[Dominic1649]

Good morning everyone,

As a bit of background, I am working as a Manufacturing Engineer and the most common question I get asked is "can we hold these tolerances?". We have various CNC machines (waterjets, oscillating knife cutters, CO2 lasers, router) and then a couple of presses. The materials we tend to cut tend to be elastomers, foams, fiber-based sheet, thermal pads. Now through my limited experience working here I found that the tolerances for us is more limited on the type of material rather than the machine's rigidity, precision, and tool life. We found that the general tolerance we can 100% hold is .015", but we still get customers asking for tolerances of +-.005" or less. I would understand those tolerances for metal fabrication because the material is rigid and stable, but for elastomers that moves and deforms a lot this is just ridiculous.

My question is then the following: For your industry, what sort of tolerances can you achieve and what do you feel most confident in achieving?

I am curious and looking forward to reading the answers.

[wilfredhampton]

@getaway shootout

As a data analysis, I can analyze large datasets to identify trends and patterns that can help improve manufacturing processes and reduce variability. I am most confident in my ability to: rrovide accurate calculations and simulations and analyze large datasets and identify trends

[peteeng]

Hi Dominic - Its an age old problem of specifiers asking for tolerances that can't be achieved. It goes to show that the person specifying the part does not know much about the material or the processes involved. I always have worked with manufacturers to establish realistic tolerances for the parts if I am specifying them. I have been involved in the auto industry and have had to do capability analysis for Toyota. My job was to follow through the manufacturing chain, establish each machine and process in that chain for that part. Then look at each operation and give it a tolerance then statistically put that together to determine that the tolerance say for a hole in a chassis can actually be achieved. It was mainly for accessories like towbars and bullbars and things that had to fit onto Toyota vehicles. The supplier had to provide a capability statement to show that they can achieve what Toyota wants. Often they could not qualify by process, then we had to use master jigs for the parts to qualify the parts fit before they were shipped to Toyota.

So to answer your question: every supplier and manufacturer has its own capacities and should inform/educate their customers what tolerances they can achieve. Being a consulting engineer, one day I'm designing a part for an ultrasound sensor spec'ed to the 0.0005mm the next day I'm dealing with structural steel spec'ed to +/- 2mm so I have to be flexible... Peter