Straight-line vs. gang rip

      Which is better suited to this moderate operation? June 24, 2002

After 20 years of specializing in installing millwork in high-end homes, I am frustrated by the ability to get product when promised. I decided to add a new molder to my operation. Since, at startup, we are only running about 5000 lf per week, I have been purchasing pre-ripped blanks, but still I am having a problem getting product when promised.

I see the need to add a rip saw. My molder operator tells me I need a gang rip while the sales rep who sold me the molder suggests a straight line rip for better yield, but this seems to me to be more labor intensive. Which would be better? I hope to be running 15-20,000 lf per week. I am on a limited budget and have noticed that I can get a newer used M-3 for about the same price as a new straight line.

Forum Responses
We run a small moulding operation. We use an older model Ekstrom Carlson straight line ripsaw. We probably run about 5 to 6000 feet per week. We looked into the gang rips but found that if you want to cut clearer blanks, the slt will do a better job because, when gang ripping, you are stuck with that blank that the second blade cuts. With a slt, you might be able to saw around by taking another pass. If I were to get a gang rip, it would be the new Raiman saw with the movable second blade.

From contributor C:
If you are ripping and moulding in long lengths, there is no process better than gang ripping first. Gang ripped strips will have parallel edges, which results in less waste at the side heads. You will rip blanks much closer to your finish width. Even if you cut to fixed lengths before you mould, as is the case in furniture type dimension, you will be better off to gang rip first.

It is too lengthy to go into here, but suffice to say that all major kitchen cabinet manufacturers gang rip long length lumber and then defect and cut parts out of the strips. Many furniture manufacturers have installed these systems as well. Although some of these systems are very expensive, there are systems available to the smaller manufacturer. The big guys don't spend that kind of money for no reason.

Get in touch with your Mereen-Johnson dealer, who will be well informed regarding equipment available for your size operation and visit similar plants to yours.

In most moulding operations, the major concern should always be yield. The advice from your machinery dealer is sound. Ask him to equip the SLR with a versatile fence system. The gang rip machines recommended here are great. In your case, I believe that they may be overkill, since their daily output potential may be in the range of 20 to 50,000 bf per day depending on the accessories. For your operation, a good (make sure it is an American machine, new or used) SL rip will process 5000 BF in 5 to 6 hours. At the price of moulding grade lumber, every 1% of yield improvement will pay for the total labor cost.

Also, please consider that a gang rip will require more KVA demand, since they are 40 to 60 hp. You will need to provide a lot more vacuum, too. You must be very good at what you do - most moulding people are upside down now.

When ripping for a moulder, parallel is of great importance. You want to leave as little oversize as possible, but enough to allow the moulder to finish your profile. Leaving too much is material waste and leaving not enough, your finished product could be waste. Here the gang rip is definitely the best solution, because the entire rip is processed in one pass. On the SLR, your second cut is made on a second pass and the parallel is just not there, so you have to compensate with excessive oversize. This equals waste.

For yield, a gang rip may not be the right answer. The "gang-rip" is a sleeve that gives you fixed dimension options. You are restricted to those options, though each board is different. With each pocket adding to a fixed value, this leaves you with some waste in most boards. The SLR has the ability to adjust for each rip through the fence, allowing you to make the best decision available for each rip.

The Raimann rip saw has the best of both worlds. It offers the gang rip and a moving blade that gives you the SLR flexibility from board to board and the gang rip accuracy. This saw also has lasers identifying the position of each blade inside the saw, allowing your operator to see what his best solution is every time.

I was a service tech with Raimann and now represent the company in TN. I have seen the machine go into everything from two-man shops to the largest furniture factories.

From contributor S:
I run a small cabinet and mill business, and do about the same quantity as you. I don't think you can beat a SLR for this size and dollar business. 800 to 1000 ft per hour is very realistic on a SLR. Start here and move up if production warrants it. Ever try being on the out-feed end of a gang rip? Put your moulder operator there for a week or two. I would get a good Mattison, equip it with a laser, and go at it. I don't regret it a bit.

From contributor C:
Contributor S, you wrote "Ever try being on the out-feed end of a gang rip? Put your moulder operator there for a week or two."

We have ways of helping the fellow on the out-feed end of the gang rip. Frankly, I like the idea of machinery that runs material faster than a man can catch it. I don't like the idea of being limited by what a man can do physically. My idea is to give the man something that he can use as a tool to do more than he can do by himself. When that tool increases production and yield at the same time, it looks pretty good to me.

From contributor S:
Machines and handling systems are great, but what works for Basset Furniture doesn't always work for smaller operations. Space and money are bigger issues than 1% yield. If 1% dictates me being in business or not, I'm going to work for someone else.

Besides, people are what make the operation go around - machines only help. What good is it to rip blanks faster than their ability to be processed or even the demand dictates at this point in this fellow's operation? If I subscribed totally to the theory that you should do what a man can physically do, I would rip my blanks with a handsaw and shape my molding by handplanes.

Point is, most people would love to have the best dimensioning system in the world, but what puts the most money in your pocket when the job is done gets my vote, new machinery or old.

When demand backs up the ripping operation for days, it's time to do something different, but it's precarious enough starting out on a new venture without having to meet a bunch of machinery payments.

From contributor C:
Contributor S, you wrote: "Machines and handling systems are great, but what works for Bassett Furniture doesn't always work for smaller operations. Space and money are bigger issues than 1% yield. If 1% dictates me being in business or not, I'm going to work for someone else."

The Bassett installation is quite imposing, but one can have a gang rip saw, rip small quantities, get the advantages of parallel edges, exact widths, etc., without spending 2 or 3 million bucks. That is what the MJ 312 in its various forms is, and what the Raimann was designed for.

I would not want to talk the questioner into spending 3 million to rip his 10,000 ft of lumber, but there is a variation of the system that will fit. There are literally hundreds of small operations that prove me to be correct.

1%? How about 15%? Let's see - $800 lumber x 10 = 8,000... and the savings are not $1,200 if you start with 50% yield and end up with 65%. The reduction in lumber purchased is actually 23.08%. Or that lumber now costs $6,163.60, rather than $8,000. The savings are $1,846.40. 20 weeks will pay for the gang rip saw. The questioner hopes to double this amount and more soon. So, the payback will be 10 months or less at that rate.

It is true that one can pay for the gang rip saw in six months or less, but one must remember that the rip saw alone is not going to give you those yields. You need a rip optimizing system of some sort. 100 weeks payback will buy a lot of very nice machinery even at the low usage of $8,000 lumber per week.

I intend to own a MJ someday. How do you calculate a 15% increase in yield over a SLR? We have both in our small millwork operation and the SLR processes probably 80% of our ripping. The main reason - setup time. I feel the savings in man-time compensates for any yield increase that there may be with a gang. Remember, we are a custom run shop, probably like the questioner's - 20 lf to 2000 lf are standard, with every combination in between.

From contributor C:
20 lineal ft? Of one width that does not repeat? Or one length of a width that repeats? I would not set up a gang for 20 lineal ft.

The new MJ 312 with the hydro shaft and a select rip saw can work. You put the short runs on the select side of the machine and the repeat or long runs on the other saw pockets. Maybe. They must be of the same specie and thickness, which may not be the case either. You need to call an experienced dealer and go over exactly what you are doing.

As for how I come up with the 15%, I know nothing about any of these operations, but I am taking a gut shot based on experience from dealing with a lot of people.

How much moulder allowance are you allowing for each side of the piece - "Probably a total of 1/4". In a small shop, you may be able to be hard nosed enough with your rip sawyer that you can get by with less, but there again... I know what I see everyday in plants.

Do you cut off to length first? If you do, you have a hard time cutting off the right number of pieces of a given length because the cut-off sawyer can not tell how many rips the rip sawyer will get out of the given lengths.

On the other hand, if you have an operation so small that you cut off a few pieces and walk them over to the saw, rip them, then go back and cut-off another few pieces to finish the job, you are probably getting pretty good yield from that end of the operation.

Strips are easier to defect and end up with the right number of parts, especially if you use a vision based optimizer that optimizes for width and length so it is, in effect, predicting the lengths you will get out of the given width, based on the defects in that strip.

I confess that there is a production level below which a gang rip saw becomes a problem. However, that level is probably the same that fits the use of a moulder rather than running it on a shaper.

Generalities, generalities. Nothing is as important as getting into your plant and looking at what you are really doing.

There are great advantages to gang ripping. And some operations are so specialized and so limited in quantities that they can not use a gang. You can only find out by getting on the scene and digging into it.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor O:
There is no need for a moulder shop that does less then 50K LF a week to even consider buying a gang rip saw. At one point we were running jobs of 10K LF and gang worked great, but if you are buying the material yield matters and you can't get as good a yield from gang over straight-line. In fact I would rather be running 2 to 3 SL over a gang which is exactly what we are doing now. I would suggest looking into a Mattison SL. They are great value and last forever.

Comment from contributor D:
I purchased a 725 Woodmaster with the ProPac and it has gang rip capabilities. I still have to buy my wood that has been straight lined ripped on one side in order to gang rip on my machine. I can hold .005 end to end on this machine and I consider that to be good. I am still going to buy a Straight Line rip saw because without it you would not be able to gang rip on lumber that has not been straightened on one side.

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