Yet another epoxy granite mill

[lukahr]

Looking really great for now !!
Great looking ATC where did you buy it - how much ? (I'm thinking of buying one for myself and not build it myself ... )

I really need to get myself together and continue with my build ...

[ardenum]

Such is the case with many many machine parts, in industrial and automotive and even agricultural use. They are designed to always have oil or grease on them.

If you take gears out of your car transmission and wash them down with soap and isopropyl alcohol to fully and completely degrease them, then leave them out for a few days, you'll have rust.

Platings/coatings are for things which are in fatless environs, such as exposed to outside air but not working surfaces for a machine.

Even something like AISI 416 stainless will rust with time (and salt).

For motors you will typically see nickel or zinc platings on the backirons because they are not generally an oil environment. 416 is used extensively because they are at least semi-protected so other than salt air environs it will rarely rust enough to be a problem.

Motor laminations are coated on the faces with a corrosion inhibitor, but the cut edges will rust like CRAZY which you will commonly see. Sometimes that surface is specifically epoxied into the mating housing to act as both mechanical bond and rust prevention. Sometimes it's coated after the cut process.

It's very common in machine tools to have easily rusting materials with just a thin film of oil. So you only have to look to protect from the particular oil-free environs where needed.

Any particular type of oil, or can I use the same one I'll use for the carriage and ballscrew lubrication?

[badhabit]

Great looking ATC where did you buy it - how much ? (I'm thinking of buying one for myself and not build it myself ... )

I bought it through the same guy who sold me my CTB servos. It was around 3500usd + shipping.

[badhabit]

It's been quiet from me for a couple of weeks. Lots of other projects and sadly not much progress on the machine.

However, today i went to visit the company who are going to mill my two castings. Really great guys, i had a tour of their awesome shop with some of their huge and awesome machinery! I saw some of their current projects, among other projects a HUGE mill from Norway which is also listed on their FB page: https://www.facebook.com/Bast-Co-539029272911359 .

I've also had some feedback from them that others might find usefull in the future: Don't use cold-rolled steel for inserts that needs machining(like i did on mine). The issue is that the steel will have internal stresses from the rolling/pulling during manufacturering, this will somewhat be released and distort the steel while machining, making it harder to get the proper tolerances. Not a big issue as they can take smaller cuts, but they said toolsteel would have been better choice...or anything hotrolled...

Secondly they wasn't big fans of belt-driven 12k spindles. It might have been their personal preference or bad experience with belts, but it's also my conclusion: It's better to use an integrated spindle as it makes everything much easier and the price is pretty close to eachother when everything is added up...should i do it over i'd go for an integrated spindle...

They are completly swamped with jobs at the moment:-( The higher you want to be on their todo-list, the bigger the bill in the end....so i'm being pretty far down their todolist ;-) But i'll keep you posted when there are any news to report :-)

/Thomas

[StrawberryBoi]

Thanks for the update, I've been wondering how it was going!

Maybe if the belt has issues you can swap out the spindle later and recoup some by selling the current spindle, assuming you don't damage it.

[ardenum]

It's been quiet from me for a couple of weeks. Lots of other projects and sadly not much progress on the machine.

However, today i went to visit the company who are going to mill my two castings. Really great guys, i had a tour of their awesome shop with some of their huge and awesome machinery! I saw some of their current projects, among other projects a HUGE mill from Norway which is also listed on their FB page: https://www.facebook.com/Bast-Co-539029272911359 .

I've also had some feedback from them that others might find usefull in the future: Don't use cold-rolled steel for inserts that needs machining(like i did on mine). The issue is that the steel will have internal stresses from the rolling/pulling during manufacturering, this will somewhat be released and distort the steel while machining, making it harder to get the proper tolerances. Not a big issue as they can take smaller cuts, but they said toolsteel would have been better choice...or anything hotrolled...

Secondly they wasn't big fans of belt-driven 12k spindles. It might have been their personal preference or bad experience with belts, but it's also my conclusion: It's better to use an integrated spindle as it makes everything much easier and the price is pretty close to eachother when everything is added up...should i do it over i'd go for an integrated spindle...

They are completly swamped with jobs at the moment:-( The higher you want to be on their todo-list, the bigger the bill in the end....so i'm being pretty far down their todolist ;-) But i'll keep you posted when there are any news to report :-)

/Thomas

A motorized spindle is at least twice as expensive. With belt bt30 you're looking at $2000(even $1000 if you're stingy) for a working setup but you wont find anything lower then $4000 for an ATC bt30.

If you're considering getting one then CTB sells BT40A or D for $4500+shipping. First has 50Nm the other 80Nm. You can make serious cuts with this. They have a 15Nm BT30 but the price is exactly the same, so there's really no point in getting that one.

[badhabit]

A motorized spindle is at least twice as expensive. With belt bt30 you're looking at $2000(even $1000 if you're stingy) for a working setup but you wont find anything lower then $4000 for an ATC bt30.

If you're considering getting one then CTB sells BT40A or D for $4500+shipping. First has 50Nm the other 80Nm. You can make serious cuts with this. They have a 15Nm BT30 but the price is exactly the same, so there's really no point in getting that one.

Hmmm, this is not my numbers. I paid 2377usd for the spindle and 1810usd for the servo, both including shipping. Thats around 4200usd. Lets say that the integrated CTB spindle you mention is 5500usd incl shipping that is a 25% more for the integrated version. BUT my spindle is "only" 35Nm compared to the 80Nm you mention... and now you have all the advantages of the integrated spindle, e.g. half the build height, fewer moving parts to align, no belt that makes noise and wear, no issue with external toolchanger cylinder, etc... I'd still take the ~25% expense and go with the integrated version :-) Again, it might be personal preference and because i'm currently struggling with getting the builtheight low enough on my clamping cylinder....

/Thomas

[ardenum]

Hmmm, this is not my numbers. I paid 2377usd for the spindle and 1810usd for the servo, both including shipping. Thats around 4200usd. Lets say that the integrated CTB spindle you mention is 5500usd incl shipping that is a 25% more for the integrated version. BUT my spindle is "only" 35Nm compared to the 80Nm you mention... and now you have all the advantages of the integrated spindle, e.g. half the build height, fewer moving parts to align, no belt that makes noise and wear, no issue with external toolchanger cylinder, etc... I'd still take the ~25% expense and go with the integrated version :-) Again, it might be personal preference and because i'm currently struggling with getting the builtheight low enough on my clamping cylinder....

/Thomas

I gotta admit your cylinder looks huge compared to other builds. I guess if that was what you paid then definitely would have been better to go with a built-in instead. I take it the return period is over?

[badhabit]

I gotta admit your cylinder looks huge compared to other builds. I guess if that was what you paid then definitely would have been better to go with a built-in instead. I take it the return period is over?

yeah, return is not an option... it is also ok as it is, i just want others who haven't ordered their spindle yet to consider an integrated spindle instead...

[ardenum]

yeah, return is not an option... it is also ok as it is, i just want others who haven't ordered their spindle yet to consider an integrated spindle instead...

What size is your spindle motor? 205 or 265?

[badhabit]

What size is your spindle motor? 205 or 265?

I got a "Z18-47P5RB20-80HF5G", ergo 205mm....( https://www.ctbservo.com/product/ser...05x205x475-mm/)

Why?

[ardenum]

I got a "Z18-47P5RB20-80HF5G", ergo 205mm....( https://www.ctbservo.com/product/ser...05x205x475-mm/)

Why?

Because I was to use the same size, but my current design isn't as stiff, massive or big as yours. So I should probably go down to 175/180.

[ardenum]

How do you align the bt toolholders with the spindle? Is that necessary for your setup? I'm wondering If alignment is necessary if I could just remove the 2 tooths on the bt cartridge so only the taper holds the toolholders.

[badhabit]

How do you align the bt toolholders with the spindle? Is that necessary for your setup? I'm wondering If alignment is necessary if I could just remove the 2 tooths on the bt cartridge so only the taper holds the toolholders.

The encoder in the servomotor will be able to tell me how the spindle is positioned and where the taps are located. They need to be in the same place for each toolchange to be able to fit into the arm on the tool-changer...

...i don't think it would be a good idea to remove the taps... i'd imagine that in the case something "grips" your tool it's better to have to tool break(because of the taps preventing spin) than the possibility for a tool spinning inside the spindle... but i don't know enough about the purpose of the taps, i'm just guessing here :-D

[badhabit]

Progress is still slow:-( Loads of other things have higher priority than this project(according to the wife!)...so...yeah...

Anyways, had the chance to get the spindlehead welded and the z-sled tacked yesterday:


...hopefully i'll be able to complete the welding of the z-sled and start on the crosstable some time next week...

Afterwards i'll need to drill a couple of holes(cooling-pipes etc) and then they are off to heat-treating(stress-relief). After that filling them with EG before the are shipped of to maching....

[badhabit]

...still slow progress....but progress none the less... so i thougth i'd post some pictures of the welds....i think everyone can appriciate a good weld:-)


Question: I can't decide if i should beadblast + epoxycoat before or after final machining. There are pros and cons for both, but currently i'm leaning towards getting them blasted before and then repair any (potential) damage to the paint after machining... i'm not sure i'd trust the beadblasting company not to screwup any of the milled/ground surfaces during blasting or painting... are there any opinions on this?

/Thomas

[peteeng]

Hi Thomas - I'd bead blast/paint then finish machine. If the paint is well attached (as it should be) then touch up is zero/minimal. With some (especially fabricated) objects when you blast them because you remove material they can change shape sort of a stress relief, which would then muck up your machining. So "finish" machining is at the finish not anywhere else... Plus there's the issue of masking your machined surfaces etc if machining done before. Peter

[ardenum]

Hi Thomas - I'd bead blast/paint then finish machine. If the paint is well attached (as it should be) then touch up is zero/minimal. With some (especially fabricated) objects when you blast them because you remove material they can change shape sort of a stress relief, which would then muck up your machining. So "finish" machining is at the finish not anywhere else... Plus there's the issue of masking your machined surfaces etc if machining done before. Peter

I second that, blast guys can totally screw up your precision surfaces. I'd not trust them with this or with following any additional 'special' instructions. Machining/grinding at the very end.

[badhabit]

Hi guys,

I have an issue i thought i'd run by you guys for input. Originally i designed the table as a two-piece design: a sub-table which was custom machined to fit linear rail carts, ballscrew housing, waycovers and so on and on top of this a cross-cut work surface. My CAD looks like this with an arrow pointing at the subtable:


But it is a very heavy component. The subtable alone is going to weigh in at around 100kg(in steel) and my poor servos has to throw this around together with the table(which has to be steel). So i'm considering making it in aluminium instead, it will reduces it to 1/3 in weight. Fusion says around 36kg if it's made in 7075 alu ... Another option is to "hollow" out the subtable. This will increase machining costs, but reduce weight significantly nomatter the material.

Any thoughts?

[badhabit]

Another question: What material for the table itself? I've thought about 1.7225 (AISI 4142), would that be an ok choice or is there something better suited?