johnston-engineering

Solar energy customer success featured in the Journal of Business

andy@johnstonpe.com (Andy Johnston) — Fri, 09 Nov 2018 19:54:02 GMT

Solar energy customer success featured in the Journal of Business

SolarXWorks: Solar Powered Refrigeration System

andy@johnstonpe.com (Andy Johnston) — Mon, 05 Nov 2018 21:24:48 GMT

Living with sink in structural injection molded parts: Sometimes you must break the rules

Project Overview:

Johnston Engineering recently completed a solar powered refrigeration system for our customer SolarXWorks . We provided complete system design, build and test. This system provides “cool” air conditioning or “cold” refrigerator conditions directly powered by sunlight. The system, solar panels and cooling tent is shown in Figure 1.

Figure 1 Solar powered refrigeration system keeping a tent cool

Advantage and usage:

Typical solar cooling systems lose up to 20% of the solar energy collected when they invert to AC voltage. Instead, this system uses 100% DC voltage and is very efficient. This product is highly flexible and can used for food transport and storage, commercial cooling applications, disaster recovery shelters or command and control shelters.

Figure 2 The system can be used for food transport and storage or remote facility cooling

Our contribution to the project:

Johnston Engineering provided the complete system design, build and testing. We provided program management, mechanical engineering including hardware design, refrigeration system design and structural analysis. We contracted the electrical engineering and software engineering, purchased all the hardware, built the system and tested and tuned the control software. The system is shown in Figure 3 and includes an evaporator and condensor, two fans, two compressors, a large battery, charge controller and many other components. The system is controlled using a Programmable Logic Controller and has a touch-screen panel interface. We designed the parts in 3D CAD software using SOLIDWORKS, and performed structural analysis in ANSYS. The exterior is covered in powder coated aluminum sheet metal which is fastened to a steel frame.

Figure 3 Solar powered refrigeration system

For more information:

Contact Johnston Engineering at 509-290-1034 or info@johnstonpe.com

Contact SolarXWorks at http://www.solarxworks.com/contact.html or contact@solarxworks.com

Process development test fixture

andy@johnstonpe.com (Andy Johnston) — Wed, 10 Oct 2018 20:31:18 GMT

Process development test fixture

Project Overview:

We recently designed and delivered a manufacturing process development test fixture. This fixture allows our customer to validate a new time, temperature and pressure dependent process without the large investment required for production hardware. This is a very inexpensive way to validate a new process and reduce risk before more expensive full-scale production machines are designed.

The fixture, shown in Figure 1, contains cartridge heaters and a thermocouple for reading temperature. The heaters are controlled by a temperature process controller running a PID loop. The operator just sets the desired temperature setpoint and the controller ramps to and holds the temperature setpoint.

Figure 1 Manufacturing process development test fixture

What we did:

Johnston Engineering provided the product development engineering design, thermal analysis, component sourcing, build, programming and testing to take this project from concept sketch to a fully functioning test fixture.

3D CAD files were generated in SOLIDWORKS and reviewed with the customer to ensure the proper design intent was met. A thermal analysis study was completed to size the heaters and verify acceptable unit maximum temperature and temperature uniformity at the process area. The study required calculating a natural convection heat transfer coefficient to determine the heat lost from the fixture. The heat transfer coefficient is one of the inputs used to complete a thermal Finite Element Analysis (FEA) study using ANSYS as shown in Figure 2. The thermal FEA was completed by iterating the heater input power and heat loss calculations until both maximum temperature and temperature uniformity are acceptable at a heat input value that can be achieved with off-the-shelf heaters. These results were then used to select appropriate heaters.

Figure 2 Thermal FEA temperature plot results show acceptable maximum temperature and temperature uniformity

Then, drawings were generated, and all machined parts were fabricated by a local machine shop. The components were assembled, and the controller was programmed to achieve the desired temperature setpoint without overshoot. Finally, the fixture was tested to validate performance before delivering to the customer for process development testing.

Living with sink in structural injection molded parts: Sometimes you must break the rules

andy@johnstonpe.com (Andy Johnston) — Thu, 21 Jun 2018 19:07:22 GMT

Living with sink in structural injection molded parts: Sometimes you must break the rules

When designing ribs in injection molded parts, engineers and designers need to consider how plastic shrinks as it cools inside injection molding tooling. As a rule-of-thumb, a rib thickness of no more than 80% of the wall thickness will prevent visible sink marks as the plastic cools. Better recommendations can be found in the plastic manufacturers technical literature. For example, when using unfilled Bayblend PC/ABS, Covestro recommends a rib thickness of no more than 50% of the wall thickness for minimal sink and 66% for a slight sink. Exceeding these recommendations will result in sink on the opposite side of the wall from the rib and can lead to part warpage as the rib cools and pushes or pulls on the wall.

This gets a little more complicated when the part needs to be strong enough to resist a relatively high structural load. The PC/ABS part shown in Figure 1 is supported at two oval-shaped locations on the top surface and must resist a 50 lbf upward force applied at the lower right of the image.

Figure 1 – Part is supported at two locations and must resist force

A design implementing manufacturers recommended rib thickness for minimal sink failed during a static structural analysis using ANSYS due to unacceptable deformation and stress in the part as shown as red surfaces in Figure 2.

Figure 2 – Stress plot shows unacceptable stress under load

A rib designed to manufacturers recommendations for rib thickness for minimal sink is shown on the left and a rib designed to accommodate the structural load is shown on the right in Figure 3.

Figure 3 – Rib designed with manufacturers recommendation for minimal sink (Left) and rib designed to accommodate structural load (Right)

After a few part design and structural analysis iterations with different shape and number of ribs, the design team determined that the best path forward was to live with the sink. Luckily, the location of the sink has little impact on the function of the part in the larger assembly. Additionally, warpage of the part due to rib relative cooling rate will not be a problem because the part is restrained against warpage when in operation. The rib which can accommodate the structural load is 84% of the wall thickness which exceeds both the manufacturers recommendation for slight sink and the 80% rule-of-thumb. The final injection molded part is shown in Figure 4. Sink can clearly be seen on the surface indicated, but this is acceptable to the function of the part.

Figure 4 – Final injection molded part shows sink due to a thick rib. Sink is acceptable on this surface.

Conclusion:

Manufacturers recommendations and rules of thumb should be used whenever possible in rib design to manage or avoid sink. This gets more complicated when parts must resist relatively high structural loads. Sometimes even after multiple design iterations, the design cannot both meet structural requirements and comply with rules-of-thumb and manufacturers recommendations to avoid sink. Under these circumstances, engineers and designers need to expect the parts to have sink on the opposite side of the rib and potentially part warpage. Only after evaluation of how tolerant the design is to sink and warpag e should the decision be made to exceed manufacturers recommendations.

Johnston Engineering was featured in the Spokane Relocation Guide

andy@johnstonpe.com (Andy Johnston) — Mon, 29 Jan 2018 20:14:19 GMT

Solar energy customer success featured in the Journal of Business

Our principal engineer, Andy Johnston, was recently featured in the Spokane Relocation Guide.

The article highlights some of our favorite things about the region and why it’s a great place to work, live and raise a family. Our highly skilled technical labor work force for design and manufacturing can be obtained at a much lower cost than Seattle or Portland which makes Spokane a good valve for product development and production. Our hope is that companies outside the area use our local product development engineering services or want to relocate to Spokane.

Some of our other favorites for the Spokane area include closeness to outdoor recreational activities, low cost of living, good schools, and tasty restaurants.

The Relocation Guide is an annual publication highlighting Spokane information, businesses, and resources to companies considering relocation to Spokane.

Read the whole article here: https://greaterspokane.org/relocation-guide/

We are featured on Pages 23-24.

Best engineering firms in Spokane

andy@johnstonpe.com (Andy Johnston) — Fri, 19 Jan 2018 20:19:58 GMT

Best engineering firms in Spokane

We are excited and proud to earn Bronze for “Best Engineering Firm” in the Spokane Coeur d’Alene Living Magazine Best in B2B awards. Perhaps the best part is that we don’t even compete in the same category as the two companies that beat us because they do not do product development work.

If you want your product designed by the best product development company in the region give us a chance and you won’t be disappointed.

Here is a link to the online version of the magazine here: https://issuu.com/ksomday/docs/scl146_online

We received awards on page 66 and 68.

Spokane Engineering: Engineering analysis saves time and money

andy@johnstonpe.com (Andy Johnston) — Thu, 12 Oct 2017 19:30:13 GMT

Spokane Engineering: Engineering analysis saves time and money

Design cycles that incorporate engineering analysis save time and money by minimizing or eliminating expensive and time-consuming design iterations.

We recently contributed to an article published at www.allaboutcircuits.com which evaluated keep-out-areas of a solid state hard drive (SSHD). We provided structural analysis showing that some of the components would short out under an applied load if the sheet metal was too thin.

“Structural analysis is an important part of the product development cycle when you have parts or assemblies that need to be strong enough to resist applied loads. Finite Element Analysis (FEA) is one tool used in structural analysis to model the stresses and strains of materials under applied loads such as forces, torques, or from thermal expansion. FEA allows the mechanical engineer to predict how the SSD assembly will react to applied loads and verify the structural fitness of the design before a prototype is ever fabricated.”

Read the article here

Andy Johnston Helps Solve Military Radar Cooling Challenges

andy@johnstonpe.com (Andy Johnston) — Fri, 28 Jul 2017 19:33:27 GMT

Andy Johnston Helps Solve Military Radar Cooling Challenges

Andy Johnston was published in Military Embedded Systems Magazine. The article is about cooling high-density military radar systems using two-phase (boiling) cold plates and phase-change thermal management systems. You can read the article here .

Summary:

Thermal management of high power dissipating electronics requires careful design and analysis to ensure the electronics are adequately cooled and the thermal management systems have the lowest possible size, weight and power.

Radar Transmit/Receive modules are high heat flux devices which can be cooled very effectively using two-phase cold plates. Two-phase systems require a fraction of the pumping power, size and weight when compared to conventional single-phase fluid systems.

13 Coins Restaurant

andy@johnstonpe.com (Andy Johnston) — Tue, 30 May 2017 20:15:25 GMT

13 Coins Restaurant

13 Coins

13 Coins is a timeless Seattle institution where generations have settled in for an unforgettable experience since 1967. Famed for its high backed booths, swiveling captain’s chairs and an exhibition kitchen known for lively, counter-side exchanges, 13 Coins has been host to countless first dates and proposals, family and company gatherings, celebrity sightings, and many late (or “early!”) nights on the town with friends.

Delicious food lining a dazzling 24-hour menu, engaging line chefs who banter playfully, and friendly, professional servers keep you coming back time and again.

Johnston Engineering had the privilege to work with this great restaurant in taking responsibility for designing the concrete form of the radial stair using 3D CAD modeling & full drawing package. Johnston Engineering also provided pick point structural analysis for this venue.

Mechanical Engineer Finds Niche in Technical Analysis

andy@johnstonpe.com (Andy Johnston) — Tue, 30 May 2017 20:08:05 GMT

Mechanical Engineer Finds Niche in Technical Analysis

Johnston Engineering focuses on element, fluid dynamics

Andy Johnston, president and principal engineer at Johnston Engineering, says he’s a different kind of mechanical engineer.

Johnston offers mechanical engineering design and analysis, specializing in technical aspects of finite element analysis and computational fluid dynamics, he says, adding, “I get to use my systems analysis experience.”

Finite element analysis involves dividing objects into a large number of parts to determine how the parts interact with each other and how they react to certain variable conditions, such as heat, pressure, and vibration, Johnston says.

“Computational fluid dynamics is similar to FEA, but it deals with voids that get filled by fluids,” he says.

Johnston designs parts and assemblies, from concept to manufacturing stages.

“People come to me with a great idea for a product,” he says. “I can help them design it and help them source the hardware.”

As of earlier this month, Johnston says he was busy with three active projects and he was working on a proposal for a government project involving high-energy lasers.

“I usually find a way to fit projects in,” he says, adding that his backlog has never been longer than a few weeks.

His clients represent biomedical, heating-and-cooling, and various entrepreneurial interests.

Johnston declines to identify his clients, citing nondisclosure agreements with most of them.

Speaking more generically, he says projects range from work on a device to attach to a wakeboard to a project aimed at desensitizing people to certain allergens.

Johnston says he worked for nearly half of 2016 providing engineering and systems-design services on a project for a company that makes atmospheric water generators, which extract drinking water from the air. The company’s generators range from a water-cooler sized device that generates three gallons of water a day to a large machine that’s mounted on a three-axle truck and produces up to 3,000 gallons a day.

The atmospheric water generator includes two connected systems—a cooling system interacting with a water treatment system—that fall under his niche engineering expertise, Johnston says.

“You’re not going to get something like that right the first time unless you get the appropriate analysis,” he says.

Johnston Engineering is based in a small office space on the second floor of the 1889 Building, at 120 N. Stevens. Johnston has no other partners or employees. Before opening his own office in late 2015, Johnston, a Gonzaga University graduate who has a bachelor’s degree in mechanical engineering, had worked in Liberty Lake at Isothermal Systems Research Inc. and its successor, SprayCool Data Systems Inc.

Cleveland-based Parker Aerospace acquired SprayCool in 2010, and Johnston continued to work there in the specialized field of thermal management of electronics used in aerospace and military applications.

“Not many mechanical engineers are into heat transfer and thermo dynamics,” he claims.

Parker Aerospace closed its Liberty Lake operations in 2015. Although the company offered Johnston a position in Ohio, he says he’s committed to staying in the Spokane area.

“I grew up here,” Johnston says. “My wife’s family is here. We designed and built our house here.”

Johnston’s wife Natalie Johnston is a principal engineer at MSI Engineers, of Spokane, which designs large mechanical systems for government, educational, health care, commercial, and industrial facilities.

As Parker Aerospace moved its operations, Johnston launched his independent engineering practice.

“I went straight from my exit interview to collect on my first invoice,” he says.

Johnston says he billed about 1,700 hours last year, and he’s on pace to bill a similar amount of hours this year.

He says that’s a respectable number of billable hours for a one-person operation.

Johnston adds, however, “I would like to get enough work to justify hiring a mechanical drafter. Right now I’m doing it, and when I’m doing it, I’m not out getting more work.”

He says potential clients find out about the Andy Johnston engineering practice through networking and word of mouth.

“The challenge is finding people who need my skills and finding them at the right time,” Johnston says. “Last year, things fell into place.”

Contrary to the stereotype of engineers being socially awkward, Johnston says he enjoys getting out and talking to people.

“I’ve always been OK in a crowd,” he says. “But I really like to get into the technical details and understand the physics of a problem and come up with the best solution.”

Johnston says he’s plugged into economic development and chamber of commerce group Greater Spokane Incorporated and its entrepreneurship program Startup Spokane, and he tries to advocate for Spokane.

“It seems like ever since the dotcom bust, companies have been leaving Spokane,” he says. “I want to do my part to help build technology and engineering in our area.”

“The challenge is finding people who need my skills and finding them at the right time.”

Andy Johnston says he enjoys the challenges of understanding the physics of an engineering problem and coming up with the best solution.

—Mike McLean

https://www.spokanejournal.com/up-close/mechanical-engineer-finds-niche-in-technical-analysis/

Johnston Engineering

(509) 290-1034

Dew Point: Atmospheric Water Generator

andy@johnstonpe.com (Andy Johnston) — Thu, 04 Aug 2016 20:45:41 GMT

Dew Point: Atmospheric Water Generator

Johnston Engineering has had the privilege to work with Dew Point Manufacturing.

What we did:

Johnston Engineering provided system level design and analysis to take this project from concept to reality.

We provided systems engineering and mechanical engineering services including:

Schematic design
Plumbing and filtration system design
Pressure drop analysis for water, air and refrigerant
Refrigeration system complete design
Psychometric analysis
Heat exchanger design
Structural analysis including structural Finite Element Analysis (FEA)
Thermal analysis including thermal Finite Element Analysis (FEA)
Component selection and design including sourcing from overseas suppliers
Build and test

About the customer:

Dew Point provides a cost-effective, sustainable and eco-friendly solution to the world’s growing water shortage.

Dew Point takes pride in being innovators. Over the past year Dew Point has been reengineering residential and commercial Atmospheric Water Generating (AWG) products.

Soon they will be launching the benchmark of AWG technology.

Their Water Tower Series which include their T40 (40 litre) and Countertop T20 (20 litre) units are going into mass production as of Sep 2016. They are very efficient, low maintenance and of the highest quality – producing pure, clean and chemical free water.

Johnston Engineering provided the services for systems engineering, plumbing and HVAC system design. Johnston Engineering also played the role of overseeing technical team coordination.

http://www.dewpointmfg.com/

Stop Box: Instant-access handgun retention device

andy@johnstonpe.com (Andy Johnston) — Thu, 04 Aug 2016 20:37:45 GMT

Stop Box: Instant-access handgun retention device

The StopBox® is a portable instant-access handgun retention device that does not use batteries, electronics or external keys. The StopBox® hand gesture code lock is instinctive to use in the dark and under stress. Secure your firearm without sacrificing accessibility when you need it the most. Proudly made in America.