[NordicCnc]

A finnish company quoted you $350 for domestic shipping a $50 product? smells like a scam

Sorry I was not clear enough. They dont have it in stock in Finland, but they can buy it from Diamant-polymer. The shipping will anyway cost that because it is dangerous goods. I stumbled on the same when I bought R&G epoxy directly from Germany. At R&G online shop they announced shipping to be 35€, which I paid. Then I got an email from them telling me that that I need to pay an additional 305€ because it is dangerous goods and requires special shipping. Lol, I canceled that order without blinking and I got my money back.

Anyway thanks for your advice! I have some ideas what to try next.

Skickat från min SM-A528B via Tapatalk

[joeavaerage]

Hi,

These cant be as good as NSK/THK/HIWIN in my view and if I wait/search enough I should be able to find what I want from these known brands instead.

To be honest I think thats wrong. Those screws look very good indeed. I'd be proud to have them in my machine. So they may not be THK,NSK etc....but look at the test
certificate. The serial number on the test certificate matches the serial number on the screw. I think these are genuine quality parts....I would not hesitate.

It is true that if you are patient you may get even better, or at abetter price, or a more well known brand....but then again you may not too.

Lets face it, the only reason we buy second hand or new old stock from vendors like dyGlobal is to save money. We, or at least I, can't afford the top brands new from a distributor.
The only way I could get the quality I wanted was to buy second hand....and so you don't have such a wide choice. Fact of life. Those screws look superb to me, I'd suggest get a set,
or even two sets, before they disappear.

Craig

[joeavaerage]

Hi,
I'm working on my fifth axis and looking for some steel, nothing flash, 100x 6 or 100 x10 would be fine. Only stuff I can find is in the scrap bin....all the steel
shops are shut. Its Sunday...so I can find plenty of places to go to church....but nowhere to buy steel. Its no bloody wonder the worlds turning to crap!

Craig

[suspension]

Hi,



To be honest I think thats wrong. Those screws look very good indeed. I'd be proud to have them in my machine. So they may not be THK,NSK etc....but look at the test
certificate. The serial number on the test certificate matches the serial number on the screw. I think these are genuine quality parts....I would not hesitate.

It is true that if you are patient you may get even better, or at abetter price, or a more well known brand....but then again you may not too.

Lets face it, the only reason we buy second hand or new old stock from vendors like dyGlobal is to save money. We, or at least I, can't afford the top brands new from a distributor.
The only way I could get the quality I wanted was to buy second hand....and so you don't have such a wide choice. Fact of life. Those screws look superb to me, I'd suggest get a set,
or even two sets, before they disappear.

Craig

When you bought THK back then, were they used or open boxed? If I were to chose from used there are more options. I was wondering if the backslash is zero for a used one wouldn't it be as good as a new one as the accuracy cannot be changed with use?

I also noticed that there are many manufacturers in US who seem to produce ground ball screws for customer orders. And they certainly give a certificate also. Any idea about the quality?

And thanks for confirming the quality. If I cannot find another option today I will finalize the design with LTM ones.

[joeavaerage]

Hi,

When you bought THK back then, were they used or open boxed?

They were sold to me as 'used in good condition'. When I got them I would have said that if they had been fitted to a machine I don't think the machine ever did any work.
They had test certs, which sort of surprised me, like they were new old stock??

I bought 20mm Koruda C5's for my first mini-mill, and they were sold as used, and they had been well used when I got them. I went on to use them in my mini-mill for another seven years
without ever detecting any backlash or loss of accuracy. The X axis screw was on the way out, all the fibre glass dust got to it eventually. I would say that I got huge value for money
with those screws.

I also noticed that there are many manufacturers in US who seem to produce ground ball screws for customer orders. And they certainly give a certificate also. Any idea about the quality?

Not really, but I would expect any credible manufacturer whom provides a certificate as producing good products. The key word here is 'credible'. That is often as much a matter of opinion than
fact. That is where the leading brand names like THK and NSK have their appeal....but they sure charge for it!

Craig

[joeavaerage]

Hi,
well I've been using a new 1/8th Destinty Tools Raptor endmill while doing the work for the fifth axis. I got about three hours machining before it 'went red hot'.
My high torque/slow speed spindle is broken, I buggered the servo drive motor, so I'v been using my 24000rpm spindle instead. I've been running it at 15000rpm
and with a 1/8th tool that equates to a surface speed of 148m/min......which really is a bit high. Ergo I only got three hours out of the tool......and three hours
of really slow cutting.

Sus, if you want to cut steel you need a high torque/slow speed spindle so you can use decent sized tools and cut at a reasonable speed.

I got finished what I wanted to do, but it took a long time, or rather the toolpaths took a long time using such a small tool.

Craig

[suspension]

Thanks Craig for info on ball screws. This give me more confidence in buying used.
Regarding the spindle, yes I've also decided to use a BT30 spindle cartridge (12000 max) and a servo - 2.2 or 3.3 with max RPM of 8000. (possibly 12,000).

[ardenum2]

Thanks Craig for info on ball screws. This give me more confidence in buying used.
Regarding the spindle, yes I've also decided to use a BT30 spindle cartridge (12000 max) and a servo - 2.2 or 3.3 with max RPM of 8000. (possibly 12,000).

regular servomotors don't go past 3000rpm, good ones go to 5000rpm, some rexroth's go 8000-12000 but you're looking at spending a lot of time on ebay to find them for a good price. You're probably best off with asynchronous spindle motors like https://www.ctbservo.com/product-cat...dle-motor-z18/ if you want 12000rpm.

[peteeng]

Hi Sus - using a servo with a pulley is a good idea. You can have two pulleys that step up speed for aluminium. Leave it on the speed that's most useful and when you do the occasional steel swap it over. Peter

[suspension]

I am trying to finalize some of the expensive materials/parts.. Now trying to select epoxy granite.
Following are some of the options I picked from various threads.

1. ResinL + GL2 from R&G and Silimix 282
2. Sika-212 HP
3. SikaGrout®-3350
4. https://www.uscomposites.com -> 635 THIN EPOXY SYSTEM

I can see some successful builds that use 1 and 4. But could not find any build that use 2 and 3. And what other options do we have? Especially ones that are available in USA or UK?

Also, has anyone in this forum checked their machine's accuracy after 2 years to see if there any issues in the frame?

[ardenum2]

I am trying to finalize some of the expensive materials/parts.. Now trying to select epoxy granite.
Following are some of the options I picked from various threads.

1. ResinL + GL2 from R&G and Silimix 282
2. Sika-212 HP
3. SikaGrout®-3350
4. https://www.uscomposites.com -> 635 THIN EPOXY SYSTEM

I can see some successful builds that use 1 and 4. But could not find any build that use 2 and 3. And what other options do we have? Especially ones that are available in USA or UK?

Also, has anyone in this forum checked their machine's accuracy after 2 years to see if there any issues in the frame?

Which country are you in? UK? I don't think silimix is available outside EU

[pippin88]

SikaGrout is not epoxy. It's cement grout.

[peteeng]

Hi Sus - What aggregate are you going to use in the epoxy? The sika products are grouts. They are guaranteed for a very long time. I have a few blocks of a similar product around that I cast over 2 years ago that I observe. They still are straight with no cracks as far as I can determine. I would choose the 3350. It has a specified modulus so you can design to that. Its a commercial product vs something you will need to make up if you are using epoxy so you will not know its modulus unless you have it tested. The grouts are pourable, self de-airing and designed for this sort of application....Peter

[peteeng]

Hey - Pippin- I was going through some Bluey docs looking for some 1000 day data and found a press release from them. Sika bought Bluey out late 2021! Sika owns everyone... Peter

[joeavaerage]

Hi,
I just had a look under a microscope at the 1/8th tool that I just wore out. Really it only the very tips that are worn, if I could regrind the tips I'd be set for another few hours work.

That's what tends to happen when you spin a tool too fast in a particular material, you over heat the tips and then the tool is toast unless you can regrind. It does seem a shame to throw out a tool
that excepting the tips, is OK.

I miss my servo spindle, would never have over-sped the tool.

Craig

[joeavaerage]

Hi Sus,
this is pretty much the simplified speed chart that I use.

You can see there is a hell of a range from 800rpm with a 20mm HSS tool in mild steel up to 160,000 for a 1mm tool in Aluminum.
Having one spindle to cover that range is impractical but having a spindle that can cover say 1000 to12000 would get the majority of it.
Clearly a spindle that cannot safely go lower than 10000rpm would severely limit your ability in steel, even if it were OK for aluminum.

Craig

[suspension]

Hi Sus - What aggregate are you going to use in the epoxy? The sika products are grouts. They are guaranteed for a very long time. I have a few blocks of a similar product around that I cast over 2 years ago that I observe. They still are straight with no cracks as far as I can determine. I would choose the 3350. It has a specified modulus so you can design to that. Its a commercial product vs something you will need to make up if you are using epoxy so you will not know its modulus unless you have it tested. The grouts are pourable, self de-airing and designed for this sort of application....Peter

Hi Pete, I have access to silica sand (fine and course), gravel of atleast 3 sizes. Please see below for some pictures. I do not know how old or stable they are however and finding that will be difficult. And sand is coming from rivers and are not washed usually.
1. smallest
2. medium
3. large

Thanks
Sus

[suspension]

Hi,
I just had a look under a microscope at the 1/8th tool that I just wore out. Really it only the very tips that are worn, if I could regrind the tips I'd be set for another few hours work.

That's what tends to happen when you spin a tool too fast in a particular material, you over heat the tips and then the tool is toast unless you can regrind. It does seem a shame to throw out a tool
that excepting the tips, is OK.

I miss my servo spindle, would never have over-sped the tool.

Craig

I know the feeling. Some time back, I wanted to mill some Aluminimum with sub milli tips. I think before finishing the job, I broke close to 10. And after that, I never even thought about any milling that involve such small tips!

[suspension]

Hi Sus,
this is pretty much the simplified speed chart that I use.

You can see there is a hell of a range from 800rpm with a 20mm HSS tool in mild steel up to 160,000 for a 1mm tool in Aluminum.
Having one spindle to cover that range is impractical but having a spindle that can cover say 1000 to12000 would get the majority of it.
Clearly a spindle that cannot safely go lower than 10000rpm would severely limit your ability in steel, even if it were OK for aluminum.

Craig

Thanks for sharing this Craig. Still trying to select a servo based spindle components so this will be very handy. Much of this can be covered if I were to use a 30,000 BT30 spindle and a 5.5KW, 8000/12000 motor through gear reduction I think. This combo will cost around 3000USD from alibaba. (around 2000 for the spindle and 1000 for motor). But I may not be able to select this combo for now due to budget. I've already hit 8000 (estimates) and want to keep it below 11000 max. The steel T-table is going to cost above everything it seems. Trying out cast iron ones from Alibaba now, but not sure how precise they are.

[joeavaerage]

Hi Sus,

This combo will cost around 3000USD from alibaba. (around 2000 for the spindle and 1000 for motor). But I may not be able to select this combo for now due to budget. I've already hit 8000 (estimates) and want to keep it below 11000 max. The steel T-table is going to cost above everything it seems. Trying out cast iron ones from Alibaba now, but not sure how precise they are.

This is very much the reality of hobby CNC. You are wise to economise where you can but without permanently degrading the capability. For instance a cheap,
even rubbishy spindle, will allow you to use what money you have on ballscrews which cannot really be swapped later. A spindle can be swapped at any time.
Use your budget on those things that you have to and be frugal with the rest.

Craig