please c7 ballscrew are good for cnc pcb or not

[p_rabid]

The two ball screws are make in China. The price doesn't include end-machining.
RM1605 500/700mm with two nuts
95.00 usd
Air shipping cost:38.00 usd
TOTAL AMOUNT:133.00USD

they are 2 ballscrew 700mm and 500mm long with nuts they are c7
pitch 5mm

are they will be good on cnc machine for pcb milling and drilling
the machine size 70 CM * 50 CM
and what type of mount bearing should i use
thanks in advance

[cnc2]

Sure they are !

I RFQed a rolled ballscrew from HiWin it was C7 grade, it had a max backlash of 0.001mm & +/-50µm per 300mm variation.

If there's 1mm or 0.5mm of space between the copper traces on your pcb, C7 is more than enough.
C0 to C5 grades are a lot more expensive...to me they're overkill/overpriced.

You should use the 7200 series bearings, you'll need TWO identical 7200 series bearings, mounted back to back, in order to make ONE fixed end support for one screw.



Also take a look at post#1 in the ballscrew basics thread for more info & schematics of bearing mounting.

Your price seems to be good, so please give us a link to the chinease ballscrew website, i'm interested to see their specs.

Regards,
cnc2.

[p_rabid]

Originally Posted by cnc2 Sure they are ! I RFQed a rolled ballscrew from HiWin it was C7 grade, it had a max backlash of 0.001mm & +/-50µm per 300mm variation. If there's 1mm or 0.5mm of space between the copper traces on your pcb, C7 is more than enough. C0 to C5 grades are a lot more expensive...to me they're overkill/overpriced. You should use the 7200 series bearings, you'll need TWO identical 7200 series bearings, mounted back to back, in order to make ONE fixed end support for one screw. Also take a look at post#1 in the ballscrew basics thread for more info & schematics of bearing mounting. Your price seems to be good, so please give us a link to the chinease ballscrew website, i'm interested to see their specs. Regards, cnc2.

thanx for ur reply what do u mean with back to back i doun know that sorry i am new in this stuff
and here
is the link of the chine ballscrew

[cnc2]

Thanks for the link !

The prices are really LOW compared to other brands with same screw diameter & dynamic load, the precision is not mentioned, i can't believe it's a real C7 grade for this price, the same C7 ballscrew from Germany would cost ~300 Euros, so i encourage you to try this cheap alternative.

Back to back means back to back look at the schematic:



Read Post#1 for more info & pictures.

I am not sure what they mean when they say: "6.We can not pack the items with wooden box because of the customs clearance problem.Therefore, the items may be disalined during the delivery. Please adjust the straightness/alinement of the spindles before you mount the items on cnc router or xyz table"...but keep in mind that a bent ballscrew is unuseable, so if it's really bent ask for replacement... try to ask them to pack the ballscrew inside a piece of metal tubing to protect it during shipment.

Regards,
cnc2.

[p_rabid]

Originally Posted by cnc2 Thanks for the link ! The prices are really LOW compared to other brands with same screw diameter & dynamic load, the precision is not mentioned, i can't believe it's a real C7 grade for this price, the same C7 ballscrew from Germany would cost ~300 Euros, so i encourage you to try this cheap alternative. Back to back means back to back look at the schematic: Read Post#1 for more info & pictures. I am not sure what they mean when they say: "6.We can not pack the items with wooden box because of the customs clearance problem.Therefore, the items may be disalined during the delivery. Please adjust the straightness/alinement of the spindles before you mount the items on cnc router or xyz table"...but keep in mind that a bent ballscrew is unuseable, so if it's really bent ask for replacement... try to ask them to pack the ballscrew inside a piece of metal tubing to protect it during shipment. Regards, cnc2.

i just talk with that guy and he tell me that
''I Mean that we willed pack the items with pater carton, so the screws may bent during the shipping.'''
when i ask him if the bent too much
he tell me
'''The screws will not bend seriously. You can not see that with you naked eyes.0.01-0.1mm bent You must inspect the straightness before mounting.''

do u know what he are meaning with inspect the straightness before mounting
i really don't know to buy or not from that guy i am quiet afraid of that

[Eurisko]

Even hardened steel will bend slightly at that length (1 meter).

The Hiwin 20mm linear rails ( 1 meter length) I bought had to be clamped to a straightedge before mounting.

The Thomson 3/4 in. case hardened rod (36 in. length) had a noticeable flex; I was using it to double check my ballscrew bearing mounts for straightness.

I purchased a couple of these screws from this seller. They are wrapped in foam, then wrapped with tape, and boxed. The box has an incredible amount of heavy packing tape protecting it.

I can't vouch for the screw accuracy because I haven't installed them yet. I can say that they are harder than hell to machine. I've just started to machine the ends for the bearings. My poor little HF 9x20 lathe was having fits. I finally rough ground the ends with a bench grinder. Makes it a lot easier to machine on the lathe.

These screws are a good deal for the price. The seller is honest and ships quickly.

[cnc2]

Thanks Eurisko, for sharing your experience !

I'm happy to know about this cheap alternative to hiwin, but still can't believe they have a maximum of 0.01mm of backlash like hiwins...do they provide a cheap solution to backlash ?

what about shipping from china ??? (price,customs...etc)

Thanks !
cnc2.

[Eurisko]

Shipping charges are reasonable considering the distance. It took less than 10 days to receive the package. The screws were delivered by the good ol' US Mail. Of course, I wasn't home and had to go to the post office to pick them up and sign for them.

I'll try to post some data on these screws, might take a week or so until I have the time.

[cnc2]

It would be great !

Thanks for sharing !
cnc2.

[renatopub]

I bought 2x RM1605-360mm-C7 for 78$US from china and they seem good. I measured 50um backlash with the dial indicator.
The only funny part is that there is another 50um of error that goes back and forth every turn as the nut progresses in the screw, can't really explain that.
By the way, about the bending. Hardening a material has very little effect on the elasticity modulus, what changes is the yield strength (hardened steel resists plastic deformation). So hardened steel and soft steel shafts will bend the same way, as long as both are in the elastic range.

[p_rabid]

Originally Posted by renatopub I bought 2x RM1605-360mm-C7 for 78$US from china and they seem good. I measured 50um backlash with the dial indicator. The only funny part is that there is another 50um of error that goes back and forth every turn as the nut progresses in the screw, can't really explain that. By the way, about the bending. Hardening a material has very little effect on the elasticity modulus, what changes is the yield strength (hardened steel resists plastic deformation). So hardened steel and soft steel shafts will bend the same way, as long as both are in the elastic range.

thanx for the information
i just recived my ballscrew from 30 Minutes from china
they look pretty good i will test them and i will post it

[tawhid]

Any updates on the ballscrew test?