We have noticed a problem in cutting keyways over 10 mm wide, head will chatter!. we received a job that is 300mm stroke, we set machine and ran machine in speed number one slowest. When the machine travels to the top of its stroke then starts to come downwards, the cutting ram falls 20mm , We found a large amount of backlash in the gearbox. So when the machine reaches the top of its stroke and starts to come down the weight of the ram causes the head to fall to compensate for the backlash. When holding the drive end of the gearbox the output end has large amount of backlash. Our Engineers dismantled the gearbox to find that the drive keys on the selector shaft were 6.8mm wide, and the keys in the gears are 11.5 wide, this appears to be the main problem from gearbox.
- 1) Re: cutting ram fall down 20mm while setting speed No. 1 :
The reason is caused by Ram gib loose , Need adjust the gib by top and bottom adjust screw , first please run machine at No. 1 speed then loose half circle bottom screw then tight the top screw to let gib tight , Then touch the ram to feel the ram run at top and bottom point , If the ram falls down at top point , It mean gib still loose , Just loose bottom screw a little (each time half circle) then tight top screw to tight gib , Step by step adjusting the gib until ram run smoothly , While ram run smoothly , It won't fall down and just a little stop feeling at top and down point . Please note that it also can not adjust too tight or it will cause ram jump at top and down point ,
(PS: please note every 1-3 month you need to check the gib adjusting screw is well or not)
- Re: gearbox ( 4 speeds gear reducer):
The keyway of gear 11.5mm key on shaft 6.8mm which is correct , It's in order to change speeds purpose , All the gear reducer use the design , Besides the backlash is normal , It's not problem.
The slotting Machine power come from the rear flywheel centrifugal force, The gearbox reducer just to keep
the flywheel continuous rotating only and the flywheel only run at one direction , The backlash is not a problem
- While slotting bigger width and long length keyway , please note:
a). speed don't need at a low speed NO. 1 because centrifugal power less than No. 2 , Usually we suggest use NO. 2 speed but reduce feed
b).Use 10mm width cutter to cut big width and long workpiece , The CNC have the funtion and controller will do it automatically.
Note: the cutting power relate a keyway width , Bigger width need bigger power , Longer length need bigger power , harder material need bigger power , Besides most important is cutting knife must sharp.
c). Regarding to more rigid cutting bigger width keyway, to release the auto tool back off device and fix the slotting bar block with Ram, It will increase slotting rigid , While the Ram no mechanical auto power back off funtion , Just set parameter No. 3415 at 500 (0.5mm) to let workpiece back while ram at bottom point , It's programable auto tool back off funtion , (But we don't suggest user to use the programable tool back off funtion often due to it's moving by ballscrew , Long time running , It's no good for ballscrew life , So after finish the special job ,Please set parameter 3405 back to "0" and use mechanical auto tool back funtion for long life running)
- Regarding how to Fix the auto tool back off device to do rigid slotting – Procedure are as below :
a) move ram at middle (confirm too at not back position)
b) release holding bush
c) loose doth side fixing M6 screw
d) tighten the front 2xM12 screw to press the inner strong spring to let tool block fix with Ram , (Please note that the inner of M12 screw is strong spring).Refer to below video.
CNC-350-The processing on fixing auto tool back off device
Try the following steps to resolve above problem:
- adjust the gib to let cutting ram run smoothly ,
- try to use No. 2 speed for slotting your job
- If workpiece material is hard , try to use smaller width cutting tool to make bigger width keyway.
- If really need use rigid cutting , just fix the slotting bar block to do rigid slotting without auto tool back funtion.