Questions About IPM, etc.

[buddym]

I have been running my DIY machine now for about 3 weeks, with great success. I have cut some parts using Mach and like what I see so far.

My question regards IPM, etc. I have the FET3 Hobbyist setup from Stepperworld, using the supplied p/s which is a PC supply. The motors are 110 oz. I use 1/4 20 threaded rod for the screws. I get about 10 IPM average and wonder if that seems low to anyone but me.... my router is a generic import 1/4 hp trim router and/or a dremel 300. I made some prototype parts from 1/4" hardboard that came out great, but the cut time was about an hour. The cuts were made on Mach using a 2-D g-code file and the multipass wizard. I set the cuts at .04 per pass. I have watched videos here and there and wonder if I might have something configured wrong. The only thing that keeps me from thinking so is that my parts come out perfect as far as the cuts and the dimensions. Am I cutting to shallow on each pass? Or is my machine slow because it has 20 TPI screws? Any input would be great.

Thanks,
Buddy

[idtkid]

Yep, your ipm is vveerryy slow. My first diy cnc ran 1/4 20 screws. I literally swapped 'em out 5 minutes in. Now I get around 30 ipm running 3/8"-16 (which is still way to fine of thread and pretty slow). .04" pass could be fine, all depends on the rigidity of your machine, run it as deep and as fast as possible before you get bad looking cuts or chatter (vibrations) throughout your machine.

[ger21]

The FET and 1/4-20 screws are combining to limit your speed.

Also, you should be able to cut 1/4" hardboard in 1 or two passes.

[buddym]

I understand the issue with the 20 tpi threads, in what way is the FET is limiting me? I am out of Delrin, if I decide to swap out the screws for something else, what else can I use to make a nut? I'd like to save the existing nuts in case I decide to go back to the 1/4 20 screws, or use them on another machine.

I wonder what the lowest tpi threads I can find locally are.....


Thanks,
Buddy

[ger21]

You're running at 12V with your PC supply, right? Higher voltage = higher speeds. Just about every machine you see here is running 24V or higher.

With the FET, to increase your voltage, you need to use big, expensive resistors that give off a lot of heat. This is very inefficient.