Thread: My Cnc build
well here is an update very well over due.
Built all the gearboxes and they worked great but i ended up with a square sided circle.
Research recommended doing some stiffening of the axis, which i did but to no avail.
I then got hold of an industrial gearbox for the stepper but it was so low geared it was not right....i.e the stepper was turning as it highest rated speed and the moment was so slow it wasn't good.
So off to drawing board and loads more research and i acquired some aluminium plate and ordered a full set of T5 16mm pulleys and belts to make a new solid style gear reducer of approx 3.2:1.
The difference was unbelievable to the stiffness of the axis. I still get a square circle but haven't completed the other 2 reducers, so at the moment i have a T5 pulley system on the x axis but geared reducers on the y axis o i think this needs eliminating first.
I have a Closed loop stepper system so wonder if this has implications with the software side.
It seems as though the x axis is stopping before reversing but the y axis is still moving , hence the straight bit.
Any thought appreciated.
Pictures to follow in no particular order...(Too lazy to organise.)
Last edited by Skiprat; 09-12-2015 at 10:20 PM.
Update from last post....i done some research on the flat circle and basically it was either slack or tightness in the axis. On looking and testing machine i knew it couldn't be the slackness as the machine is built like a small tank at the moment. Basically the x axis could be pushed with your little finger but the y axis had to be pushed hard with your whole hand.
Stripped the y axis off the machine reset it etc etc but still a load of crap.
Found the x axis was smooth and by the time the y axis had enough torque to reverse, the axis was stationary for a small time whilst the x axis was still moving hence the straight line.
Put my hand in my deep pocket and decided to get rid of the drylin rails and replace them with some hiwin rails.
Completely stripped the axis down again and fortunately the holes lined up and replaced the rails. Remade the z axis plates which were bolted to 4 Hiwin carriages.
Finished off making the aluminium plates for the motors and bolted these to the rails .......
Test cut revealed i still had a flat spot so i was well P**** off.....loads of money but no fix....
Further testing and found the large aluminium T5 pulley was a second(ish) behind the smaller pulley on the motor. Stripped it down and found the grub screws loose....tightened the up, put machine together and tested....
Perfect circles and squares...Well worth the money.
Now i can start making the machine look more cosmetically pleasing as now i know it cuts perfect.
Well pleased. Updates to come.
Thanks for that Boyan.
When i get back into shed to make it look nicer, i will cement the grub screws in as you mentioned.
Hopefully never have to replace the pulleys.
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