Your input requested

[birdsofplay]

Sunday I demod to a guy who makes wooden clamps out of maple, some soft some hard and a littel oak too. He was suprised that the SB cut in one pass !!! He has been using a pin router with more HP. I wasnt , but then I dont use my SB on an 8 hr daily basis to do one thing either. I demoed both a 3/8" HHS spiral bit and a 1/2" Carbide to cut similar paths. So ... My questions are How come the divergent experiences ? Am I not pushing my machine and therefore dont have a true view of "production" capabilities ? Does anyone else out there do that level of output with their SB ? Thaks in advance Bob

[seaside@esva.net]

That's a great question; I'm interested in hearing what others are doing also. Like many other ShopBotters, I don't have a background in CNC and there are lots of decisions I make( setting router speeds for instance ) without having any real facts to base them on. I usually cut plywood, mostly 1/4 to 1/2" but occasionally 3/4". I always cut 1/2" and less in one pass, but generally cut 3/4" in two passes, figuring it's easier on the router. Most of the "how-to" articles I've read about hand routing and using router tables also suggest making deep cuts in multiple passes, but that might just be a control issue. Bill Young

[sheldon@dingwallguitars.com]

Bob,

Were the bits going harmonic (squealing)? I've been using a 5 HP SCMI overarm router and rarely take a pass depth over 3/8" in alder or walnut, hard maple even less.

I'll let you know what I find when my shopbot arrives.

[sheldon@dingwallguitars.com]

What do others use for a drill head when a router won't do.

I will be drilling a lot of 1/8" through holes in 1/2" aluminum.

[birdsofplay]

Sheldon ...

MY SB was doing OK as demo'd
This guy, however, was SUPRISED to see that the SB
WAs doing OK since HE had experience with a pin router.
From HIS experience he didnt expect the SB to do very well, or, at least, to be required to do several passes.

To be clear I cut 3/4 maple with both a 3/8" HSS spiral upcut bit and 1/2" carbide spiral upcut.
I made a seperate cut with each.
I would plunge into the material and then cut an arc out of the material going against the rotation of the bit.
Nice smooth cuts. I used .25IPS speed, ie SS,.25

I used 16,000 rpm setting on PC7518 with the HSS bit
and the fastest setting with the Carbide bit.
I used the 3/8" bit first and then after discussion and inspection
and in light of the fact that HIS router was a single speed HI RPM model I set the PC7518 to max for the 1/2" bitr test.

Since I dont do this kind of thing on a regular basis.
Allz I wonder is ... is this is NORMAL ?
Could SB do it all day long ?

ie.
1. Would it better to cut in steps to save router wear and tear ?
2. Would it be easier on the BIT(s) to do steps since the heat build up would be lower ?
I suspect that a bit will last longer if kept cool
as opposed to using the whole LOC and heating up the bit more in general.

I ruined some "Cheapo" HSS mill bits from Enco or Griz, Cant remember which.
I was just cutting some 1/4" luan and they BLUED OUT real fast !!! :-(

I think lots of us are capable of getting most jobs done, HOWEVER, we might not be treating our BITs or SB as well as possible.

Therefore I started this thread ! :-)

Thaks to any and all participants

Bob

[Gerald Dorrington]

"How hard can you push it?" seems to be the topic of this thread. Let me state right at the beginning that I have practically zero experience of pushing a Shopbot, or even a router in wood, but do have experience pf pushing production steel cutting machines to the limits.

The Shopbot is only a servo-system which moves a seperate motorised cutting tool, so we must look at the Shopbot and the cutting tool as two seperate entities. The thrust powers of the Shopbot stepping motors are well-documented - if they are pushed too hard then they miss steps and this can be heard with the naked ear (my short experience so far).

The motorised cutter has a motor and cutter tip, each with its own limits. During steel cutting we normally have an ampmeter on the cutter motor and the feed rates are maximised so that the cutter motor draws the specified max amps. I am having a problem to determine the maximum continuous current allowed for routers.

Electrical engineers will tell us that Watts = Volts x Amps. For DIY power tools, it is normal Europe practice to measure the power INPUT at full load, multiply it with the supply voltage and then state the total number of Watts on the manufacturer's plate. The biggest "DIY" routers here are rated at about 1800 Watt, which means that they can draw 8.2 amps from a 220V power outlet.

However, what confuses me, is that these 1800 Watt routers are shown as 3.5 Horsepower on American websites. The standard conversion ratio is 746 Watt = 1 Horsepower, so the 1800 Watt only converts to 2.4 HP. Where does the extra HP come from? How many amps can be supplied by a standard American 115V power outlet?

It would seem that the same router has different power ratings depending on the market area for which it destined. This can only be explained by different "duty-cycles" Motors are damaged by heat building up between the windings, a relatively slow process. Short periods at a very high current can be compensated for by a cooling-off period. A 3.5 HP router may mean 3.5HP for 2 minutes in every 10 minutes. An 1800Watt router may mean for 5 minutes in every 10 minutes.

If a DIY router is mounted in a Shopbot, then the duty cycle will surely increase and thus one should probably run it at lower power than that recommended by the manufacturer.

The only sure way to know the limits of your motor, is to have a temperature sensor buried in the windings!

Regarding cutters, It must be obvious that only carbide tips can be considered by those wanting to push their cutting motors to the limits on a production basis.

[Dick McGuire]

My production is in red oak, soft maple and ash. When you go to my web site www.childwoodproducts.com you can see the intricate cuts that are made with my SB.

I have used HSS 3/8" and 1/2" cutters as well as carbide. Carbide is the cooler running of the choices but needs to move somewhat faster than HSS to keep from over heating. I cut 3/4" with one pass when the material cleans out 100%, i.e. without scrap to hang up on the bit. I cut 0.60" deep all other times and move the bit all the way through the material on the first plunge to provide for an access hole for the end of flute bearing bit installed in a hand held router. I turn the part over and insert the bearing bit into the hole.

My travel speed with the carbide bit is 0.25 to 0.35"/sec. I have increased my plunge to 0.50"/sec. and it helps to minimize burn marks on the material at the plunge location. When you see burn marks or smell burnt wood you know something has to change. Hope I have helped!

[northernecho]

I am will be cutting 7/8" Softwood (Pine or Spruce) I have a 1/4" carbide spiral upcut and A carbide straight cut. Anyone have any thoughts on speed, and if I should cut in one pass, and or would I be better off with a 3/8" or 1/2" bit? I use a 3.5Hp Porta Cable, and plan on using Max Speed.

Also, on a side note, does anyone know what the newest software I can use on the OLD Paralel Port based control box?

[jimt]

I believe ver 1.53 or 1.8 is the latest you can used with a parallel port box (I have one). As for the cutting speed, I would suggest a larger bit - maybe 1/2" if you want to cut in one pass. the 1/4" bit will have too much bit deflection and probably break at full depth cutting at high speed. In softwood, I wouldn't cut much more that 1/4" in a pass with a 1/4" spiral bit. Start with a speed of about .2-.3 for full depth cutting or maybe .5-.6 for 1/4" depth work.

[northernecho]

So a 1/2 spiral or just a straight? I have looked on shopbots ftp site, and the "Oldest" software they have is 210. If you have a 1.8 and it works on the Par Port, can you send me a copy?

I was told to go with the 1/4" bit because the older bot steppers didnt have the power to push a big bit in a full pass... I want to run full depth to get productivity up. In a few months, I am getting a bigger unit or the New shopbot, but for now, I have an order of 20,000 wooden scrolly things !!! and want to see how this one can do!!! Its the Shopbotters Dream job if it can do it! Can get about $1.00 CDN per unit. So a new shopbot is is only 10,000 cuts away!

[davidallen]

I typically cut 3/4 inch stock in 2 passes with a 1/4" spiral bit running at 20,000 rpm and cutting at 1"/sec.

the 1st pass is a 1/2" cut with the last pass using the tabbing feature. I get very little chattering and I'm using a 3HP router which loads only slightly. for the patterns I cut, a little chatter is fine, esp. if I can finish in 1/5 the time.

I do clamp the bit close to the chuck, only about 1" below the nut.

the only time I've broken a bit was when I was doing an air cut with the router off and accidently drove the bit into the stock with an x/z move instead of an x/y. (comma's can be tricky)

da

[birdsofplay]

A & J
Write me at birdoply@gte.net (mailto:birdoply@gte.net)
and I'll send you 1.8 as an attachment.

I have an old machine ( 2.5 yrs, but NOT a parallel ver )
My steppers do OK with side loads, but I'm NOT
doing cable drive anylonger.
With some gearing on a homemade chain drive system
I get pretty good side load capability.
Enough to do 1.5" pine with a 3/8" bit in one pass. ( bout only on a "good day" )
Most of the time I do it in two passes to make it
"easier" on bits, router and SB.

[northernecho]

Thanks for all the great input on cutting. From the input I got, I am hoping that I can make the cuts with the 1/4" bit (mounted real close, and running at 20000Rpm with a 3.5hp Port-Cable) make a 1/2" cut on first pass then a little better than 1/4" on second pass, then run the 7/8" lumber through a planer to take it down to 3/4" and have the parts drop out... and wish I had a dust collector :-) This is my plan, if it works GREAT. If not... I suspect the problem will be in acuracy of the 2nd cut with the old cable drive. I would love to see some pictures of that Gear/Chain Drive system! Sounds like 3/4" Pine would be a breaze!

[beacon14]

We routinely cut 3/4" MDF and 3/4" plywood in one pass, using mostly 3/8" and some 1/4" spiral carbide cutters, and have no problem with move speeds of .75 and even 1 ips. We use a Porter-Cable 3 1/4 HP variable speed router, usually set to highest speed. I have noticed that we are seeing some runout in the router bearings, after about 6 months of semi-production work. We keep a spare router on hand, and will soon change the routers and send the old one out for new bearings.
For clean cuts on plywood, melamine, laminated MDF and solid wood, we use a "compression" bit, it has about 3/16" of upcut on the end, and the rest is a downcut. More expensive, but worth it. I find that a single pass is less likely to leave a slight shoulder which can result from slight missalignment between passes or unequal lateral pressure on the bit coupled with slight play in the system or runout of the router arbor.
We could certainly learn more by additional trial and error, but we kind of started with these settings and they worked, so we keep using them. I was somewhat surprised to read that many others are using seemingly very slow move speeds of 1/4 ips, but I suppose solid wood (which we haven't yet done that much of) would cut differently than plywood.

[birdsofplay]

I sent my 7518 out for recondit also.
The "counter guy" told me that I could change the
bearings myself, but ...
There are "cups" internally in the frame that
have adjustment screws. IF you were inept enough
to crack the housing you'd have to buy a new frame
which would be WAY expensive.

My bill was ~$100 for bearings, brushes AND a new
speed controller PC board.
The Speed thang was the MOST expensive of
all the parts. ~$60
Brushes were less than $10

So I figure I'll always let "THEM" do the work.

Yep ... I also bought a spare router JUST for this reason !!!