Origin/consistency of chipload recommandations

(Jonathan Anderson) #54

That’s true, I forgot it has slotting, drilling, profiling, and adaptive milling strategies.

I have yet to figure out what parameters need to be changed to predict Shapeoko milling. Essentially, I don’t know what forces are acceptable to use as constraints. 5 lbs? 10 lbs? 15 lbs? Cutting forces are not something I can easily obtain nor know what might cause chatter.

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(Gerald Mackelburg) #55

Cutting forces can be estimated by measuring router/spindle input power increases when cutting. Force constraints are dictated by accuracy requirements (which is a function of machine torsional stiffness).

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(Luc) #56

Since this thread is to basically create a Shapeoko cookbook, I think that saying it can be calculated does not provide something useful in this case. This is so someone does not need to use a calculator with a million variables that are daunting for many users. As Jonathan said, should the unmodified Shapeoko 3 use 10lb or 15lb in the calculations? Would this be the same for an XL or XXL? How much could you increase if you had an HDZ modified?

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(Julien Heyman) #57

I think we agreed that the only thing we will realistically be able to determine is a set of reasonable starting points that are not out of the blue, and for me that’s already a big deal. I’m absorbing each small piece of wisdom that is left here, and will try to make a synthesis (if only for myself). Keep the comments/tricks coming !

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(Vince) #58

I haven’t heard anyone talk about tool sharpness. I’ve found hss tool to usually be sharper than lower cost carbide but that’s all by feel. This is one reason I never go under 0.001 for inserts.

Cookbook-
“Minimum chip thickness is 5-20% of the cutting edge radius. Below that level, chips will not form and the cutter will “plow” across the workpiece causing plastic deformation and considerable heat.”

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(Gerald Mackelburg) #59

You use cutters with inserts instead of endmills? Can you provide a source for your quote?

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(Vince) #60

https://www.buschmachinetool.com/milling-cutters

Two face mills for now but he was willing to make the APKT single insert in a 3/8.

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(Gerald Mackelburg) #61

So, your experience indicate that 0.001 IPT works well with inserts cutting aluminum (6061 T6?). BW says in the link that “Modern tools for aluminum are often much sharper, and can take less chip load. In general, indexable tools are less sharp than endmills, so they need higher chip loads.” What does your cutter manufacturer recommend for speeds, feeds, and maximum speed for the cutters that you use?

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800 Watt Spindle Upgrade Review - 1st Impressions
(Vince) #62

Dangerous game you play when potential runnout is more than desired chipload…take that how you will.

In my experience, hundreds and hundreds of hours cutting aluminum…0.001 maximal chip thickness has never ever ever ever lead me wrong with any tool I’ve used.

The only cutters ive used that were meant for 30,000 rpm were Datron endmills. 0.005max, I was averaging 0.0035 actual.

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800 Watt Spindle Upgrade Review - 1st Impressions
(Gerald Mackelburg) #63

Yonico makes endmills that are rated for 35,000 RPM. PreciseBits’ are rated for 100,000 RPM. What collet(s) do you use with your Makita? Have you measured their runout?

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(Vince) #64

I regularly check TIR and usually adjust 0.125 and below. Using makita collets, Elaire, and cheap reducers. They are all usable and I try to have around 0.0005 tir although it’s not unusual to have up to 0.005-0.003 tir before adjustment.

Even on a 70watt spindle for t6-6061, 0.0008-0.001 minimums work very well.

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(Gerald Mackelburg) #65

What adjustments do you make to reduce runout? Did you get a custom Makita 3/8" collet from Elaire, this one from Makita,, or?

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(Vince) #66

Check this out, I swear it works

I have the Makita 3/8s and haven’t had any issues with it except it requires a decent amount of force to clamp firmly due to its single split style. The Elaire metric set I have is very nice.

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(Luc) #67

I spoke with Elaire and they do not offer a 3/8 collet for the Makita but as stated, you can get one from Makita which is what I’ve done. I have 1/16 and 3/32 collet reducers from Treeline USA but I have had little chance to use them yet.

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(Gerald Mackelburg) #68

That’s a great demonstration of the importance of using precision collets, especially with small endmills cutting metal!

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800 Watt Spindle Upgrade Review - 1st Impressions
(Vince) #69

That technique lets you dial in runnout even with the crappiest of collets. It’s pretty easy to have sub thou runnout with collet reducers.

Sure you could spend all your lunch money on precision collets or you could just learn how to make the things you have work, usually that’s better in the long run anyway lol.

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(Gerald Mackelburg) #70

The guy that made the video said that he was going to report back regarding how well his “adjustment” held up during use. Did he? Have you checked that?

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(Paul Alfaro) #71

I presume it should hold as long as the tool holder is in proper order.

It’s the same principle as tapping stock into concentricity on a lathe during setup.
Same technique chasing runout in a chuck for example, then you rely on it to hold throughout your cuts.

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(Gerald Mackelburg) #72

But the same effect may not be the same because the cutting force on the lathe stock is relatively constant whereas that on CNC endmills isn’t because of the flutes. What moves during the adjustments?

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(Paul Alfaro) #73

True. So a single flute we can agree on, but multiple flutes the question remains.

However, turning with a interrupted cut is not uncommon on a lathe (be it a cross hole or key slot, etc). I would suspect this to have a similar start stop effect as multiple flutes and again is really a non issue when done properly.

As long as you don’t overexert the toolholder/workholder then all is well. Which should be common practice but then again it can be trial and error when employing new methods.

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