Jerky Z axis!

[h50n]

Hi guys I'm having some newbie problems here my Z axis is really jerky when going up but fine when going down here's a video of it:



I've tried greasing the lead screws with no luck any ideas?

The second problem i've been having is i've been using a 5mm 3 flute slot drill to drill holes into vinyl records (working on a project) with an unfavorable finish.



Im guessing that I'm using the wrong bit. does anyone know what the best bit to use would be?


Thanks guys

[foam27]

I'm going to guess the motor couplers need tightening.

More torque is needed going up

[ger21]

+1. The motor doesn't appear jerky, so it looks like the coupler is slipping.

What rpm are you using to drill? It may be too fast.

[Torchhead]

Drilling plastics with conventional drill bits made for metal is less than optimal.

The challenge is there are all kinds of plastics from the harder type Acrylics to the really soft foam and thermoplastics. Each needs different cutting/drilling techniques

You can get special bits or make your own by regrinding the flute angles You need something like a 6odeg angle rather than the 118 deg of conventional twist driills

RPM needs to be low enough not to heat up the plastic. A vinyl record has a VERY low temp point. As soon as it starts to soften it will gum the bit causing even higher friction and temp.

Feedrate need to combine with the RPM to allow the flute to cut, not grind the work

Cutting plastics and milling and drilling is a process of trial and error even when using the right tools.

5. In most circumstances an end cutting (milling type bit) works better for softer materials. We do a lot of 5052 aluminum routing and have done ABS type thermoplastic (molded plastics) and the speeds and feeds are critical. We mill all of it rather than trying to drill. Too many different sized holes and its hard to find a variable chuck that has a low enough runout to mount on a router. We have to use precision collets and most smaller bits we use (actual milling bits) all have 1/8 or 3/16 shanks) You need a 2 flute very aggressive spiral up-cut type bit. Something taht pulls the cut material up and out of the cut area rapidly

If you are going to stay with dill bits then consider using drill bits for plastic or something like a brad point drill bit for wood or the forstner style bits at low rpm and feedrates. This is a bit like drilling into a marshmallow You may have better success by placing the record in the freezer and make it as hard as you can prior to drilling!

When routing you need moderate low RPM and carefully adjusted feed rates. A stream of cool air at the bit (leading edge) and or mist cooling helps a lot.

Bottom line is you have to keep the cutting friction low to prevent the work from getting soft. The bit has to cut and the plastic should come off in curls rather than blobs. Biggest problem we have with the milling of plastics is the curl moves up the bit and stops at the chuck and starts to ball up then forms a cone that is getting bigger and bigger and will harden and clog the flutes, All of this can happen in a few seconds. That is where a heavy focused stream of air to keep the flutes and shank clear of the material is invaluable.

You can get good results with the right tools and process and with a CNC machine you have several alternatives.

TOMcaudle
www.Candcnc.com

[h50n]

hey guys thank you so much for all the advice :-)

I tightened the couplers now that is A okay, i'm gonna try some different drill bits tomorrow.

I was drilling it at 6000 rpm.

The feedrate I have for the actual cutting seems okay because the edged are pretty smooth, It's just the holes I need to work on now