Monday, September 14, 2015

Cheap Plywood Mill After Action Report

It has been a month since the plywood mill has gone into service.

In the beginning I had issues with nuts vibrating off, and the bearings on the DIY linear guides slipping out of place.  After repeated tightenings and various little adjustments  the nuts no longer come off.

The stainless steel threaded rod I use to drive the ,machine is now well broken in.  Turns smooth almost as smooth as a ball screw and so far no backlash.  I expect it will eventually develop backlash, and then it will be a matter of buying either a new nut or threaded rod for only a few bucks.

I neglected to initially machine the bed flat in the beginning.  Stupid mistake I know.  Just couldn't see running a 8 hour job to machine flat the entire work area with a Dremel.

I did however machine the spoil board flat last week, and fashion some clamps to hold the stock material to the machine.

I have machined aluminum with it however the results were rather poor.

I also burned out 2 Dremel tools.  

This time I purchased a trim router and some better quality bits in 1/4 inch.  

The new spindle is 440 watts vs the 100 watts of the Dremel.  For plastic it is sufficient.

I did discover that with a brushed motor I have to occasionally remove the brushes and clean them.  Mine ingested some plastic dust and got a little on the rotor.  

Acrylic machines better than polyethylene.  The polyethylene leaves fine wispy dust  and no chips.  More than likely because I have no speed control and it runs too fast.

I also machined some plywood with router bits to good effect.

So far now my biggest issue is the software and operator error.  I'm still learning.

I have someone order a acrylic plastic version of this mill so I will be making another very soon.  Using half inch acrylic with it and pretty much the same files.  I may swap to bushings instead of roller bearings.

Accuracy and being square:  it's pretty darn close.  Square is off by 0.05mm which is good enough for something as cheap as this.   That's 0.00196inches. 

Dimensional tolerances are pretty good too being off a little bit but I suspect it is a software or operator error at this point. It seems to be consistently short by 0.0236 inches no matter if I cut a 20mm square or a 300 mm x 75mm rectangle. 

It is really noisy however.  Have to use ear muffs.  I also need eye protection.  It is also very messy.  The shop vacuum has gotten the most workout it ever has had.

The other mill made from steel, have not put it too work yet.  I only got one in stock so I'm keeping it nice and pretty for a customer.  






2 comments:

Anonymous said...

Always off by .0236? Are you using tool offsets in your CAM program? Measuring to the center of the bit, not to the cutting edge of the tool? That would put you off by 1/2 or 1 full cutting tool diameter.

admin said...

Yea its fairly consistent. Runout making the tool diameter larger.

It was with a cheap China Dremel copy.

The Dremel burned out, using a trim router now. Have not measured it yet.