[mactec54]

Hi Quinn - I'm interested why you have used 7075. My experience of the stuff is that it will slowly turn to white powder unless you anodise it? Peter

You must have so really bad 7075 if that was happening ( High copper content ) and mixed it with other materials ( Fasteners Etc ) that causes Galvanic Corrosion

For general use 7075 is very good to use for structural parts

[QuinnSjoblom]

Hi Quinn - I'm interested why you have used 7075. My experience of the stuff is that it will slowly turn to white powder unless you anodise it? Peter

Yeah I've never seen it do that either. I chose 7075 because it is almost twice as rigid as 6061. Comparable to some mild steels, still easy to machine.

[mactec54]

Couple pics attached below

Almost ready to test the first version. Had to get a bit tricky with the servo mounting to get the clearance i want in the front end. Servo is mounted with the backside of the flange. Otherwise it would have stuck out past the spindle nose, which could have worked but would have limited turning tool mounting options. It's still quite stout as it is. All 7075 aluminum. Base plate and main vertical plate is 7/8 thick and 5/8 thick corner supports. I designed a simple brake assembly that tightens with a bolt but it's not assembled yet. It's purpose is just to compare surface finish with spindke locked vs unlocked. If the finish is significantly better with the spindle locked, I will probably redesign with narrower belt and actuated disk brake. This design is currently using the huge 50mm wide belt. The spindle headstock is mounted into a matching pocket that allows 15mm of lateral movement while keeping it coplanar with servo for tensioning the belt. There is a single bolt that is turned to pull the spindle over to set tension, then tighten the 4 bolts to secure it. Haven't powered up the servo yet, but I did get the tension set and turned it at about 2k rpm using a drill. Not hearing the loud popping noise that was mentioned earlier. It's very smooth and quiet. I don't think the large belt is gonna cause any issues. Should have it fired up this weekend, just waiting for line reactor, filter, and contactor to show up. This things is quite the chunk. About 80 pounds total. Not easy to pick up.

You don't get popping noises with GT series belts they have an involute tooth design almost the same as Gears and any air can escape

[QuinnSjoblom]

You don't get popping noises with GT series belts they have an involute tooth design almost the same as Gears and any air can escape

Ok, that's good. All i could hear when spinning it up was the drill itself.
It also seems that I have the tracking of the pulleys pretty dead on. The 50mm pulleys are about 4mm wider than the belt. When getting the belt centered and spinning it up, it takes a while for the belt to wander over to the pulley flange on one side

[hanermo]

Quinn .. lemme add my observations ..
as I have actually done this, and am using this, on my Mach3 lathe.

30 mm wide, HTD8 belt.
Extremely stiff mount, 20 mm thick tool steel plates, 30x30 mm tool steel posts.
Mount == 40 kg in mass.

2.5 kW ac servo spindle, cont, 220V ac, 10.000 counts, 3000 rpm, 500 kHz, s/dir.
10 Nm cont, 30 Nm peak.

1:3 via HTD taperlock pulleys, resulting 3000 rpm at servo to 1000 rpm at spindle.
CSMIO-IP-S controller, 4 Mhz.

30.000 counts/rev at spindle, == 0.01+ degrees.

The very heavy, very strong, very rigid mount, belt drive is useless for a c axis.
The belt drive absolutely cannot hold position for anything real-work causing torque.

The haas c axis lathes have a specific gear at the spindle, engaged via a separate mechanism and drive system.
These c-axis gears are ground to hopefully agme-9 standards, I have met the guy who sold the gear grinder to Haas in 2012 in germany (EMO trade fair).
9M$ for grinder.

I don´t know what I will do, one option is electromagnetic clutch to a flat plate at spindle.
Or bored detents in drive plate.
Drive via gearing of 2 preloaded gears.

[QuinnSjoblom]

Quinn .. lemme add my observations ..
as I have actually done this, and am using this, on my Mach3 lathe.

30 mm wide, HTD8 belt.
Extremely stiff mount, 20 mm thick tool steel plates, 30x30 mm tool steel posts.
Mount == 40 kg in mass.

2.5 kW ac servo spindle, cont, 220V ac, 10.000 counts, 3000 rpm, 500 kHz, s/dir.
10 Nm cont, 30 Nm peak.

1:3 via HTD taperlock pulleys, resulting 3000 rpm at servo to 1000 rpm at spindle.
CSMIO-IP-S controller, 4 Mhz.

30.000 counts/rev at spindle, == 0.01+ degrees.

The very heavy, very strong, very rigid mount, belt drive is useless for a c axis.
The belt drive absolutely cannot hold position for anything real-work causing torque.

The haas c axis lathes have a specific gear at the spindle, engaged via a separate mechanism and drive system.
These c-axis gears are ground to hopefully agme-9 standards, I have met the guy who sold the gear grinder to Haas in 2012 in germany (EMO trade fair).
9M$ for grinder.

I don´t know what I will do, one option is electromagnetic clutch to a flat plate at spindle.
Or bored detents in drive plate.
Drive via gearing of 2 preloaded gears.

Yes, it's very possible I'll have to add a brake which will require redesigning the vertical plate, but at this point I'll only be out about 50 bucks in material if i have to redesign so I'm gonna go ahead and test it how it is just to see what happens.

You mention you used htd pulleys and belts. From the research I've done, htd is good for torque handling capability, but it has far more backlash than the gt3 profile and not really optimal for accurate positioning. Not to say my gt3 setup is going to be sufficient without a brake, but I do think you would see an improvement with gt3 vs htd. Or did you mean gt pulleys? To be specific, they are referred to as powergrip gt2 sprockets and paired with newest generation gt3 belts. Powergrip htd is a different profile with more backlash.

[Jim Dawson]

Thank you for posting your experience hanermo.

I am going through the same thought process as Quinn for my lathe. The main difference is that I currently have a V-belt spindle drive, an encoder directly driven by the spindle, and a disk brake. The system currently is driven by a non-servo spindle motor/VFD combination, so no indexing capability. I have live tooling so I can do single position milling and two hole face drilling as long as no other clocking is required, but no possibility of doing any simultaneous 3 axis work or multi-hole patterns. The system works fine for rigid tapping and single point threading.

I intend to change this.

It seems that my best options are:

1) Install a 7.5KW servo motor, or

2) Install a separate indexing servo (~1.8KW) and electromagnetic clutch system.

In either case, the spindle position would controlled by the spindle encoder rather than any internal servo encoder. But a belt drive system would have to be maintained.

But, based on your experience using a timing belt drive, you are causing me to re-think this plan. It sounds like I need a more rigid coupling between the servo and the spindle. So the options there would seem to be a zero backlash gear system like the Haas, or a direct drive hollow shaft servo directly coupled to the spindle. I wonder how the big horizontal mill/turn machining centers drive their spindle(s).

Just some random thoughts

[QuinnSjoblom]

I should know pretty soon how well it's going to work with just a belt and no brake. It just might work out for me since im only milling aluminum. Just have to try and see.
I still maintain the idea that if there's rigidity problem associated with the belt, a wider belt should improve the situation by spreading the load across more tooth area, reducing tooth deflection as well as belt stretch. A 50mm belt should theoretically allow only 60% of the deflection a 30mm belt would in terms of tooth deflection and stretch. The backlash is a separate variable that doesn't change. Also I believe the tooth profile is pretty important. Gt3 is about the best you can do for this application according to the gates guy I talked to.
Last night I checked one other thing on my setup just out of curiosity. I locked the servo pulley in place using a clamp and put an indicator on the spindle with it reading on a notch on the spindle nose. When twisting back and forth on the spindle pulley by hand as hard as I could, i could see basically no movement on the dial, maybe a tenth. Not a very scientific test, but it does SEEM to be a pretty damn rigid link between the 2 pulleys.
The rest of my electronics show up today so it won't be long before it gets a real test. Havent started with lathe tooling setup yet but ill be able to test index milling.

[mjoconr]

As best as I can see nobody has mentioned using a VFD, encoder and a 3 phase induction motor. A lot of VFD's now days are able to do position control and have 200% torque at 0 RPM. They can also get very high speeds, as example the 600hz Yaskawa VFD can get a 4 pole 3 phase motor to 24,000 rpm.

The motion control is not a good as a servo but if only doing 3+1 then thats not as issue as it will stop at the correct place, but as a spindle it can not be beat.
The Omron VFDs do not go as high only 400hz so the top end is not a good but they are amazingly cheap and still great quality.

Just an idea.

[peteeng]

Hi Quinn - It is not twice as rigid as 6061. Modulus of 6061 is 69GPa, 7000 series is 72GPa. Sorry no where near steel at 200GP. Trivia - 7075 was developed in secret by the Japanese in second world war for their aircraft. Peter

[QuinnSjoblom]

Hi Quinn - It is not twice as rigid as 6061. Modulus of 6061 is 69GPa, 7000 series is 72GPa. Sorry no where near steel at 200GP. Trivia - 7075 was developed in secret by the Japanese in second world war for their aircraft. Peter

Twice as rigid was the wrong choice of words. Tensile strength of 7075 is nearly double that of 6061, comparable to mild steel. I much prefer it over 6061 when I can find drops on ebay for cheap. For me it actually machines easier than 6061. Never chip welds like 6061. I've never seen the white powder you speak of. I use it exclusively on large rc helicopter airframes. Polishes beautifully and I have parts from a couple years that still have a very nice looking finish. very strong, good abrasion resistance, much harder to strip threads. Pretty great stuff in my opinion.

[peteeng]

Hi Quinn - Thanks for clarification. Agree on all points. I had a piece of 7075 tooling plate about 500mmx100x100mm in a corner of my shed once and watched it slowly disappear into dust over a period of 2 years. What temper do you use? Are you near a coast? That maybe it. It gets used a bit on racing yachts and any stray current will turn it into sponge as well in the marine environment. UTS and YS well above mild steel. Peter

[QuinnSjoblom]

Hi Quinn - Thanks for clarification. Agree on all points. I had a piece of 7075 tooling plate about 500mmx100x100mm in a corner of my shed once and watched it slowly disappear into dust over a period of 2 years. What temper do you use? Are you near a coast? That maybe it. It gets used a bit on racing yachts and any stray current will turn it into sponge as well in the marine environment. UTS and YS well above mild steel. Peter

No saltwater near me here in montana, So im sure that helps. I use mostly fortal drops that I get for a couple bucks a pound. I believe it's t651. The chunks that I just bought for the mill turn were something else i found on ebay. I could see the 7075 markings but not the temper.

[mactec54]

Hi Quinn - Thanks for clarification. Agree on all points. I had a piece of 7075 tooling plate about 500mmx100x100mm in a corner of my shed once and watched it slowly disappear into dust over a period of 2 years. What temper do you use? Are you near a coast? That maybe it. It gets used a bit on racing yachts and any stray current will turn it into sponge as well in the marine environment. UTS and YS well above mild steel. Peter

Must of had some toxics stuff in your shed for it to do that here is some good information on different aluminum

2024
This is one of the best known of the high strength aluminum alloys. With its high strength and excellent fatigue resistance, it is used to advantage on structures and parts where good strength-to-weight ratio is desired. It is readily machined to a high finish. It is readily formed in the annealed condition and may be subsequently heat treated. Arc or gas welding is generally not recommended, although this alloy may be spot, seam or flash welded. Since corrosion resistance is relatively low, 2024 is commonly used with an anodized finish or in clad form (“Alclad”) with a thin surface layer of high purity aluminum. Applications: aircraft structural components, aircraft fittings, hardware, truck wheels and parts for the transportation industry.

6061
This is the least expensive and most versatile of the heat-treatable aluminum alloys. It has most of the good qualities of aluminum. It offers a range of good mechanical properties and good corrosion resistance. It can be fabricated by most of the commonly used techniques. In the annealed condition it has good workability. In the T4 condition fairly severe forming operations may be accomplished. The full T6 properties may be obtained by artificial aging. It is welded by all methods and can be furnace brazed. It is available in the clad form (“Alclad”) with a thin surface layer of high purity aluminum to improve both appearance and corrosion resistance. Applications: This grade is used for a wide variety of products and applications from truck bodies and frames to screw machine parts and structural components. 6061 is used where appearance and better corrosion resistance with good strength are required.

6063
This grade is commonly referred to as the architectural alloy. It was developed as an extrusion alloy with relatively high tensile properties, excellent finishing characteristics and a high degree of resistance to corrosion. This alloy is most often found in various interior and exterior architectural applications, such as windows, doors, store fronts and assorted trim items. It is the alloy best suited for anodizing applications - either plain or in a variety of colors.

7075
This is one of the highest strength aluminum alloys available. Its strength-to weight ratio is excellent and it is ideally used for highly stressed parts. It may be formed in the annealed condition and subsequently heat treated. Spot or flash welding can be used, although arc and gas welding are not recommended. It is available in the clad (“Alclad”) form to improve the corrosion resistance with the over-all high strength being only moderately affected. Applications: Used where highest strength is needed.

ALUMINUM ALLOY DESIGNATIONS
The aluminum industry uses a four-digit index system for the designation of its wrought aluminum alloys.
As outlined below, the first digit indicates the alloy group according to the major alloying elements.
1xxx Series
In this group. minimum aluminum content is 99%. and there is no major alloying element.
The second digit indicates modifications in impurity limits. If the second digit is zero, there is no special control on individual impurities. Digits 1 through 9, which are assigned consecutively as needed, indicate special control of one or more individual impurities.
The last two digits indicate specific minimum aluminum content. Although the absolute minimum aluminum content in this group is 99% the minimum for certain grades is higher than 99%, and the last two digits represent the hundredths of a per cent over 99.
Thus, 1030 would indicate 99.30% minimum aluminum. without special control on individual impurities. The designations 1130, 1230, 1330, etc.. indicate the same purity with special control on one or more impurities. Likewise. 1100 indicates minimum aluminum content of 99.00% with individual impurity control.
2xxx through 9xxx Series
The major alloying elements are indicated by the first digit, as follows:
2xxx Copper
3xxx Manganese
4xxx Silicon
5xxx Magnesium
6xxx Magnesium and silicon
7xxx Zinc
8xxx Other element
9xxx Unused series
The second digit indicates alloy modification. If the second digit is zero. it indicates the original alloy: digits 1 through 9, which are assigned consecutively, indicate alloy modifications. The last two digits have no special significance, serving only to identify the different alloys in the group.
Experimental Alloys
Experimental alloys are designated according to the four digit system, but they are prefixed by the letter X. The prefix is dropped when the alloy becomes standard. During development, and before they are designated as experimental, new alloys are identified by serial numbers assigned by their originators. Use of the serial number is discontinued when the X number is assigned.
ALUMINUM TEMPER DESIGNATIONS
Temper designations of wrought aluminum alloys consist of suffixes to the numeric alloy designations. For example, in 3003-H14, 3003 denotes the alloy and “H14” denotes the temper, or degree of hardness. The temper designation also reveals the method by which the hardness was obtained. Temper designations differ between non heat-treatable alloys and heat-treatable alloys. and their meanings are given below:
Non Heat-Treatable Alloys
The letter “H” is always followed by 2 or 3 digits. The first digit indicates the particular method used to obtain the temper. as follows:
— Hl means strain hardened only.
— H2 means strain hardened, then partially annealed.
— H3 means strain hardened, then stabilized.
The temper is indicated by the second digit as follows:
2 1/4 hard
4 I/2 hard
6 3/4 hard
8 full hard
9 extra hard
Added digits indicate modification of standard practice.
Heat-Treatable Alloys
-F As fabricated
-O Annealed
-T Heat treated
The letter “T” is always followed by one or more digits. These digits indicate the method used to produce the stable tempers, as follows:
-T3 Solution heat treated, then cold worked.
-T351 Solution heat treated, stress-relieved stretched, then cold worked.
-T36 Solution heat treated, then cold worked (controlled).
-T4 Solution heat treated, then naturally aged.
-T451 Solution heat treated, then stress relieved stretched.
-T5 Artificially aged only.
-T6 Solution heat treated, then artificially aged.
-T61 Solution heat treated (boiling water quench), then artificially aged.
-T651 Solution heat treated, stress-relieved stretched, then artificially aged (precipitation heat treatment).
-T652 Solution heat treated, stress relieved by compression. then artificially aged.
-T7 Solution heat treated, then stabilized.
-T8 Solution heat treated, cold worked, then artificially aged.
-T81 Solution heat treated, cold worked (controlled), then artificially aged.
-T851 Solution heat treated, cold worked, stress-relieved stretched, then artificially aged.
-T9 Solution heat treated, artificially aged, then cold worked.
-T10 Artificially aged, then cold worked.
Added digits indicate modification of standard practice.


Test-a-Beam - Activity - STEM curriculum for K-12 - TeachEngineering
(Grades 6 - 8) ... (steel or aluminum) ... (Answer can be found under question 2 in Test-a-Beam Assessment Sample Answers) Post-Activity Assessment.

[mactec54]

No saltwater near me here in montana, So im sure that helps. I use mostly fortal drops that I get for a couple bucks a pound. I believe it's t651. The chunks that I just bought for the mill turn were something else i found on ebay. I could see the 7075 markings but not the temper.

Fortal is different from 7075 here are some spec's, if using coolant containing Chlorine or Sulphur then you can get a reaction on these material's

[QuinnSjoblom]

Fortal is different from 7075 here are some spec's

Yeah I've heard mixed opinions from different guys. Some say it's just a brand name and is essentially t651 7075, others say it's slightly different and actually slightly outperforms 7075, which is consistent with the attachment you just posted. Either way, great stuff and I love working with it. Makes excellent durable parts, and about as good as you get for machineability. I use mist coolant, but even cutting dry I can go at it with like 1200sfm and not chip weld endmills. Every time I have to mill 6061, I have to slow down and be carefull. If coolant stops, it's surely gonna chip weld

[peteeng]

Hi Mactec - Thanks for the summary. Nothing toxic in my shed. The summary left out transparent aluminium its E=334GPa so would be excellent to make machines from... Cheers Peter

[probinson]

Hi Mactec - Thanks for the summary. Nothing toxic in my shed. The summary left out transparent aluminium its E=334GPa so would be excellent to make machines from... Cheers Peter

Your shed floor is probably pressure treated plywood. Pressure treated lumber is infused with a copper salt like copper sulfate or copper azole. If you put aluminum in contact with pressure treated lumber, it becomes a self discharging battery and your aluminum goes away.

[peteeng]

Nope floor was concrete and the piece was leaning from the floor to the wall which was concrete. Some of the tooling 7000 alloys do this. It starts as alligatoring, the sides split and expand and escalates to white powder (uncoupled corrosion). I made custom bicycle cranks out of it some years before so I hope the cranks didn't go the same way. The company I bought it from makes plastic blow moulds like coca cola bottles from of it. They machine then polish and hard anodise their parts... Peter

[mactec54]

Nope floor was concrete and the piece was leaning from the floor to the wall which was concrete. Some of the tooling 7000 alloys do this. It starts as alligatoring, the sides split and expand and escalates to white powder (uncoupled corrosion). I made custom bicycle cranks out of it some years before so I hope the cranks didn't go the same way. The company I bought it from makes plastic blow moulds like coca cola bottles from of it. They machine then polish and hard anodise their parts... Peter

There had to be something that started the Galvanic reaction, it does not do that by it's self

7000 series does not anodize that well because of the copper content, the material you had may not of been 7075 if it was being used for plastic molds they normally make molds with Q10 or other brand name mold quality aluminum, although 7075 can be used for low volume plastic molds