a "healthy" motor.

[BigSki]

Originally Posted by JohnRobHolmes

I've had both drill and dremel tool designs for years, once we get some imbedded controllers finished it would be easy and cheap.

I've heard the outrunner dewalt is using is pretty sad compared to even hobby grade stuff. It's like a sealed can quality in brushless. Low grade mags, low grade lams, low copper fill, poor torque density. Maybe they have a high dollar version in the pipeline?

You have a great ability to explain difficult subject matter in a way that helps to clarify the data, can you explain the magnetic "flux" and how the 'tooth' on the end of the stator helps to channel it? I'm trying to get a better grip on the more technical side of things with motors. I get the very basic theory of the electromags propelling against the permanent mags.

[JohnRobHolmes]

The flux path is how the magnetic field works, the path it takes. It travels easier through steel as opposed to air, the shape of the stator affects how it focuses before crossing the air gap between magnet and tooth. It always wants to take the path of least resistance. You can imagine wanting to cross a cold creek with a bunch of friends, nobody wants to get into the water longer than needed. You will naturally all go to a spot where the other bank is closest before going across. This is the same as how flux will use the tooth shape to find the easiest path.


The tooth and magnet form a complete circuit. From north magnet into the stator, all the way back around to the south magnet. The north and south magnet also form a circuit together, so it is a complete circle of flux path.

The amount of steel, in terms of tooth width and back iron, is one choke on the amount of flux that the motor can handle. This makes natural sense, as more steel means more motor. It is a balance of copper and magnet too though, so you can't increase steel in a fixed volume without reducing something else. It becomes a balancing act that mostly depends on the quality of materials used.

[danielk]

I'd throw out my dremel 4000 for a HH rotary tool in a heartbeat. My 4000 has the shakes something fierce. The speed controller is crap and it's begun having startup issues. Bring on the HH Rotary!

[Robbob]

I could forsee everyones pit bench having a brushless HHremel sitting in a docking station with a chord connecting it to a control box with adjustable RPM........

Think soldering station but brushless dremel ......... hmmmmmm

[danielk]

Better idea. Make some better speed controllers for the battlebots competitors. Jeez, those guys toast em quick.
Better better idea. Do both.