ATTEN 858D Repair


Yesterday I decided to repair my ATTEN 858D air gun.

This is a cheap chinese hot air gun to solder/rework pcb boards with smd components.

Disassembled air gun (broke pins place)

The first time I use it got broken. This hot air gun comes with 3 tips to focus the air flow that get jammed very easily. While trying to remove one of those tips I 've broken two plastic pins that hold the resistive part of the gun in place (signaled in green in the pic). The broken plastic pins made the resistance stand floppy and potentially slide out the plastic holder.

Refractory glue for fireplaces

 
Man, that day I even chipped my tooth trying to remove the tip in desperation. Since then I've never inserted those tips to the end, instead I just let them sit on the edge of the gun.

So how do you repair a hot gun that reaches temps well above 400ºC?? Some special glue must come in hand for sure. The answer: Refractory glue used in fireplaces and stoves.

The one I used resists up to 1500ºC. More then enough.
 

Standart PC case screw

The idea was simple. replace the plastic pins with to screws (those used in CD-rom drives or disks to fix the drive in the case are fine). I've started by dremel the remains of the old pins and dig a little deeper to make a bed where the screw head would rest in place (alignment) with the holes in the resistance of the gun. Then I applied the retractile glue in the void ring where the resistance rests. I've made it slightly higher so this ring of glue could work as a clamp. If too much glue is applied I would then remove the excesses with the dremel tool.As you can see the glue filled the ring completely. After trimming this ring to make a tight fit I've screwed everything in place.
 

Glued screw to the resistence support

Make sure the 12 hours of curing are respected (I didn't and the glue broke near the screw, and had to (re)glue them).

After that the resistance was tight in the holder and didn't felt flimsy any more.

Hurray ;-)

CNC Control Box - Part 1

Control box (pre)wiring

This will be the control box for my CNC. I bought the kit from Keling Inc. on e-Bay, with the NEMA 34 steppers. The KL-4030 drivers will control the stepper motors in a 1/4 or 1/8 micro stepping configuration. It will all be housed in an old PC case.

Control box wiring final

With a resolution of 1.8 degrees per step (for an 1/8 micro stepping) will allow about 1600 pulse steps per revolution. The motors will by their hand be coupled to a RM1605 ball bearing screw. This means that every pulse the driver receives the axis will travel about 0.003125mm.

The 1/4 or 1/8 micro stepping will be determined by the amount of vibration caused by the motors.

Micro stepping trades torque for vibration and smoothness and even more important trades resolution for accuracy. Make notice I did not mentioned precision because the loss of torque can affect the ability to make the structure move and the motor can actually skid under the force of the unwilling linear motion system. And micro stepping is a real torque sucker. Check this article to see what I’m talking about.

Next will be the wiring of the steppers to the control and testing the micro stepping configuration.

The begining

I decided to start this blog to share some of my ideias and home projects. I usually don't like to waist a lot of time writing but I feel that I have to return some "brainstroming" to the web cloud.

The ideia is to share some of the sucesses and failures (there's nothing like a bad project to teach a leason or two), so that maybe somebody may take advantage of it.

Hope to write soon.