gibu2 said:
I was reading through some of the discusions about lean and the sugestion of starting with low hanging fruit kept comming up. Now I know everyone has different fruit, but does anyone have some general ideas or principles to share when it comes to low volume job shops? We do low volume CNC work on mostly small parts. I have looked enough to know there is a variety of lean known as job shop lean but I have no idea what the principles of it are since I didn't want to pay for a guy to fly in and visit us or anything.
This is a good question. I will use my experience in a family owned machine shop to help you identify successes or opportunities as I found them.
1. Material identification. If you have different materials that look alike, label them so you only have to make parts once. You can use color coding with spray paint, or etch codes on the ends with a vibration marker. You can also use paint markers. Discipline is required to not cut off the marked end and replace the now-anonymous stock; either cut from the unmarked end, or re-mark it before replacing.
2. Do you mark lots of stock? We once got a shipment of bad stock that looked okay until final machining and micropolishing was done. Then they could see internal cracks running down the center of each length, but the shipment of round stock wasn't marked or segregated--it was piled along with everything else so machining was a costly Russian Roulette game until that steel was gone. Material marking should include lot numbers for traceability. If you don't look for cracks or inclusions with ultrasound upon receiving, you can mark and then reject a lot or batch of stock after the first such defects appear and thus save a portion of failures.
3. Identification after machining. Can you look at a little pile of parts and know, for example, their work order number? Segregate them or physically mark them.
4. Tool calibration needn't be a nightmare. We used 12 colors of nail polish to place a dot on each machine's set of calipers for each month. Computer records were kept on instruments, but it isn't necessary to place a label on each one--especially in a machine shop, where the lubricants break down label adhesives and there are hundreds of those little hand tools. Most nail polish comes off easily with acetone.
5. Do you environmentally control your shop? Does increased temperature/humidity increase your parts' tolerance failure rate? Use a P chart to track types of failures, and note the day--perhaps even the day's high temperature--to draw connections between environmental conditions and failures. If there are significant failures, compare those parts' prices to the costs of closing off and air conditioning spaces where those critical processes are run. You may be surprised how fast you will recoup the environmental costs even if you save half of those failed parts.
6. Don't underestimate the power of a procedure. Do your employees work on craftsmanship, or is there a method to what you do? Is their method consistent, and if not, have you traced failure rates to certain processes where better definition could have saved a part? The more complex the parts, the more helpful it could be to define the processes.
7. Tell them what you want, precisely, before they press the green button. Tell your inspector(s) what you want, and do not shift from that position. This means, if you want to deviate from what you already described as tolerance, call it what it is: a management review. This may sound simplistic, but I have a reason for bringing it up...sigh.
I know you asked for "Lean" but that concept varies per an organization's level and detail of development. Please tell me if I am being too simple, or if you want different information.
Best to you!
